The clinical trial, authored by Janne Lorenzen, PhD, and Arne Astrup, MD, professor and director of the Department of Human Nutrition at the Faculty of Life Sciences, University of Copenhagen, followed nine male subjects (average age of 32 years) as they completed four separate diets over a period of 10 days, with each diet differing in the calcium and fat content amounts.
Blood variables were measured before and after each diet period, with fecal and urine lipid profiles collected at the end of each diet period. Data showed that high fat diets increased LDL and HDL cholesterol concentrations by 9% and 13% against low fat diets. The high calcium diets, however, decreased concentrations of total and LDL cholesterol levels (10% and 4%, respectively). And while the high calcium diets did not directly affect HDL cholesterol levels, the authors credited it with a “protective effect” as it relates to cardiovascular disease.
According to the researchers, intervention studies have historically pointed to a relationship between a diet high in saturated fat and increases in total cholesterol and LDL cholesterol. As a result, some nutrition experts have recommended that consumers limit the intake of high-fat dairy products. However, observational studies have found an inverse relationship between intake of milk and other dairy products with a high content of calcium and incidence of cardiovascular disease.Drs. Astrup and Lorenzen aimed to study whether the high calcium content of dairy products influences the effect of dairy fat on the lipid profile.
“We have previously found that a high intake of dairy calcium increases fecal fat excretion and that a high intake attenuates postprandial lipidemia. This indicated that perhaps a high dairy calcium intake may have an effect on cholesterol,” Dr. Lorenzen explained to Nutraceuticals World. “In agreement, data from observational studies indicates that intake of dairy products with a high content of calcium may be inversely related to cardiovascular diseases. Our results indicate that this may at least partly be due to the calcium.”
“In theory, without calcium, dairy would have a bigger impact on LDL levels. The protective function of dairy calcium seems to set it apart from other sources of fat,” concurred Dr. Astrup. “This study supports previous research we have conducted that indicates dairy intake may actually play a role in minimizing the risk for cardiovascular disease versus increasing the risk.”
The Dairy Research Institute in Rosemont, IL,was heartened to learn about the findings of the study. “We know there are many adults today concerned about their fat intake, cholesterol levels and heart disease risk,” said Gregory Miller, PhD, president of the Dairy Research Institute and executive vice president of the National Dairy Council. “We believe this study underscores the importance of dairy as a good daily source of calcium, protein and other nutrients while mitigating the impact on cholesterol. The study reinforces findings published in the Dietary Guidelines Advisory Committee report in 2010 that suggests ‘bioactive components that alter serum lipid levels may be contained in milk fat,’ or the effect of milkfat on blood lipids is different than what might be predicted. This is valuable information for the industry and for the consumer.”
Researchers are eager to understand the mechanisms responsible for the results documented by the University of Copenhagen trial . “The effect that we found on cholesterol, especially LDL cholesterol, was larger than what could be explained by the increased fecal fat excretion,” said Dr. Lorenzen, who noted that several new studies related to dairy calcium and blood lipids are planned. “Similar results have been observed by others which indicate that other mechanism may be involved as well. At the moment we don’t know which mechanisms, but we do hope to found out in the near future."