In foods and dietary supplements, vitamin D has two main forms, D 2 ergocalciferol and D 3 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 [ 4 ]. 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 [ 4 ]. 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 [ 1 ]. In serum, 25 OH D has a fairly long circulating half-life of 15 days [ 1 ]. Assessing vitamin D status by measuring serum 25 OH D concentrations is complicated by the considerable variability of the available assays the two most common ones involve antibodies or chromatography used by laboratories that conduct the analyses [ 5 , 6 ].
As a result, a finding can be falsely low or falsely high, depending on the assay used and the laboratory. The international Vitamin D Standardization Program has developed procedures for standardizing the laboratory measurement of 25 OH D to improve clinical and public health practice [ 5 , ].
In contrast to 25 OH D, circulating 1,25 OH 2D is generally not a good indicator of vitamin D status because it has a short half-life measured in hours, and serum levels are tightly regulated by parathyroid hormone, calcium, and phosphate [ 1 ].
Levels of 1,25 OH 2D do not typically decrease until vitamin D deficiency is severe [ 2 ]. Researchers have not definitively identified serum concentrations of 25 OH D associated with deficiency e.
Optimal serum concentrations of 25 OH D for bone and general health have not been established because they are likely to vary by stage of life, by race and ethnicity, and with each physiological measure used [ 1 , 13 , 14 ]. In addition, although 25 OH D levels rise in response to increased vitamin D intake, the relationship is nonlinear [ 1 ]. The amount of increase varies, for example, by baseline serum levels and duration of supplementation.
DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and sex, include:. An FNB committee established RDAs for vitamin D to indicate daily intakes sufficient to maintain bone health and normal calcium metabolism in healthy people.
Even though sunlight is a major source of vitamin D for some people, the FNB based the vitamin D RDAs on the assumption that people receive minimal sun exposure [ 1 ]. Many other countries around the world and some professional societies have somewhat different guidelines for vitamin D intakes [ 15 ].
These differences are a result of an incomplete understanding of the biology and clinical implications of vitamin D, different purposes for the guidelines e. Food Few foods naturally contain vitamin D. The flesh of fatty fish such as trout, salmon, tuna, and mackerel and fish liver oils are among the best sources [ 17 , 1 ]. Beef liver, egg yolks, and cheese have small amounts of vitamin D, primarily in the form of vitamin D 3 and its metabolite 25 OH D 3.
Mushrooms provide variable amounts of vitamin D 2 [ 17 ]. Some mushrooms available on the market have been treated with UV light to increase their levels of vitamin D 2. In addition, the Food and Drug Administration FDA has approved UV-treated mushroom powder as a food additive for use as a source of vitamin D 2 in food products [ 18 ].
Very limited evidence suggests no substantial differences in the bioavailability of vitamin D from various foods [ 19 ]. Animal-based foods typically provide some vitamin D in the form of 25 OH D in addition to vitamin D 3. The impact of this form on vitamin D status is an emerging area of research. Studies show that 25 OH D appears to be approximately five times more potent than the parent vitamin for raising serum 25 OH D concentrations [ 17 , 20 , 21 ]. One study found that when the 25 OH D content of beef, pork, chicken, turkey, and eggs is taken into account, the total amount of vitamin D in the food is 2 to 18 times higher than the amount in the parent vitamin alone, depending on the food [ 20 ].
Fortified foods provide most of the vitamin D in American diets [ 1 , 22 ]. For example, almost all of the U. In Canada, milk must be fortified with 0. Other dairy products made from milk, such as cheese and ice cream, are not usually fortified in the United States or Canada. Ready-to-eat breakfast cereals often contain added vitamin D, as do some brands of orange juice, yogurt, margarine, and other food products. The United States mandates the fortification of infant formula with 1—2.
The U. Sun exposure Most people in the world meet at least some of their vitamin D needs through exposure to sunlight [ 1 ]. Type B UV UVB radiation with a wavelength of approximately — nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D 3 , which in turn becomes vitamin D 3.
Season, time of day, length of day, cloud cover, smog, skin melanin content, and sunscreen are among the factors that affect UV radiation exposure and vitamin D synthesis. Older people and people with dark skin are less able to produce vitamin D from sunlight [ 1 ].
UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D [ 27 ]. The factors that affect UV radiation exposure, individual responsiveness, and uncertainties about the amount of sun exposure needed to maintain adequate vitamin D levels make it difficult to provide guidelines on how much sun exposure is required for sufficient vitamin D synthesis [ 15 , 28 ].
Some expert bodies and vitamin D researchers suggest, for example, that approximately 5—30 minutes of sun exposure, particularly between 10 a. But despite the importance of the sun for vitamin D synthesis, limiting skin exposure to sunlight and UV radiation from tanning beds is prudent [ 28 ].
UV radiation is a carcinogen, and UV exposure is the most preventable cause of skin cancer. Federal agencies and national organizations advise taking photoprotective measures to reduce the risk of skin cancer, including using sunscreen with a sun protection factor SPF of 15 or higher, whenever people are exposed to the sun [ 28 , 30 ].
In practice, however, people usually do not apply sufficient amounts of sunscreen, cover all sun-exposed skin, or reapply sunscreen regularly. Their skin probably synthesizes some vitamin D, even with typically applied sunscreen amounts [ 1 , 28 ].
Dietary supplements Dietary supplements can contain vitamins D 2 or D 3. Vitamin D 2 is manufactured using UV irradiation of ergosterol in yeast, and vitamin D 3 is produced with irradiation of 7-dehydrocholesterol from lanolin and the chemical conversion of cholesterol [ 13 ]. Both forms raise serum 25 OH D levels, and they seem to have equivalent ability to cure rickets [ 4 ]. In addition, most steps in the metabolism and actions of vitamins D 2 and D 3 are identical.
However, most evidence indicates that vitamin D 3 increases serum 25 OH D levels to a greater extent and maintains these higher levels longer than vitamin D 2 , even though both forms are well absorbed in the gut [ ]. Some studies have used dietary supplements containing the 25 OH D 3 form of vitamin D.
Per equivalent microgram dose, 25 OH D 3 is three to five times as potent as vitamin D 3 [ 35 , 36 ]. However, no 25 OH D 3 dietary supplements appear to be available to consumers on the U. Most people in the United States consume less than recommended amounts of vitamin D. Total vitamin D intakes were three times higher with supplement use than with diet alone; the mean intake from foods and beverages alone for individuals aged 2 and older was 4.
Some people take very high doses of vitamin D supplements. In —, an estimated 3. One might expect a large proportion of the U.
However, comparing vitamin D intakes to serum 25 OH D levels is problematic. One reason is that sun exposure affects vitamin D status, so serum 25 OH D levels are usually higher than would be predicted on the basis of vitamin D dietary intakes alone [ 1 ]. Another reason is that animal foods contain some 25 OH D. This form of vitamin D is not included in intake surveys and is considerably more potent than vitamins D 2 or D 3 at raising serum 25 OH D levels [ 41 ].
Proportions at risk of deficiency were lowest among children aged 1—5 years 0. Rates of deficiency varied by race and ethnicity: Again, the pattern was similar for the risk of inadequacy. Vitamin D status in the United States remained stable in the decade between — and — People can develop vitamin D deficiency when usual intakes are lower over time than recommended levels, exposure to sunlight is limited, the kidneys cannot convert 25 OH D to its active form, or absorption of vitamin D from the digestive tract is inadequate.
Diets low in vitamin D are more common in people who have milk allergy or lactose intolerance and those who consume an ovo-vegetarian or vegan diet [ 1 ]. In children, vitamin D deficiency is manifested as rickets, a disease characterized by a failure of bone tissue to become properly mineralized, resulting in soft bones and skeletal deformities [ 43 ]. In addition to bone deformities and pain, severe rickets can cause failure to thrive, developmental delay, hypocalcemic seizures, tetanic spasms, cardiomyopathy, and dental abnormalities [ 44 , 45 ].
Prolonged exclusive breastfeeding without vitamin D supplementation can cause rickets in infants, and, in the United States, rickets is most common among breastfed Black infants and children [ 46 ].
In one Minnesota county, the incidence rate of rickets in children younger than 3 years in the decade beginning in was Rickets occurred mainly in Black children who were breastfed longer, were born with low birthweight, weighed less, and were shorter than other children.
The incidence rate of rickets in the infants and children younger than 7 seen by 2, pediatricians throughout Canada was 2. The fortification of milk a good source of calcium and other staples, such as breakfast cereals and margarine, with vitamin D beginning in the s along with the use of cod liver oil made rickets rare in the United States [ 28 , 49 ].
