If you’re putting in the effort to hit the gym, build muscle, and improve your health, the last thing you want is to undo all your hard work with a toxic supplement like protein powder. But the truth is, many protein powders on the market are filled with unhealthy additives, artificial sweeteners, and even heavy metals that could be doing more harm than good. Most people assume that because a product is labeled as “protein” and sold at a major retailer, it’s automatically a health-boosting option. Unfortunately, that’s far from the truth. Many popular protein powders contain preservatives, fillers, artificial flavors, and even toxic phosphates that can burden your body over time.

So what are the best and worst protein powders you can buy at Costco? Let’s break it down. Understanding which products contain harmful ingredients and which provide clean, high-quality protein is key to making the right choice. By avoiding toxic options and selecting the best alternatives, you can fuel your body properly without compromising your health.

The Worst Protein Powder at Costco

Not all protein powders are created equal. Some are loaded with harmful ingredients that can actually contribute to inflammation, gut distress, and even metabolic dysfunction. If you’re serious about your health, you’ll want to avoid these products and look for cleaner options instead.

Gold Standard Whey Protein

Gold Standard Whey is one of the most widely recognized protein powders on the market, but its ingredient list leaves a lot to be desired. Despite its popularity, this brand includes several problematic ingredients that can negatively impact your health. It may be widely available, but that doesn’t mean it’s the best choice for fueling your body.

• Contains Fillers and Preservatives – Many of the additives in this protein powder break down into phosphates, which can accumulate in the body and negatively impact kidney function over time. Phosphates are commonly used in processed foods to extend shelf life, but excessive intake has been linked to long-term health concerns. Over time, these compounds can contribute to metabolic imbalances and other issues.^[1]
• Includes Sunflower Oil – Industrial seed oils like sunflower oil are high in omega-6 fatty acids, which can contribute to chronic inflammation when consumed in excess. While omega-6 fatty acids are essential in small amounts, an overabundance can disrupt the body’s natural inflammatory response.^[2] This imbalance has been linked to a variety of chronic conditions, including cardiovascular disease and autoimmune disorders.
• Artificial Sweeteners – Many versions of this protein powder contain sucralose, an artificial sweetener that has been linked to negative effects on gut health and metabolic function. Studies suggest that artificial sweeteners may alter gut microbiota, leading to digestive discomfort and potential blood sugar dysregulation.^[3] For those looking to optimize digestion and overall well-being, avoiding artificial additives like sucralose is a smart choice.

Kirkland Brand Protein

Kirkland’s whey protein is a small step up from Gold Standard, but it’s still not a great option for those looking to avoid artificial additives. Many people assume that store-brand products are a safer alternative, but when it comes to protein, the ingredient list tells a different story. While Kirkland’s version may be slightly cleaner than some mainstream brands, it still falls short of being a truly non-toxic choice.

• Sucralose and Artificial Sweeteners – Artificial sweeteners may seem like a better alternative to sugar, but research suggests they can disrupt gut bacteria, increase cravings, and even contribute to insulin resistance over time. Consuming artificial sweeteners regularly may interfere with the body’s ability to regulate glucose levels, potentially leading to metabolic dysfunction. If your goal is to support long-term health, it’s best to opt for protein powders that use natural sweeteners or no sweeteners at all.
• Not Transparent About Sourcing – The source of whey protein matters. Kirkland’s brand does not specify whether its whey is from grass-fed cows, which raises concerns about the quality of the protein and potential exposure to antibiotics and hormones. Conventional dairy products often contain residues of synthetic hormones and antibiotics, which can contribute to hormone imbalances and gut disturbances over time.

If you’re aiming to minimize your exposure to toxic ingredients, these are two protein powders to skip. Instead of choosing low-quality options that may compromise your health, it’s worth seeking out cleaner alternatives that provide real nutritional benefits.

The Better Protein Powder Options

If you still want a convenient protein supplement but want to minimize harmful additives, here are a couple of better choices available at Costco. These options still have some drawbacks, but they are significantly cleaner than the worst offenders. While they aren’t perfect, they offer a middle ground for those looking to avoid the most harmful ingredients while maintaining convenience.

Ascent Native Fuel Whey Protein

This is one of the cleaner whey protein options at Costco and is a better choice for those who want to avoid artificial sweeteners. While it’s not completely free of processing, it does contain fewer harmful additives compared to other mainstream brands. If you’re looking for a whey protein that’s closer to natural, this is one to consider.

