Vitamin D is sometimes called the “sunshine vitamin” because it’s produced in your skin in response to sunlight. It’s a fat-soluble vitamin in a family of compounds that includes vitamins D-1, D-2, and D-3.
Vitamins are nutrients that the body cannot create, and so a person must consume them in the diet. However, the body can produce vitamin D.
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 D3, also known as the “sunshine vitamin,” provides benefits throughout your body. As it circulates through your bloodstream, it aids in the absorption of calcium and phosphorus, which helps keep your bones strong. It’s involved in a healthy immune system, and it’s beneficial to mood, heart health, and even weight loss. You can get vitamin D from food and supplements, and your skin produces D3 when it’s exposed to sunlight.
In this article, we look at the benefits of vitamin D, what happens to the body when people do not get enough, and how to boost vitamin D intake.
What Is Vitamin D
Vitamin D (also referred to as “calciferol”) is a fat-soluble vitamin that is naturally present in a few foods, added to others, and available as a dietary supplement. It is also produced endogenously when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis.
Vitamin D obtained from sun exposure, foods, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first hydroxylation, which occurs in the liver, converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as “calcidiol.” The second hydroxylation occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as “calcitriol”.
Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization and to prevent hypocalcemic tetany (involuntary contraction of muscles, leading to cramps and spasms). It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.
Vitamin D has other roles in the body, including reduction of inflammation as well as modulation of such processes as cell growth, neuromuscular and immune function, and glucose metabolism [1-3]. Many genes encoding proteins that regulate cell proliferation, differentiation, and apoptosis are modulated in part by vitamin D. Many tissues have vitamin D receptors, and some convert 25(OH)D to 1,25(OH)2D.
In foods and dietary supplements, vitamin D has two main forms, D2 (ergocalciferol) and D3 (cholecalciferol), that differ chemically only in their side-chain structures. Both forms are well absorbed in the small intestine. Absorption occurs by simple passive diffusion and by a mechanism that involves intestinal membrane carrier proteins. The concurrent presence of fat in the gut enhances vitamin D absorption, but some vitamin D is absorbed even without dietary fat. Neither aging nor obesity alters vitamin D absorption from the gut.
Serum concentration of 25(OH)D is currently the main indicator of vitamin D status. It reflects vitamin D produced endogenously and that obtained from foods and supplements. In serum, 25(OH)D has a fairly long circulating half-life of 15 days. Serum concentrations of 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL). One nmol/L is equal to 0.4 ng/mL, and 1 ng/mL is equal to 2.5 nmol/L.
What Does Vitamin D Do?
Vitamin D is a fat-soluble vitamin available via ultraviolet rays (mainly the sun), a few foods and supplements.
Vitamin D’s main purpose is to regulate calcium and phosphate to keep your bones, teeth and muscles strong and healthy. A vitamin D deficiency can lead to rickets in children and osteomalacia—the softening of the bones—in adults. Meanwhile, preliminary research suggests getting enough vitamin D is associated with a lower risk of certain diseases, such as heart disease, type 2 diabetes, and improved mental health.
Health Benefits Of Vitamin D
Vitamin D Fights Disease
In addition to its primary benefits, research suggests that vitamin D may also play a role in:
- reducing your risk of multiple sclerosis, according to a 2006 study published in the Journal of the American Medical Association
- decreasing your chance of developing heart disease, according to 2008 findings published in Circulation
- helping to reduce your likelihood of developing the flu, according to 2010 research published in the American Journal of Clinical Nutrition
Vitamin D plays a significant role in the regulation of calcium and maintenance of phosphorus levels in the blood. These factors are vital for maintaining healthy bones.
People need vitamin D to allow the intestines to stimulate and absorb calcium and reclaim calcium that the kidneys would otherwise excrete.
Vitamin D deficiency in children can cause rickets, which leads to a severely bowlegged appearance due to the softening of the bones.
Similarly, in adults, vitamin D deficiency manifests as osteomalacia, or softening of the bones. Osteomalacia results in poor bone density and muscular weakness.
A vitamin D deficiency can also present as osteoporosis, for which over 53 million people in the United States either seek treatment or face an increased risk.
D-fense for Your Health
As the research into vitamin D is accumulating, it’s hard to know where the accolades should start. “Activated vitamin D is one of the most potent inhibitors of cancer cell growth,” says Michael F. Holick, PhD, MD, who heads the Vitamin D, Skin, and Bone Research Laboratory at Boston University School of Medicine. “It also stimulates your pancreas to make insulin. It regulates your immune system.”
Just consider these recent studies:
At Boston University, after people with high blood pressure were exposed to UVA and UVB rays for three months, their vitamin D levels increased by more than 100% — and more impressively, their high blood pressure normalized. “We’ve followed them now for nine months, and their hypertension continues to be in remission,” says Holick, professor of medicine, physiology and biophysics at Boston University. One theory about how vitamin D reduces blood pressure: It decreases the production of a hormone called renin, which is believed to play a role in hypertension.
In a study published in the Journal of the American Medical Association in December 2003, of more than 3,000 veterans (ages 50 to 75) at 13 Veterans Affairs medical centers, those who consumed more than 645 IU of vitamin D a day along with more than 4 grams per day of cereal fiber had a 40% reduction in their risk of developing precancerous colon polyps.
