EXPERT ANALYSIS FROM THE AHA SCIENTIFIC SESSIONS
NEW ORLEANS (FRONTLINE MEDICAL NEWS) – While many Americans have been dithering over the relative health benefits of high- versus low-carbohydrate diets, various pop-culture weight loss programs, vegetarianism, gluten-free living, and other nutritional matters, a quiet revolution in mainstream scientific thinking has occurred regarding the role of full-fat dairy products.
Saturated fatty acid–rich dairy products, formerly viewed as the enemy of cardiovascular health, have gone from foe to friend, according to Arne Astrup, MD , professor and head of the department of nutrition, exercise and sports at the University of Copenhagen.
“A diet including cheese should be recommended for all to prevent and manage type 2 diabetes and cardiovascular disease,” he asserted at the American Heart Association scientific sessions.
“From all I have seen, I think it’s quite safe to recommend that our diabetics and heart patients eat some cheese without being afraid of it. I don’t think there’s any harmful effect, and it could actually be very beneficial,” Dr. Astrup continued.
For example, a recent comprehensive meta-analysis of 31 prospective cohort studies found that a high dairy intake was associated with a 9% reduction in the risk of stroke, compared with low or no dairy consumption. Of note, high cheese intake was associated with an 18% lower risk of coronary heart disease (CHD) and a 13% reduction in risk of stroke ( Br J Nutr. 2016;115:737-50 ).
Dutch investigators reported based upon their meta-analysis of 18 prospective cohort studies with 8-26 years of follow-up that stroke risk fell by 7% for each 200 mL of milk consumed per day. Consumption of 25 g/day or more of cheese was associated with a 13% reduction in stroke risk and an 8% lower risk of CHD (J Am Heart Assoc. 2016 May 20;5. doi: 10.1161/JAHA.115.002787 ).
A joint Chinese/Dutch collaborative meta-analysis of studies of cheese consumption found a 14% relative risk reduction for CHD and a 10% lower risk of stroke with high versus low cheese intake. The investigators concluded that the largest risk reductions occurred with consumption of about 40 g/day ( Eur J Nutr. 2016 Aug 12. doi: 10.1007/ s00394-016-1292-z ).
“The totality of evidence – meta-analyses of both observational studies and randomized controlled trials – cannot find any harmful effects of cheese on body fat, metabolic syndrome, type 2 diabetes, or cardiovascular disease,” he said. “And cheese has beneficial effects on LDL cholesterol, blood pressure, and postprandial triglycerides as compared with butter containing the same amount of saturated fatty acids.”
The classic lipid hypothesis of cardiovascular disease holds that dietary saturated fat raises blood cholesterol, in turn accelerating atherosclerosis and resultant coronary heart disease. But the published literature of the past few years indicates it’s not that simple. All saturated fats are not equally harmful. They have very different biologic effects, and the food matrix in which they occur seems to be important. The saturated fatty acids found in red meat are clearly damaging. Ditto trans fats.
In contrast, the saturated fats present in milk, hard cheeses, and fermented dairy products such as yogurt have been shown in a variety of study formats to be cardioprotective. They also appear to protect against other chronic diseases as well, according to the researcher.
“If we look at all the different meta-analyses addressing the various cardiovascular risk factors, it really looks like cheese, despite its high content of sodium and saturated fat, seems to exert some beneficial effects. So I think we need to address the food matrix much more. We’ve done controlled feeding trials in humans and found that if we give subjects the same amount of saturated fat from either butter or cheese, you see following the cheese [that] the subjects do not increase their total or LDL-cholesterol as you would expect based upon their intake of saturated fat. So there’s something going on with cheese,” Dr. Astrup said.
What’s going on, he continued, is the saturated fats in cheese benefit from the company they keep. Fermented dairy products contain an arm-long list of potentially beneficial nutrients, including protein, calcium, short-chain fatty acids, bioactive peptides, and phospholipids.
Take, for example, calcium: “We’ve found the calcium content of cheese completely modifies the metabolism of the saturated fat. The calcium seems to bind the bile acids and fatty acids, resulting in increased fecal fat secretion,” according to Dr. Astrup.
Although at the AHA meeting he focused mainly on the effects of cheese and other dairy products on cardiovascular health, in a recent review article he expanded upon the scientific evidence regarding the impact of these foods on the risks of obesity, type 2 diabetes, cancer, and osteoporosis ( Food Nutr Res. 2016 Nov 22;60:32527 ).
There is solid evidence that a diet high in dairy products reduces the risk of childhood obesity and enhances body composition in adults. It aids in weight loss by promoting satiety during periods of energy restriction. A recent meta-analysis of observational studies found an inverse relationship between consumption of fermented dairy products – yogurt and cheese – and risk of type 2 diabetes ( Am J Clin Nutr. 2016 Apr;103:1111-24 ).
Regarding cancer, the World Cancer Research Fund has issued a series of evidence reviews concluding that dairy products probably protect against colorectal, breast, gastric, and bladder cancer. The jury is still out regarding prostate cancer risk.
A wealth of evidence indicates dairy consumption has a beneficial effect on bone health in children and adolescents. However, meta-analyses haven’t shown a protective effect against osteoporosis and fractures in adults. This is consistent with the adage that osteoporosis is a pediatric disease with geriatric consequences, Dr. Astrup noted.
He reported receiving research grants from the Danish Dairy Research Foundation, the Global Dairy Platform, the Danish Agriculture and Food Council, and the European Milk Forum. He serves on advisory boards for the Dutch Beer Knowledge Institute, Suntory, Weight Watchers, and several food companies.