Protein Powder Ingredients To AVOID (And What to Choose Instead)

Protein powders are super popular in the fitness industry, and a great way to help you hit your protein goals.

But not all protein powders are created equal. Many contain unnecessary additives, fillers, or low-quality ingredients that can negatively affect digestion, blood sugar, and even long-term health.

As a coach, I always steer clients toward products with clean, transparent formulas. In this guide, I’ll break down the top ingredients to avoid in protein powders and highlight a few high-quality brands worth considering.

Key Takeaways

• Some protein powders include harmful additives that cause digestive issues, blood sugar spikes, and inflammation. These ingredients are often added by companies to cut down on costs.

• The biggest culprits to watch out for in your protein are ingredients like artificial sweeteners, cheap fillers, gums, vegetable oils/ hydrogenated fats, and low quality protein sources like collagen and soy.

• Avoid products with long ingredient lists, vague “proprietary blends,” or a lack of third-party testing.

• Products like Transparent Labs and Naked Whey prove that you don’t need long ingredient lists or hidden additives to get a high-quality protein powder.

Quick Criteria for ‘Bad’ Ingredients 

Here’s how I evaluate whether an ingredient belongs in a protein powder:

• Does it negatively affect digestion, inflammation, or blood sugar?

• Is it added purely as filler or to cut costs?

• Does it provide no nutritional benefit (or worse, carry questionable safety)?

If the answer is yes to any of those, it’s worth avoiding.

Top Ingredients To Avoid 

1. Artificial Sweeteners (Sucralose, Acesulfame Potassium)

The first thing I look out for in any protein powder or supplement I am buying is artificial sweeteners. Sucralose and Ace-K are some of the most common additives in protein powders. 

While they reduce calories, they can also cause:

• Digestive distress- many people report increased symptoms of bloating, gas, and diarrhea when consuming artificial sweeteners, and studies have shown that these sweeteners can contribute to inflammation in the gut.

• Gut microbiome disruption- studies have also shown that artificial sweeteners can have long term negative effects on your immunity and metabolism.

• Increased sugar cravings- While many people replace sugar in their diet with artificial sweeteners to try and cut down on sugar, there is a lot of evidence to show that they can actually cause you to crave sugar even more. This could ultimately lead to less adherence to your diet.

• Headaches- A very common reported side effect of consuming artificial sweeteners is headaches and migraines. It’s not a side effect that everyone experiences, but should be avoided for individuals who are very sensitive to these added ingredients.

Better choice: Look for powders sweetened with stevia leaf extract, monk fruit, coconut sugar, cane sugar, honey, or date powder.

2. Fillers & Gums (Maltodextrin, Carrageenan, Xanthan gum)

It is very common in the supplement industry for protein powders to include different fillers and gums in their formula to improve shelf life, texture, and add bulk to the product to reduce costs.

They can: 

• Be tough to digest, especially in large quantities. They end up fermenting in the gut and causing uncomfortable gas, bloating, and even diarrhea.
  
  I personally notice an immediate pain and discomfort in my gut when I consume these ingredients, and I find many of my clients with sensitive guts experience the same thing.

• Cause long term disturbances to the gut microbiome (which ultimately can affect things like your immunity and metabolism).
  
  For example, studies have linked consuming the filler maltodextrin to depleting the intestinal lining, increasing inflammation, and altering the composition of the microbiome in the gut.

• Trigger common food allergies since many use soy, corn, and wheat. These added ingredients can end up causing discomfort or a flare up for sensitive individuals.

Better choice: Pick powders with 2–5 ingredients total and avoid labels listing gums, starches, or maltodextrin. 

The most common gums and fillers include:

Gums & Thickeners	Cheap Fillers & Carbs	Other Additives
Xanthan Gum	Maltodextrin	Inulin
Guar Gum	Dextrins	Soy Lecithin
Gellan Gum	Corn Syrup Solids	Sunflower Lecithin
Acacia Gum	Rice Flour
Carrageenan	Oat Flour
Carrageenan	Tapioca Starch
	Potato Starch

3. Proprietary Blends

A “proprietary blend” hides ingredient amounts under one umbrella name.

Supplement companies will often do this so that they do not have to disclose the exact amounts of what is in their product. This is important to avoid for a few reasons:

• Underdosed ingredients- You may be paying for underdosed, ineffective ingredients.

• Risk of hidden ingredients– They often contain unnecessary fillers and/or cheap additives that are not disclosed in detail on the label
  
  A common filler found in proprietary blends in protein powder is maltodextrin, which cheapens the formula and can cause digestive issues like I talked about in the above section.

• Lack of transparency– Ultimately, proprietary blends completely lack transparency and unless a supplement company volunteers to have their product third-party tested, there is no way to know exactly what is in your protein powder.

Better choice: Look for powders with clearly labeled ingredients and third-party certifications.

For example, in the average protein powder, you should be looking for a protein source (e.g. whey), a flavoring (e.g. vanilla), and a sweetener (e.g. stevia or monk fruit).

You also want to look for protein powders that are third-party tested. In the supplement industry, third-party testing is voluntary, not mandatory. This means that if the protein powder company is opting for this extra step, they will often have more integrity when it comes to their ingredients compared to companies that do not test.

If you have to choose a protein powder brand that contains proprietary blends, at least make sure that the company opts for third-party testing to help guarantee the absence of harmful substances like banned substances, heavy metals or other contaminants.

