"Top 10 Cancer Fighting Supplements" and ChatGPT: What You Need to Know (2024 Edition)

In this article, we are going to ask ChatGPT the following question, "Top 10 cancer fighting supplements".

Here is our prompt:

Top 10 cancer fighting supplements. Provide references and ranked them accordingly.

Here is the answer provided by ChatGPT:

Ranking supplements based on their potential cancer-fighting properties is complex and depends on specific research outcomes, cancer types, and individual health factors. However, I can provide a general overview based on current evidence and research. Keep in mind that this ranking can be subjective and may evolve with ongoing research. Here’s a ranking of the supplements along with references for their cancer-related effects:

1. Curcumin

   • Evidence: Numerous studies suggest curcumin has anti-cancer properties, including the ability to inhibit tumor growth and enhance the effectiveness of chemotherapy.
   • References:
     • Aggarwal BB, Sung B. “Pharmacological basis for the role of curcumin in chronic diseases: an age-old spice with modern targets.” Trends in Pharmacological Sciences. 2009.
     • Khan N, Afaq F, Saleem M, et al. “Chemopreventive properties of curcumin in the context of its potential to inhibit cancer stem cells.” Cancer Letters. 2013.

2. Green Tea Extract

   • Evidence: The polyphenol EGCG has been shown to have potential anti-cancer effects by inhibiting cancer cell proliferation and inducing apoptosis.
   • References:
     • Yang CS, Wang H, Lu G, et al. “Dietary polyphenols and cancer prevention: a review.” Frontiers in Bioscience. 2009.
     • Sharoni Y, Schwartz B, Koren S, et al. “Green tea polyphenols and cancer prevention: a review of the mechanisms of action.” Phytochemistry. 2008.

3. Vitamin D

   • Evidence: Adequate vitamin D levels are associated with a lower risk of certain cancers and may have beneficial effects on cancer prognosis.
   • References:
     • Garland CF, Garland FC. “Do sunlight and vitamin D reduce the likelihood of colon cancer?” International Journal of Epidemiology. 1980.
     • Holick MF. “Vitamin D deficiency.” New England Journal of Medicine. 2007.

4. Omega-3 Fatty Acids

   • Evidence: Omega-3s are associated with reduced inflammation and may have a role in reducing cancer risk and improving treatment outcomes.
   • References:
     • Simopoulos AP. “Omega-3 fatty acids in inflammation and autoimmune diseases.” Journal of the American College of Nutrition. 2002.
     • Cotter MA, Mallet AI, Keogh JB. “The role of fish oil in cancer prevention and treatment.” Clinical Reviews in Allergy & Immunology. 2007.

5. Resveratrol

   • Evidence: Resveratrol has shown potential in inhibiting cancer cell growth and metastasis, though more research is needed for conclusive evidence.
   • References:
     • Jang M, Cai L, Udeani GO, et al. “Cancer chemopreventive activity of resveratrol, a natural product derived from grapes.” Science. 1997.
     • Baur JA, Sinclair DA. “Therapeutic potential of resveratrol: the in vivo evidence.” Nature Reviews Drug Discovery. 2006.

6. Garlic Extract

   • Evidence: Garlic contains compounds that have shown potential in reducing cancer risk and improving immune function.
   • References:
     • Sinha R, Kulldorff M, Michalek AM, et al. “Garlic, onions, and cancer risk: a review of the epidemiological evidence.” Cancer Causes & Control. 1999.
     • Pinto JT, Lang CA. “Garlic and cancer: a critical review.” Journal of Nutrition. 2002.

7. Selenium

   • Evidence: Selenium has antioxidant properties and some studies suggest it may reduce cancer risk, but results are mixed.
   • References:
     • Clark LC, Dalkin B, Krongrad A, et al. “Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin.” Journal of the American Medical Association. 1996.
     • Rayman MP. “Selenium in cancer prevention: a review of the evidence and mechanisms.” Cancer Causes & Control. 2005.

8. Vitamin C

   • Evidence: Vitamin C is known for its antioxidant properties, but its role in cancer treatment is still debated and requires more research.
   • References:
     • Monti DA, Mitchell E, Baserga R, et al. “Intravenous vitamin C in the treatment of cancer.” Journal of Clinical Oncology. 2007.
     • Levine M, Padayatty SJ, Espey MG. “Vitamin C: a concentration-function approach yields pharmacological vitamin C concentrations.” Advances in Nutrition. 2011.

9. Mushroom Extracts

   • Evidence: Various mushroom extracts have shown immune-boosting and anti-cancer properties in preliminary studies.
   • References:
     • Noda SE, Shiina M, Tanaka Y, et al. “Mushroom extracts as a novel anticancer agent.” Journal of Nutritional Science and Vitaminology. 2011.
     • Cui Y, Wang Z, Li Z, et al. “Effects of mushroom polysaccharides on cancer cell growth and immunity.” Journal of Ethnopharmacology. 2005.

10. Probiotics

    • Evidence: Probiotics may support gut health and immune function, potentially affecting cancer risk and treatment outcomes.
    • References:
      • Galipeau HJ, Poutahidis T, Varian BJ, et al. “Microbiota-driven cancer immunotherapy: lessons learned from studies with probiotics.” Journal of Immunotherapy. 2013.
      • Macdonald IA, Rook GA. “Probiotics and cancer: a review.” Current Opinion in Gastroenterology. 2010.

Remember, while these supplements show promise, their effects can vary, and it's crucial to discuss their use with a healthcare provider, especially in the context of cancer treatment.

As you can see (above), most of the references are outdated. In this guide (below), we will provide you with a more updated answer.

1. Vitamin D3

Evidence with Reference links: 

There are more than 12,000 search results on vitamin D and cancer on PubMed. 

