Baseline dietary glutamic acid intake and the risk of colorectal cancer: The Rotterdam study

BACKGROUND Animal studies have shown that glutamine supplementation may decrease colon carcinogenesis, but any relation with glutamine or its precursors has not been studied in humans. The primary aim of this study was to assess whether dietary glutamic acid intake was associated with colorectal cancer (CRC) risk in community-dwelling adults. A secondary aim was to evaluate whether the association could be modified by the body mass index (BMI). METHODS This study was embedded in the Rotterdam study, which included a prospective cohort from 1990 onward that consisted of 5362 subjects who were 55 years old or older and were free of CRC at the baseline. Glutamic acid was calculated as a percentage of the total protein intake with a validated food frequency questionnaire at the baseline. Incident cases of CRC were pathology-based. RESULTS During follow-up, 242 subjects developed CRC. Baseline dietary glutamic acid intake was significantly associated with a lower risk of developing CRC (hazard ratio [HR] per percent increase in glutamic acid of protein, 0.78; 95% confidence interval [CI], 0.62-0.99). After stratification for BMI, the risk reduction for CRC by dietary glutamic acid was 42% for participants with a BMI ≤ 25 kg/m2 (HR per percent increase in glutamic acid of protein, 0.58; 95% CI, 0.40-0.85), whereas no association was found in participants with a BMI > 25 kg/m2 (HR per percent increase in glutamic acid of protein, 0.97; 95% CI, 0.73-1.31). CONCLUSIONS Our data suggest that baseline dietary glutamic acid intake is associated with a lower risk of developing CRC, but this association may be mainly present in nonoverweight subjects.

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