Vitamin D is crucial for immune health — make sure you’re getting enough

9 min read

Vitamin D is crucial for immune health — make sure you’re getting enough


Vitamin D is important for many functions in your body, not just your bone health.

As the coronavirus pandemic continues to extend shutdowns, quarantines and social distancing measures — many people are wondering how to keep themselves well. You know that social distancing, working from home and staying inside in general is one way to protect yourself — but are there other measures you can take?

Boosting your immune system is one of the best things you can do because it is your body’s key defense when it comes to fighting a virus. Even if you are exposed to a virus, the coronavirus or others, if your immune system is strong, you have a better chance of not getting sick. Vitamin C is a popular choice for supporting immunity, but another key nutrient for your immune system is vitamin D. Once thought as the vitamin for strong bones, vitamin D actually does a lot more for your body — including support your immune system.

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Studies suggest that vitamin D can help prevent respiratory infections or reduce the severity of them, especially if you have a deficiency. They jury’s out on how exactly it can protect you from the coronavirus, but some medical experts recommend taking a vitamin D supplement to help boost your immune system.

Below, Jacyln Tolentino, a physician at Parsley Health in Los Angeles, explains how vitamin D works, how to get enough of it, what happens when you have a deficiency and if it can help protect your immune system.

Why is vitamin D important?

Vitamin D is unique because it’s one of only two vitamins that your body can produce on its own (the other is vitamin K), and you can also get it from other sources like food or supplements. It’s also technically a hormone that regulates how much calcium is in your blood. Unlike other vitamins, it requires conversion in the liver and kidneys to make it an active hormone. “Vitamin D is a fat-soluble vitamin that our bodies use to absorb and maintain healthy calcium and phosphorus levels, which are necessary to grow and maintain our bones,” Tolentino says.

You’ve probably heard that vitamin D is important for your bones, but it supports your body in other ways, too.”While we generally associate vitamin D with musculoskeletal health, it actually has several functions in the body, including the role it plays in immune function and reducing inflammation,” Tolentino says.

Vitamin D and immune health

Research shows that vitamin D plays an important role in immune function, and a deficiency in it is shown to increase your susceptibility to infection. “Some studies have shown that vitamin D deficiency is even associated with greater risk of self-reported upper respiratory tract infections,” Tolentino says. Further, “low serum levels of calcidiol [a form of vitamin D] are also associated with higher susceptibility to infections like tuberculosis, influenza, and viral infections of the upper respiratory tract,” Tolentino says.

One of the main functions of vitamin D is to help activate T cells, aka the “killer cells” in the body. T cells actually detect and destroy foreign pathogens — like viruses. “That makes vitamin D especially crucial for maintaining a functioning immune system that’s capable of fighting back foreign pathogens,” Tolentino says.

It’s important to know that although the coronavirus does affect the respiratory system, researchers and doctors know little about it at this time. The best ways to reduce your risk of being infected with the coronavirus is to follow CDC and WHO guidelines, what your local officials say and to take care of your health as much as you can overall. Vitamin D is known to help the immune system, which is promising for protecting you from many different types of illness.

Exposing your skin to the sun is one way to get vitamin D. Getty Images

How to get enough vitamin D

As of 2014, experts predicted that about 1 billion people worldwide have low levels of vitamin D or a deficiency making it one of the most common vitamin deficiencies. If you suspect you are low in vitamin D, you should ask your doctor for a test. This way you can make sure you are supplementing the right levels if you do need more. Always ask your doctor before starting a new supplement.

The recommendation for vitamin D for adults is between 600-800 IU, although that number is up for debate among the science and medical community.

There are three ways to get vitamin D: through food (since it is naturally occurring in some food), from direct sun exposure on your skin and through supplements.

Food sources of vitamin D

“Vitamin D naturally occurs in egg yolks, beef liver, fatty fish like salmon, tuna, swordfish or sardines and fish liver oils. Unfortunately, vitamin D isn’t naturally occurring in lots of foods, which is why some foods have vitamin D added to them. Vitamin D is added to cereals, dairy and plant milks and orange juice,” Tolentino says.

