Grant Genereux has written a couple books on the supposed toxicity of Vitamin A. His most recent, Poisoning for Profits, is a well written and researched piece arguing that vitamin A is a toxin, behind most auto-immune diseases. It’s become somewhat of a hot topic in the health/nutrition community over the past year. I don’t believe vitamin A is toxic, and I don’t think it’s helpful to look at it in isolation as the culprit in anything, but it’s important not to dismiss claims outright.
Danny Roddy discussed this ”trendy” topic of Vitamin A toxicity on a recent podcast. Here is a quote I pulled from the interview:
‘’I think that vitamin A has to be thought about in relationship to thyroid. (…) It’s a co-factor along with the LDL cholesterol for the steroid synthesis of pregnenolone, progesterone and DHEA. And so, I don’t think it’s a toxin (laughs), I think it’s a very strange (idea). But also, I don’t doubt that people restricting Vitamin A in their diets (get) improvements because if a person is hypo-metabolic, the extra vitamin A can be thyroid-suppressive. Again, if a person doesn’t have their thyroid figured out or functioning at higher rate, they might be just chronically suppressing their thyroid function with just eating liver or something like that. I do have a few references that say vitamin A is similar to the unsaturated fatty acids and Ray has expanded on the structure of vitamin A being unsaturated or something and closely aligning with lipid peroxidation which is one of the bad aspects about the PUFAs. And so again, I don’t doubt that limiting vitamin A has some therapeutic effect for people that are like profoundly low thyroid. My focus would be more on increasing the thyroid function, and maybe like the vitamin D as well rather than getting rid of vitamin A, which I think is a little bit strange.’’
So this quote is just a direct transcription of an informal discussion, but it touches on several of the key aspects of vitamin A. There is conflicting information about the true role of vitamin A, but several older articles seem to indicate that it is necessary to produce the most important hormones of the human body. However, taking large amounts of liver for example can have adverse effects. Most of the time it can increase the metabolic rate but when it is not needed it will suppress it. It’s noticeably helpful in summer, a higher amount seems needed, as Ray Peat has mentioned before:
“For several years, when I had an extremely high metabolic rate, I needed 100,000 (vitamin A) units per day during sunny weather to prevent acne and ingrown whiskers, but when I moved to a cloudy climate, suddenly that much was too much, and suppressed my thyroid. The average person is likely to be hypothyroid, and to need only 5,000 units per day.” (2)
This might explain why accutane has such drastic effects on acne but is nonetheless linked with more troublesome side-effects later on. Appropriate doses of vitamin A seem essential for an optimal metabolism, but excessive doses can bring on a variety of issues. Grant Genereux links autoimmune issues to a chronic and progressive ”poisoning” of tissues with vitamin A. I’m personally very skeptical of autoimmune problems as an umbrella term because it seems very trendy in the medical world these days. My preliminary understanding of this is that vitamin A can accumulate in the tissues if thyroid function is not adequate, which leads to a degenerative state with an impaired metabolism and suboptimal hormone production. Obviously there’s a lot more to it than that and I’m going to try to figure it out.
Figure 1: Steroid synthesis with vitamin A/thyroid (Ray Peat)
(1): Divine Superconductor Radio. 22. Sugar, Dairy and Metabolic Health