Chemistry of the vitamins D

The term vitamin D refers to a group of seco-steroids the common feature of which is a conjugated triene system of double bonds. The first two examples of this group of substances were ergocalciferol (vitamin D2); and cholecalciferol (vitamin D3); and were notable for their anti-rickets activity.

Ergocalciferol has tended to be commercially more important than cholecalciferol, being favored by the pharmaceutical and food additive industries because of the ready availability of its precursor, ergosterol. However, the substance with anti-rickets activity occurring naturally in animals is cholecalciferol. The term vitamin D was first applied to this group of substances in 1925 by McCollum and his colleagues when they were successful in resolving the anti-xerophthalmic activity of the lipid extracts of certain fats from the anti-rickets activity.

Vitamin D is a fat-soluble trace nutrient required for healthy BONES and teeth. Vitamin D2 (ERGOCALCIFEROL) occurs in plants, yeast and fungi. Commercially, vitamin D2 is produced by exposing a plant sterol, ergosterol, to UV light. Vitamin D2 is rather toxic and its use is banned in most other countries of the world, with the exception of the United States where it is added to our milk. Vitamin D3, CHOLECALCIFEROL (25-hydroxy cholecalciferol), is the form found in animal tissue and in the oil of fatty fish, and it is also synthesized in the skin from a cholesterol derivative when exposed to sunlight (UV light). Vitamin D is the only VITAMIN to be formed in this manner. This fat-soluble vitamin is stored in fatty tissue as well as in the LIVER, bones, skin and muscle. Vitamin D is required for calcium uptake, and so is linked to the formation of bones and teeth.

Vitamin D is the only vitamin that is converted to a HORMONE. Vitamin D is transported to the KIDNEYS, where it is again oxidized, yielding CALCITROL (1,25 dihydroxy cholecalciferol), which is a hormone. Calcitriol in the bloodstream travels to the intestine where it stimulates the formation of calcium transport proteins. In addition calcitriol can increase bone rebuilding by working together with parathyroid hormone. It also stimulates calcium reabsorption by the kidney.

Vitamin D as calcitriol influences many glands and tissues. This hormone affects the PANCREAS (insulin secretion), the PARATHYROID GLANDS, PITUITARY GLAND, ovaries, testes, COLON, placenta, uterus, heart, THYMUS, mammary tissue and brain (cerebellum). In a very real sense calcitriol is an immune enhancer. Calcitriol stimulates WHITE BLOOD CELLS, especially macrophages, and influences B and T lymphocytes-major classes of cells responsible for antibody production and the surveillance mechanism of the IMMUNE SYSTEM.

Possible Roles in Maintaining Health

Chronic vitamin D deficiency in children leads to RICKETS, characterized by abnormal calcification of bones. As a result, bones are soft and become deformed. Teeth do not develop normally and are subject to decay. Rickets is rare in Western societies owing to the prevalent practice of food FORTIFICATION with forms of vitamin D.

The adult equivalent of rickets is OSTEOMALACIA. In this disease bones become depleted of calcium and phosphorus. Osteomalacia is more common during pregnancy and lactation, as well as during old age. Supplementation with vitamin D can reduce the risk of osteomalacia. Though vitamin D is necessary for normal calcium metabolism, it does not seem to protect against OSTEOPOROSIS in postmenopausal women. Osteoporosis is mitigated by MAGNESIUM, CALCIUM, and possibly FLUORIDE, BORON, MANGANESE and VITAMIN K.

Population studies suggest that vitamin D and calcium deficiencies account in part for the high rate of colorectal cancer and breast cancer worldwide. CALCIFEROL inhibits cancer cells in the test tube and inhibits chemically induced cancer in mice. Vitamin D applied to the skin or taken orally may clear up psoriasis, a condition characterized by scaly, itchy red patches of skin.


There are few good food sources of vitamin D, which is the least prevalent vitamin in the food supply. Vitamin D occurs in fatty fish, fish liver oils, egg yolk and liver. Vitamin D is used to fortify MILK, and either vitamin D3 or vitamin D2 is used. Whole milk, low-fat milk, non-fat milk and non-fat dry milk are fortified with 400 IUs, equivalent to 10 mcg of vitamin D per quart, though spot-checks have revealed variations in this level. Other foods may be fortified with vitamin D: breakfast cereal, infant cereal, bread, chocolate beverages and margarine.


