African-American Males, Dairy Calcium & Prostate Cancer
A growing number of studies point to an over-consumption of dietary calcium as increasing the incidence of prostate cancer. African-American males are among those having the highest prostate cancer rates in the world. During the vigorous bone growth period of adolescence, this group consumes less calcium, but absorbs and retains more of it than other populations, leading to higher bone density, and lower rates of fractures later in life. This is so even though blacks have traditionally consumed the least amount of milk and dairy because of lactase non-persistence (lactose intolerance). In short, nature has provided a highly efficient calcium retaining mechanism for lactase non-persistent groups, who also happen to constitute 70% of the global population. But what are the consequences for a minority group possessing biological mechanisms to ensure sufficiency in calcium as they become more acculturated into the American mainstream? Nutritional experts inform them that they are calcium-deficient by Food and Drug Administration standards and should therefore consume more dairy products, and ignore symptoms of lactose intolerance for the sake of their health.
However, FDA dietary recommendations for calcium are based on studies of lactose-tolerant Americans of European descent. No known studies have been conducted on the possible side effects of dairy products on lactase-non-persistent populations, although studies have shown that they process calcium more efficiently. Thus, African-American males, even when they follow the medically-accepted guidelines, are consuming more calcium than their bodies require. If excess calcium does trigger this disorder, then black males will have a higher incidence of prostate cancer than their white counterparts, even if the former group’s dietary consumption of dairy products is less than that of the American mainstream.
African-American males suffer from the highest incidence rates of prostate cancer in the world. In an effort to gain a perspective on this issue, medical researchers have compared these statistics for black American males with those of West Africans from whom they are genetically descended. But the data was scanty and what conclusions were drawn, created even greater confusion by pointing to West Africans as having the lowest rate of prostate cancer on that continent. ([1]) Dozens of studies have also been conducted attempting to differentiate the risk factors of black and white Americans. A review of this literature from 1970 through 2008 looked at such variables as physical activity, weight/body mass index, dietary factors, occupational history, sexual behavior, sexually transmissible infections, and other health conditions. But no clear patterns were discernible.([2])
A 2001 study conducted by J. M. Chan, M. Stampfer, et al. in the American Journal of Clinical Nutrition investigated the association between dietary calcium intake from dairy products and prostate cancer risk using data supplied by the Physicians' Health Study. It concluded: “These results support the hypothesis that dairy products and calcium are associated with a greater risk of prostate cancer.” ([3]) Since that time, a sizable number of studies have supported the theory that there is a link between dairy and/or calcium consumption and an increased risk of prostate cancer. Two influential health organizations, the World Cancer Research Fund and the Agency for Healthcare Research and Quality consider the data of sufficient weight that they have both issued a warning, declaring calcium a probable cause of cancer.([4]) Even so, several other studies have proved inconclusive.([5]) But a design flaw may have muddied any data that attempted to compare black and white risk of prostate cancer in relationship to dairy consumption.
Black Americans are an admixed population of West African, European and some Native American ancestry. Some blacks have as little as five or ten percent African ancestry, while those on the other end of the spectrum may have no European ancestry. Using self-identification, rather than genetic bio-markers, as a means of classifying African-Americans has been the methodology used in most studies and tends to work well in the social sciences. However, in any biological research comparing health and medical risk factors between blacks and whites, this social research methodology will almost certainly skew the results. If for example, one were to ask the question: “does higher dairy consumption in blacks lower the risk of prostate cancer,” almost any study that looked at the subject merely as a statistical analysis would answer “yes.” But it is not because milk drinking is shown to be causally related to decreasing the incidence of prostate cancer in blacks. It is rather because people self-identifying as African-Americans can have anything from one percent West African ancestry to 100%. Those blacks who consume the most milk will also be the ones who are not lactose intolerant, because they have inherited the lactase enzyme from their (sociologically) unacknowledged but (biologically) real European ancestors. It is also true that having a larger percentage of European ancestry would in and of itself confer a lower risk of prostate cancer, thus giving the false impression of a causal relationship between dairy consumption and prostate cancer prevention. In fact, this article will show that the opposite is most likely the case.
