Humans evolved to make vitamin D (also known as the “sunshine vitamin”) provided that there is an adequate amount of UV light from sun exposure. But I don’t believe many of us are running around naked in equatorial Africa. So, it may not surprise you that many of us may be deficient, if we live, for example, in Northern climates like Canada where we are covered up over the winter months.
But does this one vitamin really matter that much? Yes, if you want to live longer.
Vitamin D is a fat-soluble nutrient, which means your body can store extra amounts of the vitamin. It is one of the micronutrients that is important for human survival. It comes in two major forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The two forms have identical metabolism and function, so the term “vitamin D” is used to represent both vitamins D2 and D3 unless specified.
Vitamin D is associated with a wide range of benefits and is best known for its role in bone health by helping our body absorb and use calcium and phosphorous. If that isn’t enough for you, recent research suggests vitamin D may also have benefits in immunity, assisting muscular function, reducing heart disease risk factors, and preventing diabetes, multiple sclerosis, and some types of cancers (particularly colorectal cancer). However, more research is still needed to fully understand the role of vitamin D in these conditions (Dietitians of Canada, 2013; Today’s Dietitian, 2014).
How do we get vitamin D?
Sunlight (UVB) is the most efficient source of vitamin D for people. If you (an adult) wear a bathing suit and get enough sun exposure to cause a slight pinkness to your skin, you would get the same amount of vitamin D as someone who ingests 20,000 IU of vitamin D (Today’s Dietitian, 2014). The angle of the sun, however, influences how much vitamin D can be produced from sun exposure. This is why vitamin D production is difficult for those living in Northern climates. Regardless of duration of exposure, the angle of the sun is too low during the winter months to produce any vitamin D in the skin.
Also, many health organizations warn against excess sun exposure because of the risk of skin cancer. As a result, many people are covering up and using high SPF sunscreen while outside, which reduces the amount of vitamin D produced by the skin. For example, an SPF 30 sunscreen reduces the body’s ability to synthesize vitamin D by at least 95% (Today’s Dietitian, 2014).
Given that many people can’t generate enough vitamin D from sun exposure, dietary sources should be considered. Dietary sources include both vitamin D3 from animal sources and vitamin D2 from plant sources. Interestingly, you may have heard that mushrooms make vitamin D when exposed to sunlight radiation; however, most mushrooms found in our grocery stores don’t have any because they’re grown in the dark.
How much vitamin D should I take?
Health Canada advises that adults over the age of 50 should take a vitamin D supplement of 400 IU each day. Supplements should, ideally, be taken with the largest meal of the day as this may enhance absorption.
While we wait for future research to clarify vitamin D’s role in the human body and the necessary intake to achieve optimal levels, we should aim for the recommended daily amount as the minimum intake that ensures maintenance of bone health and to stay below the upper limit. If you are looking for personalized recommendations, seek out a health professional or Registered Dietitian so they can consider lifestyle, environmental factors, malabsorption issues, medication use, genes, and other health conditions that can increase or decrease skin synthesis, metabolism, and usability.
Above all, enjoy the sunshine vitamin, my friends!
Article written by Courtney Chisholm, Registered Dietitian at World Health Calgary Place.