New Under the Sun:
Volume 5, Issue 5
May can be a month filled with restlessness, particularly for those involved in education. The end of the school year is approaching, the weather is warming, and thoughts of summer fill one with expectations of vacations and fun. This would be a good time to use those feelings of restlessness and hopeful expectation to take stock of your current health status and consider making some positive changes.
Getting Ds is a straight-A Strategy: Maybe, after years of pushing vitamin D, we have finally reached the tipping point and it will become the major health care issue it deserves to be. I say this because not only was there an international conference on Vitamin D in April (click here for more details from John Cannell, MD of the Vitamin D Council http://www.vitamindcouncil.com/PDFs/May2006.pdf ), but the medical news services have been highlighting vitamin D-related research the past few weeks. Here are a few.
Diabetes and Vitamin D: More research has linked vitamin D deprivation to the onset of diabetes, in this case, type 2. The subjects in this research were the 83,779 women enrolled in the Nurses Health Study. At baseline, the women were disease free. Every two to four years their intake of calcium and vitamin D was assessed by questionnaire. Over the following 20 years, 4,843 women developed type 2 diabetes. Women with the highest intake of calcium (>1200 mg) and vitamin D (>800 IU) were 33% less likely to develop type 2 diabetes than were women with the lowest intakes (< 600 mg calcium and < 400 IU vitamin D). The average intake for all the women was 309 IU of vitamin D and 867 mg of calcium. As the researchers note, vitamin D deprivation is associated with impaired glucose regulation. In this study only 3% of the women had adequate intake of vitamin D. Since “adequate” is currently defined as 200 IU for young adults, 400 IU for older adults, and 800 IU for seniors, and since all these intakes are now considered inadequate by recent research and will be revised upwards in the next year or so, it would not be surprising if more of the women developed type 2 diabetes as they age since it is probable that 100% of them were vitamin D deprived. The study would have been more useful if they had taken serum levels of 25-hydroxyvitamin D for the subjects. Pittas AG, Dawson-Hughes B, Li T, Van Dam RM, Willett WC, Manson JE, Hu FB. Vitamin D and calcium intake in relation to type 2 diabetes in women. Diabetes Care. 2006 Mar;29(3):650-6.
Comment: Although the researchers considered the average calcium intake of 867 mg inadequate, it would be quite adequate if the vitamin D intake were adequate. Those individuals living in tropical zones who have adequate levels of vitamin D have an average intake of 500 mg calcium and do not suffer from calcium deprivation. It is more important to have adequate levels of vitamin D than adequate levels of calcium. However, the dairy producers are a major economic and lobbying force in the United States so it is not too surprising that the government would exhort its citizens to ingest more calcium than is really needed. Since the vitamin D lobby does not have economic power, its message has trouble reaching policy makers.
Pregnancy and Vitamin D: The dairy producers do serve as a source of research funding. However, the research needs to show benefits of dairy. It is in this context that researchers examined the intra-uterine growth benefits provided to pregnant women who drank milk. Since the milk was fortified with vitamin D, they also examined vitamin D intake and its effects. The study enrolled 2091 pregnant women over a two-year period. During this time, 307 women restricted their intake of milk. Women who drank less than one cup of milk per day had infants who weighed on average 123 gms less than women who drank 3 or more cups of milk per day. Each additional cup of milk increased birth weight by 41 gms. Vitamin D intake was based on diet and supplements. For each additional 40 IU intake of vitamin D, birth weight increased 11gms. Cynthia A. Mannion, Katherine Gray-Donald and Kristine G. Koski. Association of low intake of milk and vitamin D during pregnancy with decreased birth weight. CMAJ • April 25, 2006; 174 (9): 1273-1277.
Comment: Interestingly, the researchers found no effect of calcium or protein on birth weight. Since milk is a source of protein, calcium, and fat, this would leave fat as the major factor in the weight increase associated with milk consumption. However, in a commentary on the article published with it, Bruce Hollis and Carol Wagner state that fat does not appear to be the factor. They believe that the difference is directly tied to differing intake levels of vitamin D. Since the researchers did not obtain 25 hydroxyvitamin D levels for the pregnant women, we do not really know whether those women with adequate levels of serum vitamin D had heavier babies or not. For more on the connection between birth weight and vitamin D, you can read my article on the topic. K. Fuller 2000 Low-Birth-Weight Infants: The Continuing Ethnic Disparity and the Interaction of Biology and Environment. Ethnicity and Disease 10: 432-445. Bruce W. Hollis and Carol L. Wagner. Nutritional vitamin D status during pregnancy: reasons for concern. CMAJ • April 25, 2006; 174 (9): 1287-1290.
Vitamin D and Cancer: It has been known for years that there is an association between low vitamin D levels and an increased risk for prostate, colon, and breast cancers. But it is good to see more research supporting the advice to optimize vitamin D levels in order to reduce cancer risks.
