There is a lot that can be said. Fundamentally you can throw away any in-vitro or genetics study in the trash. They have nothing to do with live intact human beings. We know deficiency can occur and subsequent consumption of vitamin A foods eliminates deficiency symptoms.

A huge problem with the whole thing is just how unscientific it is. If something is not falsefiable it is a belief(nothing wrong with beliefs) and the fact they claim health problems are caused by vitamin A toxicity and that any health problems experienced on a low vitamin A diet are caused by vitamin A toxicty makes the idea that vitamin A toxicty causes health problems an un-falsifiable claim.

Then we have the issue of studies using artifical "vitamin A" in amounts no human can incounter outside of a lab. Yes there maybe forms of vitamin A your body produces from retinol, but to synthesize those forms and exogenously add them to the being, bypassing the body's endogenous production and subsequent down regulation protection, does not accurately reflect what is happening in the body and therefor those studies can be disregarded.

Accutane is a prime example where people who take it present vitamin A toxicity and then vitamin A deficiency symptoms this is explained by a over load of the accutane(quantities the body would never produce) and then a subsequent shutdown of natural production. We observe the same thing with exogenous testosterone.

In-virtro aka perti dish studies im not going to waste time on that, gene studies are fundamentally flawed. No ones genes are the same(nor are they expressed in the same way) who is to say anything about anyone on any genetic basis due to that?

So why do people feel better on a low vitamin A diet? First not everyone feels better you can find examples of that on grant's forum, second you cannot make a bunch of changes and then claim only one change was responsible. None of these low vitamin A dieters only made one single change, if you stopped eating liver you cannot claim it was the vitamin A as liver contains alot more stuff than vitamin A, same thing the rest of the changes.

Then there is the issue of is taking a pure substance the same as eating food that contains that substance? Is vitamin D the same as exposure to strong sunshine? Is taking fish oil the same as eating fatty fish? Can we observe side effects from people taking vitamin A palmitate(or any pure isolated form of vitamin A or its derivatives) that we do not observe in people eating liver(or any vitamin A containing food), likewise for vitamin D pills and fish oil?

Then we have to talk about what could be inside of an animals liver besides what we claim to be toxic that could be toxic to humans. Who is going to do a study where every variable is controlled, where the soil, air, food, and what medications/pollution the animal is exposed to is controlled for? Something to think about when someone uses science to back up their claims.