From foodconsumer.org
Eating low fat dairy products reduces hypertension risk?
By David Liu, Ph.D.
Feb 21, 2008 - 11:08:56 AM
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THURSDAY FEB 21, 2008 (foodconsumer.org) -- A study by researchers from Brigham and Women’s Hospital and Harvard School of Public Health suggested eating low fat dairy products, but not taking calcium and vitamin D supplements may reduce the risk of hypertension in middle-aged women.
The study showed those who ate two servings of dairy products per day were 11 percent less likely to have hypertension than those who used less than one serving per month, United Press International reported.
The study was meant to examine the associations of intake of dairy products, calcium, and vitamin D with incidence of hypertension in a population of 28,886 US women aged 45 or older.
The participants were surveyed for their dietary patterns at the beginning of the study using semi-quantitative food frequency questionnaires. Incidence of hypertension was identified from annual follow-up questionnaires for a 10-year period.
After adjusting the major risks for hypertension, the researchers found the quintile of people who ate the highest amounts of dairy products were 11 percent less likely to develop hypertension than those in the quintile of people who ate the lowest amounts.
The highest dietary intake of calcium was linked to a 13 percent reduction in the hypertension risk while the highest dietary intake of vitamin D cut the risk by 5%. But calcium or vitamin D supplements did not change the associations.
Eating high fat dairy products on the other hand was not associated reduced risk of hypertension.
The researchers wrote "Our study found intakes of low-fat dairy products, calcium, and vitamin D were each inversely associated with risk of hypertension in middle-aged and older women, suggesting their potential roles in the primary prevention of hypertension and cardiovascular complications."
The study was published in the February 7 issue of the American Heart Association journal Hypertension.
Editor's note: Like many epidemiologic studies, this study has a number of drawbacks.
First, eating habits including supplementation of calcium and vitamin D were only surveyed at baseline, that is when participants entered the study only. Ten years is long enough for many things to happen including changing of dietary habits.
Second, even if this once time survey is sufficient, the reliability of the data is questionable. In a word, all the participants can report is their estimation. In some cases, some people may not report their real dietary patterns with their biases because they may think using dairy products is a good or bad habit.
Also, the researchers per se and their manipulation of the data such as adjustment for other risk factors may introduce biases and errors.
Anyway, this study showed an association, but not a cause-and-effect relationship. This association may also involve factors that the researchers did not consider when they do statistic analyses. Eating diary products could not guarantee your risk for hypertension is reduced.