Vitamin D seems to have made its way back into the nutrition spotlight in recent years and is becoming an increasingly hot topic when it comes to adequate intake and possible benefits from supplementation.
The suggested Adequate Intake (AI) according to the U.S. Dietary Guidelines is currently 5 µg/day (200 IU/d) for 19-50 year-olds but given recent findings, it is likely that this number will be raised. Professor Diane McKay at Tufts Friedman School of Nutrition Science and Policy predicts that the recommended amount may soon double or triple. For adults over age 50 the current AI is double that for younger adults and for adults over 70 the AI is tripled due to increasingly poor absorption and reduced intake. Vitamin D is a fat-soluble vitamin. Toxicity can not be reached by sunlight exposure or through food but can be reached if you take too much in supplement form. Currently a maximum of 2000 IU/day is considered the safe upper limit (so if you took the Sunny Gummies shown left, you should never take more than 2 gummies/day).
While most vitamins can and should be obtained through foods rather than supplements, vitamin D may be an exception. That is not to say that it isn’t worth trying. The best food sources of vitamin D are generally fatty fish, fortified dairy products, and some fortified breakfast cereals. Oily fish (such as salmon or sardines) are considered some of the best food sources of vitamin D. Because of differences in the fishes’ diets, wild caught salmon contains much higher levels of vitamin D than the farm raised variety. You can view a comparison from one study of vitamin D levels from several common fish varieties here.
While milk is often a good source of vitamin D, this is because it has been fortified. Milk products such as yogurt or cheese are only good sources of vitamin D if they are made with fortified milk. I was looking at two type of non-fat plain yogurt from the same brand recently and was trying to figure out what made the “European” style yogurt different from the regular version. Both products were organic and were the same price but I noticed that the European version, like Greek yogurt, had a much higher protein content and lower sugar content. It appeared to be the nutritionally superior product until I realized that the non-European version was the only one fortified with vitamin D. Because I am currently regularly taking a vitamin D supplement, I decided that that the high-protein, low sugar European version was still my best pick. If I wasn’t taking the supplement however, I think it would be worth the extra sugar to me to get the added vitamin D.
Why is Vitamin D So Important?
Maintaining adequate vitamin D intake has been linked to reduced risk for many of the chronic diseases that plague the U.S. today. Getting enough vitamin D is also imperative to help calcium be utilized properly in the body to keep bones strong and help prevent osteoporosis. Some studies now suggest that vitamin D may actually be more important that vitamin C in aiding the immune system to help protect us from a cold or the flu.
The “Sunshine” Vitamin
Vitamin D is sometimes referred to as a “conditional” vitamin because, unlike other vitamins, you can actually get enough of it without food sources or supplements with sufficient exposure to UV light from the sun. Sunscreen, clothing, time of year and distance from the equator, however, often prevent sufficient vitamin D levels from being obtained from the sun. In Boston, for example, it is suggested that even prolonged sun exposure will not be enough to provide adequate vitamin D intake during the months of November through March.
Before you hop in a tanning bed or head to the beach without sunscreen, keep in mind that the damage you can cause from prolonged UV exposure will be greater overall than the benefit. During optimal times of the year (for Boston this is generally March through October), it only takes 10-15 minutes of sun exposure 2 or 3 times/week (even just on the arms, face, and hands) or about 30 minutes 2 to 3 times per week for individuals with darker skin to reach high enough vitamin D levels.