Healthy meat? Researchers reignite debate

17 Jun 2020 --- Two new studies have brought the debate on the health impact of meat consumption to the fore once again. A German study found that the less animal-derived food incorporated into a person’s diet, the lower their body mass index (BMI) is on average. Meanwhile, substituting lean, unprocessed beef for carbohydrates in a Western diet had no significant effects on the heart health of test subjects with prediabetes in a US study. NutritionInsight spoke with both papers’ researchers on how their respective results may shape consumers’ dietary relationships with meat consumption.

“Our message is not to eat more meat. Instead, our view is that incorporation of some red meat – lean, unprocessed beef in our study – into a healthy dietary pattern should not be expected to worsen major risk factors for heart disease and diabetes,” principal investigator Dr. Kevin Maki, School of Public Health, Indiana University, US, tells NutritionInsight.

The US study found that lean, unprocessed beef as part of a healthy dietshould not worsen major risk factors for heart disease and diabetes.The US researchers had 33 study participants with prediabetes follow either a US-style diet with below-average red meat intake for US standards (about 1.2 oz per day), or a similar diet that contained an additional 5.3 oz per day of unprocessed, lean beef. The participants completed the crossover, controlled-feeding trial, where each subject was randomly assigned to follow one eating pattern for four weeks. This was followed by a washout of two weeks, then consumption of the other diet for four weeks.

“We used a relatively large quantity of lean beef in our study to ensure that if there were any adverse effects, we would likely observe significant differences between the diet conditions. No statistically significant adverse effects [in cholesterol levels, blood pressure or insulin sensitivity] were observed. Consumption of up to three servings per week of lean, unprocessed red meat would be consistent with most recommendations from health authorities around the world,” Dr. Maki affirms.

Slimmer vegetarians
Meanwhile, a separate study found that restricting animal-based products from the diet may exert beneficial effects on weight status. The large-scale study at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in cooperation with the University Hospital of Leipzig also investigated the link between an animal-free diet and emotional health. THe researchers did observe study participants predominantly following a plant-based diet were more introverted than those who mainly fed on animal products. However, they did not find a significant correlation between plant-based diets being more often associated with depressive moods.

The researchers included 8,943 subjects for analyses regarding diet, BMI and depressive symptoms. Using a Food Frequency Questionnaire (FFQ), linear regression models detected lower animal dietary restriction scores, meaning that higher frequency of animal-based products consumption related to higher BMI in the sample. 

“We indeed expected these results, which are in line with previous studies. However, we were curious if we could detect an association using a continuous measure of dietary intake of animal-based products with a FFQ in our large cohort; thus these results may allow a more nuanced view. For example, we did not separate between vegetarians, vegans and omnivores but considered the frequency of animal-based product consumption,” study author Veronica Witte, Day Clinic for Cognitive Neurology, University Hospital, Leipzig University, tells NutritionInsight. 

Products made from animal-based foods can be excessively rich in fat and sugar are particularly fattening, consequently stimulating the appetite and delaying the feeling of satiety, adds first author Evelyn Medawar. “Vegetarian food contains dietary fibers and has a positive effect on the microbiome in the intestine. This is another reason why they could fill you up earlier than those made from animal ingredients. People who eat predominantly vegetable foods may therefore absorb less energy,” she states. 

Plant-based meat alternatives have been called out for being high in sodium, which could be detrimental to cardiovascular health.Plant-based meat alternatives: Common ground?
The meat industry continues to go back and forth, discussing the extent to which animal-based and plant-based meat consumption is beneficial for overall health. Last October, a Canadian study encouraged adults to continue consuming red and processed meat as they already do, since cutting back has little impact on health. However, a US study reported later in February that regular consumption of red and processed meats is linked to cardiovascular disease and death. 

Meanwhile, plant-based meat alternatives have recently come under fire for containing excessive amounts of sodium, which could be detrimental to cardiovascular health. In March, Action on Salt spotlighted the “shocking” amounts of salt and saturated fat found in plant-based and vegan meals available at British fast food outlets. This came amid calls for better transparency in meat analogs during Veganuary.

Dr. Maki envisions a symbiotic state for both plant- and animal-based meat, affirming that both lean meats and meat alternatives can be part of a healthy dietary pattern. He adds that consumers need to understand how to interpret sodium differences to maintain a diet consistent with recommendations from health authorities.

“The key is to stay within recommended ranges in the overall diet. If one consumes a higher-sodium meat alternative in a meal, they will need to be more careful about how much sodium is consumed in the other foods consumed that day. Some meat alternative products are low in saturated fat and others are not,” he notes. 

Future research is warranted to further investigation in this space. Dr. Maki’s team aims to continue studying the effects of dietary interventions on risk factors for heart disease and diabetes. “We are particularly interested in defining predictors of responses to dietary interventions. These include clinical indicators, such as amount and distribution of body fat, insulin sensitivity and triglyceride levels, as well as characteristics such as gut microbiota.”

Witte also affirms that her research team will follow up on their research by looking at blood measures of dietary intake, which may add precision to the questionnaires’ data. “We are eager to study longitudinal effects of dietary habits at baseline on six-year-follow up measures of weight and psychological outcomes. We are also interested in checking the hypothesis that a more plant-based diet at baseline promotes healthier weight, and how this relates to mental health,” she concludes.

By Anni Schleicher