Vitamin D, the versatile vitamin

If you’re prone to colds, infections, asthma, allergies or brittle bones, you might want to check your serum vitamin D levels. Although most doctors don’t call for tests of vitamin D levels when ordering routine lab tests, some experts believe that over 75% of the U.S. population may be deficient.

A study published in the March 23 issue of the Archives of Internal Medicine found that vitamin D levels in Americans have steadily declined over the past two decades. Dr. Adit Ginde of the University of Colorado at Denver School of Medicine stated recently that “over three out of four Americans now have vitamin D levels below what we believe is necessary for optimal health.”

And Hispanics and African Americans are even worse off, he says: “Nearly all have suboptimal levels.”

Why you need vitamin D

Many people are aware that without adequate vitamin D levels, their teeth and bones would suffer due to malabsorption of dietary calcium and failed regulation of the ratio of calcium and phosphorus in the body. But even most doctors practicing today are unaware of the vitamin’s role in promoting overall well being.

Vitamin D modulates blood pressure by suppressing the production of renin in the kidneys and brakes uncontrolled cell proliferation that leads to cancer. Its actions affect insulin secretion by the pancreas and may increase insulin sensitivity, thereby combating obesity. Without adequate vitamin D, you become vulnerable—perhaps even prone—to various cancers; to autoimmune afflictions such as rheumatoid arthritis, fibromyalgia and psoriasis; to bone diseases such as osteopenia (bone loss), osteoporosis and osteomalacia, a condition in which the bones actually ache; to any conditions resulting from poor calcium metabolism; and to heart disease and nervous disorders.

Is Vitamin D overdose a myth?

Worries of vitamin D overdose are overdone. John Cannell, MD, Executive Director of the Vitamin D Council, points out, “Although D can be toxic in excess, the same can be said for water.”

In theory, both A and D are fat-soluble vitamins that can be consumed to toxic levels because they are not readily eliminated by the kidneys. Fortunately, the body has a fail-safe mechanism to prevent vitamin D overdose from sun exposure. As the body’s supply of the vitamin increases, sunlight converts excess vitamin D in the skin to inactive byproducts.1

Worries about vitamin D toxicity stem from the fact that ergocalciferol (vitamin D2)—a patented drug—was the form first synthesized commercially. Its early use lead to non-fatal incidents of toxicity. One is unlikely to overdose on the naturally occurring form of the vitamin, cholecalciferol (D3).

In fact, Canadian researcher Dr. Reinhold Vieth wrote a review of the literature on vitamin D toxicity and could find no evidence of overdose using reasonable amounts of the natural vitamin, though he did find incidents involving the synthetic variety. Commented Vieth, “Throughout my preparation of this review, I was amazed at the lack of evidence supporting statements about the toxicity of moderate doses of vitamin D.”

He added: “If there is published evidence of toxicity in adults from an intake of 10,000 IU [of D3] per day… I have yet to find it.”

“Vieth’s estimate of the daily requirement from all sources is [4,000 IU], an order of magnitude higher than the current dietary reference intakes,” writes Robert P. Heaney in the American Journal of Clinical Nutrition.2 “Whatever the value turns out to be, it seems inescapable that it will be substantially higher than the current values and possibly higher than nutritional policymakers may be prepared to accept.”

Among those cancers specifically linked to vitamin D deficiencies are breast cancer, prostate cancer, colon cancer and ovarian cancer.3

Dr. Michael Holick, generally considered the world’s foremost authority on vitamin D, thinks that infants born with vitamin D deficiencies who do not receive adequate supplementation during the first few months of life are likely to develop chronic diseases in adulthood, including type 1 diabetes, rheumatoid arthritis and multiple sclerosis.

Holick cites a study performed in Finland that gave infants 2,000 units of vitamin D daily for their first several years. The study then tracked the children into adulthood. The results showed they had an 80% reduced risk of contracting type 1 diabetes as young adults compared to children who did not receive vitamin D supplements.

