Stevia vs. Sugar vs. Artificial Sweeteners: What's Really in Your Protein Shake
Ever flipped over a protein shake tub and squinted at the sweetener listed in the ingredients? You're not alone. "Natural flavours," "sucralose," "stevia extract" – it can all feel like a guessing game. So let's actually break down what each one is and what the research says, because the sweetener in your shake matters just as much as the protein itself.
Sugar: the one we're all trying to avoid
Regular sugar (sucrose) is the baseline everyone's comparing against for a reason. It spikes your blood glucose and insulin fast, and it's also just extra empty calories in a drink you're having for the protein. Not exactly ideal.
Artificial sweeteners: not all created equal
"Artificial sweetener" gets used as one big umbrella term, but sucralose, aspartame, and saccharin don't all behave the same way in the body. The honest picture from the research: some studies suggest certain artificial sweeteners may affect insulin response or gut bacteria differently than others, and the science here is still evolving.(1) They generally don't spike blood sugar the way sugar does, but "no blood sugar spike" isn't the whole story – researchers are still working out exactly what these ingredients do over years of regular use.
Stevia: the natural, almost calorie-free option
Stevia comes from the leaves of the Stevia rebaudiana plant and, unlike sugar, it has a glycaemic index of essentially zero – meaning pure stevia doesn't raise your blood sugar.(2) A large 2025 systematic review looking at 27 studies found that, compared to sugar, stevia consistently led to lower post-meal blood glucose and insulin levels.(3)
Here's the part that's genuinely interesting: when researchers compared stevia head-to-head against artificial sweeteners like aspartame and sucralose, they found no meaningful differences in blood glucose or insulin between them.(3) So stevia isn't dramatically "better" than every artificial sweetener across the board – but it does come from a plant rather than a lab, with a long track record of use, and a growing body of research on how it compares with sugar for blood glucose.
One thing worth watching
Not all stevia products are created equal, either. Some contain added dextrose or maltodextrin as bulking agents, and those additions do have a high glycaemic index – so a stevia-sweetened product isn't automatically glucose-neutral unless you check what else is in the blend.(4) It's also worth knowing that the acceptable daily intake set by JECFA (the international expert committee the FDA refers to) is 4mg per kg you weigh per day, expressed as steviol equivalents – about 12mg of steviol glycosides (such as rebaudioside A) per kilo – which is a pretty generous ceiling for normal use.(4)
So what does this mean for your shaker?
It's why we sweeten with stevia rather than sugar or synthetic sweeteners. You get the sweetness without us adding sugar, with almost no extra calories, and without relying on lab-made compounds that still have open questions attached to them. Simple as that.
(1) A review of artificial sweeteners and blood glucose, PMC12378089.
(2) Does Stevia Raise Blood Sugar?, GoodRx; stevia's glycaemic index is cited near 0 in pure form.
(3) Systematic review, Current Developments in Nutrition, 2025 – 27 studies reviewed under PRISMA guidelines.
(4) Additives like dextrose/maltodextrin in stevia blends and FDA safety thresholds, per Virta Health clinical guidance.
