People consuming the most meat protein intake saw a 61% increase in cardiovascular mortality risk, compared with those in the lowest consumption group, said the team behind the study,.
Conversely, the highest consumption of protein from nuts and seeds was linked to a 40% reduction in risk, found the research team, a collaboration between Loma Linda University, California and the National Institute of Agronomic Research (INRA), Paris, France.
The results remained valid, even after adjusting for factors associated with cardiovascular disease (CVD) like fats and elements of vegetarian dietary patterns. No significant associations with CV outcomes were found for protein sourced from grains, processed foods or the collective group ‘legumes, fruits and vegetables’.
“Proteins from nuts/seeds were associated with protection, and proteins from meats (especially red meats) were associated with increased risk for cardiovascular death. These proteins were not surrogates for fats in these foods as we adjusted for those fats. Rather it appeared to be the proteins themselves or something closely associated with them,” commented co-lead researcher Professor Gary Fraser from Loma Linda University.
The adverse cardiovascular effects appear to be confined to meat, rather than other animal-based protein sources such as fish, eggs or dairy.
“Proteins from these other animal foods did not appear to convey increased risk in this study,” said Fraser.
Protein or fat?
The study of over 81,000 participants from the Adventist Health Study-2 cohort used factor analysis to develop dietary patterns based on protein consumption.
Whereas research into CVD risk factors based on animal or plant-based fat consumption is plentiful, the emphasis on protein in the study is novel.
“A focus on proteins as risk factors for CVD is relatively new, particularly when combined with an adjustment for fatty acids on the diet,” elaborated Fraser.
The results suggest that proteins, as well as fats, within food groups play a role in determining CVD risk.
“It shifts the focus from primarily fats to now include the protein content of these foods,” said Fraser.
It was also notable that a specific plant protein group (nuts and seeds) conferred the benefits on CV outcomes, rather than the wider category of generalised plant-based, he added.
“These results provide more evidence on the benefits of avoiding red meats, and including small quantities of nuts (12-14/d) in the diet to probably reduce risk of cardiovascular disease,” advised Fraser.
Interestingly, the researchers also observed a weakening of the effects with advancing age.
“Our results indicate that these effects weaken with age and disappear by age 80 years. Thus, dietary effects may largely prevent premature disease and death, which is the most consequential,” noted Fraser.
Further work is needed to examine the underlying mechanisms and to explore which specific proteins might be responsible for the harmful effects of meat protein and the protective influence of nuts and seeds.
“This study did not have data to explore these mechanisms further, although we do have amino acid data, but that has not yet been looked at,” said Fraser.
Source: International Journal of Epidemiology
Published online 2nd April 2018 doi: 10.1093/ije/dyy030
“Patterns of plant and animal protein intake are strongly associated with cardiovascular mortality: the Adventist Health Study-2 cohort”
Authors: Marion Tharrey, et al