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Are Federal Dietary Guidelines Racially Biased?

The federal dietary guidelines that form the blueprint for school lunches and virtually all other nutrition programs have evolved only very slowly since the first food guides were published in 1916. In spite of the advances in nutrition knowledge that have occurred over the past eight decades, the guidelines reflect the cultural and racial biases of the older recommendations.

The Food Guide Pyramid still promotes milk consumption by all Americans, even though research in the 1960s established that lactose intolerance affects the majority of adults in all racial groups other than whites. Moreover, federal nutrition guidelines are too weak to reduce the risk of cancer, hypertension, stroke, or diabetes—diseases that take a disproportionate toll among minorities.

Lactose Intolerance Is Normal

Prior to the mid-1960s, most American health professionals believed that lactose intolerance—abdominal pain, gas, and other symptoms caused by the milk sugar—was rare.

That changed in 1965, when researchers from the Johns Hopkins University tested hospital patients and found that while only 15 percent of whites had digestive problems from lactose, no fewer than 70 percent of African Americans had symptoms from the same dose of lactose.1 The following year, researchers studied inmates at the Maryland House of Correction, offering 20 whites and 20 African Americans extra canteen money in exchange for participating in lactose challenge tests. Symptoms developed in 90 percent of African Americans and only 10 percent of whites.2 Other studies showed that lactose intolerance was common among those whose ancestry is African, Asian, Native American, Arab, Jewish, Hispanic, Italian, or Greek.3 Sensitivity to milk varies, but for most, symptoms begin with about one cup of milk, particularly if it is not “diluted” by an accompanying meal.

In 1988, the American Journal of Clinical Nutrition reported that “it rapidly became apparent that this pattern was the genetic norm, and that lactase activity was sustained only in a majority of adults whose origins were in Northern European or some Mediterranean populations.”4 In other words, Caucasians tolerate milk sugar only because of an inherited genetic mutation.

The recognition of this fact led to an important change in terminology: those who could not digest milk were once called “lactose intolerant” or “lactase deficient.” They are now regarded as normal, while those adults who still have the enzymes that allow them to digest milk are called “lactase persistent.”

Twenty-five years after health professionals realized that the inability to digest milk sugar is the norm for people from all races other than Caucasians, the Food Guide Pyramid still recommends two to three servings of milk products each day.

Milk can be altered to break lactose into two smaller sugars, glucose and galactose. However, the health risks of galactose are under continuing investigation, particularly with regard to cataracts, infertility, and ovarian cancer, all of which are more common among milk-drinkers. Meanwhile, many people may prefer to obtain their calcium from other sources, such as green leafy vegetables and beans.5

Milk Does Not Reliably Prevent Osteoporosis

Although milk is promoted mainly as a source of calcium to slow bone loss, it has become clear that the susceptibility to osteoporosis differs dramatically between ethnic groups. A 1996 study of 503 women, aged 20 to 80 years, found that African Americans had a higher peak bone mass and a substantially slower rate of bone loss compared to white women.6

African Americans have only about half the fracture rate of whites. In one study, the rates for African Americans and whites were 60.4 versus 118.3 per 100,000 person-years, respectively.7 Similarly, a 1988 study of residents of Bexar County, Texas, found that hip fractures were much less common among African American women (55 per 100,000) and Mexican American women (67 per 100,000) than white women (139 per 100,000).8

Rates among South African blacks are lower still. Although a 1992 review reported their average daily calcium intake to be only 196 milligrams, their fracture incidence was only 6.8 per 100,000 person-years, far below that of North American or European countries.7

The loss of bone integrity that is particularly common among postmenopausal white women probably results from a combination of genetics and diet/lifestyle factors. Probably the most important of these is animal protein, which leaches calcium from the bones, leading to its excretion in the urine. A 1994 report in the American Journal of Clinical Nutrition showed that when volunteers are switched from a typical American diet to a diet eliminating animal proteins, calcium losses were reduced to less than half of baseline values.9 Sodium, caffeine, tobacco, and a sedentary lifestyle also contribute to bone loss.

