RDA: The National Academy of Sciences established the following Adequate Intake (AI) levels for vitamin D in 1997: infants and children – 5 mcg; teenagers – 5 mcg; adults up to 50 years – 5 mcg; adults 51-70 years – 10 mcg; adults 70+ years – 15 mg; pregnant and lactating women – 5 mcg. Whitaker Recommendation: 400 IU. SONA recommendation: 300 IU.

What It Is: Vitamin D is not truly a vitamin for two reasons. First, our bodies can make it upon exposure to sunlight. Second, in its active form, it is considered to be a hormone. Specifically, it has hormone-like effects on mineral absorption, bone mineralization, and some secretions. Ultraviolet rays from sunlight make vitamin D by acting on an oily substance on our skin (ergosterol). The formation of the vitamin appears to occur on the skin rather than in it. Thus birds when they preen themselves remove oil on their beaks from their preen glands and spread it over their feathers, where it is exposed to the sun and activated. It is then either absorbed by the skin or scraped off the feathers by the beak and eaten. The fur of animals in a similar way appears to be the place where the vitamin is formed. All this suggests that the incessant “washing” of cats and rabbits is really a method of gaining vitamin D. The ultraviolet rays of the sun penetrate only some 0.1 mm to 1.2 mm through the skin, so that activation must occur close to the surface. This is one argument against too frequent or vigorous bathing, as hot soapy baths wash away the oils needed to form vitamin D. The various tissues of the body store vitamin D for periods from between 1 and 2 weeks (in the brain) to 8 to 12 weeks (in the blood plasma).

The early history of vitamin D is the history of rickets, a childhood disease characterized by improper bone development. It is a depressing history: a history of perfect clinical observation on the cure of the disease being forgotten again and again for a century and a half. Rickets suddenly became recognized as a definite disease by medical writers in the last half of the seventeenth century; the poor had probably been familiar with it for many years.

There are two forms of synthetic vitamin D: vitamin D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is manufactured artificially by irradiating ergosterol with ultraviolet light, thus “activating” it. Ergosterol is a sterol only found in plants, especially in the lower plants and fungi like that of ergot from which it derives its name. Animals neither make ergosterol for themselves nor absorb it from their food. Vitamin D3 is the vitamin formed and used by animals, and the only one as yet identified in fish liver oils. Both D3 and D2 become the active hormone vitamin D after passing through the liver and kidney. Adding the synthetic vitamin D2 to milk and milk products to prevent deficiency from lack of sunlight – to counteract heavily polluted areas, or areas with low periods of sunlight – is now a widespread practice. Because dairy products have been supplemented with this synthetic vitamin D2, rickets is now rare in the United States, but hardening of the arteries (atherosclerosis) is increasing. A few scientists think the increase may be due to excessive irradiated ergosterol (synthetic vitamin D2) in our diet. The 400 units of irradiated ergosterol added per quart is roughly sixteen times as much as was originally present in the raw unpasteurized milk.

Major Functions:

Blood and Bones. The specific function of vitamin D is to increase the affinity of the blood serum for calcium, so that a normal assimilation of that element will take place from the alimentary supply. This is essential for healthy teeth, bones, nervous system, proper thyroid function, and blood clotting ability. But another factor is required to unload that calcium from the blood into the tissues when it arrives at its destination, and that factor is termed the vitamin F complex. Each alone are only are half a vitamin.

Calcium Levels. Although typically categorized as a fat-soluble vitamin, vitamin D actually functions more like a hormone than a vitamin. Calcitriol, the most metabolically active form of vitamin D, works with the parathyroid hormone (PTH) to maintain proper levels of calcium in the blood. Low levels of calcium in the blood stimulate the secretion of parathyroid hormone from the parathyroid gland. PTH, then, stimulates the conversion of inactive forms of vitamin D to calcitriol. Calcitriol acts to increase the intestinal absorption of calcium, increase the reabsorption of calcium by the kidneys, and stimulate the release of calcium from the bone, thereby increasing blood calcium levels. Alternatively, when blood levels of calcium are high, calcitriol decreases the intestinal absorption of calcium and stimulates the bones to take up calcium, thereby decreasing blood calcium levels. Calcitriol also participates in the regulation of cell proliferation, differentiation, and growth, which suggests a role for this vitamin in the prevention and treatment of various cancers.

Immune Support. Recent research has revealed that, through a chain of events, vitamin D increases the production of a substance called cathelicidin in cells (that act like natural killer cells), neutrophils, and monocytes. These are the cells of your immune system that attack invading pathogens. The increased production of vitamin D and cathelicidin increases the immune system’s ability to fight off respiratory infections, and new research indicates it also triggers the production of natural antibiotic compounds locally that can fight wounds and skin infections. As well, children exposed to sunlight are less likely to get colds, and physicians who have given high doses of vitamin D to children who were constantly sick from colds and flu found the children were suddenly free from infection. Dark-skinned individuals, with their lower vitamin D levels, are more likely to die from influenza and pneumonia than lighter-skinned people are. Ever wonder why Flu Season occurs in the months following the winter solstice (the shortest day of the year), and disappears after the summer solstice (the longest day of the year)?  Vitamin D levels are at their lowest after the winter solstice and gradually increase until the summer solstice as do daylight hours.

