9 VITAMIN D BENEFITS YOU SHOULD KNOW

You already know vitamin D is important for bone health, but its benefits don't stop there.

Vitamin D—nicknamed the "sunshine vitamin" due to its ability to be absorbed by the body through sunlight—is a major player in keeping the human body healthy. Its main job, according to the National Institutes of Health's Office of Dietary Supplements, is to promote calcium absorption, making it necessary for bone growth and bone remodeling (when mature bone tissue is removed and new bone tissue is formed). Because of that, a lack of vitamin D can lead to thin, brittle, or misshapen bones. But vitamin D offers a range of other benefits too, ranging from positives for both physical and mental health. Here are nine vitamin D benefits you need to know about—including ways to get more of the vitamin in your daily diet.

Vitamin D is famous for its bone-building and strengthening powers. “Vitamin D promotes absorption of calcium in your gut, which ultimately allows for normal mineralization of your bones,” Jackie Newgent, RDN, culinary nutritionist and author of The Clean & Simple Diabetes Cookbook, tells Health. Basically, the calcium that benefits your bones wouldn't be able to do its job without vitamin D. “You need vitamin D for bone growth—and to prevent bones from becoming brittle.” When teamed with calcium, it can help prevent osteoporosis, a disease that signifies that the density and quality of bone are reduced, she adds. 

Along with its bone-building abilities, vitamin D is also influential in strengthening muscles. “Lack of vitamin D in the body can increase the risk of having weak muscles, which in turn increases the risk of falls,” Lana Nasrallah, MPH, RD, clinical dietician at UNC Health, tells Health. This is especially important for the elderly. “Vitamin D may help increase muscle strength thus preventing falls, which is a common problem that leads to substantial disability and death in older adults.”

Dr. Nasrallah adds that vitamin D can also help build immunity. “It can support the immune system by fighting off harmful bacteria and viruses,” she says. In fact, this role in possibly preventing infections has become a critical concern during COVID-19 pandemic, as researchers are interested in its potential role in infection outcomes. “There is particular interest in its role in viral infections such as influenza and coronavirus,” Barry Boyd, MD, RDN, a Yale Medicine hematologist, oncologist, and nutritionist, tells Health. He points to a 2017 BMJ analysis of 25 randomized control trials comparing vitamin D supplements to placebos, which found that vitamin D reduced the risk of acute respiratory infection with either daily or weekly vitamin D supplementation, particularly in individuals who were deficient in it. “Studies indicate that high latitudes and winter season are risk factors for both low vitamin D, increased influenza, and other respiratory illness and adverse outcomes,” he says. “We now are seeing a similar pattern with higher mortality rates in COVID-19 infections," though more research still needs to be done to determine whether the link is causal or merely a correlation.

Because vitamin D helps our body absorb calcium, it plays a crucial role in supporting oral health, lowering the risk of tooth decay and gum disease. A 2011 review in The Journal of the Tennessee Dental Association notes that while the research is scant, there's an "emerging hypothesis" that the vitamin is beneficial for oral health, due to its effect on bone metabolism and "its ability to function as an anti-inflammatory agent and stimulate the production of anti-microbial peptides."

While studies are not conclusive, vitamin D may be helpful for preventing both type 1 and type 2 diabetes, says Newgent. One such study, published in 2006 in the journal Diabetes Care, found that while vitamin D on its own did not effectively lower the risk of an overabundance of sugar in the blood, a combined daily intake of >1,200 mg calcium and >800 IU vitamin D could effectively lower the risk of type 2 diabetes. 

According to a 2019 review published in the journal Current Protein & Peptide Science suggests that vitamin D may play a role in treatment of high blood pressure—one of the markers of cardiovascular disease—says Newgent. According to authors of the review, “even short-term vitamin D deficiency may directly raise BP [blood pressure] and promote target organ damage.” The researchers went on to add that, "due to the high correlation between vitamin D and hypertension, vitamin D supplementation therapy may be a new insight in the treatment of hypertension."