Prevention

A 2023 systematic review and meta-analysis of 14 RCTs (randomized controlled trials), published in Ageing Research Reviews (Kuznia 2023) found vitamin D3 supplementation reduced cancer mortality by 6%. This wasn’t considered statistically significant, but when only studies involving daily vitamin D intake were analyzed, cancer mortality dropped by a significant 12%.

In a 2023 meta-analysis, 116 randomised controlled trials were analysed. The meta-analysis concluded that vitamin D reduces lung cancer mortality. All-cause mortality* is decreased in patients with COVID-19 and liver diseases, especially in liver cirrhosis.

*Note: "Death from anything" may be a clearer term for the layperson as opposed to 'All-cause mortality'. This is one of the best measures for the factors that increase the risk of what eventually and most likely will take someone's life.

A 2022 randomized-controlled trial (DO-HEALTH) trial to investigate the combination of three complementary treatments for the prevention of cancer and suggest that the combination of daily vitamin D3, supplemental marine omega-3s, and a simple home exercise program may be effective in the prevention of invasive cancer among generally healthy and active adults aged 70 and older. Findings from a 3 year Randomized Controlled Trial with more than 2,000 participants observed a 61% reduction in the risk of invasive cancer among patients who completed a home exercise program and took vitamin D3 and omega-3 fatty acids daily. These results, from the DO-HEALTH trial (ClinicalTrials.gov identifier NCT01745263), were published in Frontiers in Aging 2022.

Dosage (DO-HEALTH): Supplemental 2000 IU/day of vitamin D3, and/or 1 g/day of marine omega-3s, and/or a simple home strength exercise (SHEP) programme compared to placebo and control exercise.

A comprehensive meta-analysis published June 18, 2024, in the journal Frontiers in Nutrition, examined the existing evidence surrounding this topic, highlighting the importance of maintaining optimal vitamin D levels as a potential protective strategy against thyroid cancer. The meta-analysis analyzed data from 21 studies involving 2,434 patients with thyroid cancer and 7,398 controls. The researchers focused on two key forms of vitamin D — 25-hydroxyvitamin D (25 (OH)D), a marker of overall vitamin D status, and 1,25-hydroxyvitamin D (1,25 (OH)D), the active form of the vitamin.

A number of epidemiologic studies have also investigated whether people with higher vitamin D intakes or higher blood levels of vitamin D have lower risks of specific cancers. The results of these studies have been inconsistent, possibly because of the challenges in carrying out such studies. For example, dietary studies do not account for vitamin D made in the skin from sunlight exposure, and the level of vitamin D measured in the blood at a single point in time (as in most studies) may not reflect a person’s true vitamin D status. Also, it is possible that people with higher vitamin D intakes or blood levels are more likely to have other healthy behaviors. It may be one of these other behaviors, rather than vitamin D intake, that influences cancer risk.

A Secondary Analysis of the VITAL* Randomized Clinical Trial studied the effect of Vitamin D3 Supplements on Development of Advanced Cancer. The Harvard research, published in the JAMA Network Open medical journal (2020), overturns the initial findings of a study of 25,000 people published in 2018.

*The VITamin D and OmegA-3 TriaL (VITAL) is a study to assess whether taking vitamin D (2000 IU/ day) and omega-3 fatty acids from marine (oily fish) sources lowers the risk of cancer.

Initially researchers believed there was no benefit from taking vitamin D, as they detected no reduced incidence of cancer diagnoses overall. But they were puzzled because cancer deaths went down among those taking the supplements. Meaning, there was no benefit in terms of prevention of cancer but a reduction in cancer deaths was observed.

A secondary analysis, found this anomaly can be explained by the fact that vitamin D seems to stop metastatic cancers - those aggressive types which spread to other parts of the body. That said, when stratified by BMI (body mass index), there was no significant reduction for the vitamin D arm in incident metastatic or fatal cancer among those with overweight or obesity (BMI 25-<30).

The cancers for which the most human data are available are colorectal, breast, prostate, and pancreatic cancer. Numerous epidemiologic studies have shown that higher intake or blood levels of vitamin D are associated with a reduced risk of colorectal cancer (Meta-analysis 2011). 

According to BreastCancer.org, research suggestsTrusted Source that certain cancers such as breast cancer, can have a higher risk of occurring when the body has low levels of vitamin D. 

Studies also show a link between vitamin D deficiency and cardiovascular disease, diabetes, and cancer (Sizar, 2020).

Many experts now recommend 800 to 1,000 IU a day, a goal that's nearly impossible to attain without taking a supplement. Although protection is far from proven, evidence suggests that vitamin D may help reduce the risk of prostate cancer, colon cancer, and other malignancies.

Although the role of vitamin D in cancer prevention remains an area of research interest and debate, avoiding deficient levels is recommended. (American Cancer Society 2020)

Dietary sources of Vitamin D include fatty fish, egg yolks, salmon, sardines, cod liver oil, some yogurt (read the label to see if it says "fortified with vitamin D"), some soy milk (read the label to see if it says "fortified with vitamin D") and fortified milk. Sun exposure is also another way to get vitamin D naturally.

Make sure to take 500 mg to 1000 mg of magnesium and 150 mcg of vitamin K2, (not K1) which are important cofactors for optimizing vitamin D function. And, remember the only way you know what your vitamin D level is, is to test it. Vitamin D level should be in a therapeutic range of 50 to 70 ng/ml for treatment of rheumatoid arthritis. Most people are shocked how low their level is when they finally get around to testing it.

