For a longer life, eat higher proportion of carbohydrates — grains, pulses, vegetables, sweet potato — and about 100 grams of protein in middle-age daily to cut the chances of heart disease, cancer and other diseases in old age, suggests a study.

According to researchers, diet comprising 80 percent carbohydrates — mainly vegetables, especially sweet potato, 10 percent protein — fish and soy and 10 percent fat — is thought to contribute to their longevity. The latest research suggests that eating more protein might help with weight loss in the short term, too much protein in midlife could shave years off your life.

In fact, cutting protein intake in middle age and boosting it again once in 65 could be the best way to ensure a healthier, longer life. “There's a lot of dogma about the perfect diet,” said study author Steve Simpson from the University of Sydney. “The presumption is that if you're a five-year-old or a 60-year-old, a healthy diet is the same, but we don't have the same nutritional requirements throughout life,” Simpson explained.

In 2014, the study conducted on mice fed 25 different diets, each with varying ratios of protein, carbohydrate and fat. The results indicated a low-protein, high-fat diet had the most damaging effects in terms of lifespan, ageing and health, while a conventional higher-carb, lower-protein diet had the opposite effect, reports the Mail Online.

At the same time, a team at the University of Southern California analysed the diets of nearly 7,000 middle-aged people, discovering that eating a high-protein diet between the ages of 50 and 65 increased the chances of developing cancer, diabetes and other life-limiting diseases.

The evidence suggests that in the early adult years, a diet comprising 20 percent protein seems best: this translates to around 100g of protein per day for a typical adult. From the age of 65, dietary needs change again. An international collaboration of nutritional experts, known as the PROT-AGE study, concluded that increasing protein in the diet from 65 helps protect against age-related muscle- wasting and staves off frailty.