Vitamin D has gotten a lot of attention in the past several years. Maybe you’ve heard how common it is to have low levels. Or perhaps you’ve heard the reports linking a D deficiency to various health risks and conditions. Now it’s in the news again as researchers work to figure out if vitamin D may play a role in COVID-19 outcomes.
So does that mean you should be getting more? Here’s what to know about this important nutrient and ways it can help keep you healthy.
Why You Need Vitamin D
While we humans easily get many of the vitamins and nutrients we need from healthy, whole foods, vitamin D is the exception. It’s often called “the sunshine vitamin,” because the main way we get it (outside of supplementation) is by making it when our skin is exposed to UV light. Otherwise, D is similar to other nutrients and vitamins in that it plays an essential role in ensuring cells can function properly.
Let me explain. Vitamins are generally known as cofactors: They act as a key piece or component of the complex biological machinery that allows each cell in the body to perform its specific function the way it’s supposed to. Vitamin D also acts as a chemical messenger that relays crucial signals to cells and various systems.
While vitamin D is important for many types of cells and functions throughout the body, there are two main areas where it’s especially vital:
1. Vitamin D Allows the Body to Absorb Calcium.
We all need calcium for strong bones as well as for our nervous system, and it’s pretty easy to get the calcium your body requires by eating a healthy diet and/or taking supplements. But without adequate vitamin D, it wouldn’t matter how much calcium you consume — your body could not take in the mineral from your gut nor maintain steady calcium levels in your blood.
When you aren’t absorbing or getting enough calcium, the body ends up stealing the calcium that’s stored in your bones. That leaves your bones weak — and you vulnerable to fractures.
Studies have long shown that low levels of vitamin D in the blood increases the risk of fractures in older adults. What’s more, additional research suggests that taking vitamin D supplements along with calcium may help reduce fractures in people over age 65, especially women.
2. Vitamin D Helps Regulate Immune Function.
Virtually all types of immune cells have vitamin D receptors, and the vitamin is known to help control the immune response in ways that may both enhance immunity and potentially guard against autoimmune diseases. For example, vitamin D helps regulate the activity of various types of immune system cells — white blood cells, B cells, T cells, monocytes — in ways that decrease the production of inflammatory cytokines (proteins secreted by the immune system) while increasing anti-inflammatory cytokines.
In other words, healthy vitamin D levels help promote a proper inflammatory and immune response. In that way, it helps mitigate or prevent some of the potential damage that might otherwise be caused by inflammation or an improper immune response (as is the case with autoimmune disorders).
This regulatory role is one potential factor in why low vitamin D levels are linked to autoimmune diseases such as multiple sclerosis and type-1 diabetes, as well as improved immunity against viruses, including respiratory pathogens and the flu. For example, research suggests that low levels of vitamin D may increase the risk of developing MS by around 40%. Conversely, other research finds that higher levels of the vitamin is linked to lower disease activity and progression.
As far as general immunity is concerned, one study found that adults with low levels of vitamin D were more likely to have reported recently having a cold, cough, or upper respiratory infection. It’s also been suggested that increased sun exposure during warmer months may be one reason colds and the flu are less common in summer than in the winter.
The Vitamin D and COVID-19 Connection
The new coronavirus infects the upper respiratory system and causes much of its damage by triggering an immune system overreaction — it can unleash what’s called a “cytokine storm” that kills healthy cells and damages healthy tissue. So it would make sense that vitamin D’s regulatory powers might be helpful. However, as of now, the research is mixed and there’s still a lot we don’t know about the virus, its effects, and the potential role of vitamin D.
For example, one rapid review published in early May concluded there was no evidence suggesting a vitamin D deficiency left people more prone to infection or severe illness, or that vitamin D might help treat COVID-19. Other studies have come to similar conclusions.
That said, research released around the same time by researchers in Indonesia found that vitamin D deficiency was linked to an increased risk of death due to COVID-19. Other preliminary studies likewise suggest that low vitamin D levels could be a factor in COVID-19 severity, including hospitalization.
So, while it’s still too early to say whether vitamin D is important in your body’s natural defenses against COVID-19, there are a lot of other good reasons to make sure you’re getting adequate vitamin D right now.
Other Ways Vitamin D Keeps You Healthy
In addition to supporting healthy bones and proper immune function, vitamin D also helps deliver these health benefits:
Promotes Heart Health
Inflammation — which is part of your body’s immune response and so is partly regulated by vitamin D — plays a big role in the development of cardiovascular diseases. Vitamin D is also key for keeping arteries flexible and functioning properly, which helps maintain healthy blood pressure.
Vitamin D is needed for normal brain function, and research has linked low levels with depression. Although it’s not entirely clear how exactly vitamin D may influence mood disorders, a 2008 study found that vitamin D supplements reduced symptoms.
