Healthy low-fat diet reduces risks for all-cause, cardiovascular mortality

Key takeaways:

• Low-carbohydrate diets were associated with higher mortality.
• Researchers said a healthy low-fat diet with minimal saturated fat intake may be an “effective dietary strategy for healthy aging.”

Healthy low-fat diets were associated with lower risks for all-cause and cardiovascular mortality, whereas overall and unhealthy low-carbohydrate diets were linked to increased risks, according to researchers.

Writing in the Journal of Internal Medicine, Yimin Zhao, PhD, of the department of epidemiology and biostatistics in the School of Public Health at Peking University in China, and colleagues noted that emerging evidence has “underlined the quality rather than the quantity of macronutrient subtypes” in low-carbohydrate diets (LCDs) and low-fat diets (LFDs).

“Lower intake of carbohydrates from refined grains and added sugar but not from whole grains, and reductions in saturated fat but not unsaturated fat were related to lower risks of mortality,” they wrote. “However, the long-term effects of LCD and LFD on age-related health outcomes among middle-aged and older people remain less studied.”

To establish varying mortality risk associations with each dietary pattern, the researchers performed a prospective cohort study utilizing data from the NIH-American Association of Retired Persons Diet and Health Study. They calculated overall, healthy and unhealthy LCD and LFD scores based on the energy intake of carbohydrates, fat and protein.

Overall, the study included 371,159 participants aged 50 to 71 years. Among the participants, 165,698 died during a median follow-up period of 23.5 years.

Zhao and colleagues found that participants in the highest quintile vs. lowest quintile of overall LCD scores and had a:

• 12% (HR = 1.12; 95% CI, 1.08-1.15) higher risk for total cardiovascular mortality; and
• 14% (HR = 1.14; 95% CI, 1.10-1.18) higher risk for heart disease mortality.

Those in the highest quintile for unhealthy LCD scores had similar increases, with a:

• 15% (HR = 1.15; 95% CI, 1.11-1.18) higher risk for total cardiovascular mortality; and
• 17% (HR = 1.17; 95% CI, 1.13-1.21) higher risk for heart disease mortality.

Like cardiovascular mortality risks, “the overall LCD and unhealthy LCD were associated with an elevated mortality risk from all cancers and lung cancer,” the researchers wrote.

Meanwhile, compared with participants in the lowest quintile, those in the highest quintile for healthy LFD score had lower odds for:

• total cardiovascular mortality (HR = 0.84; 95% CI, 0.82-0.87);
• heart disease mortality (HR = 0.83; 95% CI, 0.80-0.86); and
• stroke mortality (HR = 0.89; 95% CI, 0.83-0.95).

Zhao and colleagues also reported that replacing 3% energy from low-quality carbohydrates with plant protein was associated with a:

• 10% (HR = 0.9; 95% CI, 0.89-0.91) lower risk for all-cause mortality;
• 11% (HR = 0.89; 95% CI, 0.86-0.91) lower risk for all-CVD mortality; and
• 4% (HR = 0.96; 95% CI, 0.94-0.98) lower risk for all-cancer mortality.

“Isocaloric replacement of low-quality carbohydrates with high-quality carbohydrates was only related to relatively small improvements in mortality risks,” they wrote. “Nevertheless, isocaloric replacement of 3% energy from saturated fat with other macronutrient subtypes was consistently associated with reduced mortality.”

The findings have clinical relevance, according to the researchers, as previous data from the Global Burden of Diseases, Injuries and Risk Factors Study “suggested that transitioning from a typical Western diet to a diet rich in legumes, whole grains, and nuts was related to an additional gain of life expectancy for up to 10 years among young adults.”

“Such benefits, though slightly attenuated, remained significant for older people,” they wrote.

Ultimately, the associations “suggest that a healthy LFD with minimal saturated fat intake would be an effective dietary strategy for healthy aging among middle-aged and older people,” Zhao and colleagues concluded.