|
by Dallas Clouatre, Ph.D.
New Light on the Sunshine Vitamin
The Vitamin in Question? Vitamin D—Vitamin D3, to be Precise.
No doubt, most readers will be surprised by the association of vitamin D and reduced rates of cancer, resistance to tuberculosis, flu, and so forth and so on. After all, the public health line is that vitamin D is for osteoporosis. The condition known as rickets (a bone disease in children) and the bone degeneration known as osteomalacia were recognized as being caused by vitamin D deficiency 75 years ago. The fame of fish liver (cod liver) rests primarily upon its ability to prevent these conditions. The early association of vitamin D with bone health has remained the primary one for the vitamin.
In this day and age, Many vitamins are receiving skeptical reviews from much of the medical world. The antioxidant theory of aging and disease has come in for a bit of a drubbing and the use of B vitamins to reduce homocysteine and cardiovascular disease has received mixed marks. In general, nutritional supplements, other than perhaps omega-3 fatty acids, are in the bull’s-eye of researchers out to make reputations. In such a climate, it is remarkable that there is a vitamin D3...
- the Canadian Cancer Society (2007) recommends for cancer prevention
- United Kingdom researchers (2007) wrote may help prevent the development of multiple sclerosis¹
- findings from Northwestern and Harvard University (Cancer Epidemiology Biomarkers & Prevention, September 2006) show may dramatically reduce pancreatic cancer²
- accepted as being powerfully negatively correlated with prostate cancer risk³
- Harvard School of Public Health (2006) found is associated in men with a 17 percent reduction in all cancer incidences and a 29 percent reduction in mortality5
- research published in Anticancer Research (2006) supported reductions in risk for cancers at 16 different sites6
- a study published in The American Journal of Clinical Nutrition (June 2007) found supplemented in conjunction with calcium substantially reduced riskof all cancers in post-menopausal women7
- researchers from Queen Mary’s School of Medicine and Dentistry, London, and the Wellcome Trust Centre for Research in Clinical Tropical Medicine, Imperial College, London, found enhances immunity against mycobacteria, such as tuberculosis (2007)8,9
- for which scientists have linked seasonal deficiencies to epidemics of influenza10
- that may be an important factor in maintaining proper blood pressure11
...and this is just for openers. |
|
One curious thing about vitamin D is that it is not a vitamin in the ordinary sense. The usual definition of vitamins maintains these are nutrients we must consume because we cannot make them in the body. However, humans quite readily make vitamin D with the aid of sunlight. Upon exposure to a particular wavelength of ultraviolet light (UV radiation), vitamin D is synthesized in the skin. This is both a strength and a weakness. It can free us from complete dependence upon a food source, yet it also means that humans can become vitamin D deficient. Marginal vitamin D deficiency impairs immune function, as noted already. Seasonal conditions, such as increased susceptibility to flu, are one effect. More ominously, cancer researchers have noted that some cancers, for instance, prostate cancer, appear to be linked to available sun exposure and factors that control vitamin D production (skin pigmentation, sun screen usage, etc.)12,13
What is Vitamin D?
The term vitamin D generally refers to the ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). This fat-soluble vitamin is found in only a few foods. Fish liver oils are the richest natural sources, but fortified milk products and other fortified foods are the primary sources in the American diet. In fact, it has been a public health policy in the United States to fortify milk with 10 micrograms (400 IU) of vitamin D per quart.
Digestive disturbances in the assimilation of fats impair the uptake of vitamin D from the diet, just as do drugs that interfere with the metabolism of fats. Individuals with liver dysfunction, those suffering from Crohn’s Disease, and the elderly in general can easily find themselves at risk of developing vitamin D deficiency or subclinical vitamin D status. Poor uptake from foods is particularly unfortunate in those who also get inadequate exposure to sunlight, whether due to season, being too much indoors or excessive use of sunscreens.
Vitamin D is the principal regulator of calcium in the body; it controls skeletal development and bone mineralization. However, vitamin D is not itself active. Rather it is a prohormone, meaning that it is converted into a molecule that exercises hormonal actions. The active form of vitamin D usually is written 1alpha, 25-dihydroxyvitamin D or 1,25(OH2)D. It is this form that binds to vitamin D receptors in the nuclei of cells.
