The two main forms of vitamin D found are D2 and D3. D3, also referred to as cholecalciferol, is the type that your body naturally produces when your skin is exposed to sunlight. Vitamin D2 (ergocalciferol) has been shown in some studies to be as effective, yet it is created from plant sources and is therefore not as close to the form humans are most used to utilizing. Vitamin D is needed in conjunction with calcium to keep bones healthy.
In order for your body to produce the adequate amount of D3 each day, it is suggested that fair-skinned individuals have their skin exposed to the midday sun for 10 minutes in a tank top and shorts, WITHOUT sunscreen (as this blocks the UVB rays that need to get absorbed by your skin). Darker skinned individuals can require up to 6x this amount of exposure! For those of us stuck in the Midwest during longer winters, supplementation is recommended about 1,000-1,300 IU's (international units) per day. If you are already low, taking two 2500 IU tablets each day for 2 weeks and then dropping down to 1 of these 2500 IU tablets daily really helps.This is readily available over the counter and typically Vitamin D3 is easier to find, as it is more highly recommended than vitamin D2. The elderly population also has a higher tendency to be low of vitamin D, so supplementation is even more important.
Not only is vitamin D vital to healthy, strong bones, but it also protects against heart disease and cancers of the breast, prostate and colon. It also protects against depression, insomnia, and an overactive immune system.
So while we await the snow to melt (and stop coming down), consider a vitamin D supplement! To read more about good nutrition, read here! Getting out in the sun after those cold months also helps a lot --- or take a vacation somewhere sunny :) Your doctor said so.