Human requirements are difficult to establish because varying levels of this vitamin are synthesized by the skin. The RECOMMENDED DIETARY ALLOWANCE (RDA) for people over 25 is 5 mcg daily, which is equivalent to 200 IU. Factors that increase the risk of vitamin D deficiency include gallbladder removal, severe food allergies, poor fat absorption (for instance, due to CELIAC DISEASE) and liver disease. Several medications can interfere with vitamin D uptake: certain anticonvulsant agents, barbiturates and cortisone. Mineral oil blocks the uptake of this and other fat-soluble vitamins. People with kidney disease or diabetes may not be able to activate vitamin D. Institutionalized people who get little exposure to sunlight; strict vegetarians and elderly persons are more at risk for vitamin D deficiency. The efficiency of the sk?|–7s production of this vitamin declines with age.


Vitamin D can be toxic, due to high blood calcium levels (hypercalcemia) and the calcification of soft tissue. Symptoms include constipation, vomiting, fatigue, drowsiness, lack of appetite and, in severe cases, high blood pressure, kidney stones, and even kidney failure and coma. Doses at two or three times the RDA seems unlikely to cause toxicity. Young children are more susceptible, and as little as 1,800 IU of vitamin D per day may cause toxicity. Moderately high consumption over a long period of time may increase the risk of atherosclerosis. Those with elevated blood calcium levels should not supplement with vitamin D without medical supervision. SEE NOTE BELOW

Fraser, D.R., “Vitamin D,” Lancet, 345 (January 14,1995), pp. 104-07.

Vitamin D Deficiency is Common

A majority of hospital patients have moderate to severe vitamin D deficiency. This Harvard Medical School study suggests that vitamin D deficiency is also common in the general population. On the basis of what is known about vitamin D, sick adults, older adults, and perhaps all adults, probably need 800 to 1000 IU (international units) daily, substantially more than the newly established levels of adequate intake.

COMMENT: A simple generally reliable way to tell if you’re vitamin D deficient is to look at your serum calcium. It should be about 9.3. If it is much lower, below 9.0, and especially below 8.5 you will likely benefit from vitamin D.

The New England Journal of Medicine, March 19, 1998;338:777-783, 828-829.

Low Vitamin D Related to Atherosclerosis

The lower the level of vitamin D, the more likely that calcium will build up in fatty plaques in the coronary arteries. The inverse relationship also holds: the higher the level of vitamin D, the less likely calcium will build up in atherosclerotic plaque. The relationship was unexpected, because – at least in bones – the higher the vitamin D level, the more likely calcium is to accumulate.

Researchers thought that development of atherosclerotic calcification would respond in the same way as bone – that high vitamin D would lead to higher calcium absorption, but serum vitamin D seems to have an opposite effect on the skeleton as it does on the vessels. About 90% of patients with coronary heart disease have deposits of calcium in the fatty plaques clogging their arteries.

Circulation, September 1997;96:1755-1760.

NOTE: Vitamin D3 is the natural form of vitamin D our body needs. Vitamin D2, which is added to milk and other foods in the United States, is toxic and banned in just about every other country in the world.

Since vitamin D is not water-soluble the best absorption with vitamin D is obtained when the vitamin D is EMULSIFIED. That is, the vitamin D oil is transformed into an emulsion (very tiny droplets dispersed in water) where the body can now absorb the vitamin almost 100%. The emulsification process also decreases the chance that this vitamin can be toxic.


Test Values and Treatment for Vitamin D Deficiency

Before considering supplementation with vitamin D, it would be wise to have your vitamin D level tested. This is best done from a nutritionally oriented physician. It is very important that they order the correct test. The advantage of having your medical doctor perform the test is that it will usually be covered by your medical insurance.

Eventually, Krispin Sullivan, my nutritionist mentor in vitamin D, hopes to have an inexpensive saliva hormone test that you will be able to do through the mail. In the meantime, the blood test is best route to monitor vitamin D levels at this time.

Don’t Be Fooled — Order the Correct Test

There are two vitamin D tests — 1,25(OH)D and 25(OH)D. The first is active D, which is often normal even when the precursor, 1,25(OH)D, is insufficient.

25(OH)D is the better marker of overall D status. It is this marker that is most strongly associated with overall health.

The correct test is 25(OH)D, also called 25-hydroxyvitamin D.

Please note the difference between normal and optimal. We don’t want to be average here; we want to be optimally healthy.

Primitive man likely developed in tropical and sub-tropical conditions with large exposure to UV-B and its secondary consequence to skin exposure, vitamin D.

Primitive environmental availability of a nutrient does not necessarily establish the higher requirements, but these exposures would have influenced the evolution of the relevant physiology, and such concentrations should at least be considered presumptively acceptable.