African-Americans metabolize calcium more efficiently than whites, therefore their bodies require less of it. What had been determined to be a standard dietary requirement for that mineral was in fact pegged specifically to the biological needs of people of Northern European ancestry.([6]) Researchers in the field of bone health stumbled upon this difference in calcium processing quite by accident. They were initially perplexed at what appeared to be a genetically programmed advantage that protected African-Americans from osteoporosis. Further investigation showed that black adolescents accrued more calcium than their white counterparts on account of increased calcium absorption and superior renal calcium conservation, even though they consumed less dairy products. In adulthood, higher parathyroid hormone concentrations did not result in increased bone loss in African Americans because of their skeletal resistance to parathyroid hormone, and their greater renal conservation of calcium persisted.([7]) This was so even though their intake of dietary calcium was minimal on account of lactase nonpersistence, more commonly known as lactose intolerance. The National Health and Nutrition Examination Survey (NHANES III, 1988-1991) study had also documented the fact that African-Americans have lower calcium intake but higher bone mass.([8])
Researchers had misunderstood the true nature of lactase non-persistence, which made it a confounding factor in their studies. This trait is not a disease and is, in fact, possessed by seventy percent of the world’s population. The opposite ability to digest lactose and thus drink milk after childhood is created by a genetic mutation, which is found in dairy-farming cultures from Northern Europe to East Africa. However, long before dairy-farming entered the human food chain, nature had created biological processes within the human body to regulate and conserve calcium stores. Thus, the West African ancestors of African-Americans did not breed beasts of burden nor engage in dairy farming because of the scourge of the tsetse fly. But their bodies processed smaller quantities of calcium with greater efficiency, giving them denser bone mass and the range of genetic protections that have now been identified in lowering their risk of osteoporosis and other calcium-deficiency disorders.
However, what then happens when this population group becomes acculturated into a society, whose nutritional messaging pathologizes their lactase non-persistence, and admonishes them to supplement what are by European biological standards perceived to be their calcium-poor diets? ([9]) Despite the inconclusiveness of broader studies, involving Europeans or mixed populations, there is at present one study that has specifically looked at African-Americans and calcium intake. The 2012 California Collaborative Prostate Cancer Study examined 533 African-American prostate cancer cases (256 with advanced stage at diagnosis, 277 with localized stage) and 250 African-American controls. That study concluded:
Our data indicates that, although calcium intake increases prostate cancer risk in African American men as a group, it is associated with a significantly greater risk among high absorbers of calcium (men with the AA genotype). If confirmed by other dietary- seroepidemiologic studies, African American men with the AA genotype may be advised to restrict their calcium intake in order to reduce their risk of developing prostate cancer.([10])
The report also noted that because the A allele is associated both with prostate cancer risk and with African ancestry, it is possible that this particular genetic marker might simply be a trait of that population group rather than the actual culprit for the high cancer risk.
However murky the medical literature will continue to be, as new findings contradict previous ones on whether dairy consumption contributes to prostate cancer, nature has at least made itself clear on one point. Lactose intolerance in African-American males is not a digestive inconvenience. It is a dietary calcium set-point, beyond which lies a heightened risk of prostate cancer.
RELATED POST: Is an Unacknowledged Eurocentric Paradigm Widening Ethnic Disparities in U.S. Health Care?
BIBLIOGRAPHY
Aloia, J F, African Americans, 25-hydroxyvitamin D, and osteoporosis: a paradox. American Journal of Clinical Nutrition. 2008 Aug;88(2):545S-550S.
Chu, L W, Ritchey, J, Devesa, S S, Quraishi, S M, Zhang, H, Hsing, A, Prostate Cancer Incidence Rates in Africa. Prostate Cancer. 2011 (Volume 2011) Article ID 947870, 6 pages
.
