Why Vitamin D Is So Important

Have you gotten your recommended daily dose of the “sunshine vitamin”? It’s estimated that one billion people worldwide have a vitamin D deficiency, and it’s present in all ethnicities and age groups. Vitamin D has been linked to bone health, as well as immune support, heart health, and decreasing the risk of other diseases. Our bodies naturally form vitamin D after direct exposure to sunlight, but it can also come from vitamin D–rich foods like egg yolks or fish.

What Is Vitamin D?

According to the National Institutes of Health, Vitamin D, also known as calciferol, is a fat-soluble vitamin naturally found in some foods, added to others, and available as a dietary supplement. Vitamin D synthesis is also triggered in our bodies when skin is directly exposed (not just through glass) to ultraviolet-B (UVB) rays from the sun.

Vitamin D and Health

Vitamin D is essential for health, especially for building strong bones, immune system function, and protecting against diseases such as cancer. Almost every cell in your body has a receptor for vitamin D.

  • Strong bones and muscles: Vitamin D helps your body absorb calcium and phosphorus, which are key building blocks for healthy bones. Nerves also need vitamin D to carry messages throughout the body and muscles need it to move. 
  • Immune support: Vitamin D helps regulate the immune system to fight off bacteria and viruses that enter your body. 
  • Heart health: Vitamin D deficiency can increase blood pressure, which can lead to cardiovascular disease.    
  • Disease prevention: Many studies have linked vitamin D deficiency to higher risk for Type I and II diabetes as well as some cancers and other diseases.

Vitamin D Deficiency

Research suggests that vitamin D deficiency is common in children. For children, severe vitamin D deficiency can cause delays in growth or rickets, which is a disease where bones become soft. Lack of enough vitamin D could also be linked to several chronic diseases, including cardiovascular disease and cancer. Vitamin D levels fluctuate in many people depending on where you live and access to sunlight year-round, which is why it’s important to include it in your diet. According to a study by NIH, “About 50% to 90% of vitamin D is absorbed through the skin via sunlight while the rest comes from the diet. Twenty minutes of sunshine daily with over 40% of skin exposed is required to prevent vitamin D deficiency.”

How Do I Get Vitamin D?

Vitamin D has two forms, D2 and D3, both of which are naturally occurring through UVB rays and available in dietary supplements and naturally in some food. D2, or ergocalciferol, is found in certain mushrooms, while D3 can be found in oily fish (salmon, tuna, mackerel), fish liver oil, cheese, and egg yolks. 

In the United States, some foods are fortified with vitamin D, including milk, breakfast cereal, and some orange juice, yogurt, and milk-alternative drinks. Breast-fed infants are usually prescribed vitamin D supplements.

How Much Vitamin D Do I Need?

Infants to adults should have an average daily intake of 400–800 IU, or 10–20 micrograms. Here are the Institute of Medicine’s recommendations for daily vitamin D intake (assuming the person gets no vitamin D from sun exposure):

  • Infants, age 0–6 months: adequate intake, 400 IU/day; maximum safe upper level of intake, 1,000 IU/day
  • Infants, age 6–12 months: adequate intake, 400 IU/day; maximum safe upper level of intake, 1,500 IU/day
  • Age 1–3 years: adequate intake, 600 IU/day; maximum safe upper level of intake, 2,500 IU/day
  • Age 4v8 years: adequate intake, 600 IU/day; maximum safe upper level of intake, 3,000 IU/day
  • Age 9–70: adequate intake, 600 IU/day; maximum safe upper level of intake, 4,000 IU/day
  • Age 71+ years: adequate intake, 800 IU/day; maximum safe upper level of intake, 4,000 IU/day