However, the incidence of rickets is increasing globally, even in the United States and Europe, especially among immigrants from African, Middle-Eastern, and Asian countries [ 50 ]. Possible explanations for this increase include genetic differences in vitamin D metabolism, dietary preferences, and behaviors that lead to less sun exposure [ 44 , 45 ].
In adults and adolescents, vitamin D deficiency can lead to osteomalacia, in which existing bone is incompletely or defectively mineralized during the remodeling process, resulting in weak bones [ 45 ]. Signs and symptoms of osteomalacia are similar to those of rickets and include bone deformities and pain, hypocalcemic seizures, tetanic spasms, and dental abnormalities [ 44 ]. Screening for vitamin D status is becoming a more common part of the routine laboratory bloodwork ordered by primary-care physicians, irrespective of any indications for this practice [ 6 , ].
No studies have examined whether such screening for vitamin D deficiency results in improved health outcomes [ 54 ]. It added that no national professional organization recommends population screening for vitamin D deficiency. Obtaining sufficient vitamin D from natural nonfortified food sources alone is difficult.
For many people, consuming vitamin D-fortified foods and exposing themselves to some sunlight are essential for maintaining a healthy vitamin D status. However, some groups might need dietary supplements to meet their vitamin D requirements.
The following groups are among those most likely to have inadequate vitamin D status. Breastfed infants Consumption of human milk alone does not ordinarily enable infants to meet vitamin D requirements, because it provides less than 0. Although UVB exposure can produce vitamin D in infants, the American Academy of Pediatrics AAP advises parents to keep infants younger than 6 months out of direct sunlight, dress them in protective clothing and hats, and apply sunscreen on small areas of exposed skin when sun exposure is unavoidable [ 58 ].
Older adults Older adults are at increased risk of developing vitamin D insufficiency, partly because the skin's ability to synthesize vitamin D declines with age [ 1 , 60 ]. In addition, older adults are likely to spend more time than younger people indoors, and they might have inadequate dietary intakes of the vitamin [ 1 ]. People with limited sun exposure Homebound individuals; people who wear long robes, dresses, or head coverings for religious reasons; and people with occupations that limit sun exposure are among the groups that are unlikely to obtain adequate amounts of vitamin D from sunlight [ 61 ].
The use of sunscreen also limits vitamin D synthesis from sunlight. However, because the extent and frequency of sunscreen use are unknown, the role that sunscreen may play in reducing vitamin D synthesis is unclear [ 1 ]. However, whether these lower levels in persons with dark skin have significant health consequences is not clear [ 14 ].
Those of African American ancestry, for example, have lower rates of bone fracture and osteoporosis than do Whites see the section below on bone health and osteoporosis. In addition to having an increased risk of vitamin D deficiency, people with these conditions might not eat certain foods, such as dairy products many of which are fortified with vitamin D , or eat only small amounts of these foods.
Individuals who have difficulty absorbing dietary fat might therefore require vitamin D supplementation [ 62 ]. People who are obese or have undergone gastric bypass surgery Individuals with a body mass index BMI of 30 or more have lower serum 25 OH D levels than nonobese individuals.
However, greater amounts of subcutaneous fat sequester more of the vitamin [ 1 ]. Obese people might need greater intakes of vitamin D to achieve 25 OH D levels similar to those of people with normal weight [ 1 , 63 , 64 ]. Obese individuals who have undergone gastric bypass surgery can also become vitamin D deficient.
In this procedure, part of the upper small intestine, where vitamin D is absorbed, is bypassed, and vitamin D that is mobilized into the bloodstream from fat stores might not raise 25 OH D to adequate levels over time [ 65 , 66 ].
Various expert groups—including the American Association of Metabolic and Bariatric Surgery, The Obesity Society, and the British Obesity and Metabolic Surgery Society—have developed guidelines on vitamin D screening, monitoring, and replacement before and after bariatric surgery [ 65 , 67 ]. The FNB committee that established DRIs for vitamin D found that the evidence was inadequate or too contradictory to conclude that the vitamin had any effect on a long list of potential health outcomes e.
Similarly, in a review of data from nearly studies published between and , the Agency for Healthcare Research and Quality concluded that no relationship could be firmly established between vitamin D and health outcomes other than bone health [ 68 ].
