Best Protein Powder for Sensitive Stomachs (2025): Make Gains While Trusting Your Gut

Providing 28 grams of protein with only 1 gram of carbohydrate and 0 grams of fat, Transparent Labs 100% Whey Protein Isolate is the epitome of pure protein. The protein is sourced from humanely raised, grass-fed cattle, and there are no fillers, dyes, or artificial sweeteners, which is why Transparent Labs is the best overall protein powder for sensitive stomachs.

We’ll first point out that all whey protein¹ products are considered complete proteins—meaning they supply all essential amino acids, including branched-chain amino acids (BCAAs)—and aid muscle growth. However, whey protein concentrates and isolates offer subtle yet notable differences. 

Compared to concentrates, whey protein isolates contain more protein and fewer carbs, fat, and lactose. Being lower in lactose makes whey protein isolates a possible muscle-building² solution for anyone with lactose intolerance or dairy sensitivities.

And the greatness of Transparent Labs’ whey isolate doesn’t stop with its protein—it sports a tidy ingredient list without using artificial colorings, preservatives, and sweeteners, earning a 5 out of 5 for formulation. And you can choose between eight tempting flavors, including Cinnamon French Toast and Oatmeal Chocolate Chip Cookie.

GGR performance editor and product tester Anthony O’Reilly tried this product and said, “I’ve been taking Transparent Labs protein for about a month, and overall I have to say I’m a big fan! I haven’t experienced any stomach or digestive issues after drinking it as I sometimes do with other whey protein powders—several customer reviewers said the same thing. It mixes incredibly well with milk or water, and I can say that I feel full for quite a while after downing a protein shake.”

Anthony tested the seasonal Peppermint Hot Chocolate flavor and rated it a 5 out of 5. He said, “Peppermint Hot Chocolate: It’s exactly that—all you need is some whipped cream and marshmallows to complete the scene.”

One area where the Transparent Lab Whey Protein Isolate falls short is price. It costs $2.00 per serving, which earns it a 3.5 out of 5 in our pricing category. This is a high-quality product, but the high cost can also put it out of reach for some.

Transparent Lab products are third-party tested, with their Certificates of Analysis and Composition readily accessible on their website. GGR also worked with Ellipse Analytics, an independent accredited lab, to test Transparent Labs whey isolate and more than 150 other protein powders for protein content and purity. Overall, Transparent Labs whey isolate ranked as an Above Average product, and you can read more about exactly what we tested for in our Independent Supplement Testing Glossary.

If you want a more in-depth guide to this grass-fed whey protein isolate, check out our complete Transparent Labs Protein Review.

Calling all athletes with sensitive stomachs! (Or really anyone searching for a grass-fed whey protein isolate powder…) Sports Research Whey Protein Isolate is Informed-Sport certified, meaning it’s been rigorously tested for banned substances before being available for purchase by athletes and the masses. 

It does contain stevia and some thickening agents. We’ve had multiple testers try this whey protein, and all agreed there was no bloating or gastrointestinal distress, but some of those ingredients caused its formulation score to drop to 4.5 out of 5. People with tree nut allergies (i.e., coconut) should also steer clear of this protein powder.

“No protein aftertaste and zero bloating,” says certified nutrition coach and GGR performance editor Anthony O’Reilly.

You get 25 grams per scoop and a delicious-tasting addition to any smoothie or shake. Anthony went with the Dutch Chocolate flavor and says it reminds him of high-quality instant cocoa. “I want to drink this with some marshmallows and whipped cream,” he says, rating the taste a 5 out of 5.

It also comes in a Creamy Vanilla flavor, which has fewer ingredients than the chocolate and also tastes good. “It reminds me of a malted milkshake,” Anthony says in his Sports Research Whey Protein review.

The solubility, Anthony adds, is a little tricky. “There’s some bits that cling to the side of your cup or blender, but what does get mixed in is smooth,” he says, settling on a 3.5 out of 5 score for mixability.

