A new study at the University of Reading, in collaboration with the Medical Research Council, Cambridge, and three UK universities, has shed new light on dietary recommendations for good health.
Professor Julie Lovegrove's research team at the Hugh Sinclair Unit of Human Nutrition at Reading contributed to the RISCK study, funded by the Food Standards Agency.
The study looked at the impact of changing the amount and composition of fat and carbohydrate in people's diets on reducing risk factors linked to heart disease.
The RISCK study, the largest of its kind in the UK, has shown that people who replace saturated fat in their diet with carbohydrates with a low glycaemic (GI) index number or monounsaturated fat are able to improve the type of fats in their blood and reduce the risk of cardiovascular disease.
The glycaemic index is a numerical ranking of foods based on their immediate effect to raise your blood sugar. It measures how fast the carbohydrate of a particular food is converted to glucose and enters the bloodstream. A food with a high number enters the bloodstream faster than one with a lower number. Consumption of low GI foods is associated with lower blood sugar.
Saturated fats are found in animal products and are also present in foods such as cakes, biscuits and pies. Monounsaturates, in foods rich in olive and rape seed oil, are known to lower blood cholesterol levels.
The RISCK trial included 548 people all known to be at risk of cardiovascular disease. All participants followed a reference diet for one month to ensure that everyone had a similar starting point and then followed a randomly allocated diet.
The results confirmed that risk factors for cardiovascular disease were improved by substituting saturated fat with monounsaturated fat and by substituting high GI carbohydrates for low GI carbohydrates. However the effect of these diets on measures of insulin resistance was less clear.
Professor Julie Lovegrove said: "The RISCK trial is an important study as it tested the impact of changing the amount and type of fat and carbohydrate in the diet of individuals to test the effects on their health, using very detailed measurements. Replacement of dietary saturated fat with monounsaturated fats and low glycaemic index carbohydrates can reduce heart disease risk factors, although further research is required to determine the possible benefit of low GI foods on insulin sensitivity."
The results of the study will be used to inform public health policy for the prevention of heart disease, and may provide valuable information to enable food producers and manufacturers reformulate their products to make them healthier and to develop new foods.
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For a copy of the full research paper please go to: www.ajcn.org/cgi/rapidpdf/ajcn.2009.29096v1