By comparison, a group of children that suffered from rickets at age one showed a fourfold increased likelihood of developing type 1 diabetes by adulthood. Holick points to other studies done in the United States and Europe showing vitamin D can decrease the risk of contracting colon cancer by 50%, of prostate cancer by 50%, and of ovarian and breast cancers by almost the same amount. Yet, in a study where his team measured the serum vitamin D levels of 49 mothers and their newborn infants, he found that 76% of the mothers giving birth were severely vitamin D deficient, as were 81% of their newborns.

Neurosurgeon Russell Blaylock emphasizes that all brain cells have vitamin D3 receptors, both on the cell membrane and in the nucleus. He thinks vitamin D deficiency may be an underlying factor in autism.4 He further notes that the vitamin regulates calcium in all cells—including brain cells—and protects the immune system with antioxidant and antiviral benefits while it regulates cell growth and cell death. Vitamin D-3 plays a major role in a number of mechanisms that protect the brain, such as increasing neuronal levels of glutathione, an important antioxidant that protects against free radicals. Blaylock believes Alzheimer’s and Parkinson’s diseases may arise as a result of brain inflammation caused by vitamin D deficiency—cases where this protection against free radicals has failed.

Studies have linked vitamin D insufficiency to hypertension, atherosclerosis, congestive heart failure and heart attacks.5 Crohn’s Disease, ulcerative colitis, seasonal affective disorder (SAD), some depressions and other mood disorders yield to vitamin D supplementation. Even sickle cell anemia has been suggested as a possible consequence of vitamin D deficiency.

One study showed that postmenopausal women who increased their daily vitamin D intake by 1,100 IU reduced their relative risk of cancer by 60 to 77%.6

Clearly, maintaining an adequate level of this vitamin is worth the effort.

Optimal levels

Since sunlight is the most common source of vitamin D for most people, it is best to test your vitamin D levels in the spring. That’s the time of year when you are most likely to be deficient after months of sunlight inadequate for vitamin D production. In fact, David Brownstein, MD recommends having your doctor check vitamin D levels at least once a year using a simple blood test that checks serum levels of 25-Hydroxycholecalciferol (a circulating form of vitamin D). Brownstein says optimal vitamin D levels range from 75 to 125 nanomoles per liter (nmol/l).7

Currently recommended levels of vitamin D supplements are 200 International Units (IU) per day from birth to age 50, 400 IU per day from age 51 to 70, and 600 international units per day for adults aged 71 and older. Unfortunately, these recommendations were set to ensure against rickets rather than to guarantee strong general health. Most authorities now recommend 1,000 to 2,000 IU of the vitamin daily. Holick and other experts recommend obtaining about 4,000 to 5,000 IU per day for maximum health. Lactating women should receive 4,000 IU per day to assure transfering enough of the vitamin to their milk to satisfy their infant’s needs.8

It is safe to consume 4,000 to 10,000 IU of the vitamin daily for extended periods. Indeed, our ancestors may have been awash in vitamin D from hunting, fishing, or farming outdoors.

How to get it

If you spend several hours a week working or resting in the sun, your body may produce adequate vitamin D in summer. In that case, you might only need to supplement from other sources during the remaining seasons. However, research suggests erring on the side of supplementation if—like many Americans—you shower or bathe on a daily basis.

That’s because the production of vitamin D in sunlight results from the interaction of UVB rays with oils on the surface of the skin. These oils readily wash away during bathing. If they wash away before vitamin D is formed or after vitamin D is formed but before it has been absorbed back into the skin, the net result is little or no vitamin D from sunlight. So in our cleanliness-obsessed society, the average American is apt to require other sources of vitamin D besides sunlight.9

Burning, tanning, and vitamin D production

There are three different bands of ultraviolet light that interact with the body: UVA, UVB, and UVC.

UVC is entirely absorbed by the ozone layer so it does not reach the skin in nature. However, it is produced in detectable amounts by UV bulbs (including standard fluorescents) and some believe it contributes to the rising tide of skin cancers.

