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A study of nomadic tribes in Africa suggests
that people who combine a diet rich in saturated fat but low
in total calories with vigorous exercise may not be damaging
their hearts as much as previously believed.
Despite
their fatty diets, the Fulani of Nigeria had healthy
cholesterol levels. The researchers suggest the finding can
be attributed to the population's high activity level, low-calorie
intake and lack of smoking.
Researchers took blood samples from 121
Fulani men and women aged 15 to 77 and measured total, LDL
("bad") and HDL ("good") cholesterol,
as well as several vitamins, and homocysteine -- a protein
associated with heart disease risk. They also assessed the
population's nutrient intake.
Overall, men consumed about about 1,670
calories -- and women consumed about 1,485 calories -- of
which nearly one-half came from fat. And about half of total
fat calories were derived from saturated fat. In the US, individuals
are advised to consume no more than 30% of their calories
from fat, of which no more than 10% should come from saturated
fat.
The dietary protein content of the Fulani
was also found to be higher than US-recommended levels. Women
derived about 16% and men derived about 20% of their calories
from protein. US dietary guidelines advise that no more than
15% of daily calories come from protein.
What's more, the typical Fulani diet
contained only one third of the level of folate recommended
in the US and lower-than-recommended levels of vitamins C
and B-6. These vitamins have been linked to a protective effect
on the heart.
Despite all of this, participants' average
levels of total cholesterol and HDL cholesterol fell within
US recommended levels, while average LDL fell below recommended
levels. The average body mass index (BMI), a measure of weight
and height, was about 20. A BMI of at least 25 is generally
considered to be overweight.
Despite a diet high in saturated fat,
Fulani adults have a lipid profile indicative of a low risk
of cardiovascular disease. This finding is likely due to their
high activity level and their low total energy intake.
It is not clear why a diet rich in fat
and saturated fat was not associated with elevated cholesterol
and heart disease risk but the authors suggest that an overall
low intake of calories and a lifestyle marked by physical
activity and no tobacco use mitigates the effects of such
a diet.
They also note that most of the current
recommendations regarding heart disease risk factors are based
on studies conducted in Western nations, where the majority
of individuals are relatively sedentary. Studies on populations
such as the Fulani are rare.
The researchers conclude that the findings
with the Fulani do not support the dogma of the past 50 years
that high-fat diets necessarily raise cholesterol concentrations.
American
Journal of Clinical Nutrition December 2001;74:730-736
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