AnthroHealth
Something
New Under the Sun:
Adapting to Change in the 21st Century
AnthroHealth News
April 2007
Volume 6, Issue 4
Your Skin Color and Your Health
So, do you have adequate levels of 25 OHD? After completing the worksheets in the last newsletter and estimating your UVB radiation exposure and current intake of dietary vitamin D, many of you are probably somewhat concerned. But this series of newsletters is about getting real with your health. If you have moderate-to-dark skin color, you need to be more than somewhat concerned; you need to be seriously worried because the odds are extremely high that your levels of 25 OHD are grossly inadequate.
Americans with primarily West African ancestry suffer from several health problems at higher rates than is true of other Americans. They have an incidence of low-birth-weight infants and infant mortality which is at least double that of Americans with primarily European ancestry. Their rate of prostate cancer is the highest in the world. Breast cancer occurs at a younger age and in a more severe form than is true for American women with primarily European ancestry. Hypertension, a serious problem among Americans with primarily West African ancestry, often goes undiagnosed, clusters with diabetes, and is associated with heart disease. Both diabetes and heart disease result in higher incidence and mortality rates among Americans with primarily West African ancestry compared to Americans with primarily European ancestry.
These health problems have multiple causes, but one which has received little attention is a life-long inadequate level of vitamin D (25 OHD). That vitamin D is a major factor and not some trait or experience specific to Americans with primarily West African ancestry is shown by the fact that these same health problems are appearing among South Asian populations living in North America and Great Britain. The characteristic shared by Americans with primarily West African ancestry and Americans or British with South Asian ancestry is degree of skin color: individuals in both groups tend to have moderate-to-dark skin color. North America and Great Britain are in the temperate zones with most of North America and all of Great Britain at the high latitudes that receive little UVB radiation, except for a few weeks during the summer months. This means that the dark skin color of these individuals prevents them from obtaining adequate levels of vitamin D through exposure of unprotected skin to UVB radiation. This is made worse by diets which contain few of the fish that are high in vitamin D, along with little or no vitamin D supplementation.
Although not mentioned in the usual lists of health problems, one that affects Americans with West African ancestry at higher rates than is true of other groups is rickets. All but a small percentage of diagnosed cases in the United States are among Americans with West African ancestry, while in Great Britain the majority of cases are among those with South Asian ancestry. These cases of rickets are clear indications of extremely inadequate levels of vitamin D among infants and children. It is probable that a high percentage of infants and children with West African ancestry have sub-clinical rickets, but that the symptoms are not severe enough for the pediatrician to notice. The remaining infants and children probably have suboptimal levels of vitamin D which are not improved as the individual grows up and becomes an adult. A lifetime of inadequate or suboptimal levels of vitamin D provides the basis for many of the health problems that now concern public health officials.
Intriguingly, there is a health problem that occurs in one group at much higher rates than is true of the other health problems discussed here, but it is not usually thought of in the same terms. This problem is skin cancer which occurs at disproportionately high rates among those light-skinned individuals of northern European ancestry. This is particularly the case among those individuals with light skin color living in Australia, a country with high levels of UVB radiation. Individuals with light skin color have ten times the rate of melanomas that are seen in individuals with dark skin color, and the vast majority of cases of basal cell and squamous cell skin cancers are found on individuals with light skin color. No societal or economic factor or genetic difference between populations is publicized as the cause of this huge difference in incidence rates. The disparity in skin cancer rates is quite clearly due to individuals with light skin color receiving too much UVB radiation. Why, then, is it improbable that the health disparities listed above which more severely impact individuals with dark skin color would be due not to a societal or economic factor or a genetic difference between populations, but instead due to individuals with dark skin color receiving too little UVB radiation?
Inadequate levels of vitamin D play a role in breast and prostate cancers, hypertension, diabetes, and the intrauterine growth retardation which results in low-birth-weight infants and can lead to infant mortality. The hormonal form of vitamin D (1,25 OHD) acts as a tumor-suppressant. Adequate levels of vitamin D throughout life may serve to restrain tumor growth and development, while inadequate levels allow tumors to grow undisturbed. The earlier onset and more severe prognosis of cancer among Americans with West African ancestry may well be due in part to a lifetime of suboptimal levels of vitamin D. This is supported by the lower rates of breast and prostate cancers found among those of West African ancestry living in equatorial zones. These individuals have the opportunity for exposure year-round to extremely high levels of UVB radiation and so are better able to maintain optimal levels of vitamin D. Increased levels of vitamin D from infancy on may well reduce the incidence and severity of breast and prostate cancer.