Breast Cancer: Researchers in Canada found that women who had high vitamin D levels as teens were much less likely to develop breast cancer later in life. The research included women between the ages of 20 and 59, about 1/3 of whom had experienced breast cancer. Those women who between the ages of 10 and 29 had spent their summers working outdoors for ten or more years, or who had taken cod liver oil for ten or more years during their youth, were significantly less likely to have developed breast cancer. Cod liver oil reduced the risk by 25%, while working outdoors rather than indoors reduced the risk by 40%. Since exposing unprotected skin to UVB radiation is the natural way to provide our bodies with vitamin D, it is not too surprising that outdoor work produced a better result than did supplementation. Knight concluded that, “…vitamin D may reduce the risk of breast cancer and earlier exposures may be more important than recent exposure." Since vitamin D can only be stored in the body for a few months, this means that vitamin D deprivation can lead to tissue changes early in one’s life that may later become cancerous. However, optimization of vitamin D levels is necessary at every age. J. Knight, 97th Annual Meeting of the American Association for Cancer Research; Washington DC, USA; 1–5 April 2006.
Comment: While women of West/Central African ancestry do not have higher overall rates of breast cancer, they do tend to have higher rates of early onset, severe breast cancer when compared to other women. This would support the importance of having optimized levels of vitamin D when young. Since individuals who are moderately-to-heavily pigmented have great difficulty obtaining adequate vitamin D via skin exposure, it is probable that they would be vitamin D-deprived for a longer period than women with lighter pigmentation and, therefore, would have earlier onset of cancerous tissue changes.
Cancer in Men: Using information obtained from the 47,800 men enrolled in the Health Professionals Follow-Up Study, researchers determined that men with low levels of vitamin D had a higher risk of developing and dying from cancer than did men with high levels of vitamin D. They found that for those who had a 25 nmol/L (10 ng/mL) increase in 25-hydroxyvitamin D levels (as predicted by the researchers’ calculations) total cancer incidence was reduced by 17% while cancer mortality was reduced by 29%. There was a 45% reduction in mortality from digestive system cancers. The researchers concluded that in order to receive this health benefit, those men with low levels of 25-hydroxyvitamin D would need to take a daily supplement of at least 1500 IU of vitamin D (cholecalciferol). 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.
Comment: Because of the numbers of men involved in this study and the relatively high cost of vitamin D testing, the researchers calculated the predicted level of 25-hydroxyvitamin D in the men based on several indicative parameters that had been correlated with serum vitamin D levels on a sample of 1095 men. These parameters were: amounts of vitamin D obtained from diet and supplements, latitude of residence, outdoor exposure associated with leisure activities, degree of pigmentation, and degree of adiposity. Latitude of residence is significant because the further one lives from the Equator, the less exposure to UVB radiation one receives and, therefore, the less one is able to synthesize vitamin D via skin exposure. Those who are heavily pigmented have a built-in sun block which seriously inhibits synthesis of vitamin D. Fat cells sequester vitamin D so that even if one is synthesizing vitamin D, it is unavailable to the body. Using these parameters and correlating them to the serum levels of 25-hydroxyvitamin D obtained from the 1095 men, the researchers were able to develop a formula for predicting 25-hydroxyvitamin D levels in men for whom they could obtain the parameters, but not the actual blood samples. While these parameters are appropriate, what they actually used for degree of pigmentation was the individual’s race. This is a poor indicator of degree of pigmentation since black race in this country includes a huge diversity of skin color shades. Pigmentation can be accurately determined using a spectrograph. I did a pilot study on this several years ago and verified the usefulness of this device. While the researchers’ methodology is a good beginning, obtaining actual degree of pigmentation would improve their calculations considerably. For instance, some individuals of South Asian ancestry are significantly more pigmented than are some individuals who define themselves as black, but they would fall into different racial categories.
The cost of vitamin D testing is one of the factors preventing and/or inhibiting research on vitamin D and health. It is also a limiting factor for those of us who would like to monitor our own vitamin D levels since few insurance companies will cover the cost unless it is tied to a specific disease such as osteoporosis. However, you can do your own rough calculation. If you do not eat fatty fish such as sardines every day, if you do not take a vitamin D supplement, if you are heavily-pigmented, if you are overweight, if you are rarely outside during the summer between the hours of 10 am and 3 pm, and if you live in a northern state, the odds are extremely high that your 25- hydroxyvitamin D levels are in the single digits where 40 – 50 ng/mL is considered optimal. If all of the above apply except that you are thin and lightly-pigmented, then you may have levels in the high teens or low 20s (ng/mL). Unless you have a job where you work outdoors every day you should assume that your vitamin D status needs to be improved and that you need to take a cholecalciferol supplement (without vitamin A or calcium).
AnthroHealth Tip of the Month: Let’s see. What is this month’s tip likely to be? Hmm… How about, optimize your levels of vitamin D?! Before beginning, use the parameters discussed above and determine your probable level of vitamin D. The odds are it could use improvement. To optimize your levels naturally, take into consideration your degree of pigmentation and latitude of residence and then expose unprotected skin to the sun during the hours of 10 am and 3 pm for the appropriate amount of time. If this is impractical and if you cannot bring yourself to eat sardines, then take a cholecalciferol supplement (without vitamin A or calcium) of at least 1000 IU each day. And make sure that if you have children or teens that their vitamin D levels are also optimized. With kids spending more and more of their day indoors (even recess is becoming a thing of the past), vitamin D optimization is not a given.
© 2001-2009 Kathleen E. Fuller, PhD. All rights reserved.