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Very low fat diets may harm some people


The genetic make up of a person influences how he or she responds to a particular diet, and although very low fat diets may benefit some people they could be harmful to others, the American Heart Association has warned.

Dr Ronald Krauss, chairman of the association's nutrition committee, said that studies in healthy people show that there are genetic differences in the response to a low fat diet. Those who, from their metabolic profiles, are at highest risk of heart disease show the greatest benefit from very low fat diets, but the remaining two thirds of the population would show only minimal benefit, and for some it would be harmful.

"We now know that individual responses to food cannot be predicted reliably on the basis of studies of large populations of people," said Dr Krauss, who is head of the molecular medicine department at the Lawrence Berkeley National Laboratory in Berkeley, California. He said that the results of research on the interaction of genes and diet should in the future lead to diet plans and possibly drug regimens that were tailored to an individual's predisposition for heart disease and stroke.

An example of the interaction between genes and diet is the apoE4 variant of the apoprotein E. People with this genetic trait tend to have higher blood cholesterol concentrations, increased risk of heart disease, and increased risk for Alzheimer's disease. Another genetically influenced condition, low density lipoprotein (LDL) subclass pattern B, influences the blood cholesterol response to a low fat diet. This condition is characterised by small dense forms of LDL, lower blood levels of high density lipoprotein (HDL), increased blood concentrations of triglyceride, and a predisposition to the most common form of diabetes mellitus. People with the condition have a threefold higher risk of coronary heart disease than those with larger forms of LDL.

Dr Krauss has carried out research which shows that people with the small dense forms of LDL (pattern B) respond to a low fat diet better than people with larger forms of LDL (pattern A). He says that unless a person knows that they have pattern B LDL they should avoid extremely low fat diets, as they could have adverse effects.

BMJ 1998;316:571 ( 21 February )

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