That said, as researchers explained in Nutrients (2022):

“Vitamin D supplementation is not the magic pill that miraculously solves the cancer burden or that can replace a healthy lifestyle. It is necessary to foster a good environment and invigorate a healthy lifestyle, including a high-quality diet and physical activity. Both have been proven to confer health benefits in many diseases, including cancer, and are the best preventive measures available.”

 

Related: Vitamin D Level and Cancer: Vitamin D Reduces Cancer Deaths

The Optimal Vitamin D Level for Cancer Prevention

Research has shown that once you reach a minimum serum vitamin D level of 40 ng/mL (100 nmol/L), your risk for cancer diminishes by 67%, compared to having a level of 20 ng/mL or less. 

For health and disease prevention, including cancer prevention, we recommend you aim for optimal levels between 60 ng/mL and 80 ng/mL. 

It's important to remember that calcium, vitamin D3, magnesium and vitamin K2 must be properly balanced for optimal overall health. Your best and safest bet is to simply eat more calcium-, magnesium- and vitamin K2-rich foods, along with sensible sun exposure.

However, if you find supplementation is necessary after a serum vitamin D test, also supplement with magnesium and vitamin K2 (MK-7) to ensure proper balance. You'll also want to ensure you're following an overall healthy lifestyle to reduce your cancer risk as much as possible. As researchers explained in Nutrients (2022):

"Vitamin D supplementation is not the magic pill that miraculously solves the cancer burden or that can replace a healthy lifestyle. It is necessary to foster a good environment and invigorate a healthy lifestyle, including a high-quality diet and physical activity. Both have been proven to confer health benefits in many diseases, including cancer, and are the best preventive measures available."

Treatment

A 2024 post hoc analysis (Nutrients 2024) of the AMATERASU trial (UMIN000001977), a randomized controlled trial (RCT), included 302 patients with digestive tract cancers divided into two subgroups stratified by median serum levels of omega-3 into higher and lower halves. The 5-year relapse-free survival (RFS) rate was significantly higher in the higher half (80.9%) than the lower half (67.8%). In the patients in the lower omega-3 group, the 5-year RFS was significantly higher in the vitamin D (74.9%) than the placebo group (49.9%). In patients with digestive tract cancers, these results suggest that vitamin D supplementation may reduce the risk of relapse or death by interacting with marine omega-3.

Vitamin D and Chemotherapy

Multiple studies indicate that a significant proportion of cancer patients are vitamin D-deficient (level < 20 ng/mL) and that higher plasma 25-hydroxyvitamin D levels are associated with improved survival in colorectal, breast, gastric, and lymphoma cancer patients [Systematic Review 2014]. Meta-analyses and clinical trials demonstrate that vitamin D supplementation may reduce cancer mortality and improve survival in cancer patients, especially when used in combination with chemotherapy (Meta-analysis 2023). SUNSHINE (JAMA 2019), a clinical trial on metastatic colorectal cancer patients, showed that “high-dose” vitamin D3 (aiming for a level of >50 ng/mL) combined with standard chemotherapy resulted in improved progression-free survival compared to standard-dose vitamin D3.

Caution: The dosage for vitamin D in prevention (1,000 to 2,000 IU daily) is very much different from the high dose treatment dosage i.e. 20,000 to 50,000 IU daily. Always consult your doctor first! 

2. Turmeric (Curcumin)

Evidence with Reference links:  

There are more than 7,000 search results on curcumin and cancer on PubMed and more than 50 clinical trials with curcumin, most of which are still ongoing. The spice turmeric can be extremely helpful when it comes to fighting cancer. 

The use of fenbendazole and curcumin, has achieved much attention due to the reported experience of Joe Tippens. In 2016, Tippens was diagnosed with non-small-cell lung cancer with extensive metastatic disease. At the advice of a veterinarian friend, he took Fenbendazole together with nanocurcumin, and three months after starting these drugs his PET scan was completely clear. 

A review paper published in 2022, analysed 21 human studies. Sixteen out of 21 clinical trials were associated with the effectiveness of curcumin or turmeric on various types of cancer, and the other five clinical trials were related to the evaluation of the efficacy of curcumin or turmeric in relieving the side effects of cancer chemotherapy and radiotherapy. The emerging data from the clinical trials confirm that curcumin has the potential for cancer prevention and intervention. Interestingly, curcumin appears to be universally useful for just about every type of cancer (Arslan 2022), which is really odd since cancer consists of a wide variety of different molecular pathologies.

Both curcuminoids and related turmeric products have been sanctioned by the U.S. Food and Drug Administration (FDA) as safe.

Why Whole Turmeric Is Ineffective

Unfortunately, while there's some curcumin in whole turmeric, there's not enough in the regular spice to achieve clinically relevant results. The turmeric root itself contains only about 3% curcumin concentration. Another major limitation of curcumin as a therapeutic agent is that it is poorly absorbed. When taken in its raw form, you're only absorbing about 1% of the available curcumin.

Because it's not easily absorbed through your gastrointestinal tract, it's more effective to use a high-quality bioavailable curcumin extract, according to a 2013 study. A typical anticancer dose is just under 1 teaspoon of curcumin extract three or four times daily.

However, in the case of colon cancer, this poor absorption into the bloodstream may be an advantage. As there is poor absorption, higher levels of curcumin stay in the intestinal tract for longer periods of time, having an effect on gastrointestinal cancers. 

In one study, participants took a 1,080 milligram (mg) dose per day of curcumin for 10 to 30 days between their initial biopsy and surgical removal. The patients taking the supplement experienced a reduction in blood levels of inflammatory agent, improvement in their body weight and an increased number of dying tumor cells.

