Bulletin Spring‧Summer 1999

are arranged on the opposite sides of the double bond. The process o f hydrogenation converts some fatty acids from their natural cis- to trans- configuration. A research conducted by Harvard University found that people consuming more trans-fatty acids have a higher risk of cardiovascular disease. Another study published in Lancet showed that the consumption of hydrogenated vegetable oils by 85,095 nurses over an eight-year period had increased the occurrence of coronary heart diseases among them. And Dutch researchers found that volunteers on a trans-fatty acid diet have 20—30 mg more serum cholesterol than those on a cis-fatty acid diet. These findings cast doubts on the widespread use of hydrogenated vegetable oils in Western fastfood restaurants. The effects o f trans-fatty acids on health become s a controversial issue. Mother-Infant Transfer of Trans-Fatty Acids Prof. Chen Zhen Yu o f the Department o f Biochemistry of The Chinese University found a p o s i t i v e c o r r e l a t i o n between the l e v e l o f consumption of trans-fatty acids by lactating Canadian women and the trans-fatty acid content in their breast milk, in a study he conducted in 1992 as a research f e l l ow at the N u t r i t i o n Research Division of the Department of Health in Canada. This means that trans-fatt y acids present in partially hydrogenated vegetable oils are transferred to human milk through maternal diets. Another study conducted by German researchers found a correlation betwee n the consumption o f trans-fatty acids by mothers and low birth weight in infants. It is estimated tha t N o r t h Ame r i c a ns consume approximately 10g of trans-fatty acid per day. As the diet of Hon g Kong's population becomes more westernized, does it also mean that Hong Kon g women are consuming more trans- fatty acids? In 1995 Prof. Chen began the project ‘ Me t a b o l ic Rate o f T r a n s - / C i s Fatty Ac i d s Present in High-Trans M i l k and Their Effect on metabolism of Essential Fatty Acids'. The project was supported by a HK $ 1,180,000 grant from the Research Grants Council. Trans-Fatty Acid Content of Hong Kong Maternal Milk The study was divided into two parts. One part investigated the fatty aci d composition of the breast milk of 51 Hong Kong Chinese women and compared it with that of 33 mainland Chinese and 198 Canadian women. It was found that Hong Kong Chinese breast milk contained 0.88 per cent of trans-fatty cid , while mainland Chinese breast milk contained 0.22 per cent, and Canadian breast milk, 7.19 per cent. Adverse Effects of Trans-Fatty Acids The study's other part investigated the relation between the amount o f t r a n s - f a t ty acids in maternal diet and that in maternal milk by putting lactating rats on diets with varying levels of the acids in question and analyzin g their milk. A positive correlation was found: rats on a 10 per cent trans-fatty acid diet produced milk with six per cent of the acid while rats on a 25 per cent diet produced mil k with 16 per cent. Prof. Chen and his colleagues also found adverse effects associated wit h feeding newborn and maternal rats with large doses of trans-fatty acids. They could accumulate in the heart, kidney, and liver, in the place of natural cis-fatty acids. Ov e r c o n s ump t i on o f t r a n s - f a t ty acids also interferes with the metabolism of essential fatt y acids i n newborn rats. Although the adverse effects of trans -fatty acids in maternal milk hav e not been confirmed, Prof. Chen advises lactating mothers to reduce their intake o f both saturated and hydrogenated fats.• Prof. Chen Zhen Yu graduated with a BSc in chemistry from Henan Normal University in 1982. He then went abroad to the US where he obtained his PhD in food and nutritional science from the University of Massachusetts (Amherst) in 1989. For the next five years, he was first postdoctoral fellow in the Department of Nutritional Science at the University of Toronto, then research fellow at the Nutrition Research Division of the Department of Health, Canada. He joined The Chinese University in 1994. Chinese University Bulletin Spring • Summer 1999 32