The influence of high carbohydrate diets and glycaemic index on metabolic risk parameters for coronary heart disease

• Main Author: Arefhosseini, Seyed Rafie
• Published: University of Glasgow 2005
• Subjects: 616.1230654
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422493

This thesis describes a series of studies investigating the relationship between diet, and in particular carbohydrate intake, and risk factors for type 2 diabetes and coronary heart disease (CHD). The first study investigated the effect of advice to increase carbohydrate intake as part of dietary advice to follow the dietary guidelines on metabolic risk factors for CHD in postmenopausal women (Chapter 3). The results showed that subjects appeared to have followed the dietary advice given as they reported significantly reducing their total daily energy (P = 0.011), fat {P ~ 0.008) and non-milk extrinsic sugar (NMES) intake (P = 0.015), and significantly increasing their total carbohydrate (P = 0.026), starch (P = 0.013j and non-starch polysaccharide (NSP) intake (P = 0.050). Subjects also significantly increased their dietary glycaemic index (GI) (P = 0.011). There was a significant reduction in body mass index (BMI) (P = 0.014), and an adverse effect on fasting plasma lipids including an increase in fasting TAG (P = 0.014), and a decrease in HDL cholesterol concentrations (P = 0.021). Subjects reported increasing their consumption of fruit and vegetables, and there was a significant increase in the 'antioxidant power' of plasma (P = 0.007). This appears to have mostly been associated with an increase in fruit intake. Conelation analyses showed that simple sugars appeared to have a more adverse effect on plasma lipids than starch. From this a decision was made to study the relationships between GI and plasma lipids and other metabolic risk factors in data that had already been collected. The mam findings of this case control study on offspring of patients of type 2 diabetes (offspring) and control subjects (Chapter 4) showed that there were no differences in habitual dietary intake, GI or GL between the groups. Offspring were found to demonstrate many of the features of the metabolic syndrome as they had greater levels of adiposity and female offspring had significantly higher waist to hip ratio (P = 0.036), waist circumference (P = 0.063) and BMI (P = 0.083) compared with female control subjects. Offspring were significantly more insulin resistant compared with control subjects with significantly higher fasting insulin (P = 0.049) and higher HOMAIR (P = 0.052) and significantly lower HDL cholesterol concentrations (P = 0.011). However, dietary GI and GL were not found to be directly associated with any of the metabolic parameters measured in the study, but GI was positively coirelated with waist circumference (P = 0.039) and waist to hip ratio (P = 0.043), and measures of adiposity were significantly correlated with many of the metabolic parameters measured in the study. Thus, while the glycaemic quality of the diet did not appear to directly influence metabolic risk factors, the results do support the idea that they influence metabolic risk factors through their effect on adiposity, and in particular central adiposity. TFor this reason it may be safer to advise the public to consume more slowly digestible carbohydrates (such as wholegrain cereals, pulses) rather than low GI foods which could still contain a high proportion of sugar which could mask the positive effects of the low GI diet on lipids. Overall, the results from this thesis highlight the need for more research to develop safer and more appropriate dietary guidelines which can be easily and clearly communicated to the general public.