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Caffeine and heart disease
428
Information Section
Coffee and heart disease Investigators from Norway have found an association between coffee consumption and raised blood homocysteine levels (a risk factor for cardiovascular disease and adverse pregnancy outcome). The effect was observed among 16,000 men and women who provided details of their regular coffee intake. Heavy coffee consumption (around nine or more 'cups' per day) was associated with an increase of total homocysteine in the order of 2 gmol/litre. From their reading of an earlier published statistical overview of the effects of increased concentrations of homocysteine, the investigators estimated an increase of this size to be associated with a 14-20% increased risk of heart disease. "The results.., should promote future studies on [homocysteine] as a possible mediator of adverse clinical effects related to heavy coffee consumption ~ ('Nyg~rd O. et al., American Journal of Clinical Nutrition 1997, 65, 136).
Caffeine a n d heart disease An Australian scientist has offered the opinion in a leading medical journal that the widespread use of caffeine probably contributes to population cardiovascular disease by increasing blood pressure, and that habitual consumers are not immune to the effects of the drug (it has previously been suggested that regular consumers develop tolerance to the haemodynamic effects of caffeine). Noting that consumption seems to raise blood pressure on average by 2-4 mmHg, and that around 80% of the population consumes caffeine, he concluded that ~population-wide cessation of caffeine use could lead to 9-14% less coronary heart disease and 17-24% less stroke" (James J.E. Lancet 1997, 349, 279).
Dietary fibre and heart disease A large trial in Finland has confirmed the protective effect of dietary fibre against coronary heart disease. Almost 22,000 middle-aged male smokers (recruited from around 29,000 taking part in a cancer prevention trial) who were free of heart disease at the beginning of the study were followed for just over 6 years. There were around 1400 "major coronary events", 635 of them fatal. The men with the highest dietary fibre intake (median 34.8 g/day) had only about 70% the coronary death rate as did the men with the lowest intake (median 16.1 g/day) (Pietinen P. et al., Circulation 1996, 94, 2720).
A high-fibre diet may reduce the risk of diabetes A study of over 65,000 middle-aged American women revealed that the risk of developing diabetes was inversely associated with cereal fibre consumption and positively associated with the "dietary glycemic load" (an overall measure of the ability of a range of carbohydrates to raise insulin levels). Over a 6-year period of follow-up, 915 of these women had developed diabetes. The investigators concluded that ~grains should be consumed in a minimally refined form to reduce the incidence of diabetes" (Salmeron J. et al., Journal of the American Medical Association 1997, 277, 472).
Soy protein, isofiavones and cholesterol levels It has been suggested that the mechanism of the cholesterol-lowering effect of a diet rich in soy protein may be associated with the natural presence in the soy of isoflavones (mainly genistein and daidzein). A group of Italian scientists involved in three previously published studies which showed soy to have a beneficial effect on blood cholesterol has now reported that recent laboratory analyses have indicated the isoflavone content of the soy preparations used in their earlier work to be %ssentially negligible" (Sirtori C.R. et al., American Journal of Clinical Nutrition 1997, 65, 166).
Medium-chain fatty acids and blood cholesterol It has been a long-held view in nutrition that the ingestion of medium chain-length (C8-C10) saturated fatty acids, unlike their longer-chain analogues, do not increase blood cholesterol levels. The results of a carefully conducted US trial involving nine middle-aged men with mildly raised levels of blood cholesterol tends to contradict this conventional wisdom. The volunteers, housed in a hospital metabolic unit, were given as part of their diet for 3 weeks a medium-chain triacylglycerols (MCT) oil (which would be expected to be easily hydrolysed in the gastrointestinal tract to release C8-C10 saturated fatty acids). This resulted in blood cholesterol levels similar to those produced by a diet supplemented with 'cholesterol raising' palm oil (which contains high proportions of the saturated C16 fatty acid). On the basis of percentage energy, medium-chain fatty acids were deemed to have half the potency of palmitic acid at raising
Information Section
Coffee and heart disease Investigators from Norway have found an association between coffee consumption and raised blood homocysteine levels (a risk factor for cardiovascular disease and adverse pregnancy outcome). The effect was observed among 16,000 men and women who provided details of their regular coffee intake. Heavy coffee consumption (around nine or more 'cups' per day) was associated with an increase of total homocysteine in the order of 2 gmol/litre. From their reading of an earlier published statistical overview of the effects of increased concentrations of homocysteine, the investigators estimated an increase of this size to be associated with a 14-20% increased risk of heart disease. "The results.., should promote future studies on [homocysteine] as a possible mediator of adverse clinical effects related to heavy coffee consumption ~ ('Nyg~rd O. et al., American Journal of Clinical Nutrition 1997, 65, 136).