High milk intake does not appear to be protective against fractures, even for whites. The Harvard Nurses’ Study, involving 77,761 women, aged 34 to 59, revealed that those who drank three or more glasses of milk per day had no reduction in the risk of hip or arm fractures, over a 12-year follow-up period, compared to those who drank little or no milk, even after adjustment for weight, menopausal status, smoking, and alcohol use. In fact, the fracture rates were slightly, but significantly, higher for those who consumed this much milk compared to those who drank little or no milk.10

Other Calcium Sources

Many people prefer to get calcium from sources other than dairy products. Many green vegetables have calcium absorption rates of over 50 percent, compared with about 32 percent for milk.11 In 1994, the American Journal of Clinical Nutrition reported calcium absorption to be 52.6 percent for broccoli, 63.8 percent for Brussels sprouts, 57.8 percent for mustard greens, and 51.6 percent for turnip greens.11 The fractional calcium absorption from kale is approximately 40 to 59 percent.11,12 Likewise, beans (e.g., pinto beans, black-eyed peas, and navy beans) and bean products, such as tofu, are rich in calcium.

Many Americans enjoy calcium-rich green leafy vegetables and beans, and preferences are not necessarily uniform across ethnic groups. In August 1997, the Opinion Research Corporation surveyed 1,000 adults for the Physicians Committee for Responsible Medicine, finding that preference for green leafy vegetables and beans were higher among African Americans than whites, and higher in the South than in other regions.

Green leafy vegetables and beans are good calcium sources with advantages that dairy products lack. They contain antioxidants, complex carbohydrate, fiber, and iron, and have little fat, no cholesterol, and no animal proteins.

WEAK GUIDELINES TAKE A DISPROPORTIONATE HEALTH TOLL

While all demographic groups are ill-served by suboptimal dietary guidelines, this is particularly true for groups that are hardest hit by chronic diseases.

Cancer

African American males have the highest cancer incidence of any group in the U.S. The 1990 to 1994 incidence rates for all sites were 624.7 per 100,000 for African Americans and 496.1 per 100,000 for whites.13

Prostate cancer incidence is strikingly higher among African Americans: 145.8 per 100,000, compared to 107.3 per 100,000 for whites. The second most common cancer, that of the lung and bronchi, occurs with an even greater disparity, 124.1 versus 81.2 per 100,000 for African American and white males, respectively. Dietary factors play a major role in both of these forms of cancer.

In epidemiologic studies, prostate cancer is consistently associated with consumption of meat and dairy products and is less common among those who consume more rice, soybean products, or green or yellow vegetables, and among vegetarians. Diets that are low in fat and high in fiber reduce both the concentration and activity of testosterone, which, in turn, reduces the stimulation of prostate cells.

Fruits rich in the red pigment lycopene also may help protect against prostate cancer. A Harvard study of 47,000 health professionals found that men who had ten or more servings a week of lycopene-rich foods, such as tomatoes, had a 45 percent reduced risk of prostate cancer.14

Although cigarette smoking is the most important risk factor for lung cancer, the majority of smokers never develop the disease, indicating that other factors also play decisive roles. A 1979 study from Japan, including 265,118 men and women, both smokers and nonsmokers, found that frequent consumption of green and yellow vegetables was associated with a 20 to 60 percent reduction in lung cancer risk compared to those who consumed these products less often.15 A later American Cancer Society cohort study of one million subjects and a study in Norway yielded similar findings.16

Regrettably, the Dietary Guidelines do little to encourage the use of diets that would reduce the risk of cancer. They recommend multiple servings of meats and dairy products each day, even though omnivorous diets are associated with significantly higher cancer rates compared to vegetarian diets.17-19

The Dietary Guidelines target for dietary fat is 30 percent, an arbitrary goal that has persisted in federal guidelines with no scientific basis. It was chosen, not because it has been shown improve health, but rather, because it was believed that American consumers would not tolerate a more vigorous reduction. The National Academy of Sciences Committee on Diet, Nutrition, and Cancer concluded in its 1982 report: “The scientific data do not provide a strong basis for establishing fat intake at precisely 30 percent of total calories. Indeed, the data could be used to justify an even greater reduction.” Indeed, data from the Nurses’ Health Study showed that a fat intake of 30 percent of calories was associated with no benefit with regard to the prevalence of breast cancer in study participants.20

Overweight

Overweight takes a disproportionate toll among African American and Mexican American women. According to the National Health and Nutrition Examination Surveys (NHANES), 48.6 percent of non-Hispanic black women and 46.7 percent of Mexican American women are overweight, compared to 32.9 percent of non-Hispanic white women. Among adult Native Americans, those examined in a 1991 study were heavier for their height, on average, than those measured at the beginning of the century. In most height categories, weights have continued to increase since 1965.21

The role of diet, particularly fat intake, in overweight is beyond dispute. However, the Dietary Guidelines encourage only a minimal reduction in fat intake—to 30 percent of calories—and do nothing to encourage more substantial changes among those who might choose to follow them.