Vitamin D’s most famous role involves bone health. Osteoporosis results from an imbalance between bone resorption and bone formation. Decreased vitamin D levels result in decreased production of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3). This has consequences. It can lead to reduced absorption of calcium from the diet in the small intestine as well as changes in how the body regulates the movement of calcium from the blood into the bones (often resulting from a condition known as secondary hyperparathyroidism). A number of studies have indicated that for bone health the level of dietary intake or availability of vitamin D (from exposure to the sun) is as important or even much more important than is the amount of calcium supplied by the diet. Certainly, in the elderly vitamin D status commonly is impaired.14 Vitamin D may also be effective in the treatment of corticosteroid-induced osteoporosis.
Even though its bone health benefits are likely greater than those of calcium supplementation, vitamin D is not a cure-all for bone issues.15 Although its use is associated with reduced fracture risks, for instance, evidence is strongest in institutionalized populations. This suggests that factors including exercise and overall vitamin D status are important.
Supplementation is primarily useful in conditions of insufficiency.16 Nevertheless, there is recent suggestive findings that vitamin D may be more effective if used in conjunction not only with calcium, but also with another vitamin, vitamin K. A trial published in April 2007 provides evidence of a modest synergy in healthy older women from nutritionally relevant intakes of vitamin K(1) together with supplements of calcium plus moderate vitamin D3 to enhance bone health.17
Some Other Conditions Related to Vitamin D Status
Osteomalacia
Excessive turnover of bone minerals in adults can lead to bone mineral loss, soft bones, and bone pain. Vitamin D deficiency can be a cause of this condition.
Psoriasis
This skin condition famously is often improved by exposure to summer sunshine as long as there is no burning. Ointments based on vitamin D analogs increasingly are used to control the excessive turnover of the skin cells found in psoriasis.
Depression and Seasonal Affective Disorder
Poor mood often is associated with advancing years. Recent data suggests that poor vitamin D status may becommon in the elderly. Low levels of vitamin D are associated with poor mood. There are a number of trials that have suggested a role for supplementary vitamin D in the treatment of depression.18
Seasonal Affective Disorder has been treated successfully with vitamin D. Thirty days of treatment with vitamin D successfully resolved the depression, whereas two hours daily use of “light boxes” was less successful.19
Postmenopausal Weight Gain
Calcium plus D3 (cholecalciferol) supplementation has a small effect on the prevention of weight gain, which was observed primarily in women who reported inadequate calcium intakes.20
Diabetes
The role of vitamin D in diabetes is not well understood. However, there is mounting evidence that it can play a role in this condition and in the visceral-type obesity most associated with diabetes and heart disease.21
The Sunshine Vitamin Shines, but Maybe not Vitamin D2
Very few outside of the vitamin D research community are aware that vitamin D2 is considered by a number of leading scientists to be greatly inferior to “natural” vitamin D, vitamin D3. As one group has put this, “Supplemental vitamin D is available in two distinct forms: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Pharmacopoeias have officially regarded these two forms as equivalent and interchangeable, yet this presumption of equivalence is based on studies of rickets prevention in infants conducted 70 years ago. Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification.”22 Others have demonstrated that vitamin D2 is much less effective than vitamin D3 in humans.23
In conclusion, vitamin D in the form of vitamin D3 has undergone quite a remake in the scientific mind over the last decade. No longer is it considered merely a handmaid to calcium in bone health. New studies have demonstrated its potential for improving immune functioning, thus reducing the risks of a variety of cancers. Other studies show its benefits with depression, diabetes, hypertension, weight gain and even multiple sclerosis. One might say that the old has become new again. The Nineteenth Century put great stock in cod liver oil, which we now know is a superb source of vitamin D. Maybe it was onto something.
References
- Woolmore JA, Stone M, Pye EM, Partridge JM, Boggild M, Young C, Jones PW, Fryer AA, Hawkins CP, Strange RC. Studies of associations between disability in multiple sclerosis, skin type, gender and ultraviolet radiation. Mult Scler. 2007 Apr;13(3):369–75.
- Skinner HG, Michaud DS, Giovannucci E, Willett WC, Colditz GA, Fuchs CS. Vitamin D intake and the risk for pancreatic cancer in two cohort studies. Cancer Epidemiol Biomarkers Prev. 2006 Sep;15(9):1688–95.
- John EM, Koo J, Schwartz GG. Sun exposure and prostate cancer risk: evidence for a protective effect of early-life exposure. Cancer Epidemiol Biomarkers Prev. 2007 Jun;16(6):1283–6.