Reduces the Risk of Diabetes
Studies report that low vitamin D translates to a higher risk of type-2 diabetes, potentially because the vitamin may influence insulin sensitivity. (Diabetes develops when your body becomes less sensitive or resistant to the hormone, and so can’t properly regulate blood glucose.) For that reason, vitamin D may also help maintain a healthy weight.
Low serum levels of vitamin D were associated with higher all-cause mortality than normal levels (above 30 ng/mL), according to a report in the American Journal of Public Health.
Are you Vitamin D Deficient?
There’s a good chance you might be. Unlike with other common vitamins and nutrients, for which deficiency is relatively rare, having low vitamin D levels is incredibly common.
- Vitamin D deficiency: Less than 20 ng/mL (or less than 50 nmol/l — serum level of vitamin D is measured in two different units of measurements)
- Vitamin D insufficiency: Between 20 nmol/l and 30 ng/mL (or between 50 nmol/l and 75 nmol/l).
The risk for deficiency is even higher for those with darker skin. Their higher levels of melanin — natural pigments that make skin darker — naturally blocks UV light, hampering the body’s ability to readily make vitamin D with relatively modest sun exposure. One study, for example, found that a full 93% of African-American men living in Chicago had vitamin D levels below 30 ng/mL — the average was just 17.2 ng/mL — compared to 70% of Caucasian men who had insufficient vitamin D levels.
What’s more, your vitamin D stores may fluctuate with the season and can depend a lot on where you live and how much time you spend outside. For example, if you live in colder climates and spend long winters indoors, your levels during, say, December, are likely to be lower than they are in July.
So, it’s worth asking your doctor about getting tested at least once a year, if not twice, and about supplementing. Likewise, if you suffer from a chronic illness, which stresses cells and can deplete vitamin stores more readily, consider having your vitamin D levels tested a few times a year.
Guidelines on what vitamin D levels ideally should be vary a bit. For example, while the Endocrine Society recommends a target between 30 and 50 ng/mL, the National Institutes of Health considers between 20 and 50 ng/mL to be adequate for adults. In my former medical practice, I found that healthy people generally had levels between about 30 to 40 ng/mL.
And, although you’ll find some experts who suggest either you don’t need that much or need much more, be cautious — especially of overdoing it. Artificially boosting your levels higher than 50 ng/mL could cause neurological and other toxicity issues.
3 Ways to Get Vitamin D
Spend Time in the Sun.
This is not a free pass to skip SPF, however. Everyone’s skin is different and requires different exposure to fill their vitamin D coffers. However, the lighter your skin, the higher your risk of skin cancer and skin damage from unprotected UV exposure.
So, find a balance of UV exposure and skin protection that works for you — and err on the side of caution. Maybe that means spending a few minutes in the sun first before reaching for your bottle of sunscreen. Or, perhaps you always protect the sensitive skin of your face, neck, and chest before leaving home, but keep your arms or legs exposed slightly longer.
One study in the U.K., for example, found that just 13 minutes of midday summer sun three times a week (exposed to only 35% of skin surface) yielded levels between 20 and 32 ng/mL for most Caucasians. African Americans, meanwhile, may need many times that amount, according to researchers.
When considering what might work for you, take into account factors such as:
- Your tendency to burn
- Your personal skin cancer risk, including your family history
- Which areas on your body might need more protection
- Whether you take supplements or consume fortified foods to fill any potential D gap
Eating plenty of antioxidant-rich fruits and vegetables can also help provide some internal protection from small doses of sun exposure.
Eat Fatty Fish and Other Foods with Vitamin D.
Salmon and tuna are top food sources of D, while egg yolks and some cheeses also contain it in small amounts. And some foods, most notably milk, are fortified with vitamin D, so check labels.
Take a Vitamin D Supplement.
Supplements are an effective way to ensure you’re getting enough D no matter how much or little time outdoors you spend. The government’s recommended dietary allowance is 600 IU (or 15 mcg) per day for adults, but talk to your doctor about what might be best for you and how often to monitor levels.
For example, if you have darker skin you may need more than 600 IU — potentially up to 2,500 IU, suggests the researchers of the Chicago study. Those with chronic illnesses may want to consider taking more, as well. On the other hand, people with lighter skin who spend a lot of time outdoors during summer months may not need to supplement as much.
However you mix and match your lifestyle and dietary tactics to get enough vitamin D, now’s a good time to start paying attention if you aren’t already — for your immunity, bones, mood, heart and metabolic health, and overall wellness and longevity.
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5. Lee, Joseph, Oliver van Hecke and Nia Roberts. “Vitamin D: A rapid review of the evidence for treatment or prevention in COVID-19.” The Centre for Evidence-Based Medicine. May 1, 2020. https://www.cebm.net/covid-19/vitamin-d-a-rapid-review-of-the-evidence-for-treatment-or-prevention-in-covid-19/
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11. Northwestern University. “One size doesn’t fit all for vitamin D and men: African-American men in northern regions especially need high doses of supplements.” ScienceDaily. www.sciencedaily.com/releases/2011/09/110920100100.htm.
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