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Replacing animal foods such as red and processed meat or eggs with plant-based options such as nuts or legumes may reduce the risk of developing heart disease and type 2 diabetes, a comprehensive review has found.
The review published on November 16 in the journal BMC Medicine, analyzed the results of 37 earlier studies and its findings “highlight the potential health benefits of including more plant foods in the diet,” Sabrina Schlesinger, head of the systematic reviews research group at the German Diabetes Center in Düsseldorf, told CNN.
Schlesinger, who was the senior author of the report, and researchers from several German institutions collaborated on this paper, which they say is the first systematic review to focus on a wide range of health outcomes that are associated with replacing animal foods with plant based food.
Registered dietitian Dwayne Mellor, a senior lecturer at Aston Medical School in Birmingham, UK, told CNN that this review “fits the pattern” of a “larger collection of information that shapes our dietary guidelines.”
“It adds to a picture that we’re already pretty comfortable with,” added Mellor, who was not involved in this research.
Previous studies have already shown some health benefits of plant-based diets. A May study found that total cholesterol decreased by 7% for people following a plant-based diet compared to those who ate both meat and plants, while an August 2019 study suggested that eating more plants and less -little meat is associated with longer life and reduced risk of cardiovascular disease.
This latest review observed a 27% reduction in the overall incidence of heart disease when 50 grams (1.8 ounces) of processed meat per day was replaced by 28 grams to 50 grams (1 ounce to 1.8 ounces) of nuts per day and a 23% reduction when replacing meat with the same amount of legumes.
A 22% reduction in type 2 diabetes cases was also associated with replacing 50 grams of processed meat per day with 10 grams to 28 grams of nuts per day.
Replacing butter with olive oil and eggs with nuts has also been shown to reduce the risk of developing type 2 diabetes and heart disease, although replacing other dairy products, fish, seafood, or poultry has no clear link to lower rates of heart disease. the review found.
The findings in the new research “do not rely on the results of a single study, but systematically summarize all the available evidence on the topic,” Schlesinger said, adding that this was the main strength of the review.
Although such an approach did not lead to “completely new” findings, she noted the “consistency” of results from previous studies, indicating a “robust level of confidence in the effect estimate.”
The review only observes the association and neither shows cause-and-effect nor investigates whether there is one, but it does suggest some possible reasons for these trends in the data.
Processed meat, defined by the World Health Organization as having undergone salting, canning, fermentation, smoking or other processes to produce products such as sausages, ham or preserved meat, contains saturated fatty acids that potentially increase the risk of heart disease and type 2 diabetes.
Meanwhile, nuts, legumes, and whole grains contain antioxidant and anti-inflammatory compounds that appear to reduce inflammation.
The study also provides an alternative explanation for the apparent health benefits – that people who prefer plant-based foods are already likely to lead healthier lifestyles overall, and although the studies were adjusted to account for exercise, smoking, alcohol and dietary habits of the participants, this effect cannot be excluded.
“We can use this as a piece of information,” Mellor said, “but we need to use it with interventional studies … to understand why they might show this effect.”
Simply switching from animal-based products to plant-based products does not automatically lead to a healthy diet. The result depends on the products being replaced.
“We have to be careful with words like plant-based that can be used by food manufacturers,” Mellor said. “At the end of the day, a bag of sugar is plant-based, and (the study) doesn’t mean that.”
The USDA recommends making half your plate fruits and vegetables, varying your vegetables and proteins, making half your grains whole grains. The federal agency also advises choosing foods and beverages with less added sugar, saturated fat and sodium.
In addition to considering the health benefits of different foods, it’s important to consider culinary and cultural perspectives when making these swaps, Mellor said.
“Just because the statistics say that swapping reduces risk, does it make culinary and cultural sense?” And if it doesn’t, it’s unlikely to work as a council,” he said.
“So replace lentils with processed red meat because you can make sausage out of lentils … that would make sense, but replacing some carrots and some broccoli with red meat doesn’t make sense.”
Anyone considering going vegetarian or vegan should also make sure their diet is carefully planned to include enough iron, iodine, vitamin B12 and vitamin D, Mellor told CNN in May.