Two new diet-heart studies

Clinical trials in nutrition

Trials of nutritional intervention in a wide range of health and disease states, preventive and therapeutic, are required. Not only has the emergence of chronic non-communicable disease (CNCD) with acknowledged nutritional pathogenesis created this imperative need, but so also have other conditions which, previously, had not been regarded as nutritionally based. Among the latter are health problems associated with ageing: the menopause, a decline in immune function, and a decline in cognitive function. At the same time, there is a new set of materno-foetal and infant nutrition issues for investigation which relate to new food exposures and the long-term effects of nutritionally mediated gene expression. The emergence of the new food science of phytochemicals with human biological importance also sets the scene for their evaluation in traditional diets and novel foods. Such trials are more complex than comparable pharmacotherapeutic studies because of the complexity of food chemistry, as well as the food behavioural changes which may accompany a nutritional intervention, and the general problem of there not being a 'gold standard' for food intake methodology. Choice of study population is also a key issue in relation to the extrapolation of findings from a particular trial, with population representativeness being an advantage. In order to obtain useful information on manageable sample sizes, either intermediate end-points (short of morbidity and mortality) need to be studied or high-risk groups (such as the aged) need to be recruited. There are some unique ethical issues which must inform clinical nutrition trials. These include certain preventive imperatives like the right to be fed, the risks in disruption of food cultures and the need for food security and sustainability. Rapid changes in the food supply do, however, make such trials more important, while the value of food-health knowledge that cannot be obtained by trial must still be appreciated.

Transvenous coronary angiography in humans using synchrotron radiation

The risks and costs of the present method of visualizing the coronary arteries have limited the use of coronary angiography in long-term serial studies needed to establish the natural history of coronary atherosclerosis and its response to interventions. A less invasive method, in which the contrast agent is administered intravenously, has been developed using synchrotron radiation as the illuminating source. The present report describes the initial results in human subjects. The findings indicate that transvenous coronary angiograms can be acquired in this manner. Further refinements in the x-ray imaging system are expected to result in increased x-ray fluence and improved image quality.

Progression of coronary atherosclerotic disease assessed by cinevideodensitometry: relation to clinical risk factors

Progression of coronary artery stenosis was measured using a quantitative, computer-assisted cinevideodensitometric method in 144 arterial segments in 44 subjects undergoing coronary arteriography on two separate occasions at least 6 months apart. Projected coronary arteriograms were digitized into 512 X 512 pixel mode and percent stenosis was calculated by comparing background-corrected videodensitometric values over stenotic and normal segments. Subjects underwent repeat coronary arteriography because of worsening symptoms of angina or heart failure; subjects with renal failure, coronary artery bypass grafts or cardiac transplant were excluded. Clinical variables determined at the time of the first arteriogram included age, sex, serum cholesterol, systolic blood pressure and presence or absence of cigarette smoking, diabetes mellitus and left ventricular hypertrophy. The mean interval between arteriograms was 29.3 months. Overall progression of coronary stenosis was observed in 40 of the 44 subjects; the mean progression at 24 months was 39% (90% confidence interval, 33 to 45%) and at 36 months was 48% (40 to 56%). The degree of overall progression was related to the length of time between arteriograms (F = 5.81, p less than 0.05) and to serum cholesterol level (F = 4.37, p less than 0.05). These data indicate that using an accurate, quantitative method, it is possible to measure progression of coronary artery atherosclerosis within 2 to 3 years of the initial arteriogram. Serum cholesterol appears to be an important determinant of disease progression.

The cholesterol/saturated-fat index: an indication of the hypercholesterolaemic and atherogenic potential of food

A food's hypercholesterolaemic-atherogenic potential lies in its cholesterol and saturated-fat content. To help understand the contribution of these two factors a cholesterol/saturated-fat index (CSI) has been calculated. This index is based on a modification of a regression equation computed from metabolic studies designed to lower plasma lipids. A low CSI indicates low saturated fat and cholesterol content and low atherogenicity. The CSI may be used to compare different foods and recipes and to evaluate daily intake quickly and easily.