• Sweetened with Stevia – Unlike sucralose, stevia is a naturally derived, non-toxic way to add sweetness without spiking blood sugar or harming gut bacteria. Stevia has been used for centuries as a natural sweetener, and research suggests it does not contribute to metabolic dysfunction like artificial sweeteners do.^[4] This makes it a much safer option for those looking to protect their gut health while enjoying a hint of sweetness.
• Cold-Processed Whey – Ascent claims to use a less-processed form of whey, which may help retain more of the beneficial amino acids and peptides naturally found in high-quality protein. Processing methods can impact the nutritional value of whey, and minimizing high-heat processing helps preserve its natural integrity. Choosing cold-processed protein can result in better absorption and bioavailability of key nutrients.^[5]
• No Artificial Additives – Compared to other brands, Ascent keeps its ingredient list simple and clean. While it still contains whey protein, it avoids the most concerning additives found in lower-quality products. If you’re looking for a whey-based protein with minimal additives, Ascent is one of the better choices.

Orgain Organic Plant-Based Protein

For those looking for a plant-based option, Orgain’s organic protein powder is one of the better choices, but it does come with some caveats. Many plant-based proteins are marketed as clean, but there are still some concerns to be aware of. While Orgain is an improvement over many other brands, it’s not without potential downsides.

• Organic and Sprouted Ingredients – Orgain’s protein is made with sprouted plant proteins, which can help improve digestibility. Sprouted grains and seeds are easier for the body to break down, making the nutrients more bioavailable. This can be especially beneficial for those with sensitive digestion.^[6]
• No Artificial Sweeteners – It’s sweetened with natural ingredients, which makes it a better option than many other plant-based protein powders. Avoiding synthetic sweeteners is important for maintaining gut balance and metabolic health, making this a cleaner choice overall.
• Potential Heavy Metal Contamination – While Orgain has a better ingredient list than many competitors, plant-based protein powders as a whole have been found to contain high levels of heavy metals like lead, cadmium, and arsenic. This is due to how plants absorb metals from the soil, so it’s something to be aware of when choosing a plant-based protein. Regular heavy metal exposure can contribute to neurological and metabolic health issues, so this is an important factor to consider.

The Best Protein Powder at Costco

If you’re looking for the cleanest, most natural option, the winner is Vital Proteins Collagen Peptides Powder. Unlike traditional protein powder, collagen provides a cleaner and more bioavailable source of protein. It also offers additional health benefits beyond just muscle recovery.

Why Collagen is the Best Choice

Collagen is an incredible source of protein that supports not only muscle repair but also skin health, joint strength, and gut function.^[7] Unlike traditional whey or plant-based protein powders, collagen is a naturally occurring protein that doesn’t require additives, artificial sweeteners, or fillers. This makes it a superior choice for those looking to maintain a clean and non-toxic diet.

• Sourced from Grass-Fed, Pasture-Raised Cows
• Higher Protein Content Per Gram
• No Artificial Ingredients
• Supports Gut Health

If you’re serious about avoiding toxic ingredients while still meeting your protein needs, collagen peptides are the best option. With no fillers, artificial sweeteners, or questionable processing methods, this is the cleanest protein source available at Costco.

References:

1. Ritz, Eberhard, et al. “Phosphate Additives in Food—a Health Risk.” Deutsches Ärzteblatt International, vol. 109, no. 4, Jan. 2012, pp. 49–55.
2. DiNicolantonio, James J., and James O’Keefe. “The Importance of Maintaining a Low Omega-6/Omega-3 Ratio for Reducing the Risk of Autoimmune Diseases, Asthma, and Allergies.” Missouri Medicine, vol. 118, no. 5, 2021, pp. 453–59.
3. Ruiz-Ojeda, Francisco Javier, et al. “Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials.” Advances in Nutrition, vol. 10, no. Suppl 1, Jan. 2019, pp. S31–48.
4. Peteliuk, Victoria, et al. “Natural Sweetener Stevia Rebaudiana: Functionalities, Health Benefits and Potential Risks.” EXCLI Journal, vol. 20, Sept. 2021, pp. 1412–30.
5. Patel, Seema. “Emerging Trends in Nutraceutical Applications of Whey Protein and Its Derivatives.” Journal of Food Science and Technology, vol. 52, no. 11, Nov. 2015, pp. 6847–58.
6. Ikram, Ali, et al. “Nutritional and End‐use Perspectives of Sprouted Grains: A Comprehensive Review.” Food Science & Nutrition, vol. 9, no. 8, June 2021, pp. 4617–28.
7. Wu, Marlyn, et al. “Biochemistry, Collagen Synthesis.” StatPearls, StatPearls Publishing, 2025.