With all-natural ingredients, no added sugars, strong manufacturing standards, and third-party testing, Legion Whey+ is our top pick for the best natural protein powder for sensitive stomachs. And while we’ve done a top-to-bottom Legion Whey+ protein review, we’ll share the cliff notes here.

The first thing to note about Legion Whey+ is that it provides whey protein isolate, which may be better tolerated by those with dairy sensitivities like lactose intolerance. But this isn’t just any whey protein isolate—Legion makes it known its non-GMO protein supplement is Truly Grass Fed and Animal Welfare Approved certified, meaning the dairy cows live in optimal and natural conditions. We gave the formulation a 5 out of 5.

We also welcome the invitation to try exciting and nostalgic flavors (Cinnamon Cereal, anyone?), although some options contain ingredients like xanthan gum³ and stevia that may cause tummy troubles for some people. But if you don’t love Whey+, Legion will give you a full refund on the spot.

Legion Whey+ is certified to contain no banned substances by Labdoor, an independent third-party testing company. This strengthens the confidence of consumers, especially competitive athletes, that the supplement contains what it claims to and not what it shouldn’t. 

It’s also manufactured in National Sanitation Foundation (NSF)-certified, Food and Drug Administration (FDA)-inspected, Good Manufacturing Practices (cGMP)-compliant facilities. 

Further adding to Legion Whey’s cred, GGR worked with an independent and accredited lab called Ellipse Analytics to perform our own testing on label accuracy and purity, and Legion Whey achieved a Meets Standard rating overall. Learn more about these purity metrics in our Independent Supplement Testing Glossary.

Our tester, Anthony O’Reilly, CPT, CNC, tried the Cinnamon Cereal flavor and rated it a 4.5 out of 5 for flavor. He said, “It kind of tasted like when you first start eating a bowl of cinnamon toast crunch and the cereal hasn’t had a chance to fully incorporate into the milk yet. AKA, the flavor’s there but not quite as pungent as I would’ve liked.”

The solubility is also on point. “I had no problems getting it to dissolve,” Anthony said.

At $1.99 per serving, this isn’t the cheapest protein on the market and earns a 3.5 out of 5 for the price. However, the ingredient quality and third-party testing make it well worth the cost, in our opinion.

Not only is Ora Organic Daily Superfood Plant Protein the best organic protein powder for sensitive stomachs, but it’s also one of the best organic protein powders around. It sports the USDA Organic Seal, showing us it meets strict organic standards set by the United States Department of Agriculture. For those with tummy issues, you’ll be happy to hear it also contains a blend of digestive enzymes so there’s no bloating or intestinal distress.

As a bonus, it also tastes really good. Anthony O’Reilly, a certified nutrition coach and former GGR performance editor, tried the Vanilla Chai flavor and gave it a 4 out of 5. “I only took a point off because I’m a big chai person, and I like my chai to have more spice than this has,” he says. “It’s still really good, and one of the better plant proteins I’ve tasted. I would have this again in my iced coffee.”

He also rates the solubility a 5 out of 5, saying, “There were no clumps, and everything mixed easily in a shaker cup.”

This vegan alternative is formulated with six plant protein sources, with the main stars being rice and pea protein. And if you’re worried about the plant-based blend lacking protein integrity, let’s discuss why you shouldn’t be. 

While vegan proteins are often low in lysine, an essential amino acid, rice protein has some of the highest lysine contents. Research⁴ also tells us organic brown rice protein isolate can be used instead of animal and dairy-based options without losing essential nutrient value. Also, compared to other animal-derived and commercially available proteins, a study in the Nutrition Journal⁵ suggests rice protein isolate can improve body composition and exercise performance.

Moreover, research⁶ supports that pea and rice proteins are promising allergen-friendly proteins. Rice protein⁷ is also considered an easily accessible protein source and an alternative to animal-based and gluten-containing protein.

Our only complaint is the price and total servings. Unlike most protein powders, you only get 20 servings (traditionally a container has a month’s worth of protein) and the price per serving falls around $2.00, which earns it a 1 out of 5 on our pricing scale.