In a 2016 study, a team of scientists at the University of Pittsburgh and at Pondicherry University, India, discovered the bioactive ingredient in turmeric, curcumin, can both prevent and cure bowel cancers. The team found the compound triggered cancer cell death by increasing a level of protein labeled GADD45a. Lead author Rajasekaran Baskaran, Ph.D., who has more than 20 years of experience in cancer research, commented:

"Studies on the effect of curcumin on cancer and normal cells will be useful for the ongoing preclinical and clinical investigations on this potential chemo-preventive agent."

New Curcumin Forms

Convenience and efficiency has driven many of the changes in the forms of curcumin in later years. Because it's a fat-loving or lipophilic molecule, many newer preparations now include some sort of oil or fat, which improves its absorbability and bioavailability. Such preparations typically have seven to eight times higher absorption than the raw, unprocessed 95% concentration of dry powder. There are also newer sustained release preparations.

Turmeric and black pepper each have health benefits, due to the compounds curcumin and piperine. As piperine enhances curcumin absorption in the body by up to 2,000%, combining the spices magnifies their effects. (Healthline)

Click here to buy Bioavailable Curcumin. (Disclosure: Paid link)

  

Note: Although the antitumor properties of curcumin have been confirmed by multiple pre-clinical and clinical studies, its transition into mainstream cancer treatment has been limited by its subpar bioavailability. Furthermore, clinical investigations on curcumin have often involved small cohorts, which can lead to clinical variability. As a result, more expansive and well-structured clinical trials are required in the future to confirm that curcumin is a potential therapeutic agent for the treatment of cancer.

3. Fish Oil (Omega-3 Fatty Acids)

Evidence with Reference links: 

PubMed has indexed more than 3,000 research studies on Omega-3 and cancer. Most people use fish oil supplements to enhance the amount of omega-3’s in their diet. 

A 2021 report (Nature Communications) suggest that higher levels of omega 3 fatty acids in circulation correlate with lower risk of premature death from age-associated diseases such as cardiovascular disease and cancer. The analysis was conducted with data from 17 prospective cohort studies examining the associations between blood omega-3 fatty acid levels and risk for all-cause mortality. Over a median of 16 years of follow-up, 15,720 deaths occurred among 42,466 individuals. The researchers found that, after adjustment for relevant risk factors, risk for death from all causes was significantly lower (by 15-18%, at least p < 0.003) in the highest vs the lowest quintile for circulating long chain (20-22 carbon) omega-3 fatty acids (eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids). Similar relationships were seen for death from cardiovascular disease, cancer and other causes. 

The first randomized-controlled trial (DO-HEALTH trial) to investigate the combination of three complementary treatments for the prevention of cancer and suggest that the combination of daily vitamin D3, supplemental marine omega-3s, and a simple home exercise program may be effective in the prevention of invasive cancer among generally healthy and active adults aged 70 and older.

Findings from a 3 year Randomized Controlled Trial with more than 2,000 participants observed a 61% reduction in the risk of invasive cancer among patients who completed a home exercise program and took vitamin D3 and omega-3 fatty acids daily. These results, from the DO-HEALTH trial, were published in Frontiers in Aging 2022.

 

Many governments recommend eating omega-3 containing fatty fish, two times per week. But that is often not enough. Ideally, people would need to eat fatty fish four times per week, while also supplementing with omega-3 fatty acids, at least 1,000 mg of pure omega-3 (DHA and EPA) per day.

However, fish oil was shown in one study on mice (2015)Trusted Source to possibly reduce the effectiveness of chemotherapy, and for that reason ground flax seed is a worthy alternative.

Flax seed is rich in omega-3 fatty acids, which may reduce the risk of certain cancers. When supplementing, try to avoid flaxseed oil because it lacks the nutrients of ground flax seed. Ground flax seed can be purchased online or found in many larger grocery store chains. Simply sprinkle some ground flax seed on your food and enjoy.

Make sure you buy high-quality omega-3 fatty acid supplements, meaning that the omega-3 fatty acids are pure and have not oxidized much (having low “TOTOX” value).

TOTOX value stands for total oxidation value. The omega 3 fatty acids EPA and DHA from fish oil are highly sensitive to oxidation. This means that they are rapidly affected by contact with oxygen. Oxidised fatty acids are not beneficial to our health. For this reason, a good fish oil supplement has a low TOTOX value. The maximum TOTOX value is set at 26 by the Global Organization for EPA and DHA omega-3.

Caution: A 2024 study published in BMJ Medicine suggests that regular use of fish oil may contribute to atrial fibrillation and stroke among the general population.

We recommend taking a maximum of 1 gram of omega-3 per day. Higher amounts could be risky, because EPA and DHA are both polyunsaturated fats (PUFAs) and, like linoleic acid (LA), are susceptible to oxidation and the production of dangerous aldehyde metabolites.

Related: Krill-sourced Fish Oil and Omega-3

4. Vitamin C

Evidence with Reference links: 

PubMed has indexed more than 3,000 research studies on vitamin C and cancer. United States Preventive Services Task Force has recommended the use of Vitamin C and E supplementation for cancer prevention (J Oncol Pharm Pract 2024).

Prevention

Best Evidence: An umbrella review* (Xu 2022) to assess the existing systematic reviews and meta-analyses for the association between vitamin C intake and multiple health outcomes; showed that vitamin C intake was associated with reduced risk of all-cause mortality, cardiovascular disease (CVD), oesophageal cancer, gastric cancer, cervical cancer and lung cancer with an increment of 50–100 mg per day.

Beneficial associations were also identified for respiratory, neurological, ophthalmologic, musculoskeletal, renal and dental outcomes. A total of 76 meta-analyses (51 papers) of randomised controlled trials and observational studies with 63 unique health outcomes were identified. Harmful associations were found for breast cancer and kidney stones for vitamin C supplement intake. 