Hypertension also shows a latitudinal effect: lower rates occur in equatorial zones than in temperate zones. At one time this was thought to be related to temperature changes, but it is now clear that the factor is differing levels of UVB radiation exposure. Individuals with hypertension were able to lower blood pressure levels after exposure to full body UVB radiation resulting in raised levels of vitamin D. There is a clear gradient of hypertension among those of West African ancestry. Of three populations examined, the lowest rates were among Nigerians, higher rates were found among Jamaicans, and the highest rates of hypertension were found among Americans. It therefore appears that increasing exposure to UVB radiation and/or increasing blood levels of vitamin D should result in lowered blood pressure. This would also reduce the incidence of heart disease, the major cause of death in the United States.
Diabetes is an autoimmune disorder, as are multiple sclerosis and rheumatoid arthritis. Increased blood levels of vitamin D have been associated with improvements in these diseases. While Type 2 diabetes is primarily associated with obesity and a diet with a high glycemic index (this will be discussed in a future newsletter), it may well be that suboptimal levels of vitamin D disrupt glucose metabolism, setting the stage for the later development of diabetes.
Population-based studies have found that individuals with low blood levels of 25 OHD have a higher risk of developing Type 2 diabetes than do those with normal levels because vitamin D is involved in insulin release and normal glucose tolerance. In order to prevent diabetes, it appears that adequate blood levels of 25 OHD must be maintained throughout life, although a determination of “adequate” in this case has not yet been made. Once diabetes becomes established, raising 25 OHD levels has only limited effect. Therefore, in order to prevent diabetes, it would appear that in addition to maintaining appropriate body weight and eating foods with a low glycemic index, you should also make sure to maintain optimal levels of vitamin D. The best way to do this is to eat according to the Premier Nutrition plan and to get appropriate exposure to UVB radiation and/or vitamin D supplementation. Later newsletters will provide more complete information.
Intrauterine growth retardation and premature delivery are among the primary factors in the incidence of low-birth-weight infants; and being of low birth weight is one of the main factors associated with infant mortality. American infants with primarily West African ancestry are about twice as likely to be of low birth weight and are about twice as likely to die as are American infants with primarily European ancestry. This gap has remained unchanged since the first article on this topic appeared in 1904. Medical care, prenatal care, and overall health have improved tremendously since 1904, but the gap remains. What has remained unchanged over the past century is that individuals with dark skin color living in the United States, particularly in northern urban centers, have much greater difficulty in maintaining optimal levels of vitamin D than do individuals with light skin color living in the same regions.
Fetal development is dependent on the mother. In an effort to maintain appropriate blood vitamin D levels, the fetus, via the placenta, draws on the mother's stores of vitamin D. Pregnancy and lactation are major stressors on the woman's stores of vitamin D and calcium. Even well-nourished women who breast-feed can lose 5% of bone mineral density, as measured at the femoral neck and lumbar spine, although bone mineral density recovers when breast-feeding ceases. Blood vitamin D levels in pregnant and lactating females are critical to the health and development of the fetus and infant.
During pregnancy, primarily in the last trimester, approximately 30 grams of calcium are transferred from maternal stores to the fetus via the placenta, a process aided by appropriate levels of 1,25 OHD in the mother's blood. Animal studies have found a significant correlation between the mother’s levels of 25 OHD in her blood and what happens during pregnancy and delivery. Females who were vitamin D-deficient had difficulty maintaining a pregnancy and had much higher rates of poor birth results (small litters, dead litters, or mothers dying prior to or during delivery) than did vitamin D-sufficient females. A recent study found that premenopausal women who were vitamin D-deficient suffered from problems with calcium regulation which resulted in an inability to ovulate. After undergoing vitamin D therapy, 54% began having normal menstrual cycles and two became pregnant.