UVA is known as the “tanning ray,” and is indeed primarily responsible for stimulating tanning of the skin. UVB, on the other hand, is the primary cause of sunburn, with the beneficial side effect that it also stimulates vitamin D production. UVB not only causes melanocytes to secrete melanin (tanning) it also stimulates production of melanocyte stimulating hormone (MSH) which is known to aid in weight loss and energy production.10

It is now known that both UVA and UVB cause tanning and sunburn. UVA produces an immediate, but short-term tan by oxidizing the melanin already contained in the skin. UVB, on the other hand, stimulates melanin production for a more permanent tan that won’t appear for 72 hours. Sunscreens were originally designed to block UVB—but not UVA—so as to promote tanning without burning. Eventually, researchers realized that UVA caused sunburn too; it simply took longer than UVB.

According to Drs. Holick, Vieth and Cannell, the risk in exposing the skin to sufficient sunlight to produce vitamin D is minimal. Holick advocates taking sun until the feeling of “pinkness” occurs—no more than 30 minutes in most locales, half that in some—then applying sunscreen to guard against further sun damage.

Comments Cannell, “brief, full-body sun exposure (minimal erythemal doses) may slightly increase your risk of skin cancer but it is a much smarter thing to do than dying of vitamin D deficiency.”11

Indeed, despite unrelenting pressure from an industry that promotes the use of sunscreen on all possible occasions, some experts have stated that sunscreens may actually increase the skin’s supply of free radicals in excess of the action of sunlight alone.12 Free radicals in the skin lead to skin cancer.

That certainly would help to account for the continuing rise of melanoma rates despite an increased reluctance of the public to spend time in the sun without sunscreen.

Being so bold as to brave moderate sunlight without modern-day chemical shielding may turn out to be the smartest course of action.

Moreover, should you suffer from liver, thyroid or kidney disorders, your body may not produce adequate amounts of the vitamin even when exposed to sun. Forty years ago, Adelle Davis observed that a high incidence of rickets was reported in such sunny locales as Greece and Israel, presumably because dietary factors nullified the effects of sunlight, though sun-protective clothing may be a factor.13

Rickets, of course, is the classic condition associated with vitamin D deficiency and reflects inadequate calcium absorption due to lack of the vitamin. Until recently, scientists thought that stimulating calcium absorption and utilization was vitamin D’s only role in the body. Now we know that it also regulates gene expression controlling immune and renal functions. These in turn can have profound effects on insulin production, serum calcium levels, diabetes, obesity, cancer immunity and countless immune disorders. Other possible effects from the vitamin are constantly under research.

When conversion of precursors by sunlight goes successfully, the sun is the vitamin D source par excellence. Dosages of vitamin D as high as 50,000 IU have been reported from as little as 30 minutes exposure to strong sunlight, though most authorities place the likely range between 10,000 and 15,000 IU within the continental United States. Latitude, altitude, atmospheric conditions, time of day, the amount of exposed skin and skin pigmentation will influence the quantities of vitamin D produced.

As a general guide, if you live north of Atlanta you will require longer exposure to the sun and will be able to generate vitamin D only during the summer months. Using sunscreens shuts down vitamin D output. A sunscreen with an SPF of 8 reduces your vitamin D production by more than 95%. For African Americans with relatively dark pigmentation, skin pigments alone provide protection from the sun that is equivalent to an SPF 15 to 30 sunscreen, requiring up to 30 times as much exposure as a Caucasian to generate adequate supplies of the vitamin.

Natural sources of vitamin D

Aside from exposure to sunlight, the only reliable natural sources of the vitamin are foods of animal origin. The best of these is cod liver oil, if you can find a brand that does not remove the natural vitamin D. (See sidebar.) Oily fish, such as salmon, mackerel, sardines and herring; oysters and shrimp; liver of all kinds, butter, lard and egg yolks are also good sources, though none compares to the more concentrated vitamins in cod liver oil.

