One of the most hotly contested debates in nutrition is sizzling again as a large study finds that extreme carbohydrate diets could be linked to an earlier death.

In the observational study, people who ate a plant-based, moderate carb diet – with ‘moderate’ defined as 50 per cent of total energy – lived longer than those on low or high carb diets.

According to the researchers, the estimated average life expectancy for this mid-range group was 83 years old, which meant they were outliving the other dieters by one to four years on average.

Much like Goldilocks in the tale of The Three Bears, individuals who ate carbs, but not too much and not too little, were more likely to reach this sweet spot.

Publishing their findings on Friday in the Lancet Public Health, the study authors also stressed that the most important factor seemed to be what people ate, not how much they ate.

“Too much and too little carbohydrate can be harmful but what counts most is the type of fat, protein, and carbohydrate,” Walter Willett, professor of epidemiology and nutrition and study co-author, said.

Dr Sara Seidelmann from Brigham and Women’s Hospital in Boston, who led the study, told The New Daily that people who ate mostly plant-based foods benefited the most.

“Our data suggested that moderate carbohydrate intake that was rich in plant-based foods sources such as vegetables, whole grains, legumes, and nuts was associated with the longest lifespan.”

The Lancet study, which spanned three decades from 1987 to 2017, recruited around 15,000 adults aged between 45 and 64 years old to self-report their dietary habits.

Over the 30 year period, the participants, who came from diverse backgrounds across four different US communities, completed six dietary questionnaires at regular intervals.

They were asked about the types of foods and drinks they were consuming, how often and the portion sizes, which the researchers then used to roughly calculate calorie intake.

Low carb dieters eating more meat, higher death rates

The study also showed that death rates were higher among those who exchanged carbohydrates for animal-derived fat or protein.

People with the lowest carb diets ate twice as much animal-based fats than those with the highest carbohydrate intakes.

Dr Seidelmann said that, despite their popularity, low-carb diets that replace carbohydrates with animal-based protein or fat should be discouraged.

Steve Pratt, Chair, Nutrition and Physical Activity Committee at Cancer Council Australia said the study supported Cancer Council’s advice and current dietary guidelines.

“Limiting excess intake of red meat is linked to reduced cancer risk and this study suggests that it could also lead to an increase in life expectancy,” he told The New Daily. 

The Cancer Council recommends avoiding processed meats and limiting red meat intake to three to four times per week.

“Similarly, the study supports our advice to have a diet that is rich in fruit, vegetables and wholegrains,” he said.

NHS England dietitian Catherine Collins said the findings are likely to disappoint those who “continue to defend their low carb cult”.

“Following a very low carb diet prevents the inclusion of plant based proteins like beans and other pulses, so the diet distorts towards a higher saturated fat intake derived from higher consumption of animal proteins like meat and cheese,” she said.

“With a mere 100 grams of complex carb a day to play with, a lower intake of cereals, grains, and starchy vegetables is inevitable.”

“Such diets compromise the essentials of a healthy diet.”

The study authors cautioned that the observational research does not prove cause and effect. They noted that since the data was self-reported, and people’s eating habits change over time, this may have affected the study results.