Vitamin D has gotten a lot of press in the past decade. It is a fat soluble vitamin that has the properties of a hormone as well. Some of its complex functions in the body include: a role in the absorption and use of phosphorus and calcium, development of bones and teeth (especially in children), regulation of heart rate, maintenance of muscle mass, reducing inflammation, regulation of blood sugar, immune function, thyroid function and normal blood clotting. Because of its extensive role, maintaining normal levels of vitamin D is important in preventing diseases like osteoporosis, osteoarthritis, heart disease, and possibly diabetes. Recent research suggests that insufficient levels of this vitamin can even increase the risk for certain cancers and autoimmune diseases. People with medical conditions may be prone to vitamin D deficiencies: those with kidney disease, those with absorption disorders (like Crohn’s disease), and the obese.
There are a few different types of vitamin D. D2 (ergocalciferol) can be found in food sources, but it must be converted by the liver and kidneys before it can become fully available for use. Food sources of vitamin D2 include: cod liver oil, salmon, mackerel, tuna (and other fatty salt water fish), fortified milk and cereals, liver, egg yolks, oysters, sweet potatoes, mushrooms, parsley, alfalfa, and nettles. Vitamin D3 (cholecalciferol), on the other hand, is made when the skin is exposed to sunlight (a reaction to the sun’s UV rays- a cholesterol in the skin converts to a vitamin D precursor). D5 is a synthetic form of vitamin D.
The majority of people in this region have low vitamin D levels at this time of year due to lack of sun exposure. Nowadays, even during summer months, people may have low vitamin D because they wear sunscreen which prevents them from absorbing the UV rays. I often find patients who complain of fatigue, mental fogginess and depression discover they have low vitamin D levels after receiving a simple blood test (the “25-hydroxy vitamin D test”). Many physicians now routinely check levels of this vitamin (the range is roughly 30-80ng/mL) and will suggest a dosage from 500-2000IUs of a D3 supplement per day if a patient is under the target range. However, as this vitamin is fat soluble, it can cause toxicity if taken in excess, so regular blood tests should help monitor and determine whether supplementation is appropriate. Another way to increase your vitamin D levels is to expose your skin to the sun without sunscreen for a short period of time- say, 15 minutes 3 times per week. If you have dark skin, you may need more exposure to achieve the same effect.