Plain language summary
Dietary advice on the amounts of carbohydrates, protein and fat that should be consumed to decrease heart disease risk is inconsistent, as the data supporting guidelines is conflicting. This prospective cohort study of 195,658 people over roughly 10 years aimed to determine the association of macronutrients i.e., carbohydrate, fat, protein, sugar, starch and fibre consumption with death and heart disease. The results showed that the relationships between many macronutrients and heart disease were not as previously thought. Individuals with higher sugar or carbohydrate intakes were associated with a greater risk of heart disease. Individuals with a higher intake of monounsaturated fat were associated with lower risk of heart disease. Intakes of starch and saturated fat were not associated with an increased risk of heart disease at all. The relationship between heart disease and protein, fibre and polyunsaturated fat was not straight forward and depending on how much was in the diet determined the risk of heart disease. It was concluded that many of the relationships between macronutrients and heart disease risk are not simple and any dietary advice given should be based on an individual’s current intake. Dietary advice on carbohydrates needs to take into account the different associations of starch and sugar. This paper could be used by healthcare professionals to understand that dietary advice needs to be personalised based on current intakes.
OBJECTIVE To investigate the association of macronutrient intake with all cause mortality and cardiovascular disease (CVD), and the implications for dietary advice. DESIGN Prospective population based study. SETTING UK Biobank. PARTICIPANTS 195 658 of the 502 536 participants in UK Biobank completed at least one dietary questionnaire and were included in the analyses. Diet was assessed using Oxford WebQ, a web based 24 hour recall questionnaire, and nutrient intakes were estimated using standard methodology. Cox proportional models with penalised cubic splines were used to study non-linear associations. MAIN OUTCOME MEASURES All cause mortality and incidence of CVD. RESULTS 4780 (2.4%) participants died over a mean 10.6 (range 9.4-13.9) years of follow-up, and 948 (0.5%) and 9776 (5.0%) experienced fatal and non-fatal CVD events, respectively, over a mean 9.7 (range 8.5-13.0) years of follow-up. Non-linear associations were found for many macronutrients. Carbohydrate intake showed a non-linear association with mortality; no association at 20-50% of total energy intake but a positive association at 50-70% of energy intake (3.14 2.75 per 1000 person years, average hazard ratio 1.14, 95% confidence interval 1.03 to 1.28 (60-70% 50% of energy)). A similar pattern was observed for sugar but not for starch or fibre. A higher intake of monounsaturated fat (2.94 3.50 per 1000 person years, average hazard ratio 0.58, 0.51 to 0.66 (20-25% 5% of energy)) and lower intake of polyunsaturated fat (2.66 3.04 per 1000 person years, 0.78, 0.75 to 0.81 (5-7% 12% of energy)) and saturated fat (2.66 3.59 per 1000 person years, 0.67, 0.62 to 0.73 (5-10% 20% of energy)) were associated with a lower risk of mortality. A dietary risk matrix was developed to illustrate how dietary advice can be given based on current intake. CONCLUSION Many associations between macronutrient intake and health outcomes are non-linear. Thus dietary advice could be tailored to current intake. Dietary guidelines on macronutrients (eg, carbohydrate) should also take account of differential associations of its components (eg, sugar and starch).