Protein intake, chronic liver diseases, and hepatocellular carcinoma.

Abstract

Potential conflict of interest: Nothing to report. To the Editor: We read with great interest the article by Li et al.1 in which the authors demonstrate, using two different dietary indices, the Healthy Eating Index‐2010 (HEI‐2010) and the alternate Mediterranean Diet Score (aMED), that healthy eating is associated with lower risk of chronic liver disease (CLD) mortality and lower risk of hepatocellular carcinoma (HCC) incidence, in a prospective cohort of about half a million Americans. The role of diet in the insurgence of CLD and HCC is quite controversial. For instance, oleic acid, a major component of olive oil and a key ingredient of the Mediterranean diet, although it ameliorates fatty liver disease,2 paradoxically increases HCC metastasis in experimental models.3 The analysis of Li et al. to assess the role of individual dietary components positively or negatively associated with CLD and/or HCC uncovered that whole grains, dairy, vegetables, and nuts are inversely associated with deaths from CLD and with HCC using either HEI‐2010 or aMED scores1; moreover, a surprising positive association between fruit consumption, CLD, and HCC was found.1 Although these findings are very impactful, because they show that adhering to dietary recommendations may reduce the risk of developing HCC and dying of CLD, there is an important aspect to be stressed. A recent high‐profile study by Levine et al.4 showed that low protein intake, in particular the one of animal proteins (including dairy), is associated with a major reduction in all causes, cancer, diabetes, and overall mortality in the <65 years old population of 6,381 adults from NHANES III, a U.S. representative, cross‐sectional study. Despite the smaller sample size, these association data were robustly significant and received large media attention. Li et al. report conversely that total protein consumption, and even red and processed meat in the aMED score, are associated with lower HCC incidence and CLD mortality.1 It would be crucial for public health guidelines to understand and to discuss the cause of this epidemiological studies discrepancy on the role of (animal) protein intake in protecting from liver diseases on the one hand, and favoring all causes and cancer mortality on the other.