*Umbrella review: An umbrella review, or a review of reviews, is a systematic review that only considers other systematic reviews as an eligible study type for inclusion. An umbrella review compiles evidence from multiple existing reviews and is one of the highest levels of evidence.

2022 - Obese women who took vitamin C and B6 at amounts that exceeded the recommended daily intake levels were associated with a lower risk of breast cancer, according to a five-year long South Korean cohort study. 40,432 women without a history of cancer at baseline were included in this study.

2022 - A meta-analysis to review the association between vitamins and brain cancer showed that intake of vitamin C, β-carotene, and folate can reduce the risk of brain cancer, while high serum α-tocopherol (vitamin E) concentration also has a protective effect on brain cancer.

A 2017 meta-analysis of 11 studies concluded that patients with lower concentrations of serum vitamin E (the vitamin E level in your blood) had a higher risk for colorectal cancer.

Caution: However, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) found that vitamin E taken alone increased the risk of prostate cancer. The risk continued even after the men stopped taking vitamin E. Taking selenium with vitamin E or taking selenium alone did not increase the risk of prostate cancer. (JAMA 2011)

Treatment

2023 - A systematic review to evaluate the existing literature on the safety and efficacy of vitamin C, E and selenium supplementation in oncology patients. Twenty-four articles met the inclusion criteria. Of the included studies, nine evaluated selenium, eight evaluated Vitamin C, four evaluated Vitamin E, and three of these studies included a combination of two or more of these agents. Findings were generally favorable among the studies, and adverse effects of supplementation were limited. The review concluded that antioxidant supplements may provide benefits in reducing incidence or severity of treatment-induced side effects with limited risk for adverse effects.

2022 - A systematic review on the effect of vitamins C and E on cancer survival showed improvement of survival and progression rates of cancers by vitamins C and E. However, the authors concluded that more high quality trials with large sample sizes are required to confirm.

Vitamin C is known as an antioxidant, but at high concentrations, vitamin C can kill cancer cells through a pro-oxidant property (Transl Oncol. 2020). This study has also demonstrated that vitamin C treatment with magnesium supplementation provided more effective anticancer therapy than vitamin C treatment alone.

High-dose vitamin C cancer therapy was introduced by Linus Pauling and Ewan Cameron [source]. Clinical demonstration results by Pauling and Cameron showed that intravenous injection of 10 g/day of vitamin C extended the survival time of terminal cancer patients by about 4.2 times. However, results from the Mayo Clinic in 1979 showed that the survival time of vitamin C–treated patients was even shorter than that of the placebo group patients [source]. A significant difference between those two research groups was the route of AA administration: intravenous injection and oral administration, respectively. 

When treating cancer, IV needs to be used because you simply cannot take the high dosages required orally. Doses over 10 to 20 grams of ascorbic acid will cause loose stools when taken orally, but IV administration bypasses the limitation of the gut. It also allows the vitamin C to get directly into the blood to the extracellular fluid, into the tumor microenvironment, to penetrate the tumor and saturate the entirety of the tumor.

To understand the mechanism of AA's (ascorbic acid) anticancer activity, many research groups have treated colon, prostate, leukemia, lymphoma, brain, and stomach cancer cells and chemically or genetically transformed cancer cells with AA and showed cancer growth inhibition and even cancer cell death through hydrogen peroxide–mediated reactive oxygen species (ROS) generation [source]. 

In most cases, the pharmacological concentration of vitamin C required for anticancer effects (EC50 value of 1–10 mM) could only be achieved by intravenous administration. Thus, to apply vitamin C as an anticancer therapy, a high intracellular concentration in cancer cells is critically important (source).

According to the Mayo Clinic (2023):

"More recently, vitamin C given through a vein (intravenously) has been found to have different effects than vitamin C taken in pill form. This has prompted renewed interest in the use of vitamin C as a cancer treatment.

There's still no evidence that vitamin C alone can cure cancer, but researchers are studying whether it might boost the effectiveness of other cancer treatments, such as chemotherapy and radiation therapy, or reduce treatment side effects.

There are still no large, controlled clinical trials that have shown a substantial effect of vitamin C on cancer, but some preliminary studies do suggest there may be a benefit to combining standard treatments with high-dose IV vitamin C."

 

According to the concluding remarks from a 2020 article from the National Cancer Institute:

Vitamin C as a cancer therapy has had a controversial past. What has been intriguing are small clinical trials that suggest some responses, but with no clear rationale for why cancers should respond to vitamin C or a path forward for explaining which patients are most likely to respond. Now a growing number of preclinical studies are showing how high-dose vitamin C might benefit cancer patients. Importantly, these preclinical studies provide a clear rationale and potential biomarkers that may help personalize the therapeutic approach and identify patient populations that are likely to respond to high-dose vitamin C therapy. Since the mechanisms of action of vitamin C are becoming better defined, we can propose vitamin C combinations in a more rational, hypothesis-driven manner. In addition, given the current high financial cost of new cancer drugs, it seems rational to improve the effectiveness of current therapies by studying their clinical interactions with vitamin C. In our view, the implementation of this treatment paradigm could provide benefit to many cancer patients.

Ascorbic acid vs whole food vitamin C?

Synthetic Ascorbic acid is NOT the same as whole food or whole fruit vitamin C. 

If you were to compare the two to a car, vitamin C would be the whole car, fully functional, and the engine is an enzyme called tyrosinase, while ascorbic acid is the car frame, with no moving parts. A car with the engine can take you from one place to another but the car frame alone will not be able to do that.

