MedWire News: The nomadic Masai people in Africa have very low levels of cardiovascular disease, despite a diet high in animal fats, because of their high levels of physical activity, rather than their genetic make-up, say researchers.

Many studies have shown that a diet high in animal fats is associated with an increased risk of heart disease, strokes and other cardiovascular conditions, explain Dr Julia Mbalilaki, from the Karolinska Institute in Sweden, and colleagues.

However, they add: "Several studies have revealed that the Masai, pastoralists in Tanzania, have low rates of coronary heart disease despite a diet high in saturated fat. It has also been suggested that they may be genetically protected."

To investigate further, the team assessed the lifestyles, diets and cardiovascular risk factors of 985 middle-aged men and women in Tanzania, including 130 Masai tribespeople, 371 Bantu farmers and 484 Bantu town and city dwellers.

The researchers found that 82% of the Masai participants had a high fat/low carbohydrate intake, whereas 77% of the Bantu farmers had a low fat/high carbohydrate intake. Among the Bantu town and city dwellers, 55% had a diet that was high in fat and high in carbohydrates.

However, despite a high fat diet, the Masai participants had significantly lower blood pressure and cholesterol levels, and a significantly lower average body mass index than the other participants in the study.

The most striking lifestyle difference between the Masai tribespeople and the other participants was their high level of physical activity. Indeed, the Masai participants expended an average 2500 kilocalories a day more than the basic requirement, compared with 1500 kilocalories a day among the Bantu farmers and 891 kilocalories a day among the Bantu town and city dwellers.

Most Westerners would have to walk roughly 20 km a day to achieve the same energy expenditure as the Masai participants, explain the researchers.

They suggest that the Masai are protected against the development of cardiovascular disease by their high physical activity levels, rather than by some unknown genetic factor.

"This is the first time that cardiovascular risk factors have been fully studied in the Masai," said Dr Mbalilaki.

He concluded: "Bearing in mind the vast amount of walking they do, it no longer seems strange that the Masai have low waist measurements and good blood lipid [fat] profiles, despite the levels of animal fat in their food."

The research is published in the British Journal of Sports Medicine.