• Analyzing over 30 studies, German researchers found that swapping meats for plant-based alternatives may drastically reduce risks of cardiovascular disease, type 2 diabetes, and all-cause mortality.
  • Evidence showed that replacing 50 grams (1.8 ounces) of processed meat with plant-based foods on a daily basis lowered cardiovascular disease risk by 25%.
  • Substituting processed meats was associated with a 21% lower risk of death from any cause.

The Western diet is replete with red and processed meats and other animal products. Experts worry that this eating pattern strains natural resources, triggers negative climate change, and contributes to an array of noncommunicable diseases.

The environmental and health burdens associated with the Western diet are increasingly supporting the case for promoting plant-based dietary alternatives.

Some studies have suggested that plant-based foods may help lower the risk of cardiovascular disease, type 2 diabetes, coronary heart disease, and overall mortality.

So far, however, research has not considered the full cardiometabolic implications of switching out meats for plants in a systematic review and meta-analysis.

To address this deficit, researchers from institutions in Germany collaborated on a paper exploring the topic. Their systematic review and meta-analysis article was published in BMC Medicine.

“Our findings indicate that a shift from animal-based (e.g., red and processed meat, eggs, dairy, poultry, butter) to plant-based (e.g., nuts, legumes, whole grains, olive oil) foods is beneficially associated with cardiometabolic health and all-cause mortality,” the authors reported.

The research team ran a systematic literature search on MEDLINE, Embase, and Web of Science.

They included studies that used substitution analyses of animal-based food with plant-based foods. The studies consulted also discussed health outcomes such as cardiovascular disease, coronary heart disease, type 2 diabetes, and all-cause mortality.

Furthermore, the studies were prospective observational studies conducted among the general healthy population.

Each study underwent a risk of bias assessment with the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I) tool. The team evaluated the certainty of evidence for each association using the Grading of Recommendation, Assessment, Development, and Evaluations (GRADE) protocol.

The research team narrowed their search down from 1,216 to 32 studies for final inclusion in their analyses. Hand searching yielded another five studies, for a total of 37 meta-analyses.

According to the authors, their work “is the first systematic review and meta-analysis that summarized the associations between the substitution of animal-based with plant-based foods with a wide range of cardiometabolic outcomes, such as cardiovascular disease mortality; incidence of [cardiovascular disease, coronary heart disease, and type 2 diabetes]; diabetes mortality, and all-cause mortality.”

The researchers observed a “moderate certainty of evidence” that replacing one daily egg with nuts correlated with lower cardiovascular disease mortality. Substituting butter with olive oil yielded similar results.

Switching 50 grams (g) of processed meat with 28 g of nuts daily was associated with a lower coronary heart disease incidence. Replacing poultry or seafood with nuts or legumes was not.

There was only a low certainty of evidence for associations of reduced coronary heart disease risk with replacing red meat with nuts or legumes.

Replacing butter with olive oil, red meat with nuts, or one egg daily with nuts, was inversely associated with type 2 diabetes frequency, the researchers also found.

Finally, the research team noticed a moderate certainty of evidence for a lower risk of all-cause mortality when switching red meat with nuts or whole grains. Replacing processed meat with nuts or legumes, or unprocessed red meat with nuts also reduced this risk.

Substituting dairy or one egg daily with nuts or legumes, or butter with olive oil, was associated with a lower risk of all-cause mortality.

These findings agree with a prior review suggesting that replacing red meat with plant-based foods lowered the risk of coronary heart disease and all-cause mortality.

This work also supports other studies tying higher meat consumption with coronary heart disease, stroke, type 2 diabetes, and all-cause mortality.

The present study was the first meta-analysis of its kind. Validated food frequency questionnaires were used to collect dietary information. The mean follow-up duration among the cohorts was 19 years.

Most of the studies included males and females, with a few gender-specific exceptions.

Medical News Today discussed this study with Eva De Angelis, a registered dietitian nutritionist. She was not involved in the research.

De Angelis considered the investigation “quite a fascinating systematic review that further highlights the vital role plant foods can have on our overall health, and how too many animal foods can have the opposite effect.”

She was impressed that the study used many diverse prospective studies, which “provide a higher quality of evidence.”

The focus on multiple health outcomes was another strength, Ms. De Angelis told MNT.

Nevertheless, the research team also acknowledged several limitations to their study, stressing that their “findings should be interpreted with caution.”

Many of the studies analyzed used theoretical food substitutions. Moreover, portion sizes differed among studies, resulting in unequal comparisons of dietary substitutes.

Using only prospective observational studies presented the potential for residual confounding and measurement inaccuracies.

Furthermore, the limited number of studies in the final analysis did not allow for subgroup assessments. For instance, dairy products were assessed as one group. The authors noted that “dairy includes a wide range of different products (e.g., milk, yogurt, cheese) with different associations with cardiometabolic outcomes.”

De Angelis commented: “Among the weaknesses, I would mention that the information only allows us to make associations, and not causality, because many of the analyzed studies were observational. This means we don’t know for sure if any other factors may have been involved in the outcomes.”

The review authors felt that more research was needed to support the existing evidence. They expressed their hope that future work would explore new interconnections and highlight meat and dairy replacements.

MNT also discussed this study with registered dietitian nutritionist Sara Chatfield. She was not involved in the research.

Chatfield pointed out that transitioning to more plant-based foods can reap significant benefits to the planet, because animal production is so resource- and land-intensive.

In fact, both of the nutritionists interviewed by MNT agreed that focusing more on whole plant foods can only help the Earth and its inhabitants.

Chatfield referred to research suggesting that shifting to plant-based dietary patterns could reduce diet-related land use by 76% and greenhouse gas emissions by 49%.

De Angelis shared a similar view, saying that:

“There is no denying that following a mainly plant-based diet has been proven beneficial not only for our overall health but also for the planet as we reduce our carbon footprint by choosing such foods.”

Both nutritionists cautioned, however, that a fully plant-based diet may not be the best option for some, depending on an individual’s health conditions, preferences, and food accessibility.

Still, De Angelis emphasized that “trying to add more plant foods to your diet can be an easy and simple step for better health.”

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