Study beginning in 1930s suggests link, but experts unsure
MONDAY, July 27 (HealthDay News) -- A 65-year-long study finds that people who took in lots of calcium and dairy products as children tended to avoid stroke and live longer than those who didn't.
"This study shows a modest protective effect of dietary calcium intake in childhood against stroke risk later in life, and a modest protective effect against mortality from any cause from higher intake of milk in childhood," said Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine. He was not involved in the study, which was published in the July 28 online edition of Heart.
Risk factors for heart disease start in childhood, but there is little evidence of the effect dairy foods have on these risks. Some dairy products, such as whole milk, butter and cheese, have a lot of saturated fat and cholesterol. Studies have also shown that eating these foods in adulthood contributes to heart disease, researchers say.
For the study, a research team led by Jolieke van der Pols from the Queensland Institute of Medical Research in Brisbane, Australia, collected data on children from 1,343 families in England and Scotland. All of the families took part in a survey of diet and health conducted in Britain from 1937 to 1939.
The researchers were able to track the adult health of 4,374 of the children between 1948 and 2005. By 2005, 1,468 of these individuals had died, including 378 who succumbed to heart disease and 121 who died from stroke.
The researchers looked at two main outcomes: deaths from stroke and cardiovascular disease. They looked at the associations between dairy intake and mortality and the associations between individual dairy foods and mortality.
They found no clear evidence that dairy products were tied to either coronary heart disease or stroke deaths.
However, children in the group with the highest intake of calcium and dairy products had lower overall death rates than those who ate less dairy.
"Children whose family diet in the 1930s was high in calcium were at reduced risk of death from stroke. Furthermore, childhood diets rich in dairy or calcium were associated with lower all-cause mortality in adulthood," the researchers concluded.
But there is only so much we can learn from this observational study, Katz said.
"Dietary assessments were [done] in Britain before WWII, at which time low-fat and fat-free milk were all but nonexistent," Katz said "Thus, any benefits of dairy intake were likely mitigated by its high content of saturated fat."
Furthermore, "dairy intake was higher in households with higher socioeconomic status, which may itself account for a health benefit," he noted.
Studies using the American Heart Association-recommended DASH (dietary approaches to stop hypertension) diet suggest there are health benefits from dairy intake, Katz said. But, "there are some concerns as well, such as a potential association [of high dairy intake] with increased risk of prostate cancer. Unfortunately, I don't think we can find a resolution to the persistent controversies about dairy foods from the current study."
Another expert, Dr. David J.A. Jenkins, a professor in the department of nutritional sciences at the University of Toronto, noted that those who ate the most dairy also ate the most fruit and vegetables, so they had the healthiest diets overall.
"To put it all down to increased dairy products in young life seems to be a marker for those who had a more reasonable diet," he said. "If you have good nutrition in childhood it is important for longevity, but I would be wary about saying this was due to milk consumption," he said.
Another expert advocated dairy products for kids, but suggested sticking to low- or non-fat products.
"The saturated fat in dairy food is what we are concerned about, not so much the calories," said Samantha Heller, a Connecticut-based registered dietitian, clinical nutritionist and exercise physiologist. "A lot of times kids are not getting the calcium they need because they are replacing calcium-rich beverages with sugar-sweetened beverages, which have no nutritional value," she said.
There's more on healthful diets at the U.S. Department of Agriculture .
SOURCES: Samantha Heller, M.S., R.D., registered dietitian, clinical nutritionist, exercise physiologist, Fairfield, Conn.; David J.A. Jenkins, M.D., Ph.D., D.Sc., department of nutritional sciences, University of Toronto; David L. Katz, M.D., M.P.H., director, Prevention Research Center, Yale University School of Medicine, New Haven, Conn.; July 28, 2009, Heart, online
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