Any discussion of vitamin D must begin with the discoveries of the Canadian-born dentist Weston A. Price. In his masterpiece Nutrition and Physical Degeneration, Dr. Price noted that the diet of isolated, so-called "primitive" peoples contained "at least ten times" the amount of "fat-soluble vitamins" as the standard American diet of his day.2
Dr. Price determined that it was the presence of plentiful amounts of fat-soluble vitamins A and D in the diet, along with calcium, phosphorus and other minerals, that conferred such high immunity to tooth decay and resistance to disease in nonindustrialized population groups.
Today another Canadian researcher, Dr. Reinhold Vieth, argues convincingly that current vitamin D recommendations are woefully inadequate. The recommended dose of 200-400 international units (IU) will prevent rickets in children but does not come close to the optimum amount necessary for vibrant health.3
According to Dr. Vieth, the minimal daily requirement of vitamin D should be in the range of 4,000 IU from all sources, rather than the 200-400 currently suggested, or ten times the Recommended Daily Allowance (RDA). Dr. Vieth's research perfectly matches Dr. Price's observations of sixty years ago!
Vitamin D From Sunlight
Pick up any popular book on vitamins and you will read that ten minutes of daily exposure of the arms and legs to sunlight will supply us with all the vitamin D that we need.
Humans do indeed manufacture vitamin D from cholesterol by the action of sunlight on the skin but it is actually very difficult to obtain even a minimal amount of vitamin D with a brief foray into the sunlight.4,5
Ultraviolet (UV) light is divided into 3 bands or wavelength ranges, which are referred to as UV-C, UV-B and UV-A.6 UV-C is the most energetic and shortest of the UV bands. It will burn human skin rapidly in extremely small doses.
Fortunately, it is completely absorbed by the ozone layer. However, UV-C is present in some lights. For this reason, fluorescent and halogen and other specialty lights may contribute to skin cancer.
UV-A, known as the "tanning ray," is primarily responsible for darkening the pigment in our skin. Most tanning bulbs have a high UV-A output, with a small percentage of UV-B. UV-A is less energetic than UV-B, so exposure to UV-A will not result in a burn, unless the skin is photosensitive or excessive doses are used.
UV-A penetrates more deeply into the skin than UV-B, due to its longer wavelength. Until recently, UV-A was not blocked by sunscreens. It is now considered to be a major contributor to the high incidence of non-melanoma skin cancers.7 Seventy-eight percent of UV-A penetrates glass so windows do not offer protection.
The ultraviolet wavelength that stimulates our bodies to produce vitamin D is UV-B.
It is sometimes called the "burning ray" because it is the primary cause of sunburn (erythema). However, UV-B initiates beneficial responses, stimulating the production of vitamin D that the body uses in many important processes.
Although UV-B causes sunburn, it also causes special skin cells called melanocytes to produce melanin, which is protective. UV-B also stimulates the production of Melanocyte Stimulating Hormone (MSH), an important hormone in weight loss and energy production.8
The reason it is difficult to get adequate vitamin D from sunlight is that while UV-A is present throughout the day, the amount of UV-B present has to do with the angle of the sun's rays. Thus, UV-B is present only during midday hours at higher latitudes, and only with significant intensity in temperate or tropical latitudes.
Only 5 percent of the UV-B light range goes through glass and it does not penetrate clouds, smog or fog.
Sun exposure at higher latitudes before 10 am or after 2 pm will cause burning from UV-A before it will supply adequate vitamin D from UV-B.
This finding may surprise you, as it did the researchers. It means that sunning must occur between the hours we have been told to avoid.
Only sunning between 10 am and 2 pm during summer months (or winter months in southern latitudes) for 20-120 minutes, depending on skin type and color, will form adequate vitamin D before burning occurs.9
It takes about 24 hours for UV-B-stimulated vitamin D to show up as maximum levels of vitamin D in the blood. Cholesterol-containing body oils are critical to this absorption process.10 Because the body needs 30-60 minutes to absorb these vitamin-D-containing oils, it is best to delay showering or bathing for one hour after exposure.
The skin oils in which vitamin D is produced can also be removed by chlorine in swimming pools.
The current suggested exposure of hands, face and arms for 10-20 minutes, three times a week, provides only 200-400 IU of vitamin D each time or an average of 100-200 IU per day during the summer months.
In order to achieve optimal levels of vitamin D, 85 percent of body surface needs exposure to prime midday sun. (About 100-200 IU of vitamin D is produced for each 5 percent of body surface exposed, we want 4,000 iu.) Light skinned people need 10-20 minutes of exposure while dark skinned people need 90-120 minutes.11
Latitude and altitude determine the intensity of UV light. UV-B is stronger at higher altitudes. Latitudes higher than 30° (both north and south) have insufficient UV-B sunlight two to six months of the year, even at midday.12 Latitudes higher than 40° have insufficient sunlight to achieve optimum levels of D during six to eight months of the year.
In much of the US, which is between 30° and 45° latitude, six months or more during each year have insufficient UV-B sunlight to produce optimal D levels. In far northern or southern locations, latitudes 45° and higher, even summer sun is too weak to provide optimum levels of vitamin D.13-15 A simple meter is available to determine UV-B levels where you live.
