Although previous research has shown a link with heart disease, high dietary fat intake does not appear to be linked to an increased risk of stroke in men, according to results of a new study in the British Medical Journal.
There is evidence to indicate that type of dietary fat is more important than total fat intake in predicting risk of coronary heart disease, as different types of fat or fatty acids may play different or opposite roles. Monounsaturated and polyunsaturated fats seem to have beneficial effects, but saturated fat and trans unsaturated fatty acids increase risk of coronary heart disease.
However, these associations do not seem to apply to stroke. The researchers in this study note that previous studies have even suggested an inverse relation between saturated fat or trans unsaturated fat intake and risk of stroke, but the mechanisms remain unclear.
Dr Ka He and colleagues at the Department of Nutrition, Harvard School of Public Health, in Boston, Massachusettes, in the US, set out to examine the association between intake of total fat, specific types of fat, and cholesterol and risk of stroke in men.
The researchers used information obtained as part of the Health professional follow up study. Approximately 40,000 men aged 40-75 years who were free from cardiovascular diseases and diabetes in 1986 were involved in the study which took place between 1986 and 2000.
Food intake over the period was monitored using four-yearly questionnaires. Participants were asked to record the frequency of consumption of specified portions of each selected food during the previous year by using one of nine options ranging from 'never' or 'less than once per month' to 'six times a day'. The researchers also inquired about types of fat, oil, or margarine used in food preparation and at the table.
The main outcome measure was the relative risk of ischaemic and haemorrhagic stroke according to intake of total fat, cholesterol, and specific types of fat.
During the 14 year follow up 725 cases of stroke occurred, including 455 ischemic strokes, 125 haemorrhagic stokes, and 145 strokes of unknown type. He and colleagues reported no evidence however that the amount or type of dietary fat affects the risk of developing ischemic or haemorrhagic stroke.
In addition, he found that intakes of red meats, high fat dairy products, nuts, and eggs did not appear to be related to risk of stroke.
However, Jerry Doyle of the Stroke Association told BBC News Online that he urged caution in respect to the results. "The link between fat intake and cardiovascular disease is well proven and this paper does not alter the logic of the basic public health message telling people to avoid saturated fats," he told the BBC.
"Basically, if you eat a diet of saturated fats and take in a lot of cholesterol, then you are definitely at increased risk of coronary heart disease.
"The possibility of it also applying to stroke has not been excluded and indeed the heart protection study has shown that lowering cholesterol when people have already had a stroke, certainly ischaemic strokes, helps protect against further strokes," he concluded.
Full details of the study can be found in the 4 October 2003 issue of the British Medical Journal