Q: As someone who works outdoors year-round and also spends time outdoors on weekends, is Vitamin D supplementation necessary when you factor in all that sun exposure plus what I get from food?
Great question. Vitamin D is often called the “sunshine vitamin” because our bodies can produce it when skin is exposed to UVB rays from the sun. In general, exposing about 25 to 30% of your body surface area (roughly your arms and legs) for 10 to 30 minutes a few times per week is usually enough for adequate vitamin D production. However, in New Brunswick this is dependent on the time of year. From October through March, the sun’s angle is too low for UVB rays to penetrate the atmosphere, so we cannot rely on sunlight as a source of vitamin D during these months.
Even between April and September, there are many factors that affect how much vitamin D the body can produce. The time of day makes a difference, with production most efficient between 10 a.m. and 3 p.m., and peaking between 12 p.m. and 2 p.m. Sunscreen, while essential for protecting against skin cancer, blocks the UVB rays needed for vitamin D production.
While touching on skin cancer, it is important to note that once the body has produced enough vitamin D, additional sun exposure will not raise levels further- it only increases the risk of sun damage. Skin tone plays a role as well, as fairer skin produces vitamin D more quickly, while darker skin requires longer exposure. As we age, our bodies naturally become less efficient at making vitamin D, and there are environmental conditions such as cloud cover, pollution, and smog that can further reduce production.
Diet can provide some vitamin D, but it is found naturally in very few foods. The richest sources are fatty fish such as salmon, trout, mackerel, sardines, tuna, and arctic char. Smaller amounts are found in egg yolks and liver. Most people get the bulk of their dietary vitamin D from fortified foods, where vitamin D has been added. Most milk and soft margarine products sold in Canada are fortified with vitamin D as well as certain breakfast cereals, orange juice, and some plant-based beverages like soy milk.
The recommended daily intake is 400 IU (international units) for infants up to one year of age, 600 IU for children and adults up to age 70, and 800 IU for adults over 70. Because most people do not consistently reach these levels from food alone, and because sunlight is not a dependable source for much of the year, both Health Canada and Osteoporosis Canada recommend routine vitamin D supplementation for most Canadians during the winter months.
Vitamin D is important because it helps the body absorb and use calcium, which is essential for building and maintaining strong bones and teeth. It also supports muscle function, which can improve balance, and it plays a role in keeping the immune system healthy. Low levels of vitamin D can contribute to osteoporosis (one in three women and one in five men will break a bone from osteoporosis) as well as muscle loss and weaker immune system defenses.
If this information prompts you to think about taking a vitamin D supplement, it is a good idea to check with your healthcare provider for personalized dosing recommendations. Depending on your age, medical conditions, and risk factors you may be advised to take a dose that is higher than the general recommended daily intake for vitamin D. Your dose also needs to be reflective of any other supplements you may take as many products such as multivitamins, calcium supplements, and immunity boosters already contain some vitamin D.
A question I do get asked quite frequently about vitamin D supplements is, “What’s the difference between D2 and D3?” The main difference is that D2 comes from plant sources, while D3 comes from animal sources. Most supplements use D3 because it tends to be a little more effective at raising and maintaining vitamin D levels in the body. It is also important to always take vitamin D supplements with a meal - the presence of fat in the gut will help to improve its absorption.
Erin Thompson (BSc, BScPharm) is a graduate of Dalhousie University and a community pharmacist practicing at Shoppers Drug Mart in Quispamsis N.B. Her opinions expressed in this column are published for educational and informational purposes only, and are not intended as a diagnosis, treatment or as a substitute for professional medical advice, diagnosis or treatment.