However, because research has been conducted on vitamin D and numerous health outcomes, this section focuses on seven diseases, conditions, and interventions in which vitamin D might be involved: bone health and osteoporosis, cancer, cardiovascular disease CVD , depression, multiple sclerosis MS , type 2 diabetes, and weight loss.
Most of the studies described in this section measured serum 25 OH D levels using various methods that were not standardized by comparing them to the best methods. Use of unstandardized 25 OH D measures can raise questions about the accuracy of the results and about the validity of conclusions drawn from studies that use such measures and, especially, from meta-analyses that pool data from many studies that use different unstandardized measures [ 5 , 9 , 69 ].
More information about assay standardization is available from the Vitamin D Standardization Program webpage. Bone health and osteoporosis Bone is constantly being remodeled.
However, as people age—and particularly in women during menopause—bone breakdown rates overtake rates of bone building. Over time, bone density can decline, and osteoporosis can eventually develop [ 70 ].
More than 53 million adults in the United States have or are at risk of developing osteoporosis, which is characterized by low bone mass and structural deterioration of bone tissue that increases bone fragility and the risk of bone fractures [ 71 ].
About 2. Osteoporosis is most often associated with inadequate calcium intakes, but insufficient vitamin D intakes contribute to osteoporosis by reducing calcium absorption [ 1 ]. Bone health also depends on support from the surrounding muscles to assist with balance and postural sway and thereby reduce the risk of falling.
Vitamin D is also needed for the normal development and growth of muscle fibers. In addition, inadequate vitamin D levels can adversely affect muscle strength and lead to muscle weakness and pain myopathy [ 1 ]. Most trials of the effects of vitamin D supplements on bone health also included calcium supplements, so isolating the effects of each nutrient is difficult. In addition, studies provided different amounts of nutrients and used different dosing schedules.
Clinical trial evidence on older adults Among postmenopausal women and older men, many clinical trials have shown that supplements of both vitamin D and calcium result in small increases in bone mineral density throughout the skeleton [ 1 , 73 ].
They also help reduce fracture rates in institutionalized older people. However, the evidence on the impact of vitamin D and calcium supplements on fractures in community-dwelling individuals is inconsistent.
It concluded that the current evidence was insufficient to evaluate the benefits and harms of supplementation to prevent fractures. In addition, the USPSTF recommended against supplementation with 10 mcg IU or less of vitamin D and 1, mg or less of calcium to prevent fractures in this population, but it could not determine the balance of benefits and harms from higher doses. The USPSTF also reviewed the seven published studies on the effects of vitamin D supplementation two of them also included calcium supplementation on the risk of falls in community-dwelling adults aged 65 years or older who did not have osteoporosis or vitamin D deficiency.
It concluded "with moderate certainty" that vitamin D supplementation does not reduce the numbers of falls or injuries, such as fractures, resulting from falls [ 76 , 76 ]. Another recent systematic review also found that vitamin D and calcium supplements had no beneficial effects on fractures, falls, or bone mineral density [ 78 , 79 ]. Vitamin D supplements for bone health in minority populations Bone mineral density, bone mass, and fracture risk are correlated with serum 25 OH D levels in White Americans and Mexican Americans, but not in Black Americans [ 14 , 81 ].
Factors such as adiposity, skin pigmentation, vitamin D binding protein polymorphisms, and genetics contribute to differences in 25 OH D levels between Black and White Americans.
One clinical trial randomized Black women aged 60 years and older mean age The results showed no association between 25 OH D levels or vitamin D dose and the risk of falling in the participants who completed the study. In fact, Black Americans might have a greater risk than White Americans of falls and fractures with daily vitamin D intakes of 50 mcg 2, IU or more [ 14 ].
Vitamin D supplements and muscle function Studies examining the effects of supplemental vitamin D on muscle strength and on rate of decline in muscle function have had inconsistent results [ 54 ]. One recent clinical trial, for example, randomized 78 frail and near-frail adults aged 65 years and older to receive 20 mcg IU vitamin D 3 , 10 mcg 25 OH D, or placebo daily for 6 months.
The groups showed no significant differences in measures of muscle strength or performance [ 83 ]. Conclusions about vitamin D supplements and bone health All adults should consume recommended amounts of vitamin D and calcium from foods and supplements if needed.