In a report in the Journal of the American Geriatrics Society in February 2004, researchers at the University of Basel in Switzerland showed that elderly women who took a vitamin D supplement plus calcium for three months reduced their risk of falling by 49% compared with consuming calcium alone. Those women who had fallen repeatedly in the past seemed to gain the most benefit from vitamin D.
A study in the Jan. 13, 2004 issue of Neurology indicated that women who get doses of vitamin D that are typically found in daily multivitamin supplements — of at least 400 international units — are 40% less likely to develop multiple sclerosis compared with those not taking over-the-counter supplements.
Vitamin D Can Support The Immune System And Fight Inflammation
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.
Studies have shown that people with clinical depression often have vitamin D deficiencies. However, it’s not clear whether the deficiency contributes to depression or depression changes behavior (e.g., diet, time outside) and therefore causes the deficiency.
As researchers have examined the impact of vitamin D on the brain, they have uncovered possible mechanisms of action that may shine light on how a deficiency could lead to depression. They’ve also found evidence that raising vitamin D levels helps alleviate symptoms. Larger, well-designed studies still are needed, but thus far the findings are promising for vitamin D as part of a depression treatment regimen.
Reduced Risk Of Heart Disease, Hypertension And All-Cause Mortality
Research published in Scientific Reports in 2020 suggests that, for people who have vitamin D deficiency, taking supplements of the vitamin “had a favorable effect on diastolic blood pressure levels and parathyroid hormone concentrations” in comparison with people in a control group. “Therefore, vitamin D may be recommended to be used as an adjunct therapy to routine treatment in coronary artery disease patients with vitamin D deficiency.” Previous research suggests that vitamin D can help lower the risk of hypertension and all-cause mortality.
Vitamin D Reduces Depression
Research has shown that vitamin D might play an important role in regulating mood and warding off depression. In one study, scientists found that people with depression who received vitamin D supplements noticed an improvement in their symptoms.
In another study of people with fibromyalgia, researchers found vitamin D deficiency was more common in those who were also experiencing anxiety and depression.
Reduced Risk Of Flu
A 2018 review of existing research suggested that some studies had found that vitamin D had a protective effect against the influenza virus.
However, the authors also looked at other studies where vitamin D did not have this effect on flu and flu risk.
Further research is, therefore, necessary to confirm the protective effect of vitamin D on the flu.
Vitamin D Can Help Strengthen Oral Health
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.”
Studies have found that individuals with obesity and high blood pressure tend to have lower vitamin D levels. Some research suggested that the vitamin can help lower blood pressure. Some studies have shown that people with higher vitamin D levels have a higher risk of stroke and heart attack, but clinical trials haven’t shown that vitamin D supplements reduce the risk.8
In one study, postmenopausal women were given vitamin D3 supplements (compared with a placebo) for a weight loss intervention. The outcome showed that the women who had adequate levels of vitamin D3 lost more body fat, saw a greater reduction in waist circumference, and lost more weight.9
However, most research has concluded that vitamin D does not promote weight loss.
Lower Inflammation In People With Heart Failure
A meta-analysis published in 2018 in the journal Scientific Reports suggests that while vitamin D “may not be effective as a sole treatment to improve inflammation … it may be beneficial as an adjunct to existing therapies in vitamin D-deficient patients with (heart failure).
Vitamin D deficiency has links to high blood pressure in children. One 2018 study found a possible connection between low vitamin D levels and stiffness in the arterial walls of children.
The American Academy of Allergy Asthma and Immunology (AAAAI) suggest that evidence points to a connection between low vitamin D exposure and an increased risk of allergic sensitization.
An example of this is children who live closer to the equator and have lower rates of admission to hospital for allergies plus fewer prescriptions of epinephrine autoinjectors. They are also less likely to have a peanut allergy.
The AAAAI also highlight an Australian study of egg intake. Eggs are a common early source of vitamin D. The children who started eating eggs after 6 months were more likely to develop food allergies than children who started between 4–6 months of age.
Furthermore, vitamin D may enhance the anti-inflammatory effects of glucocorticoids. This benefit makes it potentially useful as a supportive therapy for people with steroid resistant asthma.
Vitamin D Can Help Prevent Type 1 And Type 2 Diabetes
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.
Improved Calcium Absorption In The Small Intestine
Consuming enough vitamin D boosts the absorption of calcium in the small intestine. “It’s important that calcium is absorbed in the small intestine, as then it makes its way into the bloodstream where it can help to build bones and regulate how blood vessels, muscles and nerves function,” Drayer says.
Lower Risk Of Several Chronic Conditions
Vitamin D deficiency is associated with several chronic conditions, including cancer, cardiovascular disease, diabetes and immune system disorders, according to research published in 2017 in the journal Aging and Disease. “Having a healthy vitamin D level may improve blood sugar control for people with or at risk for diabetes,” Angelone says.
A 2019 review suggests that pregnant women who are deficient in vitamin D may have a greater risk of developing preeclampsia and giving birth preterm.
Doctors also associate poor vitamin D status with gestational diabetes and bacterial vaginosis in pregnant women.
It is also important to note that in a 2013 study, researchers associated high vitamin D levels during pregnancy with an increased risk of food allergy in the child during the first 2 years of life.
Vitamin D May Help Reduce The Risk Of Certain Cancers
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).