Food choices: what can kill you or make you live longer?

Abstract (as presented by the authors of the scientific work):

"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."


Covered topics (the letter size corresponds to the frequency of mentioning in the text):

Strengths and limitations (as presented by the authors of the scientific work):

"Dietary information of most of the included studies derives from food frequency questionnaires, which represent a subjective approximation of past dietary behaviors rather than an assessment of absolute intakes. Hence, our results may reveal higher accuracy than is actually available (140). Substantial heterogeneity was found with respect to the analyzed population size, follow-up duration, baseline age, and food consumption. We conducted subgroup analyses for sex, follow-up duration, geographic location, number of cases, and dietary assessment methods in order to explore high degrees of statistical heterogeneity. Overall, for most food groups, high levels of statistical heterogeneity persisted in subgroup analyses. People with a high intake of whole grains, fruits, vegetables, fish, nuts, or legumes might have different lifestyles or a different socioeconomic status from those with lower intakes, representing important confounders (141). However, our main results were confirmed by sensitivity analyses including only studies with a low risk of bias [adjusted for important lifestyle factors (smoking, physical activity, and BMI)]. Another important limitation was 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 because these observations were largely influenced by 2 cohort studies showing a strong positive association (93). Among the strengths of the present meta-analysis are the a priori published systematic review protocol (14), the comprehensive literature search, and the large numbers of prospective studies, death cases, and food groups included. Furthermore, we performed different types of analyses (high compared with low intake, dose-response meta-analysis, nonlinear dose-response analysis, and subgroup and sensitivity analyses), which allowed us to detect associations where the relation was nonlinear and find an optimal consumption with the lowest risk of all-cause mortality. Finally, we assessed the quality of the studies using meta-evidence for each food group through use of the NutriGrade scoring system.

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. To obtain a complete picture, it seems useful to extend the type of food groups and the clinical end points to be considered. We will in the future develop methods that are able to rank foods and diseases according to their contribution to the prevention of chronic diseases."


Full-text access of the referenced scientific work:

Schwingshackl L, Schwedhelm C, Hoffmann G, Lampousi AM, Knüppel S, Iqbal K,
Bechthold A, Schlesinger S, Boeing H. Food groups and risk of all-cause
mortality: a systematic review and meta-analysis of prospective studies. Am J
Clin Nutr. 2017 Jun;105(6):1462-1473. doi: 10.3945/ajcn.117.153148. Epub 2017 Apr
26. PubMed PMID: 28446499.
https://www.researchgate.net/publication/316523321_Food_groups_and_risk_of_all-cause_mortality_a_systematic_review_and_meta-analysis_of_prospective_studies


Further reading:

Mortality rate (Wikipedia, accessed on June 17, 2017):
"Mortality rate, or death rate,[1] is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of deaths per 1,000 individuals per year; thus, a mortality rate of 9.5 (out of 1,000) in a population of 1,000 would mean 9.5 deaths per year in that entire population, or 0.95% out of the total. It is distinct from "morbidity", which is either the prevalence or incidence of a disease,[2] and also from the incidence rate (the number of newly appearing cases of the disease per unit of time).
...read more".

Food group (Wikipedia, accessed on June 17, 2017):
"A food group is a collection of foods that share similar nutritional properties or biological classifications. Nutrition guides typically divide foods into food groups and recommend daily servings of each group for a healthy diet. In the United States for instance, USDA has described food as being in from 4 to 11 different groups.[1]
...read more".


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