Pregnant women who were severely vitamin D-deficient and who were given 600,000 international units (IU) of vitamin D in both the seventh and eighth months of pregnancy not only increased their own levels of vitamin D, but gave birth to heavier infants than would otherwise have been the case. Women who begin pregnancy with extremely low levels of vitamin D and who do not receive vitamin D supplementation during pregnancy show an interesting birth pattern. Infants born in winter months have greatly reduced bone mineral content compared to those born in summer months. This indicates that even a slight improvement in a mother’s vitamin D levels during the months of greater UVB radiation exposure can improve the health of the infant. However, the pattern is different for mothers who receive vitamin D supplementation during the second and third trimesters of their pregnancies. For mothers whose first trimester was during the winter months, infants born in the summer months had lower bone mineral content than did infants born in winter months whose mothers’ first trimester occurred during the summer months. This is because many women do not realize they are pregnant right away and do not begin taking vitamin D supplementation until the second and third trimesters, but women who become pregnant during the summer months are at their peak level of vitamin D for the year.
Researchers in Sweden found that women of African origin (primarily from Somalia) were four times more likely to die during childbirth or soon after than were women of Swedish origin. In addition, infants of women of African origin were more likely to be preterm and small for their age. These differences were not explained by differences in risk factors. However, it is likely that the darker-skinned women of Somali origin had much lower levels of vitamin D in their blood compared to lighter-skinned Swedish women due to the fact that Sweden is so far north that it receives very little UVB radiation most of the year. If the mothers’ level of vitamin D is too low, their infants will be born with problems.
Mothers who die during childbirth are still a problem in the United States, particularly for women with West African ancestry. Their death rate is three to six times that of women with primarily European ancestry. Even when controlling for a variety of known risk factors, this difference in death rates is still not fully explained. It may be that vitamin D deprivation also plays a role here since it has been shown to do so in animal studies.
A study of hypertension among women of childbearing age found that the women with West African ancestry had twice as much hypertension compared to women with European ancestry and that this was one of the reasons there were twice as many low-birth-weight infants born to American women with West African ancestry. Hypertensive problems during pregnancy are among the five leading causes of maternal death in the United States. Hypertension is related to the interaction of skin color with latitude and is not due to genetic differences. This is supported by research done in Vancouver, Canada on an obstetric population subdivided into groups described as White, Oriental, East-Indian, and Aboriginal. The East-Indian women (who have darker skin color than women in the other three groups) had much higher rates of small-for-age infants than did the other groups. As I mentioned before, one factor causing small-for-age infants is a mother with hypertension. In addition, the average birthweight for East Indian infants was about 200 grams less than that for the infants in the White subgroup. American infants with West African ancestry also weigh about 200 grams less than American infants with European ancestry.
If you are a women and you are thinking about becoming pregnant, especially if you have moderate-to-dark skin color, you live in the temperate zone, you receive little UVB radiation exposure, and/or you get little vitamin D from your diet or from supplementation, you should seriously consider having your blood levels of 25 OHD checked. If your levels are below 40 ng/ml during the summer or 32 ng/ml during the winter months, then you should consider delaying getting pregnant until you’ve managed to reach those levels. Levels of 50 ng/ml or higher are best. If you are already pregnant, make sure to take vitamin D supplementation prescribed by your physician, although what your physician prescribes will probably be too low. A supplement of 1000 IU of vitamin D3 each day should be the minimum dosage. If possible, appropriately expose unprotected skin to UVB radiation during the summer months. Eating sardines two to three times per week would also be great, especially if you have dark skin color since you will have great difficulty getting enough exposure to UVB radiation to sufficiently raise your vitamin D levels.
Health Problems and UVB Radiation
Subtropical and Tropical Zones:
· High
levels of UVB radiation
· Light-skinned individuals need to take care to avoid overexposure and/or
heavy intermittent exposure to UVB radiation that could result in the
development of skin cancers.
Temperate Zones:
· Low
levels of UVB radiation
· Dark-skinned individuals will have trouble obtaining adequate exposure
to UVB radiation thereby causing them to have suboptimal levels of vitamin
D.
· Suboptimal levels of vitamin D are a factor in:
o Hypertension
o Diabetes
o Breast cancer
o Prostate cancer
o Rickets
o Low-birth-weight infants
o Neonatal mortality
This
link shows the distribution of skin color throughout the world:
http://anthro.palomar.edu/adapt/images/map_of_skin_color_distribution.gif
This link shows the effective daily dose of vitamin D during the winter months throughout the world:
http://i115srv.vu-wien.ac.at/uv/vitamind/vitd_h_dd_gl.gif
Summary
Americans with primarily West African ancestry have much higher rates of diabetes and hypertension than do Americans with primarily European ancestry. The highest rates in the world for prostate cancer are found among American men with primarily West African ancestry, while American women with primarily West African ancestry have earlier onset and more severe progression of breast cancer than do American women with primarily European ancestry. Low-birth-weight infants and infant deaths occur at twice the rate among Americans with primarily West African ancestry compared to Americans with primarily European ancestry. Americans with primarily European ancestry have ten times the rate of melanomas as are found among Americans with primarily West African ancestry. These health disparities, although having many causes, are also all associated with UVB radiation either through underexposure or overexposure. Therefore, they are also related to blood levels of vitamin D.
