Low- or High-Carb Diet: Which Is Better? Neither, New Study Finds

Despite the growing popularity of diets low and high in carbohydrates, research published in The Lancet found that both are linked to increased mortality. 

One arm of the long-term, multi-cohort study – the Atherosclerosis Risk in Communities (ARIC) study – used data from 15,428 male and female United States adults aged between 45 and 64 years. These participants all reported a non-extreme daily caloric intake (men: <600 kcal or >4,200 kcal per day, women: <500 kcal or >3,600 kcal per day). 

At a median follow-up of 25 years, 6,283 ARIC participants had died. Data from the ARIC cohort found that those with a 50-55% carbohydrate intake had the lowest rates of mortality. Analyzing data across the entire study, which contained 432,179 participants, low and high carbohydrate intake (<40% and >70%, respectively) were both associated with increased mortality when compared with moderate carbohydrate intake (low carbohydrate consumption hazard ratio [hr] 1.20, high carbohydrate hr 1.23). 

Eating #carbohydrates in moderation seems to be optimal for health and longevity—findings from an observational study of more than 15 400 people from the USA @TheLancetPH https://t.co/6jEuihBlbX pic.twitter.com/GNXG7AL54L

— The Lancet (@TheLancet) August 16, 2018

Researchers found that not all nutrients are created equal, though. When carbohydrates were replaced by protein and fat from animal sources, mortality increased (hr 1.18), and it decreased when plant-based alternatives were chosen (hr 0.82). 

Macronutrient ratios impacted life expectancy as well. A 50-year-old with moderate carbohydrate intake could expect to live for an additional 33.1 years. For low- and high-carbohydrate dieters, life expectancy was 29.1 and 32 years, respectively. 

Carbohydrates in the diet & death: both high & low CHO are not good (U-shape curve); but what is good = plant, not animal, sources
15,428 people w/ 25-yr follow up + meta-analysis@TheLancetPH by @sara_seidelmann et al @BrighamWomens @HarvardChanSPH https://t.co/GKYz2mDTiT #OA pic.twitter.com/7WcZzM7DQW

— Eric Topol (@EricTopol) August 16, 2018

Dietary Guidelines for Americans recommends that adults’ daily macronutrient intake is 10-35% protein, 45-65% carbohydrates, and 20-35% fat. 

The authors theorized that diets too low or high in carbohydrates make it challenging to receive essential nutrients. 

“Low carbohydrate diets have tended to result in lower intake of vegetables, fruits, and grains and increased intakes of protein from animal sources, as observed in the ARIC cohort, which has been associated with higher mortality,” they wrote. 

“On the other end of the spectrum, high carbohydrate diets, which are common in Asian and less economically advantaged nations, tend to be high in refined carbohydrates, such as white rice; these types of diets might reflect poor food quality and confer a chronically high glycemic load that can lead to negative metabolic consequences.” 

Read more on diet: Correlation Between Dinner Time and Cancer Risk?

Sources: CNN, The Lancet