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Gari / Bigpoppa
I haven't said anywhere in this thread that carotenoids are fine on a low VA diet or that they are safe in general. What I have pointed out is they don't cause Hypervitaminosis A. They are associated with negative effects but those negative effects are not primarily due to conversion to retinol.
It doesn't really matter that one betacarotene molecule can be converted into two retinol molecules. The vast majority of it is never converted in the first place, especially when we are VA replete and ISX is activated.
There are whole populations consuming 95% sweet potato and they don't have Hypervitaminosis A. There is not one case of Hypervitaminosis A that has occured from betacarotene intake. This does not mean that carotenoids are safe or good, it just means they don't cause Hypervitaminosis A.
You used cows as an example. Cows consume high carotenoid plant material as their only source of food and they consume vast quantities yet not one cow has ever got Hypervitaminosis A.
Carnivores can get it if they are fed too much liver but they are more resistant to retinol toxicity as they have adapted to liver consumption over millions of years. Polar bears are an interesting case because they were more recently descended from omnivores and still have more of an omnivore like digestive system. Natural selection has favoured bears whose livers can hold extremely high concentrations of retinol, probably an easier adaptation than evolving a more carnivore like digestive system.
I think omnivores are the most susceptible to VA toxicity as we are less evolved for high retinol intakes and we have a longer digestive tract than carnivores making it potentially more difficult to excrete retinoids. The vast majority of animal species are specialists such as carnivores, herbivores, insectivores. Only a small percentage of species are omnivores.
@tim-2 your point about ISX is key to this I think. This is one of the gene/enzymes that I was researching. IF ISX is working well then all is hunky dory...if. If not then you can have a real problem. To sweepingly say that the vast majority isn’t converted simply isn’t true. This has great variability amongst people. I began to wonder if in vA toxic people this control was messed up. I became frustrated as all the mice experiments looking at gene expression etc were in conditions of vA deficiency not toxicity. The experiments I wanted to know the answers to simply hadn’t been done (as a retired lab human genetics research scientist I found this annoying 🤣). As I said before I need to revisit this. However, I just want to let you know that you are making some assumptions that are not true. It’s not a criticism as you make some very good points. It’s a very complex field & no one can know everything. The point I’m trying to make (probably badly 🤣) is that it’s individual with lots of factors to consider - not simple.
Debating is important and I appreciate you challenging me. I would ask though that in the future you explain what assumptions you think are false and why rather than just stating I'm making them.
One mcg RAE is equivalent to 1 mcg retinol and 12 mcg dietary beta-carotene. This is the approximate conversion rate in the average person. It's also fact that not one case of Hypervitaminosis A from beta-carotene consumption has been documented despite millions of people and whole populations consuming very high carotene diets. Which means that when liver retinol concentrations reach a certain capacity or retinoic acid levels reach a certain level carotenoid conversion rates always reduce dramatically. So it isn't false that most is not converted. This is the established science. If you disagree then you do have the burden of disproving it.
You can't tell me that a faulty ISX is the rule not the exception. We know that carotenoid intake doesn't cause Hypervitaminosis A anyway so either faulty ISX is very rare or there are other factors that prevent runaway retinol production.
The Chinese sweet potato eaters sure look like they are suffereing from VA overload to me! Bent, blind... perhaps their genetics aren't good with the carotene. Maybe this is the video https://www.cbc.ca/player/play/1131719747560
And the other thing that comes to mind is the smoking study that found worse outcomes when they supplemented carotene.
What evidence is there that these people's problems are caused by the carotene in the sweet potatoes or even from the sweet potatoes themselves? Some PNG tribes have eaten mostly sweet potato for centuries.
There are multiple large trials that found increased mortality from cancer and heart disease in those consuming beta carotene supplements. In the main trail the supplement dose was the equivalent of five carrots per day. Nobody in the discussion here lilchick is saying that carotenoids are safe, it's just about their relation to Hypervitaminosis A.
Interesting! I suppose there are some big differences in genetics between the Chinese and the PNG?
I'm pretty sure in the video it explains that the only thing the Chinese can get to grow there is sweet potato (so they do eat a lot). (like me with my winter squashes).
I guess you agree that beta carotene and vitamin A are in the same family and both are unsafe. (unless you are from Papua New Guinea. But not for smokers in Great Britain)
I don't like to get too attached to the words associated with diseases. I suppose that "VA overload" means something specific to you and that is fine, and maybe you don't include beta carotene problems under that umbrella.
But then again, some people are going to be converting. So it will add to their load.
Perhaps I'm just a lot more intuitive and don't really care to be that precise?
The amount of carotene is huge in sweet potato.
Orange sweet potatoes baked in skin, one cup
Retinol Activity Equivalent1922mcg
Most carotenoids aren't even provitamin A carotenoids, carotenoids like lutein don't convert. So yeah I see carotenoid health effects as a very different issue. It is very clear that they do have negative effects in large amounts, I'm careful to avoid drawing false conclusions though, if the soil or conditions are so bad in the area native to those Chinese then there could be all sorts of potential causes for their health issues. I think following a low carotenoid and low retinol diet will improve health in two separate ways.
Carotenoids aren't VA so "VA overload" means Hypervitaminosis A to me. Beta carotene definitely supplies retinol so it's an avoid while detoxing but I've been pointing out that it doesn't lead to Hypervitaminosis A on its own.
I think I shared this video a while ago, but worth sharing it again.
There's been a huge adoption of sweet potato consumption in Okinawa after WWII. Before WWII, the people of Okinawa had the best health and longevity in the Japanese islands. They now have the highest rate of disease in Japan.
Those people we're tanned, no wonder because they are in the sun all day long. IMO.