Some experts may disagree with the following healthy ranges, but they are taken from healthy people from the tropical or subtropical parts of the world where they are receiving healthy sun exposures. It seems more than reasonable to assume that these values are in fact reflective of an optimal human requirement.

Dr. Michael Hollick is one of the top vitamin D researchers in the world and he has been advocating higher reference ranges, though not as high as the ones suggested here.

(Holick MF. Calcium and Vitamin D. Diagnostics and Therapeutics. Clin Lab Med. 2000 Sep;20(3):569-90)
Optimal 25-hydroxyvitamin D values are:

125-150 nmol/l
50-60 ng/ml

Normal 25-hydroxyvitamin D lab values are:

50-140 nmol/l
20-56 ng/ml

If you have the above test performed, please recognize that many commercial labs are using the older dated reference ranges. The above values are the newest ones from the clinical research.

How To Dose Your Vitamin D Once You Know Your Levels

Vitamin D is a fat soluble vitamin and can be quite toxic. Once you have vitamin D toxicity you can’t easily turn it around.

So don’t even think of starting this program unless you have your blood levels checked. Many of you may choose to ignore this warning, but I am telling you in plain simple English, that while vitamin D has enormous potential for improving your health, it has nearly equal potential to worsen it, if you use it improperly.

For safety purposes it is advisable to optimize your vitamin D levels only with the help of a trained health care professional. The exact protocol to optimize your vitamin D levels will be in Krispin Sullivan’s upcoming book Naked at Noon. The book will have far more information than is in this brief review and will further highlight the importance of testing.

If you need to know this information before her book is published a preliminary copy of her vitamin D research is available on her web site. While she has an e-mail listed on her site, please understand that she doesn’t have any time to respond to personal e-mails, or her book will never be finished.

Krispin Sullivan and I share the same passion, seeking to help large numbers of people regain their health with inexpensive nutritional therapies. She has researched this subject for a number of years, and, to the best of my knowledge is one of the most experienced clinicians in this area. She has provided me with much of the foundational background for this review and I am very grateful for her willingness to bring me up to speed in, not only this area, but omega three nutrition and vitamin K.

Sunlight Is the Ideal Source of Vitamin D

Ideally, the best place to get vitamin D is from your skin being exposed to the UV-B that is in normal sunlight. Vitamin D from sunlight, or supplements, acts as a pro-hormone, rapidly converting into 25-hydroxyvitamin D.

Many experts believe that there is no harm in the vitamin D concentrations associated with sun exposure, and that such levels are probably optimal for human health.

Unfortunately, the amount of sun reaching most of the U.S. is only sufficient to generate a vitamin D response for about three months of the year.

Now, I can just hear scores of you getting alarmed that this recommendation will increase your risk of skin cancer. Well folks, nothing could be further from the truth.

I will provide all of the documentation and scientific research to support this assertion in future issues. But, I am convinced beyond any shadow of a doubt that as long as you avoid being sunburned, sun exposure at noon on unexposed skin is one of the healthiest things you can do for your body.

Most of us just don’t live far south enough, or high enough in the mountains, to allow more UV-B to reach our skins. So, for those times of the year when access to the proper amount of sun is not possible, you will want to consider the cod liver oil recommendations above.

Ultraviolet-B Is What Generates Vitamin D In Your Skin

Ultraviolet (UV) light is divided into 3 bands, or wavelength ranges, which are referred to as UV-A, UV-B and UV-C.

UV-B is sometimes called the “burning ray.” It’s the primary cause of sunburn caused by overexposure to sunlight. However, UV-B sunlight produces vitamin D on the skin. The amount produced depends on exposure time, latitude and ‘itude of location, amount of skin surface exposed, skin pigmentation and season.

UV-B also stimulates the production of MSH, an important hormone in weight loss, energy production, and in giving you that wonderful tanned appearance.

However, UV-B does not penetrate very deeply into the skin. The darker the pigmentation or more tanned the skin, the less UV-B penetrates. Window glass allows only 5% of the UV-B light range that produces D to get into your home or auto.

The timing of your sun exposure is also a major factor. Sun exposure must take place when UV-B is present. The forthcoming UV-B meter, discussed below, should greatly aid in this assessment.

The actual dosing of the sun exposure is quite complex, since it involves knowing the amount of UV-B and one’s skin color.

This doesn’t sound very complex, but the amount of UV-B is not a constant. It is a major variable and is influenced by a number of factors:

* Latitude — the further north you are the less there is

* Time of Year — virtually none available in winter in continental U.S.

