BackgroundRay Peat's daily raw carrot is one of the most popular peatarian recommendations. Yet, it is among the recommendations that are the least questioned.
A daily raw carrot, shredded with a little vinegar and olive oil, can suppress bacteria. - Ray Peat
Sometimes having a daily carrot salad (grated, with salt, olive oil, and a few drops of vinegar) will stimulate (and disinfect) the small intestine enough to prevent fermentation. - Ray Peat
Where is the evidence for such claims?When Peatarians are asked, they usually just quote 1-2 in vitro studies on the antimicrobial effect of carrots, such as this one. Although they sound convincing, caution should be applied when generalizing the evidence on much more complex systems such as the human gut with its microbiome and different compartments (i.e. stomach, small intestine, colon).
Interestingly, there is one older publication out there that tested the effects of raw carrots in humans. This one is also often quoted by Peatarians because it shows a cholesterol reducing effect of carrots, which is somewhat in line with Peat's observation of changes in estrogen/progesterone ratio (clear study data on that are lacking unfortunately).
Unfortunately, the second result of the study is only rarely discussed. The authors measured stool mass/fats and breath hydrogen, the latter being a marker for bacterial fermentation. This is what they found:
- The raw carrot more than doubled breath hydrogen, which is a marker for bacterial fermentation. This effect started to occur after around 10 days of starting the raw carrot.
- The excretion of fecal bile acids and fats was still increased 3 weeks after ending the carrot phase.
ConclusionsThese studies show that the raw carrot is not "antiseptic" in the gut, but the opposite, that it increases overall bacterial mass when consumed regularly. The change takes several days to take place sugesting a slow adaption of the microbiome with a proliferation of bacteria that thrive on carrot-fiber. The change in microbiome may also explain the long lasting effect on fecal bile excretion.
By no means I am suggesting that eating the carrot is bad for you just because it favors microbial growth. The effect probably depends on how your microbiome reacts. I've heard from some people (2 of them with inflammatory bowel disease) that they got terrible stomach upset from eating the carrot. Here, the carrot seems to bring the microbial balance out of whack. In others, it might regulate things and lead to growth of beneficial bacteria while suppressing the "bad" ones.
In the light of these results, eating carrot fiber each day, but careful avoiding all other fibers doesn't make that much sense. Similar fibers such as from fruits or other vegetables could be equally beneficial (or deleterious, depending on the person). By the way, other fiber sources have also been shown to lower estrogens suggesting that the hormone regulating effects are not limited to the carrot but may apply to fiber in general.