Melanomas occur at far, far higher rates among individuals with light skin color who receive sporadic, but intense exposure to UVB radiation. Because the exposure is irregular and occasional, it is likely that these individuals also have suboptimal levels of vitamin D. Due to this, the tumor-suppressant ability of 1,25 OHD does not function well. This allows the DNA damage created by the intense overexposure to UVB radiation to develop into melanomas. The other health problems are caused in part by too little UVB radiation exposure which results in blood levels of vitamin D that are too low.
Over thousands of generations, humans have adapted to different types of environments. When an individual whose body is adapted to a particular type of environment is placed in a very different environment, problems will occur. Some of these problems can be fixed through cultural behaviors or technology such as wearing warm clothing or having a heating source during the winter, or wearing a hat to protect your face from sunburn during the summer. Individuals with very light skin color are adapted to environments in the far northern latitudes where they receive little or no UVB radiation for most of the year. However, with proper clothing, sunscreens, and adjustments in behavior and activities, they can live successfully in equatorial zones of intense UVB radiation.
Individuals with dark skin color are adapted to the intense UVB radiation of equatorial zones, but with appropriate adjustments, such as a diet which includes lots of cold water fish such as salmon, sardines, and mackerel, they can live in temperate zones. In the past few decades, this has been made easier through the use of vitamin D supplements which are now available over-the-counter in 1000 IU doses.
Health disparities could be dramatically reduced if every individual could get his or her blood levels of vitamin D (25 OHD) raised to at least 50 ng/ml. Optimal levels of vitamin D would aid in reducing the incidence of melanomas among those who have light skin color. For those who have dark skin color, optimal levels of vitamin D would reduce the incidence and severity of breast and prostate cancers. Reducing the incidence of diabetes and hypertension by maintaining optimal levels of vitamin D would also reduce the incidence of the major cause of death: cardiovascular disease. Finally, it is critically important that mothers maintain optimal levels of vitamin D prior to becoming pregnant and throughout their pregnancy and beyond if we are to reduce the rates of low-birth-weight infants and infant mortality. Maintaining optimal levels of vitamin D throughout the lifespan will improve health on a number of measures and will aid in eliminating health disparities. Taking a walk in the sunshine will help maintain optimal vitamin D levels.
Here’s the bottom line: skin color matters, but “race” does not. What matters is your individual skin color, where you live, what type of work you do, what you eat, and how much UVB radiation exposure you get. If you have very light skin color, you need to be especially careful of getting too much intense, intermittent exposure. Don’t go out on the weekends and bake yourself. It is much better to get 20 – 30 minutes of exposure each day than a massive dose once a week. You are more likely to optimize your vitamin D levels that way and to have enough vitamin D to act as a tumor suppressant which will prevent melanomas. If you want to avoid sun exposure, then make sure to take a vitamin D supplement of at least 1000 IU/day (more during winter months).
If you have moderate-to-dark skin color then in all probability you have blood levels of vitamin D that are far too low for optimal health. You are at great risk of developing various types of cancer, hypertension, or Type 2 diabetes. If you are a pregnant woman, you have a much higher risk of giving birth to an underweight baby who will be starting life at a disadvantage with low vitamin D levels. Given the fact that most of us work indoors during the prime UVB radiation hours and the fact that dark skin color prevents the penetration of most UVB radiation, thus limiting vitamin D production, those with dark skin color must take, at a bare minimum, 1000 IU/day of vitamin D. It is highly probable that higher doses will be needed to optimize vitamin D levels. If you have dark skin color, work inside, and live in the northern states or Canada, you should probably take 4000 IU/day of vitamin D3. Skin color is a factor that has to be considered when we are working to optimize our health. If you ignore it and pretend that it doesn’t matter, you put your health at risk.
Copyright
© 2001-2009 Kathleen E. Fuller, PhD. All rights reserved.
