Z-Stack Supplement Review: Does it boost the immune system, and is it safe?

Z-Stack is a multivitamin marketed as an "all-in-one immune boosting super formula." The vitamin itself, which was developed by Dr. Vladimir Zelenko, MD — a physician known for developing the "Zelenko Protocol" for treating and preventing COVID-19. The protocol has as its centerpiece, but not exclusive piece, the combined use of Hydroxychloroquine (HCQ) and Zinc as a means by which a person can both help to prevent or mitigate the contraction of COVID-19, or can actually treat the disease once it has been diagnosed. 

A retrospective study analyzing Dr Zelenko's patient data was accepted for publication after a rigorous peer review process. The study finds that early intervention and treatment of high-risk patients with COVID-19 resulted in significantly fewer hospitalizations and deaths. The treatment consisting of zinc, low-dose hydroxychloroquine (HCQ), and azithromycin, is also referred to as "The Zelenko Protocol." Dr Zelenko has since updated his protocols to incorporate new evidence.

He has evolved his protocols to include a quercetin, zinc, vitamin D and C protocol for low-risk patients as well as guidelines for COVID-19 prevention. 

In an effort to make it easier for patients, Dr Zelenko has developed an oral supplement that contains all four key ingredients: vitamin C, quercetin, vitamin D3 and zinc. It’s referred to as 'Z-Stack Supplement'. 

What ingredients are in Z-Stack and are they beneficial?

According to the product label, Z-Stack contains vitamin C, vitamin D3, zinc and quercetin. 

Some media channels argue that there is very little evidence to support the use of quercetin, zinc, vitamin D and C in supporting the immune system. We have included the scientific evidence together with the sources and references in this article below and we leave it up to you, the reader, to decide who is the real 'fact-checker'. 

Peer reviewed studies, scientific data and clinical trials show that synergistic supplement combinations involving zinc and the zinc ionophore quercetin may be effective antiviral prevention and therapeutic agents against COVID-19. An ionophore transports molecules inside cell membranes. COVID-19 viral entry and replication in cells is inhibited by zinc - significantly reducing COVID-19 infection and mortality (Source). Generally, the more zinc that can be brought into respiratory cells, the better off a COVID-19 patient will be.

Quercetin, a natural anti-oxidant and anti-inflammatory compound contained in abundance in various fruits and vegetables, is a zinc ionophore. Zinc ionophores help transport zinc inside the cells COVID-19 attacks - respiratory cells, providing significant antiviral action against COVID-19. Additionally, Quercetin has been shown to be a potent inhibitor of coronaviruses by inhibiting cellular entry as well as inhibiting proinflammatory cytokines. One of the hallmarks of COVID-19 is an imbalanced immune response cascading to cytokine storms and then hyper inflammation which then can lead to acute respiratory distress syndrome (ARDS).

Quercetin has been shown to inhibit proinflammatory cytokine production as well as inflammation due to its antioxidant properties, amongst others. By inhibiting destructive inflammation and potentially the entire cascade, quercetin may prevent severe damage to the respiratory system amongst other organs (source). 

As of October 2023, there have been more than 10 published studies of quercetin and COVID-19 (c19quercetin.com). 

Quercetin is also no. 1 in this COVID-19 prevention studies league table:

Zinc is a well known supplement that is generally contained in standard multivitamins. It provides immune support amongst other functions. Zinc inhibits coronavirus replication and is a general stimulant of antiviral immunity (source). Higher levels of intracellular zinc showed to increase intracellular pH; which affect on RNA-dependent RNA polymerase and decreases the replication mechanism of RNA viruses (e.g. COVID-19). Therefore, zinc ionophores (e.g. Quercetin) can likely be used with zinc supplement to act as antiviral against many RNA viruses including influenza and COVID-19. Suggested benefits of zinc supplementation along with zinc ionophores to prevent and treat COVID-19 and other respiratory tract infections are supported by countless studies (source). In most cases, prophylactic and early use of zinc supplementation was more effective than late therapeutic proceedings. Up to 30% of the everyday respiratory infections, briefly named “common cold,” are due to infections with coronaviruses. Studies showed reduced symptom severity, reduced frequency, and duration of the common cold after zinc administration depending on dosage, zinc compound and the start time after initial symptoms (source).

Zinc deficiency is very common especially in the elderly, diabetics, cancer patients, asthma, immunosuppressed and obese - all of which have higher levels of mortality for COVID-19. Furthermore, zinc deficiency is associated with increased risk of infectious disease, pneumonia and severity of COVID-19. Conversely, zinc supplementation is associated with a significant decrease in COVID-19 mortality as long as it is delivered with a zinc ionophore (source).

In short, a balanced zinc homeostasis is essential. Zinc supplementation improves the mucociliary clearance, strengthens the integrity of the epithelium, decreases viral replication, preserves antiviral immunity, attenuates the risk of hyper-inflammation, supports anti-oxidative effects and thus reduces lung damage and minimizes secondary infections. Especially older subjects, patients with chronic diseases and most of the remaining COVID-19 risk groups would most likely benefit.

Check out the evidence tracker on zinc and COVID-19 from c19zinc.com (constantly updated). 

The recommended dosage of zinc in Z-Stack is 273% of the Daily Value. Consult your medical doctor before taking this dosage on a long term basis.

Vitamin D is essential to a healthy immune system as it initiates the adaptive immune response. Clinical trial data shows that Vitamin D supplementation is safe and protects against acute respiratory tract infection mortality whereas low levels of vitamin D are associated with higher risk for infection and mortality (bmj.com). 

The link between vitamin D and viral infections arose from the observation of the seasonality of vitamin D with lower levels in the winter and concomitant increases in influenza. Conversely, in summer, serum levels of Vitamin D increase and influenza virtually disappears, except during pandemics. Even in pandemics, most deaths occur during cold months.

Check out the evidence tracker on vitamin D treatment and COVID-19 from c19vitamind.com (constantly updated), with more than 100 published treatment studies and more than 100 sufficiency studies by more than 700 scientists.

In addition, a meta-analysis of COVID-19 studies shows that most studies report positive effects of Vitamin D against COVID-19 (vdmeta.com).

The recommended dosage of vitamin D3 in Z-Stack is 625% of the Daily Value. Consult your medical doctor before taking this dosage on a long term basis.

Vitamin C is a potent antioxidant, likely immune system optimizer and has been shown to work synergistically with quercetin, likely increasing quercetin’s bioavailability (source). As per Integrative Medicine’s 4th edition, quercetin is a poorly absorbed nutrient but Vitamin C increases the absorption of quercetin and recommends that Quercetin should be blended with Vitamin C (source). Specifically, there is evidence that vitamin C and quercetin co-administration exerts a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties and the capacity of ascorbate to recycle quercetin, increasing its efficacy (source). It has been shown that Quercetin and Vitamin C markedly inhibited mRNA expression of pro-inflammatory cytokines - as the release of inflammatory cytokines are behind acute respiratory distress syndrome (source). The quercetin and vitamin C combination can prevent the exacerbation of inflammation. 

That said, the recommended dosage of vitamin C in Z-Stack is slightly lower than what has been shown to be beneficial especially for colds and other respiratory infections. This can be resolved by having additional vitamin C through your diet.

Check out the evidence tracker on vitamin C and COVID-19 from c19vitaminc.com (constantly updated).

Where to buy Z-Stack?

Z-stack is available on Dr Zelenko's website. Here is the link: Z Stack Supplement.

Note: To get 5% OFF, please use this coupon code: DRFRANCIS