Whole food vitamin C can also boost your copper level, as vitamin C contains an enzyme called tyrosinase, which has 2 atoms of copper in it. Ascorbic acid is prooxidant, while vitamin C complex is actually an antioxidant. Anything that has copper is going to be antioxidant.

Related: Benefits of Vitamin C in Cancer Treatment

5. Magnesium

Evidence with Reference links: 

PubMed has indexed more than 5,000 research studies on magnesium and cancer.

Magnesium and Colorectal Cancer

Several studies have demonstrated an association between high magnesium intake and reduced risk of colorectal cancer (CRC).

An analysis of the prospective, Swedish Mammography Cohort (JAMA 2005), evaluated 61,433 women aged 40 to 75 without a history of cancer for a mean follow-up of 14.8 years. The highest quintile of magnesium intake was associated with a significantly lower risk of CRC compared with the lowest quintile. This benefit was observed for both colon and rectal cancers.

A case-control study evaluated 2204 subjects from the Tennessee Colorectal Polyp Study (2007), which demonstrated that increasing total magnesium intake was significantly associated with decreasing risk of CR.. The highest tertile of dietary magnesium intake (>298 mg/day) was significantly associated with reduced risk of CRC in an age-adjusted model.

A study of 140,601 postmenopausal women from the Women’s Health Initiative (2015) with an mean follow-up of 13 years demonstrated a significant reduction in CRC risk with the highest quintile of total magnesium intake compared with the lowest quintile of magnesium intake. The benefit was driven by colon cancer, with a trend for rectal cancer.

Magnesium and Pancreatic Cancer

A study of 66,806 subjects aged 50 to 76 at baseline from the Vitamins and Lifestyle cohort (Nature 2015) evaluated magnesium intake and the incidence of pancreatic cancer during a mean follow-up of 6.8 years. Subjects with magnesium intake below the recommended dietary allowance were more likely to develop pancreatic cancer, particularly in those whose intake was less than 75% of the recommended dietary allowance. In this study, a 100 mg/day decrease in magnesium intake resulted in a 24% increase in risk of pancreatic cancer.

6. Melatonin

Evidence with Reference links: 

PubMed has indexed more than 3,300 research studies on melatonin and cancer. 

In 1996, Russel Reiter, PhD (one of the World's leading melatonin researchers), published his book on Melatonin, "Melatonin: Breakthrough Discoveries That Can Help You Combat Aging, Boost Your Immune System, Reduce Your Risk of Cancer and Heart Disease, Get a Better Night's Sleep".

Melatonin is one of the most important antioxidant molecules. In the human body — aside from having direct antioxidant effects — it also stimulates the synthesis of glutathione and other important antioxidants like superoxide dismutase and catalase.

Many people are not aware that only 5% of your body’s melatonin — which is also a potent anticancer agent — is produced in your pineal gland. The other 95% is produced inside your mitochondria — provided you get sufficient near infrared exposure which is typically from sun on your bare skin. This is why vitamin D is more than likely a biomarker for sun exposure, which is intricately involved in melatonin production. (source)

The Mediterranean Diet (MD) dietary pattern is also rich in antioxidants, such as melatonin. A systematic review of 31 studies published in Antioxidants (Elena 2023) showed high melatonin contents in MD-related foods, such as tomatoes, olive oil, red wine, beer, nuts, and vegetables. The consumption of specific MD foods increases melatonin levels and improves the antioxidant status in plasma.

Melatonin is also known to play a fundamental role in regulating the sleep-wake rhythm; however, in the last 10 years it has been discovered that it is actually involved in many other biological mechanisms, also playing an important role in the inflammatory, metabolic and neoplastic processes. In fact, the mechanisms by which melatonin performs an anti-tumor effect are many: it has an anti-oxidant effect that protects against DNA damage, acts as a scavenger of reactive oxygen species (which undermine genomic stability), stimulates DNA repair mechanisms, improves the functioning of the mitochondrial respiratory chain, and inhibits mitochondrial mitophagy and telomerase activity (Molecules 2018).

In addition, melatonin increases the expression of the p53 protein, induces its phosphorylation, inhibiting cell proliferation, promotes apoptosis, reduces the levels of the vascular endothelial growth factor and endothelin-1, fundamental for tumor growth and metastasis formation, reduces inflammatory processes and cell migration (Molecules 2018).

Reduction of melatonin production has also been seen in some types of cancer (breast and prostate) (Mogavero 2021).

Melatonin for Cancer Patients

2022 - An umbrella review from 111 different meta-analyses based on randomized controlled trials (Pharmacological Research 2022):

"Survival at one year (P < 0.005) significantly increased with cancer patients."

2020 - A case series of 14 advanced cancer patients (Trends in Oncology 2020), treated with high dose (1,000 mg/day) of melatonin; achieved a disease control of 54% of the patients:

"Moreover, this preliminary study may also suggest that high dose melatonin has no toxicity in cancer patients with poor clinical status, as well as in healthy subjects."

2005 - A systematic review of 10 randomized controlled trials (J Pineal Res 2005):

"All trials included solid tumor cancers. All trials were conducted at the same hospital network, and were unblinded. Melatonin reduced the risk of death at 1 yr (relative risk: 0.66). Effects were consistent across melatonin dose, and type of cancer. No severe adverse events were reported. The substantial reduction in risk of death, low adverse events reported and low costs related to this intervention suggest great potential for melatonin in treating cancer."

Just be careful, though, as using high-dose melatonin long term could be a prescription for disaster. This is because doses of over 5 to 10 mg are likely to draw out heavy metals like mercury and unless you are on a good detoxification program and using sauna regularly these heavy metals could cause biological damage.

Related: What You Need to Know About Melatonin

7. Green Tea (EGCG)

Evidence with Reference links: 

PubMed has indexed more than 2,000 research studies on EGCG and cancer.

