Vitamin D: The Sunshine Vitamin


Now that the long days of summer are gone, it’s more important than ever to focus on getting enough Vitamin D. The National Health and Nutrition Examination Survey found that over 40% of the U.S. population was deficient in vitamin D. That’s a really large number! 

So why is Vitamin D so important? Most of us recognize Vitamin D as being critical for bone growth, which it is. Vitamin D aids in the absorption of calcium and phosphorus, helping to form and maintain strong bones. When you don’t get enough Vitamin D, it puts you at risk for diseases such as rickets in children and osteomalacia in adults. That’s why the government started fortifying milk with Vitamin D in the 1930s- rickets was a major health problem at the time. But Vitamin D is not just important for healthy bones- it actually has several other important functions in the body including maintaining a healthy immune system and modulating proper cell growth. Recent studies have linked Vitamin D deficiency to cardiovascular disease, osteoporosis, autoimmune disease and several types of cancer.

Vitamin D is sometimes referred to as the Sunshine Vitamin because our bodies produce it when our skin is exposed to sunlight.  Exposure to ultraviolet rays specifically triggers the conversion of cholesterol in the skin to Vitamin D3, a form of Vitamin D. We’ve all been taught to use sunscreen to prevent the harmful effects of exposure to UV rays but all of this sunscreen use has led to another problem- Vitamin D deficiency. Sunscreen blocks the absorption of UV rays- correctly applied sunscreen reduces our ability to absorb Vitamin D by more than 90%.

So how much Vitamin D do you need? Currently there is a lot of scientific debate over what the optimal amount of Vitamin D is. The official Recommended Dietary Allowance (RDA) in adults is 600 International Units (IU) per day and 800 IU for those over age 70. But many groups including Harvard’s School of Public Health are recommending much larger amounts based on the most current research.

What are the best ways to get an adequate amount of Vitamin D? The best way is through exposure to sunlight. Just 10-15 minutes of sunlight exposure can provide 3,000-20,000 IU!  The problem is that the amount of Vitamin D that we get from sun exposure varies considerably depending on several factors including geographic latitude and skin color. Sunlight is generally weaker in Northern latitudes, leading to less Vitamin D synthesis. Also, people with darker skin tones generally need a lot more sun exposure to synthesize Vitamin D as melanin reduces the skin’s ability to produce Vitamin D from sunlight. Of course, it is important to also protect our skin from the harmful effects of sun exposure, which leads to millions of cases of skin cancer every year in the US. To further complicate the issue, there are relatively few natural food sources of Vitamin D. The best sources are fatty fish like salmon, tuna, sardines and mackerel. Canned fish generally has more Vitamin D than fresh. Small amounts of Vitamin D are also found in egg yolks, beef liver and some cheeses. In fact, an analysis done by the USDA found that eggs contain 64% more Vitamin D than the last time they were analyzed by the government in 2002. This increase is probably due to changes in the diet of chickens by egg producers. In addition to natural food sources, many cereals, milk and dairy products are also fortified with Vitamin D. The US also mandates the fortification of infant formula with Vitamin D. Mushrooms also can be a source, especially if treated with UV rays during growth.  

If you are concerned that you are still not getting enough Vitamin D through sun exposure and food sources, you can always take a vitamin supplement.  Most multivitamins provide about 400 IU of Vitamin D.

So what’s the take home message with Vitamin D? Vitamin D is very important for the body and the more we learn about it, the more true this seems to be.  If you’re concerned about Vitamin D deficiency, consult your physician and get tested.  Try to get brief periods of sun exposure daily, but after 5-15 minutes, make sure you apply sunscreen. To get the rest of your daily needs, incorporate natural food sources into your diet and if needed add a vitamin supplement.

Sonali Ruder, DO is a board-certified Emergency Medicine physician, trained chef, mom, and cookbook author. She is a graduate of Brown University, Midwestern University- Chicago College of Osteopathic Medicine, and the Institute of Culinary Education. Dr. Ruder is a contributing writer, recipe developer, and health and wellness expert for several national magazines, cookbooks, and websites. She is the founder of The Foodie Physician website and the author of several cookbooks including the Natural Pregnancy Cookbook and Natural Baby Food.