Answers to your questions about gardening, energy, homesteading and other sustainable living topics.
I’ve read that most people don’t get enough vitamin D. How much do we really need, and what are the best sources of vitamin D?
A 2009 study published in The Journal of the American Medical Association found that 75 percent of adolescents and adults in the United States have insufficient levels of “the sunshine vitamin” in their blood. Our bodies convert the sun’s ultraviolet rays to vitamin D, but because many of us work mostly indoors — and often apply sunscreen when we do spend prolonged time outside — our exposure to vitamin D-producing rays is low.
In 2010, the Institute of Medicine increased its official recommended daily dietary allowance for vitamin D from 200 international units (IU) to 600 IU. Some experts, however, think our daily intake should be much higher. The Vitamin D Council recommends 5,000 IU per day for adults — more than eight times higher than the official recommended daily allowance.
So why do we need this nutrient? Vitamin D is commonly associated with bone health because it helps the gut absorb calcium, which is the building block for strong bones. Vitamin D also activates genes that regulate the immune system, and a growing body of research suggests this important nutrient plays a role in the prevention of colon, prostate and breast cancers; high blood pressure; and diabetes. Seasonal Affective Disorder — which often strikes during winter, the darkest time of the year — has also been linked to low levels of vitamin D.
Most people are able to meet at least some of their vitamin D needs through exposure to sunlight. The amount of time needed in the sun varies greatly from person to person, and the variables include skin type, the amount of skin exposed, your age, the time of day and the season. Aim to find a balance between soaking up vitamin D-rich rays and protecting your skin from sun damage.
Stacked up against the sun’s rays, most foods aren’t rich sources of vitamin D — but mushrooms are an exception. When exposed to sunlight for a day or two (but no longer), their vitamin D levels soar from about 100 IU per 100 grams up to an incredible 46,000 IU per 100 grams! So, before you cook your mushrooms, give them their day in the sun. You can also take a cue from the mushroom experts at Fungi Perfecti and make a mushroom-based “sunshine” pill at home.
If you can’t spend time outside and don’t eat mushrooms, consider a vitamin D supplement. Two types of vitamin D supplements are available over the counter: D3 and D2. The D3 supplements are superior, because our bodies naturally produce D3 and are more receptive to absorbing and retaining it.