As we head into what might be a very long and isolating winter, everyone is looking for answers on how to prevent Covid-19. Even those who have previously avoided getting flu shots are now heeding the advice to do so. And while washing our hands regularly, wearing masks and social distancing are among the first lines of defense, many are desperately searching for the silver bullet. Needless to say, in this era of disinformation, there are plenty of snake oil salespeople out there offering magical potions.
Not surprisingly, nutritional remedies are among the leading candidates. Vitamin D, zinc and vitamin C are included as those with the most buzz.
But before you load up your medicine chest with a slew of supplements, there are some key facts to keep in mind.
Your nutritional status definitely plays a vital role in how your immune system functions and fights off infectious invaders. In spite of what you may hear, there is no one particular nutrient that will keep your immune system working in top form. But while being short on various nutrients may put you in harm’s way, taking in an excess also doesn’t provide you a better defense against infection or disease. (Check out my post on vitamin D.)
Balance doesn’t sound sexy
In fact, you can get too much of a good thing. It depends on the nutrient but your genetics can also factor in.
The mineral selenium is a great example. There was a time when taking selenium supplements was being touted as the way to prevent prostate cancer. Many men were popping them like candy. Yet research shows that for some men, those with a less aggressive form of prostate cancer, too little selenium promoted tumour growth.
For others, those with a different gene pattern that put them at risk for a more aggressive form of prostate cancer, high blood levels of selenium went hand in hand with greater tumour growth.
What’s the story about zinc in fighting against the coronavirus?
Scientists are urgently looking for possible preventions and treatments to change the course of this pandemic. As a result, zinc, like vitamin D, has been a hotbed in coronavirus research as there seems to be a link between deficiencies of this mineral and both Covid risk and severity.
In a small Indian study, just published in September, researchers looked at fasting zinc levels in COVID-19 patients at the time of hospitalization and compared them to healthy subjects with normal zinc levels. The data clearly show that a significant number of COVID-19 patients were zinc deficient and were more likely to develop a greater number of complications, have a prolonged hospital stay and experience increased mortality.
In a review study of 118 publications, the data suggests that the use of zinc may potentially reduce the risk, duration and severity of SARS-CoV-2 infections, particularly for populations at risk of zinc deficiency including people with chronic disease, other illnesses and older adults. More research, though, is needed.
But what is clear is that there is no evidence that zinc offers benefit in those with adequate blood levels of the mineral.
Who’s at risk of zinc deficiency?
For the average person, being deficient in zinc is not really a concern. But there are some groups that should take heed of their zinc. For one, evidence in the U.S. shows that a significant number of people, aged 60 years or older, simply consumed too little zinc. Even when the investigators assessed intakes from both food and dietary supplements, they found that 20%–25% of older adults still had inadequate zinc intakes.
Vegetarians can also be at risk for zinc deficiencies as plant-based sources of zinc may not be as well absorbed as zinc from animal sources. Whole grains and pulses (legumes) do offer zinc but due to other compounds contained – anti-nutrients such as phytates – there may be decreased absorption of the mineral. Cooking with onions and garlic may also boost absorption of minerals such as zinc. (Here’s more evidence of the wisdom of the ages: many traditional vegetarian cuisines and dishes containing whole grains and pulses have onions and/or garlic in them.) Sprouted grains and pulses also contain less in the way of phytates.
Those with gastrointestinal illnesses, such as ulcerative colitis and Crohn’s disease, can also be more likely to suffer from zinc deficiencies.
Food sources of zinc
Oysters are a top notch source of zinc, followed by red meat, poultry, seafood such as crab and lobsters, fortified breakfast cereals, pulses, nuts, whole grains, and dairy products.
Zinc is also found in multivitamin and minerals supplements. But before you consider zinc supplements on their own, be aware that large amounts can cause gastrointestinal upsets and over the long term, excess zinc can also cause also impair your immune system function and can lower blood levels of your heart healthy HDL-cholesterol as well.
Enlightened Eater 
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