Factors in cod liver oil selection

In the process of  preparing cod liver oil, many manufacturers remove the natural vitamins A and D. They may replace all or most of these after further processing the oil to remove potential toxins such as PCBs and mercury. In some cases, however, they will replace them with artificial (manufactured) versions, which are cheaper to produce, or with lower quantities relative to the DHA and EPA (omega-3 oils) that are also present in cod liver oil.

This practice enables them to sell the vitamins A and D as separate commodities, leaving you with an oil that has been robbed of nutrients. If anything, you want a cod liver oil that has been enriched with natural vitamins or concentrated so that a serving as small as a teaspoon gives you half or more of your planned daily dosage.

So-called “fermented” cod liver oils are reappearing on the market too. These are prepared the old-fashioned way used before molecular distillation and other modern techniques. Basically, the cod livers are allowed to age in a vat. Fermentation—otherwise known as putrefaction—sets in, and the resulting bacterial action enriches the oily soup with additional nutrients. Some believe that cod liver oil produced in this way may have been rich in vitamin B12 and other vitamins due to the thorough breakdown of the hepatic tissues.

In selecting a cod liver oil, look for an oil in which the ratio of vitamin A (measured in international units, or IU) is no more than 10 times the amount of vitamin D measured in IU. (Some brands of cod liver oil will have A to D ratios of 20:1 or more.) This ensures that you are getting enough vitamin D in relation to the other nutrients. It also guards against overdosing on vitamin A while seeking therapeutic quantities of D.

Another reason to consume cod liver oil as a source of vitamin D is that vitamins A and D are synergistic, and high-vitamin cod liver oil is an excellent source of both. Additionally, the presence of vitamin D allows the body to handle much higher quantities of the antioxidant vitamin A safely.14 But perhaps more important, recent evidence suggests that vitamin D cannot adequately perform some of its essential gene-expression functions without the presence of vitamin A. In the absence of vitamin A, molecules called “corepressors” bind to vitamin D receptors and prevent vitamin D from functioning.15

Although milk is normally supplemented with vitamin D, the amount tends to be well below the levels that are now known to be adequate for optimal health.

For vegans and others who cannot obtain an adequate supply of the vitamin from their diets, vitamin D supplements are essential. Tablets containing 1,000 IU and even 5,000 IU are now readily available without prescription, so there is no reason for anyone to suffer from inadequate reserves. If you know that you are deficient because your blood has been tested, supplementing with around 4,000 to 5,000 IU per day is a good idea until blood tests show you have reached an optimal level. If you are overweight, it may take longer to achieve normalcy because vitamin D is readily absorbed into body fat for storage. Some sources advocate doubling D supplementation for the overweight.

Vitamin D and Autoimmune diseases

The list of known autoimmune diseases is long and growing. One source states that there are over 80, and that women are the most affected by them.16

As an example, Type 1 (insulin-dependent) diabetes, classified as a simple hereditary dysfunction a generation or so ago, has more recently become considered an autoimmune disease according to most experts. Along with multiple sclerosis (MS), rheumatoid arthritis, osteoarthritis, irritable bowel syndrome (IBD) and other autoimmune disorders, Type 1 diabetes may arise primarily as a result of vitamin D deficiency and apparently yields, at least in some cases, to treatment with natural vitamin D.

One of the clues that these disorders are linked to vitamin D deficiency springs from an examination of their prevalence at different lattitudes. It turns out that these diseases are all more common at higher lattitudes, which includes Canada, the northern United States and northern Europe. Their symptoms also tend to worsen during winter and spring.

Such diseases continue to worsen in spring because, despite the availability of strong enough sun during the spring months for Caucasian skin to produce vitamin D from exposure near midday, there is a two-month lag involved in overcoming vitamin D deficiency. That lag prevents these diseases from improving immediately upon exposure to the sun, especially for those who are overweight. Indeed, the lag time itself may have served to confound investigators in the past.

