Climate scientists believe that one of the most impactful things that people can do for the environment is to reduce their consumption of meat and dairy products.
Research notes that global production of animal-based foods — including livestock feed — accounts for 57% of total greenhouse gas emissions from agriculture, whereas production of plant-based foods accounts for only 29%.
Another study estimates that if everyone became vegan, this would reduce the amount of land worldwide that farmers need to grow food by 3.1 billion hectares or 76%.
In addition to cutting emissions from food production, say the authors, rewilding the freed-up land would remove around 8.1 billion tonnes of carbon dioxide from the atmosphere every year for the next 100 years.
Of course, the idea that billions of people worldwide would voluntarily give up their steaks, sausages, and cheeseburgers simply to curb climate change may seem far-fetched.
But perhaps they would think twice if they knew how much it would benefit their own health.
Recent research suggests that people who eat little or no meat tend to have a lower risk of cancer, in particular colorectal cancer and prostate cancer in men.
Diets that combine a reduction in meat and dairy consumption with increased intake of fruits, vegetables, whole grains, and healthy fats, bring further health benefits.
People who eat a typical Mediterranean diet, for example, have a lower overall mortality rate and a lower risk not only of cancer but also cardiovascular and metabolic diseases.
A series of clinical trials now suggests that eating a “green” Mediterranean diet, or green Med diet, may provide additional benefits on top of those provided by the regular Mediterranean diet.
The diet, which adds extra plant foods rich in polyphenols and aims to avoid meat completely, is also better for the planet.
“[E]liminating meat intake — beef, pork, lamb — is by far the most important single way to reduce the carbon footprint from diet,” said Dr. Meir Stampfer, Ph.D., professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health in Boston, and one of the authors of the green Med studies.
“The contribution of meat to greenhouse gas emissions is enormous compared with other foods,” he told Medical News Today.
Biodiversity and human health
Dr. Stampfer pointed out that the total area needed for meat production includes a lot of land for growing crops to feed livestock.
So by reducing the amount of land around the world that is devoted to producing meat, the green Med diet could play a major role in the preservation of biodiversity.
In its 2020 report “Biodiversity for Nutrition and Health”, the World Health Organization (WHO) describes a virtuous circle that links varied, plant-based diets, human health, biodiversity, and sustainability.
“The significance of pressures generated by human activity on both climate change and biodiversity loss, and their impacts on nutrition and health outcomes, cannot be overstated,” the authors conclude.
What is the classic Mediterranean diet?
A traditional Mediterranean diet contains the following elements:
- vegetables, fruits, and whole grains
- sources of healthy fats, such as nuts, seeds, and olive oil
- moderate amounts of dairy and fish
- less red meat than a traditional western diet
- fewer eggs
- red wine in moderation
The diet provides an abundance of polyphenols, monounsaturated and polyunsaturated fatty acids, and plant fiber.
Importantly, the classic Med diet also avoids refined grains, highly processed foods, and products with added sugars.
Scientists believe that, in combination, these features help lower levels of bad cholesterol, reduce oxidative stress and inflammation, and improve insulin sensitivity.
Green Mediterranean or ‘green Med’ diet
Scientists in Israel, Germany, and the United States reasoned that replacing all the remaining meat in the diet with plant-based proteins could supercharge these health effects.
Over the past few years, they have conducted three clinical trials of their green Med diet on a cohort of 294 people with abdominal obesity. Participants’ average age at the start of the trials was 51 years.
Over the course of their studies, they were all given free gym membership and advice about physical activity.
The researchers randomly assigned them to three diets:
- Healthy dietary guidance — basic advice on how to achieve a healthy diet.
- A calorie-restricted traditional Med diet, with advice to reduce red meat consumption, plus 28 grams (g) of walnuts each day.
- A calorie-restricted green Med diet, which incorporated 28 g of walnuts per day, plus 3–4 cups of green tea, and 100 g of Mankai duckweed in a shake. They were asked to avoid red and processed meats completely and discouraged from consuming poultry.
People in Thailand and other Southeast Asian countries eat Mankai as a “vegetable meatball.” Previous research by the same scientists showed that Mankai provides all the essential amino acids plus vitamin B12, making it an ideal meat substitute.
In the first study, the researchers examined possible extra heart health benefits of eating a green Med diet.
They report that after 6 months, both Med diets led to greater weight loss and metabolic benefits than standard dietary advice.
However, the green Med diet led to a greater reduction in waist circumference and several other measures of cardiovascular risk.
For example, participants who ate this diet had improved insulin sensitivity, lower blood pressure, lower levels of bad cholesterol, and less inflammation compared with those on a standard Med diet.
Fat storage in the liver
For their next study, the researchers compared the amount of fat in the liver of subjects after 18 months on the three different diets.
They discovered that people who ate the green Med diet lost more fat in their liver than those on the regular med diet.
This may reduce their risk of nonalcoholic fatty liver disease, which affects around 25% of people worldwide and can lead to potentially fatal cirrhosis and liver failure.