Diabetes

Diabetes affects minorities much more frequently than whites. The National Health Interview Survey (1986 to 1990) found the age-adjusted prevalence rates of diabetes for African American, Hispanic, Asian American, and white men were 4.13, 3.74, 3.37, and 2.45 percent, respectively. Among women, the corresponding figures were 4.89, 3.53, 2.38, and 2.36 percent, respectively.22 Among Native Americans, diabetes prevalence was found to be 4.2 percent for men and 9.0 percent for women. For Pima Indians, the prevalence is near 50 percent.22

Clinical trials using diets emphasizing whole grains, legumes, vegetables, and fruits, along with regular exercise, have demonstrated that diabetics’ need for medication can often be substantially reduced, as can the prevalence of neuropathy and retinal damage.23-27 Less than optimal Dietary Guidelines promote a higher prevalence of diabetes and its complications than would be expected with diets that are richer in plant products and lower in fat.

Ischemic Heart Disease

Ischemic heart disease take a disproportionate toll among Hispanic women. The age-adjusted heart disease prevalence rates for 1986 to 1990 were twice as high for Hispanic as non-Hispanic women.

Research studies suggest that reducing fat to 30 percent of dietary calories will not significantly reduce Americans’ risk of ischemic heart disease. Research studies using a 30-percent-fat diet lead to no more than minimal benefits for heart patients, do not spare patients from the need for cholesterol-lowering drugs, and do not reverse atherosclerotic lesions.28-29 Those Americans seeking to reduce their risk of heart disease are poorly served by such unhelpful Guidelines.

Hypertension and Stroke

Hypertension is common in the U.S. population as a whole, but affects African Americans disproportionately. The age-adjusted prevalence rates in African Americans, Mexican Americans, and whites were 34 percent, 23.2 percent, and 25.4 percent, respectively, for men, and 31.0 percent, 21.6 percent, and 21.0 percent, respectively, for women.30

Stroke also occurs disproportionately among African Americans. The age-adjusted prevalence of stroke among men (1986 to 1990) was 1.54 percent for African Americans and 1.14 percent for whites. For women, the corresponding figures were 1.20 and 0.98 percent, respectively.

Dietary factors play a key role in hypertension. While the importance of limiting salt use is well known, reducing the use of fatty foods and meats below those levels recommended in the current Dietary Guidelines is also clearly beneficial. For example, a study of Seventh-day Adventists showed that among whites, blood pressure medications were used by 22 percent of omnivores, compared to only 7 percent of vegetarians. Among African Americans, blood pressure medications were used by 44 percent of omnivores and only 18 percent of vegetarians.31 The use of vegetarian diets in controlled trials leads to significant blood pressure reductions in 30 to 75 percent of hypertensive subjects.32,33

While Americans vary in their willingness to modify their diets, the current nutrition policies provide no encouragement at all for those who are willing to make more than minimal changes.

By recommending daily milk consumption to population groups for whom lactose intolerance is the rule, and only very modest dietary changes for those who are at risk for heart disease, cancer, diabetes, hypertension, obesity, and other chronic illnesses, the Guidelines fail to address the needs of Americans.