Green tea also contains chemicals called polyphenols that have antioxidant, anti-inflammatory properties and anti-angiogenic properties, and the catechins in green tea polyphenols show very strong anti-angiogenic properties.

Epigallocatechin 3-gallate (EGCG), the active compound in green tea, is synthesized from epicatechin and gallic acid, has garnered considerable attention in the scientific community due to its multifaceted biological and pharmacological properties. These include its anti-oxidant, anti-inflammatory, anti-angiogenic, anti-proliferative, pro-apoptotic, and anti-metastatic functions. 

The Minnesota Green Tea Trial (MGTT. 2015) is the largest and longest double-blind, placebo-controlled, randomized intervention study that specifically evaluated the effects of oral GTE (green tea extract) containing defined quantities of EGCG on established biomarkers of breast cancer risk.

They randomized and stratified 1075 healthy postmenopausal women at high risk of breast cancer according to their breast tissue density and catechol-O-methyltransferase genotypes and divided them into two groups: 537 placebo and 538 green tea groups. Green tea group participants took 4 capsules that contained 843 mg EGCG, whereas the placebo group took capsules without green tea extracts.

Researchers measured changes in percent mammographic density, circulating endogenous sex hormones, and proteins of the insulin-like growth factor axis. Their results showed that supplementation with green tea extract could modify and reduce mammographic density (MD) and protect against breast cancer, even though it was only significant in younger women (50–55 years) and had no effect in older women (R), an age-dependent effect similar to those of tamoxifen.

According to a 2018 review, EGCG and green tea extracts may help prevent or delay cancer onset, cancer recurrence, and secondary growths from cancer.

However, the National Center for Complementary and Integrative Health (NCCIH) state that studies of green tea and cancer in humans have so far produced inconsistent results.

Several epidemiological studies (2011) have reported that the consumption of green tea may decrease cancer risk. Studies have also confirmed numerous health benefits of green tea including prevention of cancer (R, R) and cardiovascular disease, as well as anti-inflammatory, antioxidant, antiarthritic, antibacterial, and antiviral effects. (R, R, R, R).

Given these promising insights, a phase I clinical trial (NCT00516243) has been initiated that targets women with hormone receptor-negative stages I-III breast cancer and aims to explore the safety and effectiveness of EGCG. Concurrently, several clinical trials for CRC (NCT02321969 and NCT01360320) are also in progress. However, while these studies are promising, the potential therapeutic application of EGCG in cancer treatment is still restricted by its limited bioavailability.

If you have cancer, consider drinking up to 3 cups of green tea per day to experience the benefits. Green tea pills are also available, but may be too concentrated. Some studies show health benefits in people who drink as little as one cup per day, while other studies deem five or more cups per day to be optimal (Source, Source).

8. Quercetin

Evidence with Reference links: 

PubMed has indexed more than 4,000 research studies on quercetin and cancer. The safety and potential usefulness of quercetin for the prevention and treatment of cancer have been documented in both animal experiments.

One of the most promising avenues for quercetin lies in its potential as a senotherapeutic agent.

A paper published in August 2022 in Nutrition Research analyzed the pro-apoptotic effect that quercetin has on aging cells. The paper reviewed preclinical and early phase data using quercetin as a senolytic agent and found the data showed it was effective in “preventing or alleviating cancer formation.”

The authors reviewed the importance of cellular aging in the development of cancer cells and the effect that quercetin may have on the suppression of cancer cell proliferation. 

Cellular senescence is a dynamic and multi-step process that is associated with alterations in metabolic activity and gene expression. This can compromise tissue regeneration and contribute to aging. On the other hand, by removing senescent cells, age-related dysfunction can be attenuated and potentially extend the lifespan.

Quercetin was found to promote senescence in glioma cells by inhibiting the activity of HDACs. Moreover, in HepG2 liver cancer cells, quercetin was shown to reactivate P53, thereby inhibiting RNA degradation and protein ubiquitination, leading to the upregulation of P21 expression and concurrent downregulation of cyclin D1, a crucial player in cell cycle arrest (source). 

Thus, quercetin stands out as a potent tool to induce senescence in cancer cells. In the burgeoning field of senolytic treatments, combining quercetin with other agents has also shown promise in efficiently targeting senescent cells.

 

In addition, pre-treatment with quercetin protected against DOX (doxorubicin)-induced normal cell senescence by reducing the number of senescent cells and suppressing the release of SASP factors (source).

The ability of cancer cells to exploit senescence as a defense mechanism against therapies necessitates innovative approaches. 

Repurposing quercetin as an oncological drug has emerged as a strategic solution, as evidenced by a Phase II clinical trial that combined dasatinib and quercetin for the treatment of head and neck squamous cell carcinoma (NCT05724329). 

However, the broader application of quercetin in oncology has several challenges, and issues such as its limited bioavailability, instability, and lack of precise tumor targeting need to be addressed. Thus, novel strategies that augment the bioavailability of quercetin using lipid nanoparticles and chitosan nanoparticles have been developed. For example, a recent Phase II clinical trial assessed the therapeutic efficacy of both quercetin and its nanoparticle variant against oral squamous cell carcinoma cell lines (NCT05456022). 

According to Mount Sinai, quercetin should be used with caution as it may interact with certain antibiotics by reducing the effectiveness of the drug. It may also enhance the effect of some blood thinners, which can increase your risk of bleeding. In addition to these, it may interact with corticosteroids, digoxin, cyclosporine and fluoroquinolones.

9. Zinc

Evidence with Reference links: 

PubMed has indexed more than 20,000 research studies on zinc and cancer.

