Nutritional Pearls: Diet Quality and Mortality

For those who enjoy eating land animal protein from time to time, today's research should come as a bit of welcome news.

We've seen plenty of research assessing the possible relationships between overall mortality and certain dietary patterns, such as Mediterranean diet or DASH diet. Other studies have examined the relationship between certain food types, such as legumes, red or processed meats, or whole grains, and mortality.

Today's research takes a holistic approach. The authors of this study examined the research regarding the relative healthfulness of specific plant-based and animal-based foods with respect to overall mortality. Based on that research, they created a Diet Quality Index that gives positive points for 11 plant-based foods and negative points for 6 animal-based foods. Upon assessing an individual's usual diet, the authors could assign a score to that person's diet quality—the higher the score, the better.

The Research

In their study, the authors accessed data gathered for the National Health and Nutrition Examination Survey (NHANES) for the period between 1999 and 2014. This included dietary, health, and demographic questionnaires for over 36,000 men and women at least 20 years of age.

Using the dietary surveys that trained interviewers conducted with the participants, the authors were able to score each participant's dietary quality according to their Dietary Quality Index.

The authors assigned a positive score to 11 plant-based foods: "whole grains, vegetables (excluding white potatoes), whole fruits, nuts/seeds/legumes, vegetable oils, and coffee/tea," while 6 animal-based foods received a negative score: "fish/seafood, dairy, and poultry" as well as "processed meats, unprocessed red meats, and eggs." For positively scored foods, participants got more points for greater intake of that food, while higher intake of animal-based products meant a greater number of points were deducted from the participant's overall score.

The authors utilized the National Death Index to identify all participants who passed away before December 31, 2015 and further identified whether that participant's cause of death was heart disease, cancer, or another cause.

The Results

After taking into account demographic and lifestyle factors such as age, sex, body mass index, smoking status, and education, the authors found that those with Dietary Quality Index scores in the top 75% were 25% less likely to die of any cause than those with a score in the bottom 25%.

When the authors also controlled for the individual's score for animal-based foods, those who scored in the top 25% for plant-based foods were 34% less likely to die of any cause than those in the bottom 25% for plant-based foods.

Somewhat surprisingly, when the authors controlled for the individual's score for plant-based foods, there was no difference in risk of mortality between those with a higher score for animal-based foods (that is, who ate more animal-based foods), than those who had a much lower score for animal-based foods.

What’s the Take Home?

There are two takeaways here: first, that the quality of the plant-based foods you consume appear to have a greater impact on your health by far than the animal-based foods you eat, and second, that good quality animal foods, including fish/shellfish, unprocessed red meat and poultry, and dairy products, in moderation, are unlikely to do you much harm in the context of an overall healthy, mostly-plant-based diet.

Reference:

Keaver L, Ruan M, Chen F, et al. Plant- and animal-based diet quality and mortality among US adults: a cohort study. Published online September 18, 2020. Br J Nutr. doi: 10.1017/S0007114520003670.

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Timothy S. Harlan, MD, is a board-certified internist and professional chef who translates the Mediterranean diet for the American kitchen with familiar, healthy recipes. He is an assistant dean for clinical services, executive director of The Goldring Center for Culinary Medicine, and associate professor of medicine at Tulane University in New Orleans.