A new position paper from the Academy of Nutrition and Dietetics highlights the health benefits of vegetarian diets, claiming they can reduce the risk of obesity, heart disease, diabetes, and some forms of cancer, compared with non-vegetarian diets.
Updating their 2009 position on plant-based diets, the Academy say an "appropriately planned" vegetarian or vegan diet is suitable for "all stages of the life cycle," and adopting such diets in childhood can reduce the risk of chronic disease later in life.
Additionally, the paper says plant-based diets are more environmentally friendly and sustainable than diets rich in animal products, noting that they can reduce greenhouse gas emissions by up to 50 percent.
"Becoming vegetarian can be beneficial to personal health and the environment," says Vandana Sheth, a spokesperson for the Academy of Nutrition and Dietetics.
The new paper was recently published in the Journal of the Academy of Nutrition and Dietetics.
Vegetarian diets: Healthful if `well planned`
According to a 2016 poll from The Vegetarian Resource Group, around 3.3 percent of adults in the United States are vegetarian or vegan.
While a vegetarian diet is widely perceived as a diet that simply excludes meat, poultry, and fish, there are many variations.
These include a lacto-vegetarian diet (devoid of meat, poultry, and fish, but includes dairy products) and a pescatarian diet (excludes meat, poultry, dairy, and eggs, but allows fish). A vegan diet excludes meat, poultry, fish, eggs, dairy products, and animal-derived products. It may also exclude honey.
A number of studies have hailed the health benefits of a plant-based diet, which include a lower risk of obesity and diabetes. However, some studies have suggested that vegetarian diets may do more harm than good.
One study published in 2014, for example, linked a vegetarian diet to increased risk of allergies, cancer, and mental health disorders. Such health issues have been put down to lack of essential nutrients from animal products.
The Academy of Nutrition and Dietetics, however, say a "well-planned" plant-based diet - high in vegetables, fruits, nuts, seeds, legumes, and whole grains - can offer a wealth of health benefits.
Diabetes risk 62 percent lower with a plant-based diet
For the new paper - written by nutritionist Susan Levin of the Physicians Committee for Responsible Medicine in Washington, D.C., and co-authors - the Academy reviewed a variety of studies looking at the effects of plant-based diets on health and the environment.
From the evidence to date, the authors say adopting a plant-based diet can reduce the risk of prostate cancer by 35 percent, while overall cancer risk can be reduced by 18 percent with a plant-based diet.
In terms of heart health, the Academy say a plant-based diet can lower the risk of heart attack by 32 percent and the risk of heart disease by 10-29 percent.
Furthermore, the authors say the risk of type 2 diabetes may be reduced by 62 percent with a plant-based diet.
"People who adopt vegetarian diets have lower body mass indexes [BMIs], better control of blood pressure and blood glucose, less inflammation and lower cholesterol levels compared with non-vegetarians," notes Sheth. "Registered dietitian nutritionists can help people who want to follow a vegetarian eating plan in any life stage to make well-informed choices to achieve these benefits."
A plant-based prescription `would become a blockbuster drug overnight`
The paper notes that a plant-based diet in childhood and adolescence may have significant benefits for current and later-life health.
The authors point to studies that have shown children and adolescents with a vegetarian diet are less likely to be overweight or obese than their meat-eating counterparts.
"Children and adolescents with BMI values in the normal range are more likely to also be within the normal range as adults, resulting in significant disease risk reduction," they add.
"Other benefits of a vegetarian diet in childhood and adolescence include greater consumption of fruits and vegetables, fewer sweets and salty snacks, and lower intakes of total and saturated fat. Consuming balanced vegetarian diets early in life can establish healthful lifelong habits."
The authors also point to the environmental benefits of a plant-based diet, noting that a vegetarian diet and a vegan diet can reduce greenhouse gas emissions by 29 percent and 50 percent, respectively.
They say this is because vegetarian diets use less water, fossil fuel resources, pesticides, and fertilizers than meat-based diets.
As an example, the authors say producing 1 kilogram of protein from kidney beans would require "18 times less land, 10 times less water, nine times less fuel, 12 times less fertilizer, and 10 times less pesticide in comparison to producing 1 kilogram of protein from beef."
Concluding their paper, the American Academy of Dietetics say that, compared with omnivorous diets, vegetarian diets can protect our health and the environment.
"If you could bottle up a plant-based prescription, it would become a blockbuster drug overnight. This way of eating creates an efficient energy source not just for the planet, but for our bodies.
What other drug increases metabolism, lowers blood pressure, stabilizes blood sugar, and instead of increasing the risk for heart disease or diabetes - stops it in its tracks?"