References

1. Cuatrecasas P, Lockwood DH, Caldwell JR. Lactase deficiency in the adult: a common occurrence. Lancet 1965;1:14-8.
2. Bayless TM, Rosensweig NS. A racial difference in incidence of lactase deficiency: a survey of milk intolerance and lactase deficiency in healthy adult males. JAMA 1966;197:968-72.
3. Mishkin S. Dairy sensitivity, lactose malabsorption, and elimination diets in inflammatory bowel disease. Am J Clin Nutr 1997;65:564-7.
4. Scrimshaw NS, Murray EB. The acceptability of milk and milk products in populations with a high prevalence of lactose intolerance. Am J Clin Nutr 1988;48:1083-5.
5. Cramer DW, Xu H, Sahi T. Adult hypolactasia, milk consumption, and age-specific fertility. Am J Epid 1994;139:282-8.
6. Aloia JF, Vaswani A, Yeh JK, Flaster E. Risk for osteoporosis in black women. Calcif Tissue Int 1996;59:415-23.
7. Abelow BJ, Holford TR, Insogna KL. Cross-cultural association between dietary animal protein and hip fracture: a hypothesis. Calif Tissue Int 1992;50:14-8.
8. Bauer RL. Ethnic differences in hip fracture: a reduced incidence in Mexican Americans. Am J Epid 1988;127:145-9.
9. Remer T, Manz F. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Am Clin Nutr 1994;59:1356-61.
10. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. Am J Publ Health 1997;87:992-7.
11. Weaver CM, Plawecki KL. Dietary calcium: adequacy of a vegetarian diet. Am J Clin Nutr 1994;59(suppl):1238S-41S.
12. Heaney RP, Weaver CM. Calcium absorption from kale. Am J Clin Nutr 1990;51:656-7.
13. Ries LAG, Kosary CL, Hankey BF, Miller BA, Harras A, Edwards BK (eds). SEER Cancer Statistics Review, 1973-1994. National Cancer Institute. NIH Pub. No. 97-2789. Bethesda, Md, 1997.
14. Giovannucci E, Ascherio A, Rimm EB, Stampfer MJ, Colditz GA, Willett WA. J Natl Cancer Inst 1995;87:1767-76.
15. Hirayama T. Diet and cancer. Nutr Cancer 1979a;1:67-81.
16. Colditz GA, Stampfer MJ, Willett WC. Diet and lung cancer: a review of the epidemiologic evidence in humans. Arch Intern Med 1987;147:157-60.
17. Thorogood M, Mann J, Appleby P, McPherson K. Risk of death from cancer and ischaemic heart disease in meat and non-meat eaters. Brit Med J 1994;308:1667-70.
18. Chang-Claude J, Frentzel-Beyme R, Eilber U. Mortality pattern of German vegetarians after 11 years of follow-up. Epidemiology 1992;3:395-401.
19. Chang-Claude J, Frentzel-Beyme R. Dietary and lifestyle determinants of mortality among German vegetarians. Int J Epidemiol 1993;22:228-36.
20. Willett WC, Stampfer MJ, Colditz GA, Rosner BA, Hennekens CH, Speizer FE. Dietary fat and the risk of breast cancer. New Engl J Med 1987;316:22-8.
21. Knowler WC, Pettitt DJ, Saad MF, et al. Obesity in the Pima Indians: its magnitude and relationship with diabetes. Am J Clin Nutr 1991;53:1543S-51S.
22. Centers for Disease Control. National Center for Health Statistics. National Health Interview Survey, 1986-1990.
23. Anderson JW, Zeigler JA, Deakins DA, et al. Metabolic effects of high-carbohydrate, high-fiber diets for insulin-dependent diabetic individuals. Am J Clin Nutr 1991;54:936-43.
24. Barnard RJ, Massey MR, Cherny S, O’Brien LT, Pritikin N. Long-term use of a high-complex-carbohydrate, high-fiber, low-fat diet and exercise in the treatment of NIDDM patients. Diabetes Care 1983;6:268-73.
25. Munoz JM. Fiber and diabetes. Diabetes Care 1984;7:297-300.
26. Crane MG, Sample C. Regression of diabetic neuropathy with total vegetarian (vegan) diet. J Nutr Med 1994;4:431-9.
27. Roy MS, Stables G, Collier B, Roy A, Bou E. Nutritional factors in diabetics with and without retinopathy. Am J Clin Nutr 1989;50:728-30.
28. Hunninghake DB, Stein EA, Dujovne CA, et al. The efficacy of intensive dietary therapy alone or combined with lovastatin in outpatients with hypercholesterolemia. New Engl J Med 1993;328:1213-9.
29. Ornish D, Brown SE, Scherwitz LW, Billings JH, Armstrong WT, Ports TA. Can lifestyle changes reverse coronary heart disease? Lancet 1990;336:129-33.
30. Burt VL, Cutler JA, Higgins M, et al. Trends in the prevalence, awareness, treatment, and control of hypertension in the adult US population. Data from the health examination surveys, 1960 to 1991. Hypertension. 1995;26:60-9.
31. Melby CL, Goldflies DG, Hyner GC, Lyle RM. Relation between vegetarian/nonvegetarian diets and blood pressure in black and white adults. Am J Publ Health 1989;79:1283-8.
32. Margetts BM, Beilin LJ, Armstrong BK, Vandongen R. A Randomized controlled trial of a vegetarian diet in the treatment of mild hypertension. Clin Exp Pharmacol Physiol 1985;12:263-6.
33. Lindahl O, Lindwall L, Spangberg A, Stenram A, Ockerman PA. A vegan regimen with reduced medication in the treatment of hypertension. Br J Nutr 1984;52:11-20.



 

Autumn 1997

Autumn 1997
Volume VI
Number 4

Good Medicine
ARCHIVE

 
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