From Seed Oil Scout

What stevia is doing to your hormones

Brought to you by animal., starring Dr. Ken Berry, Dr. Eric Berg, and Dr. Anthony Chaffee

Stevia is everywhere—from electrolyte powders to protein bars to toothpaste.
It’s sold as a plant-based, zero-calorie sweetener, and for many people, it feels like a safe, natural alternative to sugar. But the research tells a more complicated story, especially when you look beyond short-term human trials. We’re breaking it down, and explaining why stevia doesn’t get the SOS stamp of approval.

@reallytanman

What the studies show
Although stevia is generally considered safe by regulatory bodies, a growing body of evidence—particularly from animal and in vitro studies—raises questions about its long-term biological effects.
A 2016 in vitro study found that steviol glycosides disrupted human progesterone receptor function and reduced sperm fertilization capacity (PubMed).
A 2010 study in male rats reported reduced testosterone levels, decreased testicular weight, and structural changes in reproductive tissues following chronic exposure to stevia extract (PubMed).
Additional studies observed decreased fertility and smaller litters in female rats after prolonged stevia intake. (PubMed, PubMed)
While these outcomes haven’t been observed in short-term human trials, most clinical studies to date are limited in duration and often exclude reproductive endpoints altogether.

The takeaway: Stevia appears to have pharmacologic activity. And repeated exposure—not just one-time use—is where the concern lies.

Stevia as birth control
Before it was a fixture in wellness products, stevia was studied for its effect on fertility.

In the 1960s and ’70s, researchers in Paraguay and Brazil reported that female rats given daily doses of stevia extract over several weeks experienced a drop in fertility. Litter sizes shrank. Conception rates fell. When the extract was removed, normal fertility resumed—suggesting the effect was hormonal, not toxic (PubMed).

These were early, well-documented findings. But they’ve rarely resurfaced in the decades since—at least not in ways most consumers would notice.

@jessicagenetics

What you’re eating isn’t the stevia plant
The version used in most products is a purified compound—usually rebaudioside A—processed with solvents or resins. It’s typically blended with erythritol, monk fruit, or sucralose to mask bitterness.

Why that matters: these ingredients are consumed together, often several times a day, across supplements, drinks, and snacks. A 2025 mouse study found that erythritol impaired memory and learning, possibly by disrupting synaptic plasticity. (Journal of Applied Physiology)

Stevia was never fully approved by the FDA
The FDA has never approved whole-leaf stevia or crude stevia extracts for use in food. Instead, it granted GRAS (generally recognized as safe) status to isolated compounds like rebaudioside A, based on short-term studies in healthy adults.

Despite this narrow approval, stevia gained popularity because it was marketed as natural, plant-based, and calorie-free.

Why we don’t approve stevia at SOS
Brands that partner with Seed Oil Scout can earn the Seed Oil Safe stamp to use on their packaging and be listed in our marketplace. But stevia-containing products don’t qualify.

This decision comes from our guiding philosophy: we apply scrutiny to ingredients with questionable safety data, regulatory ambiguity, or a track record of underreported risks—especially when they’re used daily under the assumption of safety.

We built the SOS Grocery Scanner around this principle.
Stevia doesn’t meet our standard. Here’s why:
Hormonal and reproductive effects have been documented in multiple animal studies
Long-term safety data in humans is limited
It’s rarely consumed alone and typically paired with other additives like erythritol or sucralose.
It’s marketed as natural, but chemically refined and far from a whole food
This isn’t about trends—it’s about applying consistent standards to ingredients that haven’t earned our confidence.

Try the SOS Grocery Scanner. It flags more than just seed oils.

Bottomline
Stevia demonstrates biological effects in animal models.
Long-term safety in humans has not been established.
The version used in products is highly processed.
It’s not Seed-Oil Safe. 🫡

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You are what you eat. And you've been eating a lie.

No! I drank two or three zevias one hot July day in early 2010's and it wrecked me for the following 2 days. I might as well have had Drano.

I repeated the same mistake with a Real Lemonade packet also stevia mixture.

That's when I finally figured it out. This sweetener nukes my gut!

I had a horrible experience with equal in early 2000 when I was doing Atkins. This was neurological in nature. At Dunkin I order and extra large coffee with Xtra Xtra cream and the girl asked if I wanted 2 packets of equal so I said sure. I sucked the coffee down and an hour later had vision problems. that was the end of equal for me

cephalic phase insulin response is very strong with stevia also. Before all this info was on the Internet I used stevia drops in my coffee and it made me very hungry. Now thanks to Jason fung and gin Stephens I know why.

Lately I have been fasting and putting allulose in my black coffee, it doesn't give me any problems. I started out slow but have added more and it isn't presenting anything.

I never purposely used any of the artificial sweeteners. The closest was I used the drink mixers for a long time.

I even considered myself going cold turkey with the 'sugar' when I started carnivore but I was using the drink mixers to help me drink water.

It was eye opening and a learning point. Just because the label says No Sugar does not necessarily mean there is no sugar.

I don't think I had any adverse reactions but I am guessing over the long term there would be issues.

Scott

Brother I'm not paying for that Seed Oil Scout app #1 as I'm not supporting any of that nonsense.

For myself I've not had a sweet tooth, didn't need to find alternative to no sugar in my coffee I just stopped using sugar.

Soda hasn't been in my diet for about 2 decades when I started drinking my bourbon neat. (Yes there was OCCAISIONAL soda)

Candy, cookies cakes IF I ate any would definitely had sugar no fake crap.

Unfortunately I didn't give a ratz arse on my carb intake, boxed /prepared foods etc.

So if I fell prey to anything it was due to my laziness not ignorance.

I used honey in my coffee up until recently, but stopped using any sweeteners years ago. I think of my eating plan right now in terms of eliminating any unnecessary variables to see most clearly how my body is responding. But eliminating has been a more gradual approach to get to where I am and so far it has worked well for me. I find if the question of whether I should be doing something comes up and if Im in touch with myself I usually know what to do.

Uh oh. I used stevia in my tea each morning. Never caused me any issues.

I've tried switching to allulose, but I end up having explosive diarrhea about an hour later.

30 minutes ago, Bob said:

Uh oh. I used stevia in my tea each morning. Never caused me any issues.

I've tried switching to allulose, but I end up having explosive diarrhea about an hour later.

Call it a 'cleanse with pressure'. I try to look for the positives.

Scott

4 hours ago, Scott F. said:

Call it a 'cleanse with pressure'. I try to look for the positives.

Scott

I appreciate the information.

I do drink Zevia periodically, but that's the only stevia I consume. I only use monk fruit and allulose and actively avoid erythritol when I can. I've never had any issues with any of the NNS (natural or otherwise).

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