Given the important role of zinc in a wide range of enzymatic reactions and physiological processes, zinc deficiency has been identified in a variety of diseases, notably cancer. In recent years, multiple meta-analyses and reviews looking at zinc levels in individual cancer types have been published, as have a plethora of primary studies demonstrating a link between low zinc levels and specific types of cancer.

In a 2023 review, the authors summarize recent evidence implicating low zinc concentrations in serum or tissues as a characteristic in a wide range of cancers.

On the basis of the correlation between low zinc levels and poor cancer outcomes, many authors have speculated that zinc supplementation could be used to reduce the risk of developing cancer. A retrospective analysis published by Hosui et al. in 2018 reported that zinc supplementation appears to maintain liver function and decrease the risk of developing hepatocellular carcinoma. A more recent study by the same group found that oral zinc supplementation decreased the risk of hepatocellular carcinoma development in patients who received direct-acting antivirals to eradicate HCV [Hosui et al. 2021]. Valenzano et al. in 2021 also reported that in Barrett’s esophagus, administration of zinc gluconate resulted in the upregulation of several tumor-suppressive miRNAs and downregulation of inflammation-inducing proteins. Additionally, a 2022 mini-review by Iqbal et al. noted limited evidence for a correlation between high dietary intake of zinc and a reduced risk of breast cancer, suggesting that dietary supplementation could decrease the chance of developing this malignancy. These preliminary studies suggest that there could be potential for using zinc supplementation in the clinical setting to help prevent cancer development.

The extensive evidence demonstrating the prevalence of zinc deficiency in a wide range of cancer types suggests that zinc deficiency should be considered a relatively widespread feature of multiple cancers. While research regarding the potential clinical utility of testing zinc levels in patients with or at risk of developing cancer is still preliminary, the data suggest that zinc deficiency may be a potential biomarker for identifying patients at risk of developing cancer, predicting outcomes in patients with cancer, and even as a preventive or adjunctive treatment for cancer.

10. Garlic (Allicin)

Evidence with Reference links: 

PubMed has indexed more than 1,200 research studies on garlic and cancer. Garlic and onions belong to the Allium genus of plants.

2023 - A randomized controlled trial (RCT) on garlic and gastric cancer (GC), published in January 2023, found a significant reduction in the risk of developing GC with increasing dietary intake of allium vegetables, particularly garlic vegetables. 

The study was conducted on the basis of the Shandong Intervention Trial, a randomized, placebo-controlled, factorial-designed trial (1995-2003) in a well-recognized high-risk area for GC in China. Participants were continuously followed up to December 2017 for 22.3 y (1995-2017). A total of 3,229 subjects were included.

2020 - A meta-analysis of 11 studies, published in January 2020, did find evidence that garlic could reduce the risk of ColoRectal Cancer. 

Another study published in the Asia Pacific Journal of Clinical Oncology (2019) revealed the odds of getting ColoRectal Cancer were 79% lower in those who a diet high in allium vegetables, which include garlic, leeks and onions.

One study of 543,220 participants found that those who ate lots of Allium vegetables, such as garlic, onions, leeks and shallots, had a lower risk of stomach cancer than those who rarely consumed them (Source).

A study of 471 men showed that a higher intake of garlic was associated with a reduced risk of prostate cancer (Source).

Based on these findings, including 2–5 grams (approximately one clove) of fresh garlic into your diet per day can help you take advantage of its health-promoting properties.

Garlic is a great choice when it comes to giving your body a little extra protection. To reap the benefits of garlic, you should eat one clove per day, or 300 to 1,000 milligrams (mg)Trusted Source of garlic extract.

The active component in garlic is allicin, a compound that has been shown to kill off cancer cells in multiple test-tube studies (Source, Source, Source).

There is evidence demonstrating garlic can kill cancer cells in vitro. Several studies have analyzed the effects that dietary garlic may have on the development of colorectal cancer. 

Several clinical studies have found an association between garlic intake and a lower risk of certain types of cancer.

Despite the promising results showing an association between garlic and a reduced risk of cancer, more studies are needed to examine whether other factors play a role.

Related: Garlic, the ‘King of Cancer Prevention’

Caution and Concern

It's important to emphasize caution when it comes to these natural products. 

Dietary beta carotene vs beta carotene supplement, what's the difference?

It wasn't long ago that, after finding that people who ate a diet rich in foods containing beta-carotene had a lower risk of lung cancer, researchers set out to study the potential effect of supplements of beta-carotene on risk. Unlike the reduced risk seen with dietary beta-carotene, however, beta-carotene in supplement form was associated with an increased risk of developing the disease.

Key Takeaways

The best way to prevent cancer is to utilise a menu of strategies by maintaining good health, like from eating a nutritious fresh whole-food diet with lots of fruits and vegetables, avoid ultra processed foods and a healthy lifestyle with less stress. 

Everyone’s situation is different, however, it is important to arm yourself with medical knowledge that cancer doctors (Oncologists) may simply not give you.

While supplements can be beneficial, they should complement, not replace, these fundamental preventive strategies. Taking supplements as a stand alone strategy cannot replace an unhealthy lifestyle i.e. heavy smoker, alcoholic, a very stressful and non-active lifestyle, overweight and obesity.

While there’s no silver bullet supplement, there are some anti-cancer supplements on the market that may help you keep the disease at bay or stop it from getting worse. Whether you’re living with cancer, a survivor, or just concerned for your health, talk to your doctor to determine the best treatment for you. 

Read More: This article is part of the Winning the War on Cancer series.

For more information on treatment, causes and prevention, screening, and the latest research, check out this comprehensive resource page (by cancer type) from the U.S. National Cancer Institute: https://www.cancer.gov/types.

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