Why Plant-Based Protein Powder Can Upset Your Stomach—And What to Replace It With

March 30, 2023

Although getting enough protein as a vegan isn’t particularly difficult, I do try to incorporate more protein into my diet when possible. But the first time I tried blending plant-based protein powder with my morning smoothie, I began having cramps afterward. At first, I didn’t make the connection, and admittedly, the fact that the powder tasted exactly like chocolate cake discouraged me from cutting it out of my diet to see if it was causing the problem. After putting a scoop into my smoothie every day for a week or two and consistently experiencing cramps after breakfast, I reluctantly decided to go without it for a few days to see if I felt better. Sure enough, the protein powder was the culprit.

Recently, I decided to try another brand, only to end up dealing with the same symptoms again. I realized that the problem wasn’t just the first brand of plant-based protein powder—maybe I was reacting to plant-based protein powder itself. I was surprised by this: I figured that vegan varieties would be far easier on the digestive system than whey-based protein powders. However, there was no doubt that plant-based protein powder was giving me an upset stomach, no matter which brands I tried. I decided to do some research to find out why—and after learning about the manufacturing process, I wasn’t surprised that plant-based protein powder didn’t agree with me.

A woman in a white t-shirt is putting a scoop of plant-based protein powder into a plastic shaker bottle.

Why plant-based protein powder can upset your digestion

Additives and preservatives

Like non-vegan protein powder, plant-based protein powder is a processed food. Even if you purchase an organic version (which I did), some additives and preservatives are going to end up in the final product. In general, supplements are not regulated by the FDA, which means that there is really no way of knowing if a supplement actually contains everything on its ingredients list. It could also include ingredients that are not actually on the list.

And some of the compounds that end up in protein powders definitely do not sound appetizing. In 2018, the Clean Label Project conducted quality tests on 134 samples of the top-selling protein supplements, which included plenty of plant-based products. They were looking for traces of toxic substances like heavy metals, and the results of these tests definitely revealed cause for concern.

Heavy metals—especially in organic plant-based powders

Out of the plant-based protein samples tested for the Clean Label Project’s study, 75% tested positive for traces of lead. In fact, the plant-based samples were worse offenders in this category than the non-vegan samples. Surprisingly, the organic samples actually contained higher levels of lead than the non-organic samples. Other heavy metals that were commonly found in the plant-based samples included arsenic and cadmium. The researchers also detected high levels of compounds like BPA.

After going over this research, I wasn’t interested in trying another protein powder—clearly, the supplement industry needs some serious regulations, and using supplements unnecessarily meant consuming unknown ingredients. But I still wanted to make sure my smoothies were packed with plenty of protein, especially on days when I knew I would be getting a workout in. It was time to stock my pantry with vegan protein staples that could help replace that scoop of powder—without all of the heavy metals, additives, and other ingredients that were probably upsetting my stomach.

A hand is holding a smoothie made with plant-based-protein powder against a dark wooden background.

Safe alternatives to plant-based protein powders

If you’re looking for a tasty and healthy way to add protein to your morning smoothies, I recommend all-natural nut butters: peanut, almond, cashew, sunflower seed, or even pumpkin seed butters can all give your smoothies a protein boost. Mixing two tablespoons of peanut or almond butter into a smoothie with frozen berries is the perfect combo if you want to create a PB & J flavor! This is also a great way to include more healthy fats in your diet.

You can also try using seeds for protein. Ground flax seeds and hemp seeds have a totally neutral flavor, and adding a tablespoon of each will add protein to your smoothie without affecting the taste. Another option? Try mixing in a scoop of rolled oats! Yes, it will make the texture of your smoothie noticeably thicker, but otherwise, you won’t notice much of a difference—even if you’re not a huge fan of oatmeal.

You may not think of tofu as a smoothie ingredient—and to be fair, there’s no way that the extra firm variety would taste good blended into a smoothie. But if you’re looking for a protein-packed addition to your morning smoothie, try silken tofu! It blends easily, and you won’t be able to taste it at all. You don’t need to turn to plant-based protein powder for a balanced diet—stick to whole foods to stay on the safe side.

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This article was first published on November 20, 2020 and updated on March 30, 2023.


Photo: Unsplash

Jane Harkness is a freelance writer based in New Jersey. She writes about veganism, travel, and wellness, and her writing has been published on platforms like Thought Catalog, Student Universe, The Financial Diet, and Wholesome Culture. She blogs daily on Medium, and you can check out more of her work on her website.


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