Abstract
Background: Suboptimal diet is one of the most important factors in preventing early death and disability worldwide. Objective: The aim of this meta-analysis was to synthesize the knowledge about the relation between intake of 12 major food groups, including whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy, fish, red meat, processed meat, and sugar-sweetened beverages, with risk of all-cause mortality. Design: We conducted a systematic search in PubMed, Embase, and Google Scholar for prospective studies investigating the association between these 12 food groups and risk of all-cause mortality. Summary RRs and 95% CIs were estimated with the use of a random effects model for high-intake compared with low-intake categories, as well as for linear and nonlinear relations. Moreover, the risk reduction potential of foods was calculated by multiplying the RR by optimal intake values (serving category with the strongest association) for risk-reducing foods or risk-increasing foods, respectively. Results: With increasing intake (for each daily serving) of whole grains (RR: 0.92; 95% CI: 0.89, 0.95), vegetables (RR: 0.96; 95% CI: 0.95, 0.98), fruits (RR: 0.94; 95% CI: 0.92, 0.97), nuts (RR: 0.76; 95% CI: 0.69, 0.84), and fish (RR: 0.93; 95% CI: 0.88, 0.98), the risk of all-cause mortality decreased; higher intake of red meat (RR: 1.10; 95% CI: 1.04, 1.18) and processed meat (RR: 1.23; 95% CI: 1.12, 1.36) was associated with an increased risk of all-cause mortality in a linear dose-response meta-analysis. A clear indication of nonlinearity was seen for the relations between vegetables, fruits, nuts, and dairy and all-cause mortality. Optimal consumption of risk-decreasing foods results in a 56% reduction of all-cause mortality, whereas consumption of risk-increasing foods is associated with a 2-fold increased risk of all-cause mortality. Conclusion: Selecting specific optimal intakes of the investigated food groups can lead to a considerable change in the risk of premature death. Am J Clin Nutr 2017;105:1462-73.
Generated Summary
This meta-analysis of prospective studies investigated the associations between the intake of 12 major food groups and the risk of all-cause mortality. The study utilized PubMed, Embase, and Google Scholar for prospective studies. Summary RRs and 95% CIs were estimated using a random effects model for high-intake versus low-intake categories, as well as linear and nonlinear relations. The risk reduction potential of foods was calculated by multiplying the RR by optimal intake values. The study’s aim was to synthesize knowledge about the relationship between the intake of various food groups, including whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy, fish, red meat, processed meat, and sugar-sweetened beverages, and the risk of all-cause mortality. The research was conducted according to the standards of the Meta-analysis of Observational Studies in Epidemiology (11).
Key Findings & Statistics
- Whole Grains: With each daily serving, the risk of all-cause mortality decreased (RR: 0.92; 95% CI: 0.89, 0.95). Each additional daily 30 g of whole grains was inversely associated with mortality risk (RR: 0.92; 95% CI: 0.89, 0.95). Optimal consumption of risk-decreasing foods results in a 56% reduction of all-cause mortality.
- Vegetables: Increased intake decreased mortality risk (RR: 0.96; 95% CI: 0.95, 0.98). The risk of mortality decreased by 11% with increasing intake of vegetables up to ~300 g/d.
- Fruits: Increased intake decreased mortality risk (RR: 0.94; 95% CI: 0.92, 0.97). Each additional daily 100 g of fruits was inversely associated with mortality risk (RR: 0.94; 95% CI: 0.92, 0.97). The risk of all-cause mortality decreased by ~10%, with increasing intake of fruit up to ~250-300 g/d.
- Nuts: Increased intake decreased mortality risk (RR: 0.76; 95% CI: 0.69, 0.84). For each additional daily 28 g (RR: 0.76; 95% CI: 0.69, 0.84). The risk of all-cause mortality decreased by ~17% with increasing intake of nuts up to ~ 15-20 g/d.
- Fish: Increased intake decreased mortality risk (RR: 0.93; 95% CI: 0.88, 0.98), and for each additional daily 100 g (RR: 0.93; 95% CI: 0.88, 0.98). The risk decreased by 10% with increasing intake of ≤200 g fish/d.
- Red Meat: Higher intake increased mortality risk (RR: 1.10; 95% CI: 1.04, 1.18). Each additional daily 100 g of red meat was positively associated with risk of all-cause mortality (RR: 1.10; 95% CI: 1.04, 1.18).
- Processed Meat: Higher intake increased mortality risk (RR: 1.23; 95% CI: 1.12, 1.36). Each additional daily 50 g of processed meat was associated with a risk of all-cause mortality (RR: 1.23; 95% CI: 1.12, 1.36). The risk of all-cause mortality increased by ~60% with increasing intake of processed meat up to ~200 g/d.
