Impact of high drinking water nitrate levels on the endogenous formation of apparent N-nitroso compounds in combination with meat intake in healthy volunteers.
Level 2 - randomized trial
Randomized dietary intervention trial
PubMed 31623611 · doi:10.1186/s12940-019-0525-z
What was done
Twenty healthy volunteers were randomized into two groups consuming either processed red meat or unprocessed white meat (3.75 g/kg body weight/day, max 300 g/day) for two weeks. In week 1, drinking water nitrate was low (< 1.5 mg/L); in week 2, it was adjusted to the acceptable daily intake level (3.7 mg/kg body weight). At baseline, week 1, and week 2, 24-hour urine and fecal samples were collected to evaluate nitrate excretion, compliance markers (1- and 3-methylhistidine), apparent total N-nitroso compounds (ATNC), and genotoxic potential in human colonic Caco-2 cells.
What was found
The abstract reports statistical significance and directions without providing exact numerical measurements: - Urinary nitrate excretion significantly increased during the high drinking water nitrate phase for both meat types. - Compliance markers for meat intake were significantly increased in urine (1-methylhistidine for processed red meat, 3-methylhistidine for unprocessed white meat). - Fecal ATNC levels significantly increased during the high-nitrate drinking water period, with a more pronounced effect in the processed red meat group. - Caco-2 cell genotoxicity exposed to fecal water was significantly increased only during the low drinking water nitrate period in the processed red meat group. - A positive correlation between the nitrate/vitamin C intake ratio and fecal ATNC in the processed red meat group did not reach statistical significance.
Why it matters
Drinking water nitrate contributes measurably to the endogenous formation of carcinogenic N-nitroso compounds at acceptable intake levels, indicating that water nitrate should be accounted for when evaluating colorectal cancer risks related to diet.
Limits
The study had a very small pilot sample size (n = 20), a short intervention period (two weeks), was retrospectively registered, and the abstract omits effect sizes, baseline values, and confidence intervals.
Cited by
- supports Nitrites in processed meats form carcinogenic nitrosamines in the colon and when cooked with water and heat.