This sounds like the naturalistic fallacy [1]. A naturally occurring substance is not automatically less carcinogen, or harmful, than a manufactured one. Coffee is associated with elevated risk for bladder cancer. Cycad trees are known to be highly carcinogenic. Mycotoxins (mold) are toxic and carcinogenic. Aflatoxin from peanuts is found to be carcinogenic.
I'm not saying that stevia is not safe, but safety has nothing to do with being natural or not.
It would be a fallacy to suggest that one group or the other were unconditionally safer, but I find no dilemma in generalizing that the human body is more capable of processing plant-based substances. Just like I would generalize that consuming plant-based substances is healthier than consuming paint. Sure you can nit pick outliers, safe paint or oleander or whatever, but the heuristic is still of value.
For stevia to be arguably safer due coevolution with humans, the following would need to be true:
1. There is a selective pressure for stevia to not increase the risk of cancer in humans.
2. There is a selective pressure on humans to not have an increased risk of cancer from consuming stevia.
In other words, it is firstly to argue that a stevia plant which had a tendency to increase cancer risk in humans would be significantly less likely to reproduce. This effect would be hard enough even if the hypothetical carcinogen were to be otherwise selectively neutral, but it could have a selectively positive pressure if it were an essential hormone or defence against insects, pathogens, competitors, etc.
Secondly, it is to argue that if stevia were potentially carcinogenic, then humans that were susceptible to its effects were significantly less likely to reproduce. This fails on two levels. First, consider that even in the cut-and-dried cause of cancer that is smoking, lung cancer is still extremely rare among young smokers. Lung cancer patients are virtually always well past their reproductive age, meaning that even if a genetic mutation to be immune to tobacco were to appear (or indeed it may well already exist) then said mutation still has no selective advantage with regards to the consumption of tobacco. Second, even if a hypothetically-carcinogenic stevia[0] could exert selective pressure on humans to become unaffected by it, then that effect would only have taken place on the populations which consumed significant amounts of stevia over generations and not humanity as a whole.
[0] Which I insist, I don't believe is the case.
Humans are pretty observant, and have decent odds of noticing over time when particular things correlate with health problems. A plant known to cause health problems is less likely to become and remain a dietary staple. A plant that isn't a dietary staple misses out on a wealth of opportunity for propagation.
I think you're also hyperfocusing on the issue of evolution. The point isn't that stevia is a plant which merely exists, but rather its longevity in human culture[0].
What you're saying makes sense for random plants picked up in the woods; less so for plants that have been consumed by humans since antiquity. By the same logic, there would be no a priori difference in risk profile between vegetables and random research chemicals.
And lots of cultivated plants have downsides.
> By the same logic, there would be no a priori difference in risk profile between vegetables and random research chemicals.
No, that's a strawman. Nobody is suggesting that "random research chemicals" should be considered safe. And extracting random chemicals out of plants would also be dangerous!
https://en.wikipedia.org/wiki/Nixtamalization
It makes me wonder if some of the things like, e.g. the supposed success of the Mediterranean diet, are due to bits of food culture like this that we've lost or never fully understood.
An optimal organism doesn't imply an optimal environment.
fitness(org, food) = -2 org^2 + org * food + 7
Evolution doesn't optimize the environment for the organism. Evolution performs stochastic gradient descent, improving the organism for the environment, which can easily get stuck at global optima. More importantly, it improves the organism for the environment/food/etc. The idea that the food is optimal for the organism gets the improvement mechanism backward.
Doesn't make it a good idea.
Clothes, refrigeration, and Pasteurization are all extremely recent on an evolutionary timescale. They're all artificial and extremely beneficial to human well-being.
Also, the idea that something is good because we've evolved with it gets the mechanism of evolution backward. Even if it were true that evolution's stochastic gradient descent had found the global maximum 15k years ago (instead of perhaps approximating a local maximum), that would imply no changes to the human would improve human reproductive success. It would not imply that no changes to the environment (such as available foods) would improve human reproductive success.
https://www.who.int/news/item/15-05-2023-who-advises-not-to-...
Liquid stevia is my go-to sweetener for most purposes, or if I'm baking I'll use a stevia-monk-inulin mix that measures 1:1 for sugar.
More recently, I've been using freeze dried miracle berries as a sweetener for low-sugar fruits. They essentially convert sour taste signals to sweet, which works great for strawberries, raspberries, cranberries, kiwi, passion fruit, and citrus. Also has a bit of an effect on blackberries and dragon fruit, and starfruit is on my list to try.
Related LPT: most of the fruits I eat are frozen with a few minutes of thawing at room temperature. Easier to store, easier to prep, and turns out to be pretty similar to Italian ice.
I can’t stand the taste, I’d rather go without than have a product with stevia.