Objective: We have evaluated the effects on mortality of habitual low carbohydrate-high-protein diets that are thought to contribute to weight control.
Design: Cohort investigation.
Setting: Adult Greek population. SUBJECTS METHODS: Follow-up was performed from 1993 to 2003 in the context of the Greek component of the European Prospective Investigation into Cancer and nutrition. Participants were 22 944 healthy adults, whose diet was assessed through a validated questionnaire. Participants were distributed by increasing deciles according to protein intake or carbohydrate intake, as well as by an additive score generated by increasing decile intake of protein and decreasing decile intake of carbohydrates. Proportional hazards regression was used to assess the relation between high protein, high carbohydrate and the low carbohydrate-high protein score on the one hand and mortality on the other.
Results: During 113 230 persons years of follow-up, there were 455 deaths. In models with energy adjustment, higher intake of carbohydrates was associated with significant reduction of total mortality, whereas higher intake of protein was associated with nonsignificant increase of total mortality (per decile, mortality ratios 0.94 with 95% CI 0.89 -0.99, and 1.02 with 95% CI 0.98 -1.07 respectively). Even more predictive of higher mortality were high values of the additive low carbohydrate-high protein score (per 5 units, mortality ratio 1.22 with 95% CI 1.09 -to 1.36). Positive associations of this score were noted with respect to both cardiovascular and cancer mortality.
Conclusion: Prolonged consumption of diets low in carbohydrates and high in protein is associated with an increase in total mortality.