Transparent Labs Vegan Protein Powder is a great vegan protein powder for sensitive stomachs, especially for people intolerant to dairy products. Each two-scoop serving provides 24 grams of protein sourced from organic rice protein and organic pea protein isolate, earning it a 5 out of 5 for formulation.

Pea protein⁸ is a complete protein since it provides all essential amino acids, although it’s relatively low in methionine and cysteine compared to other plant- and animal-based proteins. However, combining other plant-based sources enhances the amino acid profile and provides beneficial nutrients like omega-3 fatty acids and antioxidants.

One of the reasons we recommend Transparent Labs so often is they live up to their name, even showing how much stevia they use per serving (270 milligrams). That’s about half a teaspoon’s worth, so unless you’re really sensitive to stevia you probably won’t notice it much.

And recall all Transparent Lab products are free of “artificial junk” like artificial sweeteners, coloring, and preservatives. You can also view the Certificate of Analysis, conducted by a third-party lab, of any Transparent Labs product conduct. We rate it a 5 out of 5 for transparency.

One downside is the flavor. Product tester and former GGR editor Frieda Johnson says, “The French Vanilla flavor tastes kind of artificial. I think it may be the stevia, I generally don’t like the flavor of it.” 

Compared to traditional whey proteins, vegan protein powders often have a bit of a gritty texture, which our tester found to be true. She gave this a 4 out of 5 for solubility, saying, “It mixes well, but this has a different texture than whey proteins. It’s not gritty, but there is more residue/film in the shaker and I can feel that extra texture in my mouth too. It’s really not terrible but it’s not comparable to whey.”

Check out our full Transparent Labs vegan protein review for our comprehensive thoughts on this protein powder option.

Whether you opt for Vanilla or Mexican Chocolate, each scoop of Onnit provides 20 grams of protein sourced from whey protein isolate. The virtually lactose-free and gluten-free protein may make it easier to digest, and this protein earns a 4.5 out of 5 for the formulation.

Moreover, Onnit sources their dairy from New Zealand cows that can freely roam and graze the pasture. Also, rest any concerns about hormones and antibiotics in the dairy. 

In addition to high-quality protein, Onnit’s whey isolate provides a digestive enzyme blend to aid digestion. It also supplies probiotics to support immune and gut health, although we still recommend checking out the best probiotics to address your targeted needs.

Former GGR staff writer and expert product tester Amanda Capritto says, “The Mexican Chocolate actually tastes different from other chocolate protein powders, which I honestly wasn’t expecting. It’s rich when mixed with whole or oat milk.”

She rated the flavor a 3.5 out of 5 overall, saying, “The flavor is good, although the texture is extremely thin, especially when mixed with water. It’s rich when mixed with whole or oat milk.”

Another callout is that this is a pricey protein powder at $2.00 per serving. Since this is one of the more expensive options out there, we rated the price per serving 2 out of 5 stars.

Our Onnit grass-fed whey isolate review will provide more of our thoughts on this product if you’re intrigued.

If you’re searching for a reputable, unflavored whey protein isolate, your hunt stops now! Gainful Low-Lactose Protein Powder provides 26 grams of protein with zero grams of fat and only 1 gram of carbs.

This is an unflavored powder that’s free of added sugar and artificial ingredients, making it a great option for those sensitive to artificial sweeteners. You can add individual flavor boosters to the powder to give it a flavor if you want, though they contain stevia and other sweeteners that might not agree with some people’s digestive tracts.

However, the flavors we tested are delicious, earning a 5 out of 5 from Nicole Davis, a certified personal trainer and nutrition coach.

“This is good! I like that you can control how much flavor you want in each shake via the packs, and even mix them, like chocolate and vanilla for instance,” says Nicole. “I mixed with milk as suggested on the instructions and all flavors have tasted good—even Sea Salt Caramel, which is not something I’d normally choose.”

Certified personal trainer and expert product tester Nicole Davis hasn’t tried the powder by itself, but she says the solubility isn’t the best and rated it a 3.5 out of 5. “Pretty clumpy when mixed with milk in a shaker,” she says in our Gainful Protein review. “Because I liked the taste I just dealt with it, but not great by any means.”