- Refined Grains: No significant association was observed in any of the stratified analyses.
- Eggs: Positive association was observed for the highest compared with the lowest egg intake category (RR: 1.06; 95% CI: 1.00, 1.12), and for each additional daily 50 g (RR: 1.15; 95% CI: 0.99, 1.34). The risk of all-cause mortality increased by ~10% with increasing intake of eggs up to ~60 g/d.
- Dairy: No association was observed for the high compared with the low intake (RR: 1.03; 95% CI: 0.98, 1.07), or for each additional daily 200 g of dairy products (RR: 0.98; 95% CI: 0.93, 1.03). Intakes of ≤1000 g/d were associated with a 15% increased risk of mortality.
- Sugar-Sweetened Beverages: No association between all-cause mortality and SSBs was observed in the analysis of high compared with low intake (RR: 1.02; 95% CI: 0.97, 1.06). The risk of all-cause mortality increased by ~7% with increasing intake of SSBs up to ~250 mL/d.
- Optimal consumption of risk-decreasing foods results in a 56% reduction of all-cause mortality, whereas consumption of risk-increasing foods is associated with a 2-fold increased risk of all-cause mortality.
Other Important Findings
- Nonlinearity was observed for the relations between vegetables, fruits, nuts, and dairy and all-cause mortality.
- The study found a clear indication for nonlinear dose-response relations between vegetables, fruits, nuts, and dairy with all-cause mortality.
- The NutriGrade tool for evaluating the meta-evidence suggested high confidence in the effect estimate for whole grains.
- The risk of all-cause mortality decreased by ~80% in the relative risk of premature death with optimal intake of whole grains, vegetables, fruits, nuts, legumes, and fish, and reduced consumption of red and processed meats and SSBs.
Limitations Noted in the Document
- Dietary information was primarily derived from food frequency questionnaires, which represent a subjective approximation of past dietary behaviors.
- Substantial heterogeneity was found with respect to population size, follow-up duration, baseline age, and food consumption.
- High levels of statistical heterogeneity persisted in subgroup analyses for most food groups.
- The indication of small study effects such as publication bias in the analyses of vegetables, fruits, nuts, dairy products, and red meat.
- The results of the nonlinear association between dairy and all-cause mortality should be interpreted with caution.
- The study did not consider the effect of environmental contaminants present in fish.
Conclusion
The meta-analysis of prospective studies reveals significant associations between food group consumption and the risk of all-cause mortality. The study shows an inverse association between the consumption of whole grains, vegetables, fruits, nuts, legumes, and fish and reduced mortality risk. In contrast, higher intakes of red and processed meats were associated with an increased risk. The study underscores the importance of food choices for public health, highlighting that optimal intakes of risk-decreasing foods, such as whole grains, vegetables, fruits, nuts, legumes, and fish, can considerably reduce the risk of premature death. In contrast, the consumption of risk-increasing foods, like red and processed meats, eggs, and sugar-sweetened beverages, can lead to a two-fold increase in mortality risk. The NutriGrade tool suggests high confidence in the effect estimate for whole grains. However, the study’s reliance on food frequency questionnaires and the presence of heterogeneity across studies pose limitations. The findings suggest that making informed dietary choices can substantially impact lifespan. The study does not directly argue the causal relationships between mortality and consumption, but rather reveals specific biological relationships related to the etiology of chronic diseases and/or preclinical disorders and risk factors. The study also notes that future research should expand the scope of food groups and clinical end points considered. The study’s insights support dietary guidelines and recommendations aimed at promoting health and preventing premature death by focusing on the consumption of beneficial food groups and limiting the intake of detrimental ones. “In conclusion, an optimal intake of whole grains, vegetables, fruits, nuts, legumes, and fish, as well as reduced consumption of red and processed meats and SSBs, can lead to an important decrease-by ~80%-in the relative risk of premature death when compared with intakes always from the highest risk category.” (Figure 2). The study supports a shift towards plant-based diets. The authors state that “The investigation of single food groups (or other dietary factors) with respect to mortality is based on the paradigm that compounds of the food groups can be linked to specific disease mechanisms because of their biological activity and other physiologic properties. For example, protective effects of whole grains, fruits, vegetables, nuts, and fish might be explained by anti-inflammatory, antioxidative, antiproliferative, or chemopreventive mechanisms, which have been described for a number of bioactive compounds (e.g., fiber, minerals, trace elements, vitamins, carotenoids, polyphenols, alkylresorcinols, omega-3 fatty acids).”