According to the study lead by Andres Ardisson Korat, author of the study and a scientist at the Jean Mayer USDA Human Nutrition Research Centre on Ageing at Tufts University in Massachusetts, women who get more of their protein from plant-based foods instead of meat tend to be healthier as they age.

This means that middle-aged women are almost 50 percent more likely to be healthier as they get older if they eat plenty of beans, nuts and other animal-free forms of protein rather than meat.

In addition, researchers said they observed notably fewer cases of heart disease, cancer, diabetes, and cognitive and mental health decline in those who ate the most fruits, vegetables, bread, legumes, and pasta.

On the other hand, women who ate greater amounts of animal protein, however, were more likely to have some form of chronic disease, according to the findings.

“Consuming protein in midlife was linked to promoting good health in older adulthood,” said Andres Ardisson Korat, lead author of the study and a scientist at the Jean Mayer USDA Human Nutrition Research Centre on Ageing at Tufts University in Massachusetts.

“We also found that the source of protein matters. Getting the majority of your protein from plant sources at midlife, plus a small amount of animal protein, seems to be conducive to good health and good survival in older ages”, they said.

Additionally, “those who consumed greater amounts of animal protein tended to have more chronic disease and didn’t manage to obtain the improved physical function that we normally associate with eating protein.”

Although plant-based proteins are the queen, the researchers don't suggest a diet based 100 per cent on fruit, vegetables, nuts and seeds, they say that people should also consume some fish and animal proteins for their iron and vitamin B12. “The results suggest that an omnivorous diet, which leans towards plant-based sources, is probably best for middle-aged women to ensure a long and healthy life”.

“Dietary protein intake, especially plant protein, in midlife, plays an important role in the promotion of healthy ageing and in maintaining positive health status at older ages,” Dr Ardisson Korat said.

This study was based on the Harvard-based Nurses’ Health Study, which followed female healthcare professionals from 1984 to 2016. Those women were between the ages of 38 and 59 in 1984 and deemed to be in good physical and mental health at the start of the study.

Researchers looked at data on how frequently people ate certain foods to identify dietary protein and its effects on healthy ageing. The diets of women who did not develop 11 chronic diseases or lose a lot of physical function or mental health were compared with the food intake of those who did.

According to the findings, women who ate more plant-based protein - which in 1984 was defined as protein obtained from bread, vegetables, fruits, pizza, cereal, baked items, mashed potatoes, nuts, beans, peanut butter, and pasta - were 46 percent more likely to be healthy into their later years.

Those who consumed more animal protein such as beef, chicken, milk, fish and cheese, however, were six percent less likely to stay healthy as they aged. The study found that plant protein was also more closely linked with sound mental health later in life.

With regard to heart disease in particular, the results indicate that people who consume more plant proteins have lower levels of bad cholesterol, blood pressure and insulin sensitivity, while a higher intake of animal proteins is associated with higher levels, along with an increase in insulin-like growth factor, which has been detected in various types of cancer.

According to the same study, the consumption of dairy proteins alone, such as milk, cheese and yoghurt, was not significantly associated with better health status in adulthood.