Dr. Boyd points out that obesity is a known risk factor for low vitamin D levels—which means more vitamin D may help with weight loss. One 2009 study in the British Journal of Nutrition found that, in overweight or obese women with low calcium levels, those who took a daily dose of calcium paired with vitamin D were more successful shedding pounds than those who took a placebo supplement, due to an “appetite-suppressing effect” of the combination.

The sun can brighten up your mood, and so can vitamin D. According to a 2017 review article in the journal Neuropsychology, researchers found "a significant relationship between depression and vitamin D deficiency.” While they acknowledged that more research is needed to define the exact workings of it—such as, if low vitamin D levels are a cause or effect of depression—the authors recommend “screening for and treating vitamin D deficiency in subjects with depression” noting that it is an “easy, cost-effective and may improve depression outcome.”

Dr. Boyd points to various studies—most of which are referenced on the National Cancer Institute's (NCI) website—that provide some evidence that vitamin D may have cancer fighting powers. “Evidence is increasing that vitamin D supplementation may improve cancer outcomes,” he explains. The cancers for which the most human data are available are colorectal, breast, prostate, and pancreatic cancer. 

The NCI specifically calls out a few reasons why researchers are interested in a link between vitamin D and a lowered risk of cancer. The organization points out that some research shows that incidence and death rates for certain cancers were lower among individuals living in southern latitudes, where levels of sunlight exposure are relatively high, than among those living at northern latitudes, though additional research needs to be done to find a specific causal or correlational link between more sunlight exposure and a lower risk of cancer. More experimental evidence, per the NCI, shows, that cancer cells and of tumors in mice, vitamin D has been found to have several activities that might slow or prevent the development of cancer cells and tumors in mice, including promoting cellular differentiation, decreasing cancer cell growth, stimulating cell death (apoptosis), and reducing tumor blood vessel formation (angiogenesis).

Despite being readily available through sunlight, some foods, and supplementation, many Americans are still getting inadequate amounts of vitamin D—according to the most recent information from the Centers for Disease Control and Prevention, two-thirds of the population had sufficient vitamin D, defined by the Institute of Medicine as a serum 25-hydroxyvitamin D (25OHD) value of 50–125 nmol/L. Because you can't necessarily find out if you a vitamin D deficiency on your own, the best thing to do is to consult a medical expert, says Cynthia Sass, RD, MPH, contributing nutrition editor for Health. "Ideally the best approach is to have your blood vitamin D level tested to find out if your blood vitamin D level is within the adequate range,” she explains. “This determines if a supplement is needed in order to achieve adequate blood vitamin D status, and if so, the proper dosage of supplemental vitamin D.” 

If you find out you are deficient or lacking in vitamin D intake, there are a few key ways you can up your daily dosage—staring with getting around 20 minutes of sunlight several times a week, according to Newgent. "The major cause of vitamin D deficiency is inadequate exposure to sunlight, an increasing feature in modern life," says Dr. Boyd. But remember: You still need to wear sunscreen whenever you step outside—even to get vitamin D.

Aside from the sun, you can also get extra vitamin D through a few (albeit very few) foods, like fatty fish (including salmon, tuna, mackerel, and sardines) and mushrooms (some of which are exposed to ultraviolet (UV) light to increase vitamin D levels), says Drs. Nasrallah and Newgent. Foods like milk, orange juice, yogurt, and breakfast cereals can also be fortified with vitamin D. And of course, you can always go the supplement route, in the form of vitamin D3, if your doctor thinks it's necessary. According to Dr. Boyd, many doctors now consider a daily dose of 1000-2000 IU of D3 safe and will assure optimal levels for most adults. As for when to take it, because vitamin is fat soluble, he suggests pairing it with your largest meal of the day, “containing fat to assure maximal absorption.” But again, check in with your doctor before you decide to try vitamin D in supplement form. 

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