This can cause conditions such as rickets in children, or osteomalacia and osteoporosis in adults. Evidence suggests vitamin D may help to prevent some medical conditions, including some types of cancer. However, scientists are still trying to understand how vitamin D may influence specific conditions.
Research into its ability to influence diseases, such as diabetes , hypertension , and multiple sclerosis , is ongoing. People can get vitamin D from exposure to sunlight or, to a lesser extent, from food. If someone does not get enough vitamin D from these sources, they may develop a deficiency. The symptoms of a vitamin D deficiency can be subtle , but the classic symptoms are bone aches and muscle weakness. Department of Health and Human Services , some people are more at risk of developing vitamin D deficiency than others.
This includes:. Some health conditions and medications can also make it more difficult for someone to absorb vitamin D, including:. People can get at least some of their daily vitamin D from exposure to sunlight. However, as light levels vary, depending on location and the time of year, a person may not be able to get all the vitamin D they need from sunlight.
A study in Switzerland found that only 10—15 minutes of sun exposure per day was enough to provide 1, IU of vitamin D in spring and summer. However, getting this amount in fall and winter was unrealistic, requiring someone to spend over 6 hours a day outdoors.
This suggests that people who live in colder climates, or who spend most of their time indoors, may benefit from vitamin D supplements. However, a person should talk to their doctor before taking vitamin D, as it can interact with some medications.
Sunlight can also cause skin damage and sunburn , so it is essential to use sunscreen when spending time outside. A study on Australian office workers found that applying sunscreen meant people could spend more time outdoors, leading to higher vitamin D levels overall. People can also get some of their vitamin D from food. According to the Office of Dietary Supplements , food sources of vitamin D include:. The study on Australian office workers found that fish consumption, in particular, had a positive effect on vitamin D levels during winter.
A person can take too much vitamin D. Since vitamin D occurs naturally in only a few food sources, the most likely way a person can get too much vitamin D is through taking a high strength supplement. Background Vitamin D deficiency is thought to be common in Australia.
It is unclear when vitamin D supplementation should be prescribed. Objective We assess the evidence that guides clinical decision-making on supplementation with vitamin D following a vitamin D test result.
Discussion Vitamin D assays are inconsistent and inaccurate and there is weak evidence around the level of hydroxyvitamin D 25 OH D that is optimal. Evidence of links between vitamin D deficiency and disease come from observational studies and there is little support from randomised controlled trials of vitamin D supplementation. New evidence indicates that both high and low 25 OH D levels may be associated with increased health risks.
Taken together these considerations present a considerable challenge to clinical decision-making around treatment on the basis of 25 OH D levels. Vitamin D metabolic pathway For most Australians, the main source of vitamin D is cutaneous synthesis after sun exposure of the skin.
Measuring vitamin D status Most commercial pathology laboratories use an automated immunoassay, such as Diasorin Liaison, to measure the 25 OH D concentration. References Bilinski K, Boyages S. Evidence of overtesting for vitamin D in Australia: an analysis of 4. BMJ Open ;3:e The rising cost of vitamin D testing in Australia: time to establish guidelines for testing. Med J Aust ; Search PubMed Medicare Australia. Medicare Australia Statistics. Available at www. Position statement: Use and interpretation of vitamin D testing.
Vitamin D and health in adults in Australia and New Zealand: a position statement. Med J Aust ;— Sun exposure over a lifetime in Australian adults from latitudinally diverse regions. Photochem Photobio [epub ahead of print].
Effects of vitamin D on the peripheral adaptive immune system: a review. Autoimmunity Rev ;— Vitamin D metabolism and function in the skin.
Mol Cell Endocrinol ;— Br J Nutr ;— Current status of clinical 25—hydroxyvitamin D measurement: an assessment of between-laboratory agreement. Clin Chim Acta ;— Variability in vitamin D assays impairs clinical assessment of vitamin D status. Intern Med J ;— Br J Cancer ;— Prospective study of serum vitamin D and cancer mortality in the United States.
J Natl Cancer Inst ;— J Clin Endocrinol Metab ;— Association between vitamin D and risk of colorectal cancer: a systematic review of prospective studies. J Clin Oncol ;— Search PubMed Peterlik M. Vitamin D insufficiency and chronic diseases: hype and reality. Food Funct ;— Search PubMed Institute of Medicine. Common misconceptions about vitamin D-implications for clinicians. Nat Rev Endocrinol ;— Both high and low levels of blood vitamin D are associated with a higher prostate cancer risk: a longitudinal, nested case-control study in the Nordic countries.
Int J Cancer ;— Sun exposure may increase risk of prostate cancer in the high UV environment of New South Wales, Australia: a case-control study. Both high and low serum vitamin D concentrations are associated with tuberculosis: a case-control study in Greenland. Vitamin D, nervous system and aging. Psychoneuroendocrinology ;34 Suppl 1 :S— Neonatal vitamin D status and risk of schizophrenia: a population-based case-control study.
He agreed with the authors of the NEJM article that we are currently over-screening for vitamin D deficiency, and overtreating people who are getting enough vitamin D through diet and sun exposure. If vitamin D is so critical to humans, why would we evolve in this way, to require something that is hard to come by, and then evolve in such a way as to make it harder to absorb?
Finkelstein and his colleagues published a study of over 2, perimenopausal women who had been followed for almost 10 years, and they found that vitamin D levels less than 20 were associated with a slightly increased risk of nontraumatic fractures. All that said, most experts, including Dr. Finkelstein, agree we should be checking vitamin D levels in high-risk people — those most at risk for a true deficiency.
These include people with anorexia nervosa, people who have had gastric bypass surgeries, who suffer from other malabsorption syndromes like celiac sprue, or who have dark skin, or wear total skin covering and thus absorb less sunlight. This can include perimenopausal women, people diagnosed with osteopenia reduced bone density, but not osteoporosis and osteoporosis or other skeletal disorders, as well as pregnant and lactating women.
All of these groups should be screened and treated as appropriate. JoAnn E. Manson, M. Brannon, Ph. Rosen, M.
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