Ray Peat is as quacky as health quacks can get. Completely nuts.
Edit: Some people are getting angry (and in some cases, deleting their comments). Let me be clearer: I have no idea who Ray Peat is. The OP commented that Peat is a "quack" and I was just asking why, because they didn't provide any supporting documentation.
Oddly enough, I just now discovered that I used to live down the street from Peat, before he passed away. I don't recall ever meeting him, though.
Avocados
Peat claimed that avocados are carcinogenic because they contain a lot of unsaturated fat.[8] Like all the other nonsense he spouted, he failed to back up this ridiculous claim with any scientific evidence.
Orange juice
Peat was a big fan of orange juice which he said is "anti-estrogenic".[41] He also claimed that orange juice is good because it raises people's cholesterol.[42] There is not any evidence in the medical literature that shows orange juice consumption raises cholesterol. Studies have found the opposite, as it lows LDL-c and total cholesterol.[43][44] A 2022 review of clinical trials found that orange juice significantly reduces circulating total cholesterol levels.[45] Everything Peat said about foods should be fact-checked because in most cases he was entirely wrong in what he had claimed.
Guess it’s why it takes half the population forever to still be “doing their research”
"He made many other ridiculous claims such as avocados causing cancer.[8]" https://rationalwiki.org/wiki/Ray_Peat#cite_ref-Vegetables_8...
Link [8]: "Vegetables". raypeat.com. Goes to: https://raypeat.com/articles/articles/vegetables.shtml
The quote in question: "Not all fruits, of course, are perfectly safe--avocados, for example, contain so much unsaturated fat that they can be carcinogenic and hepatotoxic."
Note that phrasing "can be", "Not... perfectly safe.". Also btw, did you know that carrots "can be" hepatotoxic (toxic to the liver) because of all the vitamin A? This doesn't mean that carrots are bad, but rather that they shouldn't be an excessively large part of one's daily diet. They are not "perfectly safe".
Let's examine how Peat came to this idea based on the research. Remember, the actual claim is that "avocados.. can be carcinogenic and hepatotixic." Not that avocados cause cancer. That is not what he wrote. That wiki article has a clear bias.
Anyways, his research for the actual claim:
"In Vivo 1998 Nov-Dec;12(6):675-89. Comparative anticancer effects of vaccination and dietary factors on experimentally-induced cancers. ... Experiments in mammary glands cancer showed that a 15% olive-oil diet reduced significantly the tumor incidence caused by 9,10-dimethyl-1,2-benzanthracene. The antitumor effect of the olive-oil diet was connected to its content of monounsaturated fatty acids, such as oleic and palmitic acids. The promotive tumorigenic effects of other high-fat diets (avocado, soybeans) were associated with high content of some polyunsaturated fatty acids (linoleic and alpha-linolenic). Different diets have different targets. The effect of the same diet depends on its anti-tumor substances content. CONCLUSIONS: Vaccination and some diets have similar mechanism in their tumor-preventive effects."
"Ann Nutr Metab 1991;35(5):253-60. Effect of dietary avocado oils on hepatic collagen metabolism. Wermam MJ, Mokady S, Neeman I Department of Food Engineering and Biotechnology, Technion - Israel Institute of Technology, Haifa. The effect of various avocado and soybean oils on collagen metabolism in the liver was studied in growing female rats for 8 weeks and in day-old chicks for 1 week. In comparison with rats fed either refined avocado oil, refined or unrefined soybean oils, rats fed unrefined avocado oil showed a significant decrease in total collagen solubility in the liver, while there were no changes in total collagen, protein and moisture content. Chicks fed unrefined avocado oil as compared to those fed refined avocado oil also showed a decrease in hepatic total soluble collagen while hepatic total collagen remained unaffected. Electron micrographs and light-microscope examinations of rats' liver revealed collagen accumulation in the periportal location. This is suggestive of the early stages of fibrosis."
All he did was link real-world research to a possible hypothesis. A logical argument. Now you can criticize this argument and say that we can't draw any such conclusions from in vivo and animal model experiments, but at least then you'd be actually engaging with the content of the ideas, not outsourcing your thinking to a poorly-written Wiki article.
"avocados, for example, contain so much unsaturated fat that they can be carcinogenic and hepatotoxic" is exactly what he says in the article text. That explicitly read as "consumption of avocados can cause cancer", not the much weaker claim "it's possible that there's a mechanism by which avocados might cause cancer or be hepatotoxic but we don't actually know", which is what you actually get if you look at those reference.
Even the quotes he chooses are mismatched to what he says in the text. The liver one is about dietary avocado oils specifically, not avocados generally, and has the weakest possible conclusion that the chicks have something "suggestive of early stages of fibrosis" for unrefined but not refined. It's beyond just in vivo and animal model limitations, it: doesn't address dietary avocado consumption and doesn't conclusively show liver toxicity. That this reference is so weak, and yet the one he chose, is itself quite damning.