Chung M, Balk E, Brendel M, Ip S, Lau J, Lee J, Lichtenstein A, Patel K, Raman G, Tatsioni A, Terasawa T, Trikalinos T. Vitamin D and Calcium: Systematic Review of Health Outcomes: Evidence Report/Technology Assessment No. 183. Rockville, MD: Agency for Healthcare Research and Quality; 2009.
Hayes RB, Ziegler RG, Gridley G, Swanson C, Greenberg RS, Swanson GM, Schoenberg JB, Silverman DT, Brown LM, Pottern LM, Liff J, Schwartz AG,Fraumeni JF Jr, Hoover RN. Dietary factors and risks for prostate cancer among blacks and whites in the United States. Cancer Epidemiology, Biomarkers & Prevention. 1999 Jan;8(1):25-34.
(Mordukhovich I Reiter PL, Backes DM, Family L, McCullough LE, O'Brien KM, Razzaghi H, Olshan AF A review of African American-white differences in risk factors for cancer: prostate cancer. Cancer Causes Control. 2011 Mar;22(3):341-57.
National Health and Nutrition Examination Survey, http://www.cdc.gov/nchs/nhanes.htm (Accessed June 16, 2014)
Pettersson A, Kasperzyk JL, Kenfield SA, Richman EL, Chan JM, Willett WC, Stampfer MJ, Mucci LA, Giovannucci EL. Milk and dairy consumption among men with prostate cancer and risk of metastases and prostate cancer death. Cancer Epidemiology, Biomarkers & Prevention. 2012 Mar;21(3):428-36.
Rowland GW, Schwartz GG, John EM, Ingles SA. Calcium intake and prostate cancer among
African Americans: effect modification by vitamin D receptor calcium absorption genotype. Journal of Bone and Mineral Research. 2012 Jan;27(1):187-94.
([1])Chu, L W, Ritchey, J, Devesa, S S, Quraishi, S M, Zhang, H, Hsing, A, Prostate Cancer Incidence Rates in Africa. Prostate Cancer. 2011 (Volume 2011) Article ID 947870, 6 pages
([2]) Mordukhovich I Reiter PL, Backes DM, Family L, McCullough LE, O'Brien KM, Razzaghi H, Olshan AF A review of African American-white differences in risk factors for cancer: prostate cancer. Cancer Causes Control. 2011 Mar;22(3):341-57.
.
([3]) Chan JM, Stampfer MJ, Ma J, Gann PH, Gaziano JM, Giovannucci EL. Dairy products, calcium, and prostate cancer risk in the Physicians' Health Study. American Journal of Clinical Nutrition. 2001 Oct;74(4):549-54.
([4])Chung M, Balk E, Brendel M, Ip S, Lau J, Lee J, Lichtenstein A, Patel K, Raman G, Tatsioni A, Terasawa T, Trikalinos T. Vitamin D and Calcium: Systematic Review of Health Outcomes: Evidence Report/Technology Assessment No. 183. Rockville, MD: Agency for Healthcare Research and Quality; 2009.
([5] )Pettersson A, Kasperzyk JL, Kenfield SA, Richman EL, Chan JM, Willett WC, Stampfer MJ, Mucci LA, Giovannucci EL. Milk and dairy consumption among men with prostate cancer and risk of metastases and prostate cancer death. Cancer Epidemiology, Biomarkers & Prevention. 2012 Mar;21(3):428-36.
([6]) Hayes RB, Ziegler RG, Gridley G, Swanson C, Greenberg RS, Swanson GM, Schoenberg JB, Silverman DT, Brown LM, Pottern LM, Liff J, Schwartz AG,Fraumeni JF Jr, Hoover RN. Dietary factors and risks for prostate cancer among blacks and whites in the United States. Cancer Epidemiology, Biomarkers & Prevention. 1999 Jan;8(1):25-34.
([7]) Aloia, J F, African Americans, 25-hydroxyvitamin D, and osteoporosis: a paradox. American Journal of Clinical Nutrition. 2008 Aug;88(2):545S-550S.
([8] )National Health and Nutrition Examination Survey, http://www.cdc.gov/nchs/nhanes.htm (Accessed June 16, 2014)
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