* Clouds — can block UV-B

* Pollution — smog and ozone can block UV-B

* Altitude — the higher up you are the more UV-B reaches you

I am working with a company now to bring a very inexpensive UV-B meter so you can know exactly how much sunlight you need on any given day to generate an optimum vitamin D exposure. I hope to have that UV-B meter available later this year so you can use it to time your dose of sun exposure.

It is important to know the level of UV-B exposure. Unlike the typical American strategy, more is better, that is not the case for UV-B exposure. Longer exposure will not increase vitamin D production, but will increase the danger of skin damage and possible skin cancer.

Major Caution: Avoid Sunburn

Again, it is important to stress that you should never get burned and should only implement sun exposure very gradually.

While we all benefit from regular exposure to sun, it is important to recognize that you should always limit your exposure so that you don’t get burnt. Sunburn has been clearly related to an increased risk of skin cancer.

Interestingly, if you don’t get sunburned and actually have regular sun exposure, you will have a decreased risk of the dangerous skin cancer, melanoma.

However, don’t let dermatologists scare you. We all need sun. It is very similar to water. Just because you can drown while swimming, doesn’t mean you should never drink water or swim in it. Similarly, as long as we avoid sun exposure that will cause burning, it will help improve our health.

Later this year I will provide all the scientific documentation for this. It is a complex issue though. Skin cancer is largely related to the over abundance of omega 6 oils that we have in this country. When sunlight hits these fats it can convert them to cancer causing molecules, and if one is not healthy, these cells can go on to developing cancer.

This cancerous transformation doesn’t happen with omega three fats. So, changing the ratio of omega 3 to omega 6 oils in your diet is one the keys to prevent this. The best sources of omega three fat would be cod liver oil and grass fed animals like beef.

Remember: Don’t Ever Get Sun Burned

It is also important to point out the obvious. Fair skinned individuals need far less exposure to receive their dose of sun to produce vitamin D. Lighter skin allows for greater penetration of UV-B, leading to higher levels of D.

African Americans however, would need considerably more sun to generate vitamin D. This is one of the reasons why breast and prostate cancers are so much higher in Africans who are living in temperate climates. They just aren’t able to get enough sun to generate vitamin D. In fact, in the Northern U.S. cities, they will find it impossible to get adequate D from sunlight in any season.

Elderly individuals will also have a great difficulty getting enough vitamin D from sun exposure, since an enzyme in their skin decreases with degenerative aging and, as a result, their skin has a limited capacity for producing vitamin D.

Interestingly, it is impossible to get vitamin D toxicity from too much sun exposure. Your body just won’t let it happen. That is why receiving your vitamin D from the sun is the best option if possible.

Ultraviolet exposure beyond the minimal dose required to produce skin redness, does not increase vitamin D production any further.

An equilibrium occurs in white skin within 20 min of ultraviolet exposure, in which further increases in vitamin D is not possible, since the ultraviolet light will actually start to degrade the vitamin D.

It can take 3-6 times longer for pigmented skin to reach the equilibrium concentration of skin previtamin D. However, skin pigmentation does not affect the amount of vitamin D that can be obtained through sunshine exposure.

It is commonly thought that only occasional exposure of the face and hands to sunlight is “sufficient” for vitamin D nutrition. Indeed, this exposure can provide 200-400 IU vitamin D during those months when the appropriate sunlight is available.

Supplemental Vitamin D

Unfortunately the vast majority of u???ving in the U.S. just do not have access to the proper amount of sun most of the year. Even if the sun is out there, most of us are working during the week and don’t have time to go out and capture some sunlight on our skins.

So, that leaves supplementation as the only practical option for most of us.

Vitamin D Toxicity

First, let me state that there are two types of vitamin D supplements: vitamin D3 (cholecalciferol) which comes from fish oil and plant source D2 (ergocalciferol) which is found in fortified foods and some supplements. D2, found in plants and made active by irradiation, is less biologically active.

Vitamin D3 is found in eggs, organ meats, animal fat, cod liver oil and fish. It is the equivalent to the vitamin D3 formed on our skins from UV-B.

You should stay away from the synthetic D2 as it is the one that has been shown to have toxicity at the higher dose ranges. You will only want to use vitamin D3.

There are newer reasons why vitamin D2 has a greater potential for harm. First, vitamin D binding protein has a weaker affinity for the vitamin D2 metabolites than vitamin D3. Second, unique biologically active metabolites are produced in humans from vitamin D2, but there are no analogous metabolites derived from vitamin D3.

