Americans Continue to Consume High Intake of Low-quality Carbs 

The macronutrient composition of diets among US adults has improved, but high intake of low-quality carbohydrates and saturated fats are still present on their menu, a new study has shown. 

During 1999–2016, the average proportion of daily calorie intake coming from refined grains, added sugar, and starchy vegetables decreased by 3% in the U.S., according to the new JAMA study.

However, these low-quality carbohydrates still account for 42% of daily calories, while high-quality carbohydrates — such as whole grains and fruits — only account for 9%.

Over the same period, total fat intake went up by 1%. Half of this increase was due to saturated fat, which now accounts for 12% of daily calories. This figure is above the 10% maximum in the U.S. dietary guidelines.

“Although there are some encouraging signs that the American diet improved slightly over time, we are still a long way from getting an ‘A’ on this report card,” says co-author of the study, Dr. Fang Fang Zhang, a nutrition epidemiologist at the Friedman School of Nutrition Science and Policy at Tufts University in Boston, MA, according to 

The researchers estimated the nutrient intake with the help of a U.S. Department of Agriculture (USDA) database.

They assessed dietary quality using the USDA’s Healthy Eating Index (HEI), which measures how well a diet aligns with the U.S. dietary guidelines.

The results showed that during 1999–2016, the estimated calorie intake from carbohydrates, fat, and proteins in the U.S. diet altered as follows:

  • Total carbohydrates fell from 52.5% to 50.5%.
  • Total protein increased from 15.5% to 16.4%.
  • Total fat increased from 32.0% to 33.2%.
  • Low-quality carbohydrates fell from 45.1% to 41.8%.
  • High-quality carbohydrates increased from 7.42% to 8.65%.
  • Plant protein increased from 5.38% to 5.76%.
  • Saturated fat increased from 11.5% to 11.9%.
  • Polyunsaturated fat increased from 7.58% to 8.23%.

The increase in high-quality carbohydrate consumption came mostly from whole grains, while the reduction in low quality carbohydrate consumption was primarily due to lower intake of added sugar.

“Because low quality carbs are associated with disease risk, taking in higher quality carbs could mean better health for Americans in the future,” says first study author Zhilei Shan, Ph.D. 

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