Vitamin D

Studies in people

• Benefit

  Thyroid health³

  People with Hashimoto's often have lower vitamin D, and taking vitamin D lowered their thyroid antibodies.

• Open question

  Obesity and vitamin levels⁵

  People with obesity tend to have low vitamin D, but vitamin D supplements do not help with weight loss.

• Benefit

  Pregnancy and baby health⁶

  In pregnant women with low vitamin D, supplements may improve fetal growth and lower risks of preterm birth and other problems.

• Open question

  Dietary intake shortfall⁸

  Vitamin D is hard to get from food alone, so many people do not get enough.

• Open question

  Pregnancy outcomes¹⁰

  Scientists do not yet know whether taking vitamin D in pregnancy prevents problems like early birth or low birthweight.

• Open question

  Bone health and falls¹²

  Vitamin D with calcium may slightly help older adults' bones and lower fall risk, but evidence is mixed.

• Benefit

  Walking speed in older adults¹⁵

  In older people with weak muscles, a whey protein with vitamin D and leucine helped walking speed more than diet advice alone.

• Open question

  Sun exposure and supplements¹⁸

  In male team players, outdoor training with vitamin D supplements was linked to higher vitamin D levels.

• Concern

  Blood calcium levels²⁰

  In people with sarcoidosis, taking vitamin D was linked to more high blood calcium.

Study type not stated

• Benefit

  Body-wide health effects²¹

  Vitamin D helps the immune system, heart, hormones, and metabolism, and may play a role in depression, pain, and cancer.

• Benefit

  Immune system and autoimmune disease²²

  Vitamin D may help the immune system, and studies suggest it could play a role in autoimmune diseases like type 1 diabetes.

• Benefit

  Athletic performance²³

  Vitamin D seems very important for general health and for athletic performance.

• Open question

  Overall human health²⁴

  Vitamin D may help overall health, but scientists do not yet know whether its benefits and safety hold up.

• Benefit

  Gut health and calcium²⁵

  Vitamin D helps the gut absorb calcium and may also calm gut inflammation, but how this helps people is still unclear.

How it’s made and used

• Getting enough from diet²

  Vitamin D comes from sunlight on skin, plus foods like fish, mushrooms, eggs and fortified milk.

• Breastfed babies need supplements⁴

  Breast milk has little vitamin D, so breastfed babies may need extra vitamin D drops.

• Infant bone development⁷

  Babies who are breastfed may not get enough vitamin D, which can lead to weak bones.

• Bone and muscle health⁹

  Vitamin D levels vary worldwide with sun, skin colour, season and supplements, and low levels can cause weak bones.

• Global nutrition gap¹¹

  Vitamin D deficiency is a global problem, and many foods don't naturally contain enough vitamin D.

• Pregnancy complications¹³

  Not having enough vitamin D in pregnancy is linked to more miscarriages and early births.

• Skin health¹⁴

  Vitamin D is made in skin from sunlight and is used in creams for skin conditions like psoriasis.

• Sunlight and skin¹⁶

  In people, the skin makes about 90% of the body's vitamin D from sunlight, with diet and supplements as other sources.

• Nutrient knowledge and intake¹⁷

  Many college athletes took in less vitamin D than recommended, and those who knew more about vitamin D took in more.

• Babies missing nutrient target¹⁹

  Most babies in a national WIC study got less vitamin D than recommended, especially breastfed babies.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.