We buy that bottle of vitamin D, guessing at the potency, simply because we are told to do. But why? We know it has something to do with the lack of sun, but do we really understand why we need this vitamin, or what it does to promote health?
Vitamin D has been shown to help with thyroid issues, psoriasis, muscle weakness and kidney problems. But its primary role is to regulate calcium and phosphorous, in order to build healthy bones. Part of this job of regulating calcium is to aid in absorption and maintain healthy calcium, phosphorus and other mineral levels in our blood. We are often told we need calcium for strong bones, but if our levels of vitamin D are low, we will not absorb calcium in a way that supports this. Rickets, a severe form of vitamin D deficiency, results in the softening of bones. This lack of vitamin D in the blood causes calcium and phosphorous to leach from the bones to maintain the amounts needed to sustain life. This is why vitamin D is so important: if we don’t have the right blood levels, we cannot build strong bones.
Vitamin D is actually made in our skin when we are exposed to the ultraviolet rays of the sun. Egg yolks, butter, oily fish, and especially cod liver oil, also contain vitamin D, but food has never been our primary source. So how do you know if you are low in vitamin D? Until recently, research on vitamin D deficiency has been primarily in its relation to rickets prevention. Since vitamin D is a fat-soluble vitamin, which means we store it, there is also a concern for its potential toxicity.
Recent studies revealed an increasing problem of low levels of this vitamin in our population. No one has been able to narrow in on the culprit, as there are many factors that could contribute to this problem. Skin type plays a part, as those with darker skin do not absorb D as well as those with lighter skin. Location is a factor, as it has been noted that if you live above the 37th parallel (that would be us northerners) the sun does not rise high enough in the sky to provide adequate levels between the months of November through March. Exposure to the mid-day sun for 15 minutes, 3 times a week, should provide adequate levels, yet our increasing amount of time spent indoors could be playing a role in this as well. The reality is that we are all very different as to how long we store vitamin D or how well we absorb it from our food or supplementation. The only way to truly know is to have a physician test your vitamin D levels. However, this will only give a small snapshot in time, as the body is in constant flux.
To maintain healthy vitamin D levels in the dead of winter we must not ignore the benefits of a healthy diet. Eat plenty of fish (also an excellent source of Omega-3’s) and eggs. Consider a few plant sources, such as mushrooms or dark, leafy greens.
Supplementation is an option, too. Vitamin D supplements are readily available and are typically taken in a soft gel pill form. Look for vitamin D3 as this is the natural form your body produces and utilizes from the sun. Potencies range from 400IU (the recommended daily allowance is 600IU) to 10,000IU. Cod liver oil is another excellent supplement as this source contains some of the highest levels of naturally occurring vitamin D.
To further understand vitamin D’s role in our lives, it helps to look to cultures that have survived climates colder and darker than ours, such as the natives of the Arctic. They ate a wide variety of sea and land mammals. Caribou, seal, whale, walrus, geese, ducks and fish. Vegetables and fruit including wild greens, seaweeds, and berries were eaten fresh and collected and preserved for the winter. It takes 25,000 years for a genetic adaptation to appear in the human population. With the amount of time spent indoors on the rise, maybe someday we will adapt a need for less vitamin D, or we will be able to acquire more from our food.