Vitamin D From Food
What the research on vitamin D tells us is that unless you are a farmer, lifeguard or a regular sunbather, you are highly unlikely to obtain adequate amounts of vitamin D from the sun. The balance must be obtained from food.
So-called primitive peoples instinctively chose vitamin-D-rich foods including the intestines, organ meats, skin and fat from certain land animals, as well as shellfish, oily fish and insects. Many of these foods are unacceptable to the modern palate.
Fish make vitamin D from the precursor of vitamin D found in algae. In the higher mammals, vitamin D is made from precursors in lichen and green grass. Reindeer fat, for example, is a good source of vitamin D because reindeer feed on lichen.16
Vitamin D will be found in the butterfat of ruminant animals that feed on green grass, and in pigs that spend time in the sunlight. (Pigs resemble humans in that they convert sunlight to vitamin D.) Eggs will contain vitamin D if the chickens have obtained it from insects or fishmeal. Salmon must feed on algae in order to store vitamin D in their fat. Thus, modern farm-raised salmon are poor sources of this essential nutrient.
Modern diets usually do not provide adequate amounts of vitamin D2;17 because of the trend to lowfat foods and because we no longer eat vitamin-D-rich foods like kippers, tripe, chitterlings and lard. Deficiencies are therefore pervasive and widespread.
Food Sources of Vitamin D
USDA databases compiled in the 1980s list the following foods as rich in vitamin D. The amounts given are for 100 grams or about 3 1/2 ounces. These figures demonstrate the difficulty in obtaining 4,000 IU vitamin D per day from ordinary foods in the American diet. Three servings of herring, oysters, catfish, mackerel or sardines plus generous amounts of butter, egg yolk, lard or bacon fat and 2 teaspoons cod liver oil (500 iu per teaspoon) yield about 4,000 IU vitamin D-a very rich diet indeed!
Vitamin D Miracles
Sunlight and vitamin D are critical to all life forms. Standard textbooks state that the principal function of vitamin D is to promote calcium absorption in the gut and calcium transfer across cell membranes, thus contributing to strong bones and a calm, contented nervous system. It is also well recognized that vitamin D aids in the absorption of magnesium, iron and zinc, as well as calcium.
Actually, vitamin D does not in itself promote healthy bone. Vitamin D controls the levels of calcium in the blood. If there is not enough calcium in the diet, then it will be drawn from the bone. High levels of vitamin D (from the diet or from sunlight) will actually demineralize bone if sufficient calcium is not present.
Vitamin D will also enhance the uptake of toxic metals like lead, cadmium, aluminum and strontium if calcium, magnesium and phosphorus are not present in adequate amounts.18
Vitamin D supplementation should never be suggested unless calcium intake is sufficient or supplemented at the same time.
Receptors for vitamin D are found in most of the cells in the body and research during the 1980s suggested that vitamin D contributed to a healthy immune system, promoted muscle strength, regulated the maturation process and contributed to hormone production.
During the last ten years, researchers have made a number of exciting discoveries about vitamin D. They have ascertained, for example, that vitamin D is an antioxidant that is a more effective antioxidant than vitamin E in reducing lipid peroxidation and increasing enzymes that protect against oxidation.19;20
Vitamin D deficiency decreases biosynthesis and release of insulin.21 Glucose intolerance has been inversely associated with the concentration of vitamin D in the blood. Thus, vitamin D may protect against both Type I and Type II diabetes.22
The risk of senile cataract is reduced in persons with optimal levels of D and carotenoids.23
PCOS (Polycystic Ovarian Syndrome) has been corrected by supplementation of D and calcium.24
Vitamin D plays a role in regulation of both the "infectious" immune system and the "inflammatory" immune system.25
Low vitamin D is associated with several autoimmune diseases including multiple sclerosis, Sjogren's Syndrome, rheumatoid arthritis, thyroiditis and Crohn's disease.26;27
Osteoporosis is strongly associated with low vitamin D. Postmenopausal women with osteoporosis respond favorably (and rapidly) to higher levels of D plus calcium and magnesium.28
D deficiency has been mistaken for fibromyalgia, chronic fatigue or peripheral neuropathy.1;28-30
Infertility is associated with low vitamin D.31 Vitamin D supports production of estrogen in men and women.32 PMS has been completely reversed by addition of calcium, magnesium and vitamin D.33 Menstrual migraine is associated with low levels of vitamin D and calcium.81
Breast, prostate, skin and colon cancer have a strong association with low levels of D and lack of sunlight.34-38
Activated vitamin D in the adrenal gland regulates tyrosine hydroxylase, the rate limiting enzyme necessary for the production of dopamine, epinephrine and norepinephrine. Low D may contribute to chronic fatigue and depression.39
Seasonal Affective Disorder has been treated
successfully with vitamin D. In a recent study covering 30
days of treatment comparing vitamin D supplementation with
two-hour daily use of light boxes, depression completely resolved
in the D group but not in the light box group.40
High stress may increase the need for vitamin D or UV-B sunlight and calcium.41
People with Parkinsons and Alzheimers have been found to have lower levels of vitamin D.42;43
Low levels of D, and perhaps calcium, in a pregnant mother and later in the child may be the contributing cause of "crooked teeth" and myopia. When these conditions are found in succeeding generations it means the genetics require higher levels of one or both nutrients to optimize health.44-47
Behavior and learning disorders respond well to D and/or calcium combined with an adequate diet and trace minerals.48;49