4. Low-Quality Protein Sources (e.g. collagen as main source, soy isolate)

Protein sources need all 9 essential amino acids for protein synthesis and to help build muscle. Powders that use lower quality protein sources typically have less protein per serving overall.

They also may be less bioavailable, meaning that they don’t absorb as efficiently in your body.

The most common low quality protein sources are:

• Soy protein isolate- it is usually heavily processed and can have negative effects on hormones due to the high concentration of phytoestrogens.

• Collagen or gelatin– Unfortunately, these don’t contain all 9 essential amino acids, and therefore are not effective for muscle building on their own. But they are great for hair, skin, and joints.

• Rice protein (alone)- Rice protein when used on its own, has an incomplete amino acid profile and is considered a low quality protein source. It can be more effective when it is combined in a formula with pea protein.

Better choice: Stick to whey isolate, whey concentrate, casein, egg white, hemp, or rice + pea blends.

5. Vegetable Oils & Hydrogenated Fats

While it’s rare to see a protein powder that contains vegetable oils, there are some companies that use these unhealthy fats in their formulas. They may be used to enhance flavor, increase shelf life, or to reduce the cost of production.

However, these reasons definitely do not outweigh the cost that ingredients like this have on your health. The health risks that these fats are linked to include:

• Heart Disease
• Insulin Resistance
• Increased inflammation

In addition to this, when these fats are exposed to heat, they oxidize and can create harmful free radicals that can cause cell damage and increase your risk for chronic disease.

Better choice: If fats are added, they should be from MCT oil or coconut oil.

Bonus: Red Flags on the Label 

• More Than 10-12 Ingredients

When it comes to protein powder ingredients, more does not mean better. It can mean a lower quality product, lower protein content, and an increase in digestive issues due to unnecessary fillers. 

Stick with protein powders that have a list of 3-5 ingredients on the nutrition panel.

• “Natural flavors” as a catch-all

Although natural flavors may sound like a good thing, it is actually a vague way of stating how a formula is flavored and can mean just about anything. Common sneaky ingredients that hide under the name natural flavors in formulas include things like maltodextrin, artificially processed extracts, and sugar alcohols.

However, natural flavors don’t always equal bad, and many reputable companies do use them in their formulas. The difference is, these companies are usually happy to disclose what makes up their natural flavors if questioned.

Instead of natural flavors, you can look for simple ingredients like cocoa powder or vanilla extract to flavor a product.

• Lack Of Third-Party Testing

Since the supplement industry is largely unregulated, the only way to guarantee the safety and purity of your protein powder is through third-party testing. For this reason, I would never recommend a protein powder to my client that was not third-party tested.

The most common companies that do this are NSF, Informed Sport, and Clean Label Project.

Clean Label Protein Powders Worth Trying

Here are a few examples of protein powder brands with clean labels:

Transparent Labs Protein Powder

I love to recommend Transparent Labs protein powder to my clients, since they use minimal ingredients that are all high quality and third-party tested.

While they do use natural flavors in their formula, they are very transparent on their website as to where these flavors are derived from, and that they make up a very minimal part of the formula.

Naked Whey Protein Powder

Naked Whey protein powder is another product I like to recommend to my clients since it contains minimal ingredients and is third-party tested. 

You can choose an unflavored version with only 1 ingredient, or a flavored one that uses organic natural flavors and cane sugar.

If you want a similar guide for your pre-workout look here. 

References

Li X, Liu Y, Wang Y, Li X, Liu X, Guo M, Tan Y, Qin X, Wang X, Jiang M. Sucralose Promotes Colitis-Associated Colorectal Cancer Risk in a Murine Model Along With Changes in Microbiota. Front Oncol. 2020 Jun 3;10:710. doi: 10.3389/fonc.2020.00710. PMID: 32582527; PMCID: PMC7286428.

Bokulich NA, Blaser MJ. A bitter aftertaste: unintended effects of artificial sweeteners on the gut microbiome. Cell Metab. 2014 Nov 4;20(5):701-703. doi: 10.1016/j.cmet.2014.10.012. Epub 2014 Nov 4. PMID: 25440050; PMCID: PMC4494042.

Zangara, M. T., Ponti, A. K., Miller, N. D., Engelhart, M. J., Ahern, P. P., Sangwan, N., & McDonald, C. (2022). Maltodextrin consumption impairs the intestinal mucus barrier and accelerates colitis through direct actions on the epithelium. Frontiers in Immunology, 13, Article 841188. https://doi.org/10.3389/fimmu.2022.841188

National Research Council (US) Subcommittee on the Tenth Edition of the Recommended Dietary Allowances. Recommended Dietary Allowances: 10th Edition. Washington (DC): National Academies Press (US); 1989. 6, Protein and Amino Acids. Available from: https://www.ncbi.nlm.nih.gov/books/NBK234922/

DiNicolantonio JJ, O’Keefe JH. Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis. Open Heart. 2018 Sep 26;5(2):e000898. doi: 10.1136/openhrt-2018-000898. PMID: 30364556; PMCID: PMC6196963.

Chandimali, N., Bak, S.G., Park, E.H. et al. Free radicals and their impact on health and antioxidant defenses: a review. Cell Death Discov. 11, 19 (2025). https://doi.org/10.1038/s41420-024-02278-8