Older women and men should consult their healthcare providers about their needs for both nutrients as part of an overall plan to maintain bone health and to prevent or treat osteoporosis. Cancer Laboratory and animal studies suggest that vitamin D might inhibit carcinogenesis and slow tumor progression by, for example, promoting cell differentiation and inhibiting metastasis. Vitamin D might also have anti-inflammatory, immunomodulatory, proapoptotic, and antiangiogenic effects [ 1 , 85 ].
Observational studies and clinical trials provide mixed evidence on whether vitamin D intakes or serum levels affect cancer incidence, progression, or mortality risk. Total cancer incidence and mortality Some observational studies show associations between low serum levels of 25 OH D and increased risks of cancer incidence and death.
In a meta-analysis of 16 prospective cohort studies in a total of , participants who had 8, diagnoses of cancer, 5, participants died from cancer [ 86 ]. Importantly, not all observational studies found higher vitamin D status to be beneficial, and the studies varied considerably in study populations, baseline comorbidities, and measurement of vitamin D levels.
Clinical trial evidence provides some support for the observational findings. The study reports included 3—10 years of followup data.
The study included 25, men aged 50 years and older and women aged 55 years and older who had no history of cancer, and most had adequate serum 25 OH D levels at baseline. Rates of breast, prostate, and colorectal cancer did not differ significantly between the vitamin D and placebo groups. However, normal-weight participants had greater reductions in cancer incidence and mortality rates than those who were overweight or obese.
A few studies have examined the effect of vitamin D supplementation on specific cancers. Below are brief descriptions of studies of vitamin D and its association with, or effect on, breast, colorectal, lung, pancreatic, and prostate cancers.
Breast cancer Some observational studies support an inverse association between 25 OH D levels and breast cancer risk and mortality, but others do not [ ]. The Women's Health Initiative clinical trial randomized 36, postmenopausal women to receive IU vitamin D 3 plus 1, mg calcium daily or a placebo for a mean of 7 years [ 96 ]. The vitamin D 3 and calcium supplements did not reduce breast cancer incidence, and 25 OH D levels at the start of the study were not associated with breast cancer risk [ 97 ].
In a subsequent investigation for 4. Colorectal cancer A large case-control study included 5, individuals who developed colorectal cancer and whose 25 OH D levels were assessed a median of 5. Levels of 75 to less than The association was substantially stronger in women. In the Women's Health Initiative clinical trial described above , vitamin D 3 and calcium supplements had no effect on rates of colorectal cancer. Another study included 2, healthy individuals aged 45 to 75 years who had had one or more serrated polyps precursor lesions to colorectal cancer that had been removed [ ].
These participants were randomized to take 25 mcg 1, IU vitamin D 3 , 1, mg calcium, both supplements, or a placebo daily for 3—5 years, followed by an additional 3—5 years of observation after participants stopped the treatment.
Vitamin D alone did not significantly affect the development of new serrated polyps, but the combination of vitamin D with calcium increased the risk almost fourfold. The VITAL trial found no association between vitamin D supplementation and the risk of colorectal adenomas or serrated polyps [ ]. Lung cancer A study of cohorts that included 5, participants who developed lung cancer and 5, matched controls found no association between serum 25 OH D levels and risk of subsequent lung cancer, even when the investigators analyzed the data by sex, age, race and ethnicity, and smoking status [ ].
Pancreatic cancer One study comparing men who developed pancreatic cancer to matched controls found no relationship between serum 25 OH D levels and risk of pancreatic cancer [ ].
Another study that compared male smokers in Finland with pancreatic cancer to matched controls found that participants in the highest quintile of 25 OH D levels more than Prostate cancer Research to date provides mixed evidence on whether levels of 25 OH D are associated with the development of prostate cancer.
Several studies published in suggested that high levels of 25 OH D might increase the risk of prostate cancer. This U-shaped association was most pronounced for men with the most aggressive forms of prostate cancer. A case-control analysis of 1, cases of prostate cancer and 1, controls found no associations between 25 OH D levels and prostate cancer risk [ ]. Since , however, several published studies and meta-analyses have found no relationship between 25 OH D levels and prostate cancer risk [ , ].
For example, an analysis was conducted of 19 prospective studies that provided data on prediagnostic levels of 25 OH D for 13, men who developed prostate cancer and 20, control participants [ ]. Vitamin D deficiency or insufficiency did not increase the risk of prostate cancer, and higher 25 OH D concentrations were not associated with a lower risk.
