To investigate the impact of different protein sources on mortality in older women, a team of researchers from the University of Iowa School of Public health conducted an 18-year prospective generational study on more than 102,000 postmenopausal women. The results found that replacing animal proteins such as red meat, poultry, dairy products and eggs with plant-based proteins such as nuts reduced total and cause-specific mortality by up to 50%.
The results of the study have been published in the February 2021 issue of the Journal of the American Heart Association. The paper points out that protein is an essential nutrient for the human body; current protein intake recommendations focus on total daily intake; however, the existing literature is too simplistic and insufficient for the intake recommendations of different protein sources.
More specifically, do different protein sources have an impact on total and cause-specific mortality? To answer this question, the research team obtained consent from 102,521 women who had stopped menstruating through the U.S. Women’s Health Promotion Program and began an 18-year follow-up until February 2017.
During the 18-year follow-up period, 25,976 people died; of these, approximately 6,993 died from cardiovascular disease, 7,516 from cancer, and 2,734 from dementia-related diseases.
According to the research team’s regular follow-up questionnaires, the average daily protein intake of each woman was about 1 in 6 of the total diet; 68.6% of the daily protein intake came from animal protein, such as meat, eggs and dairy products. At the same Time, women who consume mainly animal protein tend to be Caucasian women with good Education and economic status. They are also more likely to have smoking, alcohol abuse and sedentary lifestyle patterns.
These lead to a higher risk of second-stage diabetes and a higher body mass index (BMI) for those whose primary protein intake is animal-based, making them a higher risk group for cardiovascular disease.
Studies have also found that even small adjustments to protein intake can have a dramatic impact. For example, replacing 5% of animal protein intake with plant-based protein can reduce the risk of premature death by 14%. In addition, replacing eggs with nuts reduced the risk of death by 47%, and replacing red meat and dairy products with nuts reduced the risk of premature death by 11% and 12%, respectively.
The team also found that older women who adopted a vegetarian diet used nuts as a daily source of protein, reducing the risk of death from cardiovascular disease by 56%. In contrast, if participants increased their intake of non-processed meat, eggs and dairy products, the risk of death from cardiovascular disease increased by 12%, 24% and 11%, respectively; participants who consumed the most processed red meat had a 20% increased risk of death from dementia.
In terms of egg intake, participants who consumed large amounts of eggs had a 24% increased risk of dying from cardiovascular disease and a 10% increased risk of dying from cancer; however, the risk of dying from dementia was reduced by 14%. The team said, “It is still unknown why eggs increase the risk of death from cardiovascular disease and cancer, and further research is needed. This may be related to the way they are cooked or the ingredients they are added to”.
The paper concluded that replacing animal proteins with plant proteins did reduce the risk of total mortality, cardiovascular disease mortality and dementia mortality, while replacing red meat, eggs and dairy products with nuts was associated with a greater risk of total mortality. Existing dietary guidelines focus only on total protein intake, and should be adjusted to the different health effects of different total protein categories in the future.
However, the study also emphasizes that the sample size of the study was all postmenopausal women. Therefore, the results may not be applicable to young men and women. Further studies are needed to investigate the specific effects on young men and women.
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