The main source of vitamin D in many parts of the world is moderate sun exposure. However, here in the Northwest, the sad truth is that it’s probably not possible to get enough vitamin D from sunlight during the winter. This is especially true for people with dark skin, because they require even more sun exposure to synthesize an adequate amount of vitamin D.
Portlanders are not alone in our dearth of D: vitamin D deficiency is very common in North America. Well over half of the patients admitted to U.S. hospitals have frank vitamin D deficiency. A deficiency of this vitamin (which is actually a hormone) is associated with increased risk of weak bones and muscles, chronic pain, many autoimmune diseases, multiple sclerosis and diabetes.
Vitamin D and cancer risk
Vitamin D levels take on special significance for people at risk for developing cancer. This hormone is one of the most potent factors regulating cell growth. A deficiency of D is associated with a greater incidence of (and mortality from) some of the most common cancers, including breast, colon and prostate cancer. For cancer patients who are at risk of osteoporosis from taking corticosteroids or other hormonal cancer treatments, getting adequate vitamin D may be even more important to preserve bone and muscle health.
Food sources of vitamin D
The best food sources of vitamin D are fatty fish (such as salmon, mackerel and sardines), cod liver oil and fortified foods (such as some cereals, milk and yogurt products). It's worth noting that wild salmon has more vitamin D than farmed salmon. However, even with these foods in your diet, most people need to take a vitamin D supplement as well. Typically, we suggest a supplement of at least 1000 IU daily.
Try this recipe from Good Food, Great Medicine for kedgeree (tuna and rice), which can be prepared easily during winter months. Tuna is a great source of fat-soluble vitamins A and D. It's also a fish that is rich in omega-3 fatty acids, which have been demonstrated to significantly reduce the risk of heart disease.