Other Functions. Vitamin D, by increasing calcium absorption and favoring its retention and utilization by the body, can indirectly affect the mind. Adequate calcium is needed to relax nerves, induce sound sleep, and decrease sensitivity to pain. Vitamin D may be particularly needed by women during menopause, when calcium intake is usually low. Calcium and vitamin D supplements are usually effective in treating the hot flashes, night sweats, leg cramps, irritability, nervousness, and depression of a woman’s change of life. Vitamin D combined with calcium has been found to possess anti-cancer properties. In some people, low levels of vitamin D may increase blood pressure, suggesting that therapeutic levels may help regulate it. Vitamin D has also been found to play a role in the treatment of some immunological disorders such as multiple sclerosis and psoriasis. It may also improve muscle strength. Stimulation of growth, especially in children, is an important function of vitamin D.

Complementary Nutrients: Vitamins A, C, F (Essential Fatty Acids), Choline, Calcium, Phosphorus, Magnesium, Sodium.

Best Sources: Sunshine. Vitamin D is poorly represented in food. The only good sources are dairy produce and fish. Milk loses none of its vitamin D by boiling or pasteurization. Green vegetables do not contain active vitamin D. Precursors are found in yeast and plant foods, which must be acted upon by sunlight to become active. Mushrooms (150 IU), Butter (90 IU), Sunflower Seeds (90 IU). Vitamin D is contained in certain fats. It exists in butter if the cows have been grazing in the summer sunshine and eating the summer grass. It does not exist in butter during the fall and winter months. It exists to a certain degree in eggs when the chickens have been exposed to spring and summer sunshine, but does not exist in eggs laid during the winter months.

Other Good Sources: Fruit Sources: Papaya, red raspberry, rosehips. Herbal Sources: Alfalfa, chickweed, eyebright, fenugreek, mullein, watercress.

Destructive Agents: Anticonvulsants, barbiturates, cortisone, mineral oil, sleeping pills, smog. The bad effect of cereals, especially oatmeal, on rickets, has been known since Trousseau’s day (1865), though this is probably not true for Scotch oatmeal. Harrison and Mellanby have shown the action of cereals is due to their phytic acid combining with the calcium of the diet to form a compound that cannot be absorbed. The effect therefore of increasing the cereals in the diet is the same as decreasing the calcium. The phosphorus, of course, of the phytic acid is also lost when it combines with calcium.

Signs Of Deficiency:

Children and Youth. In children, vitamin D deficiency (rickets) is not uncommon in sunlight-deprived urban areas, where pollution blocks the sun. The well-known knock-knees and bowed legs have been known as signs for many generations. Other signs are changes in the shape of the head, producing a high broad forehead which is wide above the ears and bulges out over the temples, and “pigeon breast” in which the chest projects forward and comes to a point at the sternum. Infants deficient in vitamin D are tired, restless, fretful creatures. Stomachs are typically distended, partly because the intestines lack tone and are blown up by the carbohydrate fermentation from the faulty diet, and partly because the abdominal muscles are flabby. Joints are lax and fall into bizarre positions, and may be tender as well.

General Deficiencies. In adults, hypocalcemia (low level of calcium in the bloodstream), osteomalacia (reduction of the mineral content of the bone), and osteoporosis (reduction in total bone mass) are associated with vitamin D deficiencies. Lack of vitamin D leads to inadequate absorption of calcium from the gut and retention of phosphorus in the kidney, causing faulty mineralization of the bones. The bones become soft (osteomalacia), and the victim experiences rheumatic pains and exhaustion. If severe, the condition is fatal. Less extreme signs include restlessness, lack of vigor, low blood calcium and phosphate, decaying teeth, respiratory infections, irritability, constipation, burning sensation in mouth and throat, diarrhea, insomnia, myopia, poor metabolism.

Therapeutic Uses: Acne, alcoholism, allergies, arthritis, cystitis, colds, eczema, eye disorders, psoriasis, stress. Therapeutic dose of 500 to 1,500 IU/day.

Related Diseases: Sunstroke (acute toxicosis due to excessive Vitamin D activity, permitting lime salts to clog the kidneys). Slight headache or feeling of nausea indicate overexposure to sunshine and thus Vitamin D.
Toxicity From Overdose of Animal Or Synthetic Source: Toxicity level of 1,000 IU/day. All forms and preparations of natural and synthetic vitamin D are toxic when given in sufficiently large amounts. Vitamin D2 is definitely more toxic than vitamin D3, although sunlight in excess is a powerful, though delayed, poison which may cause not only severe sunburn, but also fever, headaches, nausea, loss of appetite, diarrhea, general malaise, fatigue, restlessness and shock. As these symptoms do not appear for some hours after sunbathing, no warning is given at the time that it has been too prolonged. Mild cases of hypervitaminosis – a condition caused by vitamin overdose – are treatable. However, doses of more than 1,000 international units can cause hypercalcemia (high levels of calcium in the blood). This can lead to calcium deposits in soft tissues, such as those of the kidneys, heart, lungs, and vascular system – deposits that may be irreversible. The use of vitamin D alone is very dangerous, may be fatal to babies, with the toxic effect being first noticed by vomiting after feeding or kidney irritation shown by blood or albumen in the urine. Vitamins A, B1 and F are the antidotes for this poison effect of excess vitamin D.