Vitamin D and Light

Vitamin D and Light

There are rumblings in the health field about a nationwide deficiency of Vitamin D. Physicians and other health professionals on a botanical medicine list-serve that I am on have been finding low levels in their patients. This issue is of some concern, as low Vitamin D levels are related to a number of health conditions. Optimum levels of Vitamin D in the body (in the form of cholecalciferol) are clearly associated with protection against a number of common diseases, including diabetes, osteoporosis, osteoarthritis, hypertension, cardiovascular disease, metabolic syndrome, depression, MS, and cancers of the breast, prostate, and colon.¹

It is especially important for our bones, as Vitamin D is necessary to absorb calcium from the small intestine, as well as in the assimilation of phosphorus.

This fat-soluble vitamin is actually more like a hormone, as it is synthesized by the body itself. The action of sunlight on a cholesterol derivative in the skin oils prompts the formation of a precursor, provitamin D, which then is absorbed through the skin back into the body, and goes to the liver for initial processing, and then to the kidneys which produce the active Vitamin D3, also called cholecalciferol, it in its final form, a process that takes about 36 hours. Vitamin D from food sources is absorbed through the intestines in the company of essential fatty acids. NOTE: This means that a low fat diet could be damaging to the bones!

Interestingly, sufficient Vitamin D also prevented falls, which are a major risk for fractures. In a review paper in the April 2004 Journal of the American Medical Association it was determined that a daily intake of 400 IU or more resulted in a 20% reduction in the likelihood of being injured in a fall. This may be because Vitamin D appears to strengthen the thigh muscles, which are crucial for gait and balance.²

The body stores significant reserves of this vitamin in the liver, spleen, bones, and brain, which is helpful in areas where there is little sun in the fall and winter – and which explains why Northern people are so anxious in the summer about getting “a tan”, which is more likely a way to replenish body stores of this important substance.

We do take it totally for granted, but natural light is as much a nutrient as food and water. Given enough sunshine, people need no Vitamin D from foods. In the absence of enough sun, as in Northern climates, foods need to make up the lack, or in the final instance, one can resort to supplementation. According to a 2004 review study in the journal Alternative Therapies in Health and Medicine by Alex Vazquez and others, the original upper limit for safe intake of Vitamin D was set too low, at 2,000 IU per day, or 50 μg. It is now believed that the physiological requirement may be as high as 5,000 IU daily.

With sunlight, the endogenous production of this “vitamin”, which is really a hormone, can be as high as 20,000 IU with full-body sun exposure in areas around the Equator. The natural exposure is preferable, as the body will make what it needs and no more, thereby avoiding toxicity. Therefore, the best source for natural Vitamin D, which will prevent excesses, is daylight, or sunlight whenever possible, while avoiding sunburn. It is possible to accumulate Vitamin D in the tissues during the season with high amounts of sunlight, which will be stored and then can be used up slowly during the darker months. It should be remembered that Vitamin D is fat soluble, so it is important to have sufficient good quality fats in the diet in order to be able to store it for the winter months.

An excess of supplemental Vitamin D — now measured by serum blood levels in excess of about 80 μg per milliliter of blood – can be seriously toxic, causing calcification of soft tissues and of the walls of the blood vessels, heart tissues, lungs, and kidney tubules, a condition known as “hypercalcemia” or “milk-alkali syndrome.” Hypercalcemia is a serious condition, as it can result in calcium deposits in the soft tissues and organs, and arteriosclerosis, sometimes within a day or two of exposure. In one unusual case in New England in the early ‘90’s and reported in the New England Journal of Medicine, some infants developed this condition from excess Vitamin D fortification of milk through a measuring error at the dairy: instead of the standard 400 IU per quart, the concentration in some samples went as high as 232,565 IU per quart. In the case of these infants, this excess caused hardening of the cranial bones and premature closing of the fontanel, which resulted in irreversible brain damage.

According to Michael F. Holick, the director of the Vitamin D, Skin and Bone Research Laboratory at Boston University Medical Center, about 30 to 40% of the people who get hip fractures are vitamin D-deficient. In an interview published inNutrition Action, the health letter of the Center for Science in the Public Interest, he pointed out that regardless of the amount of calcium consumed, this deficiency accelerates bone loss and increases the risk of fractures.

To prevent Vitamin D deficiency, Dr Holick recommended walking with face, hands and arms exposed to the sun, or at least to daylight, three or more times a week, for about half the time it would take for one to get sunburned, or between 10 and 20 minutes, depending on the person’s skin, the season, and the distance from the Equator. The best time of day for this would be between nine a.m. and four p.m. in the winter, and between eight a.m. and five p.m. in the summer.

Most importantly, Dr Holick recommended this exposure to the sun be without sunscreen, as sunscreen interferes with the production of Vitamin D. Remember this:
A sunscreen with SPF (Sun Protection Factor) of 8 gives you only 5% of your normal the Vitamin D production; any SPF higher than that insures you get NONE.

About 50-60% of the American public is deficient in Vitamin D. The liberal use of sunblock is partly to blame for this situation

Food sources

Vitamin Dз in foods is found mostly in fish oils. It can also be made synthetically by ultraviolet light irradiation of a derivative of cholesterol. Vitamin D 2 is a different synthetic form, known as ergocalciferol. The Vitamin D added to milk, a practice begun in the 1930’s to prevent rickets, can be either one of those two synthetic forms. However, according to studies published in the New England Journal of Medicine in 1991 and 1993, seven out of ten samples of milk contained less than 80% of the amount listed on the label, five didn’t even have 50%, and 14% of the skim milk samples had no Vitamin D at all.

Cod Liver Oil is the classic Vitamin D source that has been used for generations in Northern Europe, where there is little sun and therefore much less opportunity to obtain this nutrient.


1) Grind a teaspoon to tablespoon of flax seeds in a coffee or spice grinder once a day. Add just before serving to porridges, grains, breads, or even drinks. According to Paul Stitt, a biochemist and author of Beating the Food Giants, the regular consumption of flax seeds increases vitamin D levels as well as the retention of calcium, magnesium, and phosphates, which is all good news for the bones.

2) Consume wild ocean fatty fish such as mackerel and salmon (make sure to eat the skin!), as well as caviar or fish eggs. Try salmon caviar or the Greek taramasalata; two or three servings per week are quite sufficient.

3) If you have little exposure to the sun, in whatever season, don’t neglect cod liver oil. A teaspoon per day should be enough.

4) There are vitamin D precursors in plant foods and leafy greens, known as ergosterols; parsley is a particularly rich source. So are mushrooms. I found from my nutritional software (ESHA Research) that 1½ ounces cooked shiitake mushrooms contain 69% of the vitamin D RDA’s for a 55-year old woman).

So — eat lots of fatty ocean fish, parsley, and shiitake mushrooms, take a walk in the sun, and use plenty of good quality olive oil and other healthful fats to keep enough vitamin D in your body for your health and wellbeing!


1. Vasquez A, Manso G, Cannell J. The clinical importance of vitamin D (cholecalciferol): a paradigm shift with implications for all healthcare providers.Altern Ther Health Med. Sep-Oct 2004;10(5):28-36; quiz 37, 94.
2. Bischoff-Ferrari HA, Dawson-Hughes B, Willett WC, et al. Effect of Vitamin D on falls: a meta-analysis. Jama. Apr 28 2004;291(16):1999-2006.