For years, leading health organisations have urged use to choose reduced-fat dairy foods – and not too many of them – to protect against heart disease.
The accepted wisdom is that reduced fat dairy is lower in saturated fat and helps to maintain healthy cholesterol levels.
But an emerging body of research is questioning the evidence linking saturated fat to cholesterol production and heart disease – the leading cause of death in Australia.
A large study published in The Lancet this September adds weight to this body of evidence.
It examined data from 130,000 people in 21 countries and found that people who had three servings of full fat dairy foods a day were better off when it came to heart disease risk thanthose who consumed less than 0.5 servings a day.
Further research published in The American Journal of Clinical Nutrition in July measured the blood levels of three fatty acids found in dairy products of almost 3000 adults aged 65 years and older.
The 22-year study found no link between the fatty acids and a higher risk of heart disease or mortality, including fats found in full fat dairy foods.
And an international expert consensus published in the same journal last year reports evidence “does not support a positive association between intake of dairy products and risk of cardiovascular disease”. It said fermented dairy products, such as cheese and yoghurt, were generally associated with improved health outcomes.
These findings contrast with dietary guidelines that advise minimising consumption of full fat dairy products to help prevent heart disease.
Beth Meertens, a dietitian at the Heart Foundation, said research linking full fat dairy foods with a reduced risk of heart disease was inconclusive.
“We know there’s different types of saturated fat and they’re found in different types of foods, usually in varying combinations,” she said.
“There is a bit of research into whether saturated fat from dairy has different effects … but there’s nothing conclusive to draw from it at this point in time.
“Reduced fat dairy is linked to a lower risk of high blood pressure, which is an important risk factor for heart disease, and we don’t see that consistent relationship with full fat dairy.”
She said dairy foods – whether full fat or reduced – did not increase the risk of heart disease.
The Australian Dietary Guidelines recommend at least two serves of reduced fat milk, yoghurt and cheese every day. The Heart Foundation recommends aiming for two to four serves.
“Our position is currently that reduced fat dairy products and unflavoured dairy products [without added sugar] are the healthier choice,” Ms Meertens said.
“What we see, time and time again and quite consistently in big studies, is having less saturated fat and more unsaturated fat is more protective for heart health.”
Manohar Garg, a professor of clinical and experimental nutrition at the University of Newcastle, said the chemical structure of saturated fat found in dairy foods differed to that found in other foods. This affected the way it was metabolised in the body and its role in disease risk.
“Saturated fat is not a single nutrient – it’s not like vitamin A or vitamin C. We find saturated fat in a variety of foods, like coconut oil, dairy, chocolate, palm oil, eggs and meat,” Professor Garg said.
“Dairy fat has short chain fatty acids compared to something like palm oil, which has long chain fatty acids.
“The way the body metabolises short and medium chain fatty acids is vastly different from the long chain saturated fatty acids.”
Professor Garg said the scientific community needed evidence that showed a direct, causal relationship between full fat dairy foods and a reduced risk of heart disease.
The Lancet study, for example, was observational and therefore unable to show cause and effect. Until that evidence was found, it was unwise to update dietary guidelines, experts said.
“We need to conduct a large intervention trial to show the effects of dairy foods on heart health,” he said.