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> That helped them pinpoint a molecule called retinoic acid—a derivative of vitamin A found in many skincare products—as a key ingredient for limb regeneration

> That helped them pinpoint a molecule called retinoic acid—a derivative of vitamin A found in many skincare products—as a key ingredient for limb regeneration Hoo boy, I am seeing some serious fuel for snake oil, here. I wonder how long before I start getting spam selling retinoic acid as an aid in growing ... er, a ... limb ... Also, I wonder if the article was edited by AI. That may not be a bad thing, but it would be interesting if The Smithsonian is using AI editors.

adrian_b 1y ago
Excessive vitamin A is quite dangerous. Even with chicken livers, which have a lower content of vitamin A than many other kinds of livers, if you would eat for some days chicken livers as your only source of proteins that would become a serious health risk. Without the danger posed by vitamin A, that could have seemed like a valid choice, as chicken livers are usually cheaper per amount of protein than most other kinds of meat, while being tasty and containing many beneficial nutrients. With vitamin A there is a narrow range between getting too little and getting too much. Only getting your vitamin A as carotene from plants poses no danger (one carrot per day, i.e. about 100 g, typically matches the recommended daily intake for vitamin A), because the body will not convert carotene into vitamin A when there already is enough vitamin A.
- nottorp 1y ago
  > if you would eat for some days chicken livers as your only source of proteins How many days? Because when we cook chicken livers we make enough for like 3 days here... perhaps I'm dead and I don't know it.
  - adrian_b 1y ago
    Unfortunately it is impossible to predict how many days, because you do not know what have the chicken been fed with. I have read a study that sampled chicken livers for a detailed chemical analysis. The values were consistent for a given producer, but between producers the content of vitamin A could vary ten times. There is no doubt that chicken from the brands with high vitamin A content have been fed with vitamin supplements. The values of typical vitamin A content for chicken liver that you see in various databases correspond to traditionally fed chicken and if you would eat such chicken livers to cover about half of your daily protein intake that would be slightly below the maximum acceptable intake of vitamin A. Raw chicken liver has slightly more than 1/6 of its weight as protein. Cooked chicken liver retains about 2/3 of the weight of raw chicken liver, due to losing water. Unfortunately, you cannot know whether the chicken liver that you buy is not one of those with much higher vitamin A content, and the excess of vitamin A is eliminated very slowly from your body. Eating chicken liver for a week from time to time should not cause any problems, but you cannot use them as a staple food, like you can with the more expensive and more bland chicken breast.
- aziaziazi 1y ago
  > chicken livers are usually cheaper per amount of protein than most other kinds of meat Any idea why? My layman guess is it’s a non-famous byproduct of chicken muscle, that people tends to consume more. Would removing the availability/demand (=make it more popular) reverse the price? Thanks for the information about carotene > vitA, it resonates like the heme/non heme iron where the heme one is easier to get but can slip to too much, leading to more oxidation and then (in extreme case) concert (IIRC that’s one of the way too much read meat induce cancer risks). OTOH non heme iron (in cereals, peas, fruits, vegetables and milk) is directly used for catalysis and isn’t store, so one can’t get too much. I’m a layman, don’t take what I said as authoritative. You’re welcome to point out if I’m wrong or add precision.

adrian_b 1y ago

Excessive vitamin A is quite dangerous. Even with chicken livers, which have a lower content of vitamin A than many other kinds of livers, if you would eat for some days chicken livers as your only source of proteins that would become a serious health risk. Without the danger posed by vitamin A, that could have seemed like a valid choice, as chicken livers are usually cheaper per amount of protein than most other kinds of meat, while being tasty and containing many beneficial nutrients. With vitamin A there is a narrow range between getting too little and getting too much. Only getting your vitamin A as carotene from plants poses no danger (one carrot per day, i.e. about 100 g, typically matches the recommended daily intake for vitamin A), because the body will not convert carotene into vitamin A when there already is enough vitamin A.

nottorp 1y ago
> if you would eat for some days chicken livers as your only source of proteins How many days? Because when we cook chicken livers we make enough for like 3 days here... perhaps I'm dead and I don't know it.
- adrian_b 1y ago
  Unfortunately it is impossible to predict how many days, because you do not know what have the chicken been fed with. I have read a study that sampled chicken livers for a detailed chemical analysis. The values were consistent for a given producer, but between producers the content of vitamin A could vary ten times. There is no doubt that chicken from the brands with high vitamin A content have been fed with vitamin supplements. The values of typical vitamin A content for chicken liver that you see in various databases correspond to traditionally fed chicken and if you would eat such chicken livers to cover about half of your daily protein intake that would be slightly below the maximum acceptable intake of vitamin A. Raw chicken liver has slightly more than 1/6 of its weight as protein. Cooked chicken liver retains about 2/3 of the weight of raw chicken liver, due to losing water. Unfortunately, you cannot know whether the chicken liver that you buy is not one of those with much higher vitamin A content, and the excess of vitamin A is eliminated very slowly from your body. Eating chicken liver for a week from time to time should not cause any problems, but you cannot use them as a staple food, like you can with the more expensive and more bland chicken breast.
aziaziazi 1y ago
> chicken livers are usually cheaper per amount of protein than most other kinds of meat Any idea why? My layman guess is it’s a non-famous byproduct of chicken muscle, that people tends to consume more. Would removing the availability/demand (=make it more popular) reverse the price? Thanks for the information about carotene > vitA, it resonates like the heme/non heme iron where the heme one is easier to get but can slip to too much, leading to more oxidation and then (in extreme case) concert (IIRC that’s one of the way too much read meat induce cancer risks). OTOH non heme iron (in cereals, peas, fruits, vegetables and milk) is directly used for catalysis and isn’t store, so one can’t get too much. I’m a layman, don’t take what I said as authoritative. You’re welcome to point out if I’m wrong or add precision.