New research finds that saturated fats, like those found in butter, may not increase the risk of heart disease.
In a new Norwegian diet intervention study (FATFUNC) published in The American Journal of Clinical Nutrition, study leader assistant Prof. Simon Nitter Dankel and colleagues have questioned and overturned the dietary theory that saturated fat is unhealthy for most of the population. This theory has dominated health literature for more than 50 years.
The notion of limiting saturated fats to support a healthy body weight and reduce the risk of chronic disease has featured in health guidelines for decades. Recently, however, scientists and health organizations have contrasting opinions on the dangers of saturated fats.
The American Heart Association (AHA) agree with government warnings and echo that the consumption of saturated fats can lead to levels of "bad" cholesterol in the blood that may raise the risk of heart disease.
The Academy of Nutrition and Dietetics, however, recommend de-emphasizing the role of saturated fat in developing heart disease, due to the lack of evidence connecting the two.
The majority of foods that are naturally rich in saturated fat come from animal sources, including meat and dairy products. The AHA recommend limiting saturated fats - such as those found in butter, cheese, red meat, and other animal-based foods - based on decades of sound science, they say.
Dankel and his team tested the risk of saturated fat on 38 men with abdominal obesity. The participants were divided into two groups and followed either a very high-fat, low-carbohydrate diet or a low-fat, high-carbohydrate diet for 12 weeks.
The researchers measured fat mass in the abdominal region, liver, and heart. They also assessed cardiovascular risk factors.
Quality of fat and carbohydrates drives a healthy diet
The current theory surrounding saturated fat would suggest that the high-fat, low-carbohydrate group would be at greater risk of heart disease than the low-fat, high-carbohydrate group. However, this was not the case; there was no difference between the groups.
"The very high intake of total and saturated fat did not increase the calculated risk of cardiovascular diseases," says professor and cardiologist Ottar Nygård, who contributed to the study.
"Participants on the very high-fat diet also had substantial improvements in several important cardiometabolic risk factors, such as ectopic fat storage, blood pressure, blood lipids (triglycerides), insulin and blood sugar," he adds.
"We here looked at effects of total and saturated fat in the context of a healthy diet rich in fresh, lowly processed and nutritious foods, including high amounts of vegetables and rice instead of flour-based products," says Ph.D. candidate Vivian Veum. "The fat sources were also lowly processed, mainly butter, cream, and cold-pressed oils."
The intake of energy, proteins, polyunsaturated fatty acids, and food types was similar across both groups, with variation mainly in quantity. The intake of added sugar was kept to a minimum.
The energy intake of both groups was mostly within normal range. Those participants that increased their energy intake still saw a reduction in fat stores and risk of disease.
"Our findings indicate that the overriding principle of a healthy diet is not the quantity of fat or carbohydrates, but the quality of the foods we eat," says Ph.D. candidate Johnny Laupsa-Borge.
Saturated fat increases 'good' cholesterol levels
The FATFUNC study challenges the theory that the route to heart disease from saturated fat is paved by raising levels of "bad" low-density lipoprotein (LDL) cholesterol in the blood. The study authors not only observed no significant rise in LDL cholesterol, but they also found that the high-fat diet was only associated with an increase in "good" cholesterol levels.
"These results indicate that most healthy people probably tolerate a high intake of saturated fat well, as long as the fat quality is good and total energy intake is not too high. It may even be healthy."
"Future studies should examine which people or patients may need to limit their intake of saturated fat," points out Dankel, who led the study together with the director of the laboratory clinics, Prof. Gunnar Mellgren, at Haukeland University Hospital in Bergen, Norway.
"But the alleged health risks of eating good-quality fats have been greatly exaggerated. It may be more important for public health to encourage reductions in processed flour-based products, highly processed fats, and foods with added sugar," Dankel concludes.