Another clue that vitamin D is involved in these autoimmune diseases is that people with inherited deficiencies in their vitamin D3 receptors are known to have a higher incidence of autoimmune diseases of all types.

But now, armed with new insights and new information about the roles vitamin D plays at the cellular level, scientists are beginning to unravel the mysteries. Heart disease, hypertension, schizophrenia and blood levels of inflammatory factors such as C-reactive protein and interleukin-10 all have in common a link to this vitamin that has turned out not to be a vitamin (it can be manufactured by the body in the presence of sunlight) but is nevertheless a substance that controls either directly or indirectly over 200 genes and plays a role in immune system modulation, cell proliferation and differentiation, even cell death.

And all you need to do to minimize your risk of all those diseases is to maintain healthy levels of vitamin D, the sunshine vitamin.

  1. Michael Holick, “Vitamin D Deficiency,” New England Journal of Medicine, 357, no. 3 (2007):266-81. ↩
  2. Robert P. Heaney, American Journal of Clinical Nutrition, 69, no. 5, (1999). ↩
  3. Mike Adams, The Healing Power of Sunlight and Vitamin D an exclusive interview with Dr. Michael Holick, (Truth Publishing, 2005), 2. ↩
  4. Russell Blaylock, MD, “Vitamin D’s Hidden Role in Your Health,” The Blaylock Wellness Report, 5, no. 9 (2008): 2. ↩
  5. “Renin-angiotensin-aldosterone System: Target of Vitamin D Protection and Therapy,” University of Chicago (2009). http://www.ibridgenetwork.org/uctech/uchi-1709 (accessed June 10, 2009). ↩
  6. JM Lappe et al, “Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial”, Am J Clin Nutr, 85 (2007): 1586-91. ↩
  7. Dr. David Brownstein, Natural Way to Health, 1, no. 3 (2008): 8. ↩
  8. Holick, “Vitamin D Deficiency,” 277. ↩
  9. A. C. Helmer and C. H. Jansen, “The Absorption of Vitamin D Through the Skin” and “Vitamin D, Precursors Removed from Human Skin by Washing,” Studies of the Institutum Divi Thomae, I 83 (1937): 207. ↩
  10. M Ranson et al, “Human melanocytes as a target tissue for hormones: in vitro studies with 1 alpha-25, dihydroxyvitamin D3, alpha-melanocyte stimulating hormone, and beta-estradiol,” J. Invest Dermatol., 91 (1988):593-8. ↩
  11. “The Truth about Vitamin D Toxicity”. Vitamin D Council. http://www.vitamindcouncil.org/vitaminDToxicity.shtml (accessed June 10, 2009). ↩
  12. Kerry M. Hanson et al, “Sunscreen enhancement of UV-induced reactive oxygen species in the skin”. Free Radical Biology and Medicine 41, no. 8 (2006): 1205–1212. doi:10.1016/j.freeradbiomed.2006.06.011. ↩
  13. Adelle Davis, Let’s Eat Right to Keep Fit, (New York: Harcourt Brace Jovanovich, 1970): 142. ↩
  14. Myhre, et al., “Water-miscible, emulsified, and solid forms of retinol supplements are more toxic than oil-based preparations,” Am J Clin Nutr, 78 (2003): 1152-9;

    Aburto, et al, “The influence of Vitamin A on the Utilization and Amelioration of Toxicity of Cholecalciferol, 25-Hydroxycholecalciferol, and 1,25-Dihydroxycholecalciferol in Young Broiler Chickens,” Poultry Science, 77 (1998): 570-577;

    and Metz, et al., “The Interaction of Dietary Vitamin A and Vitamin D Related to Skeletal Development in the Turkey Poult,” J. Nutr. 115 (1985): 929-935. ↩

  15. R. Sánchez-Martínez, “Vitamin D-Dependent Recruitment of Corepressors to Vitamin D/Retinoid X Receptor Heterodimers,” Molecular and Cellular Biology, 28, no. 11 (2008): 3817-3829. ↩
  16. Blaylock, 6 ↩