Retailers are reporting a sales surge in supplements that support a healthy immune system. Leading ingredients with a particularly healthy halo about them include zinc, elderberry and vitamins C and D.
Vitamin D in particular should be of interest when talking with customers about ingredients that can help support a healthy immune system.
Vitamin D has been repeatedly shown to modulate both the innate and adaptive immune response. Controlled trials show that vitamin D decreases acute respiratory infections.
And a deficiency of vitamin D is associated with increased autoimmunity and an increased susceptibility to infection. Most studies show that adequate supplementation can “prevent and improve” the development of some of these autoimmune diseases.
Vitamin D's role in COVID-19 research
As for COVID-19 concerns specifically, it is of course a disease and supplements by law cannot claim to prevent, cure or treat a disease state. That is in the exclusive purview of pharmaceutical drugs.
However, since April 2, an incredible 22 studies have been published on vitamin D and COVID-19. Currently, 11 formal clinical trials are listed at clinicaltrials.gov aimed at testing vitamin D supplementation in COVID-19 patients in combination with other drugs, and comparing high doses versus standard doses.
“Vitamin D is not a specific treatment for COVID-19, it is a treatment for vitamin D deficiency,” said Paul Bergner, director of the North American Institute of Medical Herbalism. “Vitamin D deficiency is highly correlated to the frequency of respiratory infections in general. Vitamin D deficiency is also highly correlated to the intensity of cytokine storms. A vitamin D deficiency also correlates with poorer outcomes in intensive care units generally. A vitamin D deficiency correlates with most known co-morbidities including cardiovascular disease, hypertension and diabetes.”
Researchers first began noting a general correlation between low vitamin D levels and incidence of COVID-19 (a correlation noted by numerous other research studies in the past few months).
Researchers in the Philippines who assessed 212 cases of COVID-10 found lowest vitamin D levels in the most critical cases whereas the milder cases had higher vitamin D levels. “Vitamin D status is significantly associated with clinical outcomes,” they wrote. An increase in vitamin D status in the blood “could either improve clinical outcomes or mitigate worst (severe to critical) outcomes, while a decrease in serum 25(OH)D level in the body could worsen clinical outcomes of COVID-19 patients. Vitamin D supplementation could possibly improve clinical outcomes of patients infected with COVID-19.”
Disease severity and death rates are also higher in the elderly, African-Americans, patients with diabetes and chronic lung and cardiovascular diseases—all groups with low vitamin D levels.
European researchers noted that vitamin D levels are severely low in the aging population especially in Spain, Italy and Switzerland—the most vulnerable group of the population in relation to COVID-19.
One provocative correlation is that there is a well-known disparity in COVID-19 prevalence due to racial groups. Black and minority ethnic people, who are more likely to have vitamin D deficiency because they have darker skin, seem to be worse affected than white people are.
Researchers in a study published in April noted that vitamin D can reduce the risk of infections through several means. Vitamin D, wrote the researchers, “can lower viral replication rates and reduce concentrations of pro-inflammatory cytokines that produce the inflammation that injures the lining of the lungs, leading to pneumonia, as well as increasing concentrations of anti-inflammatory cytokines.”
These researchers suggested those at elevated risk of infection begin by taking 10,000 IU/day vitamin D for a few weeks, followed by a maintenance dose of 5,000 IU/day.
A follow-up commentary, however, also published in the journal Nutrients, contested that recommendation.
Observational studies, it is true, show vitamin D deficiency is associated with increased risk of infections. In particular, those with larger deficiencies tend to have significantly longer and more severe upper respiratory tract infections.
But the researches in their response noted that the best results—a 12% overall reduction in acute upper respiratory tract infections—was found to have outsized benefit among those with vitamin D blood levels of a significantly deficient 10 ng/dl—half that of even the lowball deficiency level from the National Institutes of Health of 20 ng/dl. These are people who do not go outside in the sun much, nor consume much dietary sources of vitamin D such as fortified milk, egg yolks, cheese or fatty fish like tuna, mackerel and salmon.
In one of the recent COVID-related studies, researchers suggested vitamin D (as well as melatonin) may play a role by down-regulating the inflammatory response related to the bodily system that regulates blood pressure and fluid balance in the body, called the renin-angiotensin system. Hypertension, or high blood pressure, is one of the co-existing conditions that has consistently been reported to be more common among critical COVID-19 patients.
A Turkish researcher postulated that vitamin D could work against COVID-19 infection-induced multiple organ damage not just by reducing the level of renin but also by decreasing the inflammatory cytokine storm, decreasing other pro-inflammatory markers and by increasing antimicrobial activity.
How much vitamin D should you recommend to shoppers?
The official Daily Value—that is, the minimum amount required to stave off a bone-related deficiency disease like rickets—is a paltry 600 IU per day (800 IU for those over age 70). This recommendation was issued for vitamin D as it relates to only bone health.
Vitamin D has actually shown benefit for a wide range of health states, including immune function. A Harvard School of Public Health review summarized evidence suggesting optimal vitamin D blood levels in relation to bone mineral density, lower-extremity function, dental health and risk of falls, fractures and colorectal cancer. Benefits begin at 30 ng/ml, preferably between 36-40 ng/ml. “In most persons,” wrote the researchers, “these concentrations could not be reached with the currently recommended intakes of 200 and 600 IU vitamin D per day for younger and older adults.” The concluded that at least 1,000 IU each day would bring levels up to 30 ng/ml for half of the population.
Researchers in New Zealand gave pregnant women at the start of their third trimester and their subsequent infants for the first six months of their lives either placebo/placebo, 400/1,000 IU, or 800/2,000 IU vitamin D per day. Only the higher doses of vitamin D led to a significant decrease in acute respiratory infections.
In a study among basic training marines, researchers gave male and female recruits 1,000 IU per day of vitamin D plus 2,000 mg per day of calcium for 12 weeks. They found the supplements improved markers of immune response during high-stress basic training.
Many holistic practitioners advocate peoples’ serum blood levels of vitamin D for optimal health (not just bone health, as the Institutes of Health would have it) should not be merely 20 ng/ml but rather between 40-60 ng/ml. To that end, studies have shown that a vitamin D intake of 4,000 IU/day and up is required for that level throughout the year.
That suggests that minimum doses of vitamin D should be 1,000 IU, perhaps 2,000 IU per day. And as noted, some researchers believe a maintenance dose as high as 5,000 IU per day is appropriate.