Several studies have examined whether levels of 25 OH D in men with prostate cancer are associated with a lower risk of death from the disease or from any cause. One study included 1, men treated for prostate cancer whose plasma 25 OH D levels were measured 4. Among the participants who died 41 deaths were due to prostate cancer , 25 OH D levels were not associated with risk of death from prostate cancer or any cause [ ]. However, a meta-analysis of 7 cohort studies that included 7, men with prostate cancer found higher 25 OH D levels to be significantly associated with lower mortality rates from prostate cancer or any other cause [ ].
For men with prostate cancer, whether vitamin D supplementation lengthens cancer-related survival is not clear. Conclusions about vitamin D and cancer The USPSTF stated that, due to insufficient evidence, it was unable to assess the balance of benefits and harms of supplemental vitamin D to prevent cancer [ ].
Taken together, studies to date do not indicate that vitamin D with or without calcium supplementation reduces the incidence of cancer, but adequate or higher 25 OH D levels might reduce cancer mortality rates.
Further research is needed to determine whether vitamin D inadequacy increases cancer risk, whether greater exposure to the nutrient can prevent cancer, and whether some individuals could have an increased risk of cancer because of their vitamin D status over time.
Recommendations for how much daily vitamin D adults need through diet have changed over the years. Currently, different recommendations exist. The Institute of Medicine has placed the recommended dietary allowance, or RDA, for vitamin D at international units IU per day for young adults and IU per day for adults older than However, 1, to 2, IU per day of vitamin D from a supplement is generally safe, should help people achieve an adequate blood level of vitamin D, and may have additional health benefits.
While there are no guidelines for checking your vitamin D blood level, it may be prudent in people with osteoporosis or certain other health conditions. Discuss with your health care provider if it may be beneficial to check your vitamin D level. If you have ongoing health concerns or a chronic health condition, talk to your health care provider before you begin taking any dietary supplement, including vitamin D.
He or she can help you decide if supplements are appropriate for your situation. By Liza Torborg. Generally, research on the role vitamin D may play in disease prevention and management is murky.
Particularly with regard to the benefits of taking supplements, most of the studies have been observational or done on small groups or both. Until recent years, there has been a lack of large randomized, controlled trials, which are the gold standard for medical research because such studies point to cause-and-effect relationships between factors. The data now coming in from such trials fails to back up previous claims about the benefits of vitamin D supplementation.
Bone Health As mentioned, vitamin D helps in the absorption of calcium in the gut. Type 2 Diabetes Observational studies have associated low vitamin D levels with a higher risk of developing type 2 diabetes. A dose of 4, IU of vitamin D per day did not result in a significantly lower risk of developing type 2 diabetes compared with a placebo. Cardiovascular Disease Taking vitamin D supplements does not reduce the risk of heart attack, stroke, or death from heart disease, according to the findings of a randomized, controlled clinical trial involving more than 25, participants that was published in the aforementioned January in The New England Journal of Medicine.
Cancer In the same study, researchers found that vitamin D supplementation was not found to reduce the risk of cancer in participants overall. However, those who had developed cancer and were taking vitamin D were less likely to die early than those who took a placebo. Researchers also found a possible reduction in cancer risk for African Americans, and they called for further study to confirm those results.
Rheumatoid arthritis RA A small observational study of 44 people with RA and 25 controls found that vitamin D deficiency appeared to be more prevalent among people with RA , suggesting these people may benefit from taking a supplement. Mood Disorders Vitamin D is an established therapy for seasonal depression, also called seasonal affective disorder , according to the National Institute of Mental Health.
Thyroid Disease The connection between vitamin D and people with hypothyroidism seems clearer, though larger-scale research is necessary. They can perform a blood test to see if you may benefit from upping your intake of vitamin D—rich foods like salmon, fortified milk, and eggs , or taking a vitamin D supplement, according to MedlinePlus.
Additional reporting by Melinda Carstensen and Jamie Ludwig. By subscribing you agree to the Terms of Use and Privacy Policy. Health Topics. Health Tools.
Reviewed: May 18, Medically Reviewed. Read on to learn about the surprising factors that can influence how much vitamin D you need. When it comes to vitamin D, age matters, and for different reasons than you might expect. Editorial Sources and Fact-Checking. The New England Journal of Medicine. January August Scragg R. May March 24,
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