Vitamin D 101

November 25, 2009

Vitamin D 101

If you’ve been to your doctor’s office recently you have probably heard that many of us have Vitamin D deficiency these days. While some may blame the amount of sunscreen used or the lack of consuming dairy products, the reality is that Vitamin D, is the sunshine vitamin and we need more! The sun is setting earlier, is not as strong this time of year, and on top of that we tend to stay indoors to avoid the chilling cold of late fall and winter. But how are we supposed to obtain this essential ‘sunshine’ vitamin when nature is working against us?

Vitamin D refers to a group of fat-soluble vitamins that can be obtained through exposure to sunlight (ultraviolet B), by consuming certain foods, and supplements. In the summer months, most people meet their vitamin D needs through planned sun exposure, like laying out at the beach or unintentional sun exposure- like gardening, or exercising outdoors in a tee shirt. Various factors affect our body’s ability to produce vitamin D from sunlight including, season, geographic latitude, time of day, cloud cover, smog, skin melanin content, age, and sunscreen. Direct sunlight exposure for 15 minutes three times a week, despite the factors mentioned above, is thought to keep our body’s vitamin D stores at healthy levels. 

Few foods are natural sources of vitamin D. Salmon, tuna, sardines, mackerel and fish liver oils are the best sources, and vitamin D can be found in small amounts in beef liver, cheese, egg yolks and some mushrooms. Other foods have been fortified with vitamin D, thus do not naturally contain the vitamin, and include milk, some brands of orange juice, margarine, and yogurt. Breakfast cereals often contain around 10% of the daily recommended intake of vitamin D as well. The Food and Drug Administration recommends consuming 400 IU of vitamin D daily. 

So why do we need it? Vitamin D’s main and most well known role in the body is to aid in the absorption and regulation of calcium, and thus deficiency can result in a variety of bone disorders- rickets and osteomalacia result in bone softening which are the most extreme. Long term calcium and vitamin D insufficiency result in osteoporosis, which is characterized as a loss in bone mass and increased fragility; osteoporosis currently affects over 10 million Americans over 50. 

Research has also suggested vitamin D may aid in the reduction and protection from hypertension, cancer, and several autoimmune diseases- by modulating neuromuscular and immune function and helping to reduce inflammation. Vitamin D also helps control the cell life cycle, keeping good cells and getting rid of cells that are no longer necessary. Like all vitamins and minerals, vitamin D is important in maintaining optimal health. 

Like all vitamins and minerals, it is important to obtain at least the recommended daily intake or adequate intake through the consumption of whole foods. According to the 2005 Dietary Guidelines for Americans, "Foods provide an array of nutrients and other compounds that may have beneficial effects on health. In certain cases, fortified foods and dietary supplements may be useful sources of one or more nutrients that otherwise might be consumed in less than recommended amounts. However, dietary supplements, while recommended in some cases, cannot replace a healthful diet." For those who don’t consume the natural or fortified sources of vitamin D on a regular basis, or do not have a varied, balanced diet, supplementation is probably something to consider- consult your health care provider before making any changes.