| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Letters to the Editor |
12 Sir Francis Wyatt Place Newport News, VA 23606-3660 E-mail: wbgrant{at}norfolk.infi.net
Dear Sir:
The recent publication of a paper in this Journal suggesting that lactose maldigestion should not be considered an impediment to consuming dairy products to obtain dietary calcium (1), which was sponsored by the National Dairy Council, may mislead the readers. First, dairy products may not be a good source of calcium for reasons other than lactose intolerance. A recent report from the Nurses' Health Study, which included 121701 women aged 30–55 y at enrollment in 1976, concluded that the cohort study data do not support the hypothesis that a high consumption of milk or other food sources of calcium by adult women protects against hip or forearm fractures (2).
To examine the link between milk and osteoporosis further, an ecologic approach was used to study hip fracture incidence rates for the white and total populations from 9 countries (3). The data for Finnish women were omitted because they were both an outlier with respect to women from other countries and inconsistent with rates of hip fracture for the Finnish men. As shown in Table 1, dietary milk and its components, especially milk protein, have a much higher statistical association with hip fracture incidence than do other likely factors such as fat, protein, and sweeteners (4). When linear regressions were run for milk protein, the r value for women was 0.800 (P = 0.005) and for men was 0.593 (P = 0.054). What the statistical results show is that living in countries with a high dairy consumption is a risk factor for osteoporosis. They do not necessarily imply that consumption of dairy products causes osteoporosis; however, they do suggest that further investigations be conducted to determine why the associations are so high.
In addition, the annual hip-fracture rate of black females in California was 43% that of white females (219 compared with 559 cases/100000 persons) (3), whereas the hip-fracture rate of black females in Washington, DC, was 51% that of white females (118.8 compared with 231.8 cases/100000 persons) (5, 6). African Americans are generally lactose intolerant and have lower milk consumption rates than do white Americans. Perhaps their diet, genetic makeup, or both lead to strong bones and therefore dairy products or large amounts of dietary calcium are not as important as they are for whites.
Other common chronic diseases are now linked to calcium and milk consumption. Lactose from unfermented dairy products such as milk and yogurt has the highest association with ischemic heart disease of any dietary macronutrient for men of all ages and postmenopausal women (7–9). A possible mechanism is the metabolism of lactose into triacylglycerol and its incorporation into VLDL cholesterol. In addition, milk and calcium intakes have been found in cohort studies in 5 countries to be the highest risk factors for prostate cancer (10). The proposed mechanism is a reduction in circulating vitamin D by calcium because vitamin D is involved in the incorporation of calcium into bone (10). Vitamin D has been shown to kill prostate cancer cells in vitro (11).
Thus, there are many good reasons not to consume dairy products. Those concerned about osteoporosis, which has a complex etiology, should review the report by Brown (5), which delves far beyond the relation between osteoporosis and calcium intakes into such other factors as the dietary acid-alkaline balance, trace minerals, exercise, and exposure to sunlight.
REFERENCES
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
