Low vitamin D levels may be linked to a higher chance of dying from the coronavirus — here's how to avoid a deficiency

• Low levels of vitamin D may be linked to a higher risk of death or serious illness from the coronavirus, according to early research.
• Experts emphasize the importance of vitamin D in maintaining general good health.
• To get enough vitamin D, you can go on walks in the sun, eat vitamin D-rich foods, and take supplements.

There's no evidence that vitamin D alone prevents or cures the coronavirus. But some research suggests that people who don't have enough vitamin D may have a higher chance of suffering severe cases and even dying.

An Italian study published Sunday in the Journal of Endocrinological Investigation found that after 10 days of hospitalization, 50% of patients with severe vitamin D deficiencies died, compared with just 5% of patients who did not have severe deficiencies.

Similarly, July research from the Philippines, which hasn't yet been peer-reviewed, found a significant correlation between how high a COVID-19 patient's vitamin D levels were and how likely they were to have a mild case of the illness. And a May preprint study — also still awaiting peer review — showed that people in countries with high rates of mortality from COVID-19 had lower vitamin D levels overall, compared with people in countries that weren't as hard-hit.

Vitamin D strengthens parts of the immune system

Vitamin D is both a hormone our bodies produce and a nutrient found in some foods; it helps the body absorb other critical nutrients, like calcium and phosphorus. Deficiencies can increase your risk of bone disorders like rickets and may even influence the likelihood of other diseases, like cancer and diabetes.

Vitamin D strengthens parts of the immune system that fight viruses, like white blood cells, and can also help quell cytokine storms. That's when the immune system overreacts, flooding the bloodstream with messenger proteins that lead the body to attack its own cells rather than just the virus. Many patients with severe COVID-19 cases experience cytokine storms, which can destroy lung tissue and cause fatal pneumonia.

In June, three health organizations in the UK published reports detailing what we know (and still don't) about the role vitamin D might play in coronavirus cases. They advised people to ensure they're getting adequate amounts of vitamin D through supplements and sun exposure, though they concluded more research was needed.

The latest study offers more evidence that vitamin D may be a factor to pay attention to. As the Italian researchers saw more patients, they wrote, they noticed many people with severe COVID-19 cases were also vitamin D deficient. That prompted them to study a possible connection. They looked at data from 42 patients with COVID-19-induced respiratory failure and found that 34 of them had low levels of vitamin D, while a smaller group had severe deficiencies.

Within 10 days of being hospitalized, the severely deficient group had a 50% mortality rate. Only 5% of the other patients died, including those with mild vitamin D deficiencies.

Getting enough vitamin D can be tricky for some people

Getting enough vitamin D can be challenging for some people who are already vulnerable to the coronavirus, including those with darker skin, who must spend more time outside to synthesize enough of the hormone; incarcerated people, who don't have much access to the outdoors; and older people, who often don't spend time in the sun and have a harder time synthesizing vitamin D even if they do.

For people with lighter skin who have regular access to the outdoors, going on a 15-minute walk outside between 11 a.m. and 3 p.m., when sunlight is especially rich in UVB rays, can stimulate the skin to synthesize enough vitamin D3, the active form of vitamin D. The needed length of that walk can double on a cloudy day, when UVB rays are reduced by 50% according to the National Institutes of Health.

Those concerned about not getting enough vitamin D can also take supplements or eat foods rich in vitamin D, like milk, eggs, and fatty fish. Orange juice and breakfast cereals are often fortified with a synthetic version.

Vitamin D supplements can also help people at risk of deficiencies. But don't take more than one or two a day — and if you think you're probably getting enough vitamin D, don't take supplements at all. Too much vitamin D can cause diarrhea, hair loss, and kidney issues.