Even though you can get vitamin D from food, it’s difficult to get enough from that source on its own since the amount of vitamin D in most foods is pretty small. “It’s not that easy to get your daily recommended intake of vitamin D through food. We’re just not eating large quantities of most of these foods. How much beef liver or sardines are you realistically eating every day?” Tolentino says.

Sunlight exposure and vitamin D

Vitamin D is associated with the sun for a reason — your body can produce its own vitamin D when you expose your skin to the sun for a period of time. About 15 minutes of sun exposure per day is what many experts say is sufficient to make vitamin D. This means you want to have a good amount of skin uncovered by clothing or sunscreen (like your arms and legs) since those things inhibit Vitamin D production, according to Tolentino.

How much sun you should get is also a bit complicated. “UVB radiation from the sun triggers vitamin D synthesis in our bodies, but there are a lot of factors to consider here,” says Tolentino

She continues, “Where you live (your geographic location), sunscreen usage and coverage and the amount of melanin in your skin can all impact vitamin D absorption. That makes it really difficult to provide generalized guidelines for the appropriate amount of sun exposure. What may be a sufficient or healthy amount of time in the sun with no sun protection for one person might not be advisable for another person.”

You body can easily absorb a liquid vitamin D or tincture since you can take the drops under your tongue. Getty Images

Vitamin D supplements

Because it’s hard to get enough vitamin D from food, and you may be spending most of your time inside, many people need to supplement to get enough vitamin D.

“Vitamin D supplementation may be the most practical solution for many people, especially if you live in the northern half of the country (latitudes above the 37th parallel north), have been advised not to venture out in the sun for long periods of time — especially without sun protection due to skin cancer risk, or have a diet lacking in the foods listed above,” Tolentino says.

You can find vitamin D in many different types of supplements, including multivitamins and vitamin D capsules. “Vitamin D supplements generally come in two forms — D3 and D2. D2 is a form derived from plants and is the form often found in fortified foods. D3 is the vitamin D naturally produced by our bodies and is the type found in animal sources,” Tolentino says.

Tolentino prefers D3 with vitamin K2, since she says K2 works synergistically with D3. “Research suggests that vitamin D3 — the type of vitamin D naturally produced in the human body – tends to raise blood concentrations more, and maintain those levels for a longer period of time.” She also says a liquid vitamin D in a tincture form that includes fat (like coconut oil or MCT) can be helpful since a liquid supplement can be taken under the tongue, which speeds absorption. Since vitamin D is fat soluble, taking it with a fat source helps the body absorb it better, too.

What can happen if you are deficient in vitamin D

Vitamin D deficiencies can mean your immune system is more vulnerable, but there are some other important conditions to know about too.

“Severe vitamin D deficiency can lead to a condition called rickets in children, and osteomalacia in adults. Osteomalacia is the softening and weakening of bones, and symptoms include joint and bone pain, muscle weakness, difficulty walking and bones that are easily fractured,” Tolentino says.

Another connection that scientists are researching is the link between mood disorders and vitamin D deficiency. Many studies have looked at depression risk specifically, like this one that found a link between vitamin D deficiency and risk for depression in older adults. In another study, adults with depression were given vitamin D supplementation and it did help improve symptoms in many of them.

Too much of a good thing: overdoing vitamin D

It’s important to not overdo vitamin D supplements since taking unsafe amounts of it can have negative effects on your health, like kidney problems, kidney stones, or hypercalcemia, a toxic condition where there is too much calcium in the blood. Generally, taking more than 4,000 IU per day is considered too much.

This is why it’s important to talk to your doctor before you take a supplement, and also ask for a test. If you think you get a decent amount of sun, eat foods with vitamin D regularly, and your levels are healthy, your doctor will likely say you don’t need any extra.

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