Vitamin D is a hot topic in microbiology. For good reason. We know it’s important to bone health. But we now know that vitamin D is active in many cells outside the skeleton – and can also influence genetics that affect cancer, infection and autoimmune disease.
A deficiency can make many problems worse, including cardiovascular disease, breast cancer, multiple sclerosis, depression and diabetes. One recent study adds another to the list; respiratory infection. That is particularly noteworthy during a global pandemic caused by a respiratory virus.
A potential role in respiratory health
In 2017, two years before the emergence of the coronavirus that causes COVID-19, a study on vitamin D’s role in preventing respiratory infection appeared in The BMJ – formerly known as the British Medical Journal.
It was a large and statistically significant study, a survey of previous research. The researchers reviewed 25 past studies with 10,933 participants, aged 0 to 95 years.
The evidence showed that vitamin D supplementation reduced the risk of respiratory tract infection among all participants – especially among those with existing deficiency.
Of course, we can’t jump to the conclusion that taking vitamin D supplements will prevent COVID-19. But the evidence for vitamin D making the respiratory tract healthier and more resilient is compelling. For that, and all its other benefits, I recommend it for most of my patients.
History: the calcium connection
By 1900, medical science knew that a deficiency of vitamin D weakened the bones, causing the disease known as rickets. It is especially debilitating in children, keeping their bones from growing and hardening properly.
Later, researchers discovered the connection; the body cannot absorb calcium without Vitamin D. Even if you have more than enough calcium on board, it cannot get where it needs to go without vitamin D. That’s what makes it so important to bone health.
For most of the 20th century, that was the end of the story. But study after study performed in the last few decades have expanded its footprint, proving the nutrient has wider effects in many parts of the body.
Why it’s hard to get enough
Vitamin D is known as “the sunshine vitamin,” because sunlight is the body’s natural source. Sunlight doesn’t deliver vitamin D, but it spurs a reaction that causes your body to make it. With daily, significant exposure to sunlight, your needs are taken care of.
For light-skinned people, the recommended daily minimum is 30 minutes of sunlight exposure over 30 percent of the skin. If you have dark skin, you need about four times as much to achieve the same effect.
This was never a problem when people lived in hunter-gatherer societies, spending most of their time outdoors, in warm climates where heavy clothing was unnecessary.
Today’s situation is drastically different for almost everyone on earth. We spend more time indoors. We bundle up against cold winters. And we know that ultraviolet radiation in sunlight causes all kinds of other problems. So, even when we go out in the sun, we tend to cover up or wear lots of sunscreen.
It’s probably safe to assume social distancing and stay-at-home orders associated with the pandemic are keeping us out of the sun, even more.
The shortlist of D-rich foods
Foods naturally rich in vitamin D make a fairly limited menu, including only mushrooms and fatty fish, like salmon, tuna, sardines, mackerel and eel. Fortified cereal, milk and other dairy products provide a moderate source, it is added to complement the calcium they also provide. But unless you consume a lot of these foods, you’re unlikely to get enough without big daily doses of sunshine.
When supplements make sense
It’s safe to say most people living in the United States and working indoors could benefit from a vitamin D supplement. The recommended daily allowance is 600 units for adults up to age 65 and 700 units after, when bone weakening from osteopenia and osteoporosis can begin. The recommendation is different for pregnant women, so it’s best to consult your doctor if you are pregnant or planning a family.
We know it’s difficult to get those levels from food and sun alone. But that’s not so say you should run out and buy it. Every situation is unique. And vitamin D is fat-soluble, meaning it builds up in the body if you get too much. It’s best to have a conversation with your healthcare provider to determine your best plan. For example, you may already be taking a multivitamin that includes it. And many calcium supplements also include it, since it’s critical to calcium absorption.
The takeaway: vitamin D is critical to the healthy function of many organ systems. We have significant evidence that a deficiency can weaken the respiratory system. So, it should be on your radar.
Talk to a trusted health professional, who will ask the right questions to determine if you’re a candidate for supplements – and start taking advantage of one of nature’s most powerful nutrients.
Learn more about vitamin D in our previous blog post here