Perhaps the next big eating trend is the not-too-sexy-sounding medium-carb diet.

A study from Brigham and Women’s Hospital, Boston, which involved more than 15,000 Americans tracked for a quarter of a century, found a U-shaped link between carb intake and life expectancy. During the study period, those who ate a low-carb diet (less than 40% of daily calories) or a high-carb diet (more than 70% of daily calories) were more likely to have a lower life expectancy than those who ate a moderate-carb diet, where 50%–55% of calories hailed from carbs. Published in the August 2018 edition of The Lancet, the study also linked low-carb diets that replaced carbs with animal-based proteins and fats to a greater risk of early death than low-carb diets that subbed in plant-based proteins and fats, like those found legumes and nuts.

People eating lofty amounts of carbs might be consuming too many refined grains and sweeteners, whereas animal-based, low-carbohydrate diets like Paleo® and keto might set some people up for a shortfall in certain important nutrients and antioxidants. A moderate carb intake can be an indication that someone is eating a well-balanced diet.

Yes, this study found only an association between moderate carb intake and longevity based on self-reported diet intake. It did not prove that low- or high-carb diets cause an increase in early death rates. Nevertheless, we may be getting closer to finding that elusive sweet spot for carbohydrate intake.

Matthew Kadey, MS, RD

Matthew Kadey, MS, RD, is a James Beard Award–winning food journalist, dietitian and author of the cookbook Rocket Fuel: Power-Packed Food for Sport + Adventure (VeloPress 2016). He has written for dozens of magazines, including Runner’s World, Men’s Health, Shape, Men’s Fitness and Muscle and Fitness.

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