As Vitamin D is naturally present in very few foods, added to others, and can be hard to get safely in adequate amounts from the sun, it’s one nutrient that I tend to recommend as a supplement, and one that’s the focus of ongoing nutrition research.
Vitamin D not only enhances calcium absorption for bone growth and helps prevent osteoporosis, it has other important roles in the body such as boosting immune function (i.e. staving off the flu and more) and reducing the “I” word: Inflammation! (Read: increased risk for infection, heart disease, certain cancers, diabetes, and more.)
How much vitamin D do we need? The Recommended Dietary Allowance (RDA) is 600 IU (International Units) a day for people up to age 70, and 800 IU over 70.
Fatty fish such as salmon, swordfish, tuna, and mackerel are among the best sources of vitamin D, while small amounts are found in beef liver (40 IU per ounce), cheese (5 IU per ounce), and egg yolk (40 IU). Mushrooms are the only plant source of vitamin D, containing a precursor to the nutrient that’s converted to the active form when exposed to ultraviolet light, much like the response of our skin to sun exposure.
As most commercially cultivated mushrooms are grown indoors in the dark, they usually contain little vitamin D. In recent years, some growers are exposing mushrooms briefly to UV lamps after harvesting. These are typically labeled “UV-treated” or “high in vitamin D,” but you can do this with mushrooms you buy not labeled this way. Simply place the mushrooms with the “gills” (known as the lamellae) under the caps facing upward towards the sun. In just 15 minutes of direct sunlight, 3 ounces of mushrooms can produce 200-800 IU of vitamin D.
Wild mushrooms, most notably chanterelles, maitake (aka “hen of the woods”), and morels are typically rich in vitamin D because they naturally get sun exposure.
What’s in your daily diet?
Consider how often you might consume something like this in a single day:
· 3 ounces of swordfish or salmon = 400-500 IU
· 8 ounce of orange juice fortified with vitamin D = 137 IU
· 6 ounces of yogurt = 80-100 IU
· 3 ounces of UV treated mushrooms = 400 IU
Because dietary vitamin D is limited, and low levels in the body have been tied to significant health issues, nutrition research studies continue to focus on supplementing the diet with vitamin D. Most recently, obese subjects following a low-calorie diet were given either a placebo or a vitamin D supplement. After three months, subjects were tested for insulin sensitivity, or how well the body recognizes and responds to the insulin it produces so that it can clear glucose (sugar) from the bloodstream. In this study, insulin sensitivity improved only in the vitamin D takers.
Other recent research randomly assigned overweight or obese people with low blood vitamin D levels to take either a placebo or a vitamin D supplement. After four months, subjects who supplemented their diets with vitamin D showed a decrease in artery stiffness. We want arteries to be flexible so they can expand and contract to carry blood with oxygen and nutrients from the heart to the rest of the body.
Might you need a vitamin D supplement?...
...fortunately, they're readily available, inexpensive and easy to take :)