- Bodiwala D, Luscombe CJ, French ME, Liu S, Saxby MF, Jones PW, Fryer AA, Strange RC. Polymorphisms in the vitamin D receptor gene, ultraviolet radiation, and susceptibility to prostate cancer. Environ Mol Mutagen. 2004;43(2):121–7.
- Giovannucci E, Liu Y, Rimm EB, Hollis BW, Fuchs CS, Stampfer MJ, Willett WC. Prospective study of predictors of vitamin D status and cancer incidence and mortality in men. J Natl Cancer Inst. 2006 Apr 5;98(7):451–9.
- Grant WB, Garland CF. The association of solar ultraviolet B (UVB) with reducing risk of cancer: multifactorial ecologic analysis of geographic variation in age-adjusted cancer mortality rates. Anticancer Res. 2006 Jul/Aug;26(4A):2687-99.
- Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr. 2007 Jun;85(6):1586–91.
- Martineau AR, Honecker FU, Wilkinson RJ, Griffiths CJ. Vitamin D in the treatment of pulmonary tuberculosis. J Steroid Biochem Mol Biol. 2007 Mar;103(3–5):793–8.
- Martineau AR, Wilkinson RJ, Wilkinson KA, Newton SM, Kampmann B, Hall BM, Packe GE, Davidson RN, Eldridge SM, Maunsell ZJ, Rainbow SJ, Berry JL, Griffiths CJ. A single dose of vitamin D enhances immunity to mycobacteria. Am J Respir Crit Care Med. 2007 Jul 15;176(2):208–13.
- Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E. Epidemic influenza and vitamin D. Epidemiol Infect. 2006 Dec;134(6):1129–40.
- Scragg R, Sowers M, Bell C. Serum 25-hydroxyvitamin D, ethnicity, and blood pressure in the Third National Health and Nutrition Examination Survey. Am J Hypertens. 2007 Jul;20(7):713-9.
- Dawson-Hughes B. Racial/ethnic considerations in making recommendations for vitamin D for adult and elderly men and women. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1763S–6S.
- Stoff J, Clouatre D. The Prostate Miracle. Kensington Publishing Corp., (September 2000).
- Heaney RP. Barriers to optimizing vitamin D3 intake for the elderly. J Nutr. 2006 Apr;136(4):1123–5.
- Steingrimsdottir L, Gunnarsson O, Indridason OS, Franzson L, Sigurdsson G. Relationship between serum parathyroid hormone levels, vitamin D sufficiency, and calcium intake. JAMA. 2005 Nov 9;294(18):2336–41.
- Izaks GJ. Fracture prevention with vitamin D supplementation: considering the inconsistent results. BMC Musculoskelet Disord. 2007 Mar 9;8:26.
- Bolton-Smith C, McMurdo ME, Paterson CR, Mole PA, Harvey JM, Fenton ST, Prynne CJ, Mishra GD, Shearer MJ. Two-year randomized controlled trial of vitamin K1 (phylloquinone) and vitamin D3 plus calcium on the bone health of older women. J Bone Miner Res. 2007 Apr;22(4):509–19.
- Berk M, Sanders KM, Pasco JA, Jacka FN, Williams LJ, Hayles AL, Dodd S. Vitamin D deficiency may play a role in depression. Med Hypotheses. 2007 May 10.
- Gloth FM 3rd, Alam W, Hollis B. Vitamin D vs broad-spectrum phototherapy in the treatment of seasonal affective disorder. J.Nutr.Health Aging 1999;3:5–7.
- Caan B, Neuhouser M, Aragaki A, Lewis CB, Jackson R, LeBoff MS, Margolis KL, Powell L, Uwaifo G, Whitlock E, Wylie-Rosett J, LaCroix A. Calcium plus vitamin D supplementation and the risk of postmenopausal weight gain. Arch Intern Med. 2007 May 14;167(9):893-902.
- Speer G, Cseh K, Winkler G. Vitamin D and estrogen receptor gene polymorphisms in type 2 diabetes mellitus and in android type obesity. Eur J Endocrinol. 2001 Apr;144(4):385–9.
- Houghton LA, Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. Am J Clin Nutr. 2006 Oct;84(4):694–7.
- Armas LA, Hollis BW, Heaney RP. Vitamin D2 is much less effective than vitamin D3 in humans. J Clin Endocrinol Metab. 2004 Nov;89(11):5387–91.
|