There is no doubt that vitamin D2 is a synthetic analogue of vitamin D, with different characteristics. It is inappropriate to regard vitamin D2 as a vitamin. Future research into the toxicity of this vitamin needs to focus on vitamin D3 as being something distinct from vitamin D2, for which almost all our current toxicity data relate to.

Even without careful attention to the type of vitamin D being used, a recent expert review on vitamin D was unable to find any published evidence of vitamin D toxicity in adults from an intake of 10,000 IU per day that was verified by the blood 25(OH)D concentration.

People Who Should Not Take Supplemental Vitamin D

Some patients with sarcoidosis, tuberculosis, or lymphoma become hypercalcemic in response to any increase in vitamin D nutrition. For these persons, it may be wise to avoid any dietary or environmental sources of vitamin D, unless they are carefully monitored with serum calcium and 25(OH)D levels.

Cod Liver Oil

First of all let me warn you that if you have sub-tropical or summer sun exposure I do NOT advise any vitamin D supplementation unless you perform the above described test.

Having said that let me emphasize that the vast majority of the readers of this newsletter can not possibly receive enough UV-B to generate vitamin D from September to May.

This is certainly true for just about the entire US and all of Europe. Please remember that just because it is sunny and hot outside this is absolutely no indication of the UV-B level that is present. If your latitude is above 30 degrees north or below 30 degrees south, you will likely benefit from vitamin D supplementation from September to May.

If you don’t know the latitude of your city you can use a latitude finder If your latitude is lower than 30 degrees you have access to good sunshine and may not need vitamin D supplementation.

My top recommendation for obtaining supplemental vitamin D3 would be to use Carlson’s lemon flavored cod liver oil. It is one of the best tasting brands on the market. The dose is about one teaspoon for every 25 pounds of body weight.

The only caution here, and from my perspective it is a theoretical one only, is that pregnant woman should probably limit themselves to one tablespoon per day, as that would keep their daily vitamin A intake to below 10,000 units per day. However, pregnant women probably need cod liver oil the most, since their baby’s brain profoundly benefits from the fish oils, DHA and EPA.

This will not only provide you, the average 150 pound adult, with 2-3,000 units of vitamin D, but you will also provide you with vitamin K which is an essential co-factor in building strong bones. Natural vitamin A is also in the cod liver to support your immune system and the oil is full of the beneficial omega three fats that nearly all of us are deficient in.

Additionally, there maybe a protective benefit of vitamin A in limiting high calcium levels from vitamin D. (Johansson S, Melhus H. Vitamin A antagonizes calcium response to vitamin D in man. J Bone Miner Res. 2001 Oct;16(10):1899-905)

What To Do If You Have a Tough Time With Cod Liver Oil

Some people will have a difficult time digesting cod liver oil. If this is the case please take it on an empty stomach. You can start with small quantities and build up.

If you do not use Carlson cod liver oil, there is a chance that the cod liver oil maybe rancid. This is easy to tell as it will not taste good and will have a “fishy” odor or taste. If this is the case do not use the cod liver oil the fats are spoiled.

If you can’t take tolerate cod liver oil you will need a source of omega three fats. Please review my future article on that topic which should be published soon.

Let me remind you that eating fish just won’t cut it anymore.

We have irreversibly polluted the environment by burning coal for electricity and there is more than enough mercury in the waters of the world to contaminate virtually all of the fish.

Even the conservative U.S. government warns pregnant women to avoid eating fish, since 60,000 kids are born brain injured from that mercury exposure every year. Farm raised fish do not avoid the problem — they still have the mercury and are worse since they are high in omega 6 not omega 3 because they are fed corn.

Mercury is not oil soluble and therefore, is not present in the cod liver oil, so this problem is avoided.

Milk does provide vitamin D, but it is only about 250 units per 8 ounces. So, one would need to drink a half-gallon per day to receive enough vitamin D. There are a large number of reasons that one should avoid drinking milk to stay healthy.

Carlson also makes a vitamin D capsule that is also available which is natural and free of mercury, that can be used to implement the recommendations above. If you use the capsules, be sure to take it with some fat or it will not be absorbed as well.

Please remember that it is best to have your levels regularly checked as supplemental vitamin D in certain clinical settings can have toxicity.

It will be important to make certain that you are taking calcium while you are receiving the vitamin D, or it will tend to take calcium out of your bones. Your normal calcium requirements are easily attained if you are following the vegetable juicing program.

It will be helpful to put the cod liver oil in the vegetable juice, since you will need some type of oil to actually absorb vitamin D.

VITAMIN D – Reference List