Medically reviewed by Susan Kerrigan, MD and Marianne Madsen

As grocery stores restock depleted shelves, shoppers should be filling their carts with rainbows. These are the colorful fruits and vegetables that help keep us healthy. They also improve immune function. 

Food is the best source for vitamins and minerals. Supplements should be used to . . . well . . . supplement your diet. There is no evidence that specific supplements will protect you against COVID-19. However, boosting your immunity with vitamins D and C along with minerals like zinc is a great idea no matter what the circumstances. Taking care of yourself and your loved ones is vital during this difficult time.

Vitamin D

Across the world, millions are under lockdown. Vitamin D deficiency is a real concern. Why is it so vital when people are staying inside? Because sunlight is the number one source for Vitamin D. It is produced in the skin when we are exposed to the sun’s ultraviolet B (UVB) rays. Unfortunately, more than one-third of people in the U.S. were deficient before the lockdown. Many of us spent our days in offices. People with dark skin and those who live in places with less winter sunlight are also at risk.

There are even studies suggesting that sunscreen use contributes to this, although most suggest its protection from cancer and premature aging outweigh the deficiency risk. Some experts recommend spending at least 10 minutes out in the sun without sunscreen each day to improve your body’s ability to manufacture this necessary vitamin. Even in lockdown, if you’re able to spend a few minutes in your yard, on your balcony, or near an open window with the sun shining on you, this can help increase your Vitamin D levels.

Lack of Vitamin D was once responsible for rickets in children and osteomalacia in adults. While these bone diseases are fairly rare in the developed world, today older adults face “thin bone” disease or osteoporosis. Most encouraging, several recent studies suggest that Vitamin D supplements might protect against acute respiratory infections (ARIs) while improving outcomes among those suffering from ARIs. While more studies are needed, this is a positive development since COVID-19 hospitalizations are often respiratory-related.

Vitamin D is not technically even a “vitamin.” It isn’t found in most food. Instead, it is produced in the body. When we eat fish or egg yolks or drink a glass of fortified milk, it travels to the liver collecting extra oxygen and hydrogen molecules to become 25-hydroxyvitamin D, or 25(OH)D. Lack of this chemical is a marker for Vitamin D deficiencies. It doesn’t do its job, however, until it reaches the kidneys. Receiving its final pair of oxygen and hydrogen molecules, it becomes what we know as Vitamin D.

Supplement recommendations vary. Although doctors once recommended 400 IU for those at risk, many say as much as 1,000 IU a day is ideal for adults. Because it is stored in fat, too much can become toxic but even 2,000 IU a day is considered safe. Talk to your healthcare provider if you are concerned about the amount of Vitamin D that will work for you.

Vitamin C

Vitamin C has been seen as a miracle cure for decades. Soon after it was isolated in the 1930s, it was offered as a treatment for respiratory infections. In the 1970s, Nobel laureate Linus Pauling became well known for his work suggesting that taking high doses could prevent the common cold. Since COVID-19 affects the respiratory system and is a virus like the common cold, many are understandably curious about Vitamin C.

However, studies have shown that Vitamin C doesn’t prevent colds in the general population. It may, however, lessen their severity. It has been shown to reduce the number of colds among marathoners, other high performance athletes, and anyone exposed to intense physical stress. Lack of vitamin C is responsible for impaired immunity. If you are not getting enough, you will be more vulnerable to infection. A strong antioxidant, it is vital for a healthy immune system. So if you haven’t been getting enough of this essential vitamin, now is the time to make a change.  

Many of us have enjoyed the placebo effect of chugging a glass of orange juice when we start showing cold symptoms. Still, since OJ is loaded with sugar and most adults don’t get enough Vitamin C, supplements are recommended. The good news is unlike Vitamin D, it is water soluble so your body will get rid of any extra. While the recommended amount is around 100 mg a day (depending on age and gender) even ten times that will be safe. However, since you will be urinating whatever your body doesn’t use, the money you spend on mega-doses will be  literally going down the toilet.

Of course, food is the best source for Vitamin C–and food tastes way better than supplements. Maybe one benefit of the lockdown is that we can finally ditch our excuses about not having the   time to make a healthy meal. Even if your favorite store’s produce shelf is fairly depleted, the good news is there are tons of different options. Cantaloupes, oranges, grapefruits, and other citrus fruits along with pineapples and berries including strawberries and raspberries are all rich in vitamin C. So are broccoli, green peppers, spinach, and many dark, leafy vegetables such as spinach and kale.

In Wuhan, China, where patients with COVID-19 first appeared, the Zhongnan Hospital used high doses of Vitamin C as a treatment. Although the results have not been published, what we do know is that getting enough Vitamin C will prevent bad breath, split ends, and dry skin. Maybe looking your best when you see the same four people every day isn’t your priority, but it’s nice to know a vitamin may do more than a makeover.

Zinc 

While Vitamin C seems to get all the attention as a cold-fighter, zinc may be an even better immune system booster. Often added to multivitamins and lozenges, like Vitamin C it is vital for a healthy immune system. Not only have zinc supplements been shown to prevent respiratory infections but last year a study showed it reduced the severity and duration of acute respiratory tract infections in children. 

Worldwide, over two billion people have zinc deficiencies. This heightens their risk for infection, especially respiratory infections like pneumonia. So taking zinc supplements seems pretty essential right now. One caution––although safe at doses up to 40 mg of elemental zinc, too much will interfere with your body’s ability to absorb copper which ironically will increase your risk of infection.

The best thing you can do

There are numerous other supplements that are promising. Black elderberry has been studied for its effect on the duration of colds. It has also been used to treat patients with upper respiratory illnesses. Although some studies are promising, because one of the most widely cited was sponsored by an elderberry syrup maker, clearly more work needs to be done. Likewise with silver colloidal or silver sol, which may have antiviral properties. No matter what supplement you take, please consult your physician as some may interfere with prescription medication.

Food isn’t everything. Neither are supplements. Getting enough sleep is a crucial immunity booster. So is reducing stress. Tired, anxious people get sick more often, and the COVID-19 pandemic is surely increasing their number. No matter what your circumstances, try to exercise every day—even if it’s just walking around your apartment or stretching in your living room. Instead of reading news sites at night, pick up a book. Take a hot bath and maybe try some lemon balm or lavender. Stay close to the loved ones that are with you. Pets are also great stress reducers. Indeed, many shelters are reporting that for the first time they are running out of adoptable animals. With all that’s happening, that is a bit of good news.

References

• The effect of sunscreen on vitamin D: a review
• Vitamin D supplementation to prevent acute respiratory infections
• Vitamin C for preventing and treating the common cold
• Vitamin C and Immune Function
• Vitamin C Infusion for the Treatment of Severe 2019-nCoV Infected Pneumonia
• Silver nanoparticles as potential antiviral agents
• Sleep and immune function