Our other big issue is the price. Although Gainful has now allowed you to purchase their supplements without a subscription, it’s still a bit expensive at $65 for two 14-serving containers that comes out to a per-serving cost of $2.32. That’s a 1 out of 5 on our pricing scale.

The protein powder is free of GMOs and hormones and packaged in a U.S.-based, GMP-certified facility. While the protein powder is not manufactured with common food allergens, like wheat and gluten, it is also important to note that it is produced in a GMP facility that processes other products with these ingredients. This is important for anyone allergic or sensitive to certain allergens, as there’s a risk for cross-contamination. 

Jacked Factory Authentic ISO provides 25 grams of protein with only 1 gram of carbs and 0.5 grams of fat, making it suitable for low-carb and keto dieters. And you can enjoy delicious flavors—like Blueberry Muffin and Cinnamon French Toast—without added sugars!

However, if you mix the protein powder with water, the flavor may be a little light. Our tester tried Jacked Factory Authentic Iso with both milk and water, and gave it a 4 out of 5 for flavor. “I did not like the water version,” He said. “I honestly can’t describe the taste except it just kind of feels like protein water—the vanilla is barely noticeable. The milk version was a little better due to the creaminess the milk gives, but it kind just tastes like an artificial milkshake. So not bad, but wouldn’t be the first protein powder I grab in the morning.”

However, he was very impressed with the solubility, rating it a 5 out of 5. He said, “I shook it with moderate intensity, and everything came out fine. No powder stuck to the side of the cup.”

The grass-fed whey protein isolate mostly contains natural ingredients, including Himalayan rock salt and stevia extract. We give the formulation a 5 out of 5 due to the high protein content and low carb and fat content, but it is formulated with artificial flavors and the artificial sweetener sucralose. Both stevia and sucralose have been known to cause GI distress in some people, so it’s helpful to know if you are sensitive to either of these sweeteners while looking for the best protein powder for you.

The vanilla flavor also contains a gum blend, so you might opt for a different flavor if you’re sensitive to guar gum, gum acacia, or xanthan gum. If you want to avoid any additional ingredients beyond whey protein isolate, Authentic ISO comes in a single-ingredient Unflavored option. 

Even though this protein is made from grass-fed whey protein isolate, which slightly drives up the price, it’s still affordable for most at $1.33 per serving. Overall, we rate this a 4.5 out of 5 for its pricing and value.

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Jacked Factory Authentic ISO manufactured in the U.S. in a cGMP, FDA-registered facility. And if you aren’t satisfied with the product, Jacked Factory offers a 100% hassle-free, money-back guarantee. Read more in our full Jacked Factory Authentic Iso Whey review.

Bulking, slimming down, or simply getting enough protein doesn’t have to be costly, thanks to Nutricost Whey Protein Isolate. This is actually a case where buying a larger container pays off because it comes out to a lower price per serving, with some container options costing as little as $1 per scoop. Also, as a gluten-free whey protein isolate, it’s a viable option for sensitive tummies—unless you’re strictly dairy-free or vegan. 

RELATED: Nutricost Whey Protein Concentrate Review

The whey protein isolate comes in 10 flavor options, and while it uses some artificial flavors and sweeteners our expert product testers felt no negative side effects. “I have stomach issues with some dairy protein powders, but I didn’t have any with this one,” says Jacob Penner, a USA Weightlifting Level 2 coach. “All around, a great product.”

The formulation earned a 4.5 out of 5 from our testers. It provides 30 grams of protein with virtually no carbs and fat, though some flavors may have more than others. It’s a great option to sneak in extra protein, whether blended as a protein shake or mixed into your favorite baked goods. However, we rated the solubility a 3.5 out of 5.

“It leaves behind some clumps when mixed in a shaker bottle,” says GGR Managing Editor Amanda Dvorak. “I don’t mind it because the taste isn’t bad, but the solubility could definitely be better.”

As a bonus, Nutricost products are third-party tested for purity and banned/harmful substances. Still, we gave it a 4 out of 5 for third-party testing because we couldn’t determine who does the testing.