Caffeine a n d heart disease An Australian scientist has offered the opinion in a leading medical journal that the widespread use of caffeine probably contributes to population cardiovascular disease by increasing blood pressure, and that habitual consumers are not immune to the effects of the drug (it has previously been suggested that regular consumers develop tolerance to the haemodynamic effects of caffeine). Noting that consumption seems to raise blood pressure on average by 2-4 mmHg, and that around 80% of the population consumes caffeine, he concluded that ~population-wide cessation of caffeine use could lead to 9-14% less coronary heart disease and 17-24% less stroke" (James J.E. Lancet 1997, 349, 279).
Dietary fibre and heart disease A large trial in Finland has confirmed the protective effect of dietary fibre against coronary heart disease. Almost 22,000 middle-aged male smokers (recruited from around 29,000 taking part in a cancer prevention trial) who were free of heart disease at the beginning of the study were followed for just over 6 years. There were around 1400 "major coronary events", 635 of them fatal. The men with the highest dietary fibre intake (median 34.8 g/day) had only about 70% the coronary death rate as did the men with the lowest intake (median 16.1 g/day) (Pietinen P. et al., Circulation 1996, 94, 2720).
A high-fibre diet may reduce the risk of diabetes A study of over 65,000 middle-aged American women revealed that the risk of developing diabetes was inversely associated with cereal fibre consumption and positively associated with the "dietary glycemic load" (an overall measure of the ability of a range of carbohydrates to raise insulin levels). Over a 6-year period of follow-up, 915 of these women had developed diabetes. The investigators concluded that ~grains should be consumed in a minimally refined form to reduce the incidence of diabetes" (Salmeron J. et al., Journal of the American Medical Association 1997, 277, 472).
Soy protein, isofiavones and cholesterol levels It has been suggested that the mechanism of the cholesterol-lowering effect of a diet rich in soy protein may be associated with the natural presence in the soy of isoflavones (mainly genistein and daidzein). A group of Italian scientists involved in three previously published studies which showed soy to have a beneficial effect on blood cholesterol has now reported that recent laboratory analyses have indicated the isoflavone content of the soy preparations used in their earlier work to be %ssentially negligible" (Sirtori C.R. et al., American Journal of Clinical Nutrition 1997, 65, 166).
Medium-chain fatty acids and blood cholesterol It has been a long-held view in nutrition that the ingestion of medium chain-length (C8-C10) saturated fatty acids, unlike their longer-chain analogues, do not increase blood cholesterol levels. The results of a carefully conducted US trial involving nine middle-aged men with mildly raised levels of blood cholesterol tends to contradict this conventional wisdom. The volunteers, housed in a hospital metabolic unit, were given as part of their diet for 3 weeks a medium-chain triacylglycerols (MCT) oil (which would be expected to be easily hydrolysed in the gastrointestinal tract to release C8-C10 saturated fatty acids). This resulted in blood cholesterol levels similar to those produced by a diet supplemented with 'cholesterol raising' palm oil (which contains high proportions of the saturated C16 fatty acid). On the basis of percentage energy, medium-chain fatty acids were deemed to have half the potency of palmitic acid at raising