The best protein powder delivers at least 20 grams of protein per serving with minimal filler, a complete amino acid profile, and ideally a third-party testing seal on the label. Beyond that, the right choice depends on your goals, your gut, and how carefully you read the ingredient list. Here’s what actually matters when you’re comparing options.
Protein Type Shapes Your Results
Not all protein sources build muscle equally. Whey protein (derived from milk) is digested quickly and contains high levels of leucine, the amino acid most responsible for triggering muscle repair and growth. You need roughly 2 to 3 grams of leucine per serving to maximally stimulate that process, and whey delivers that more reliably than most plant sources. For adults over 65, hitting the higher end of that leucine range matters more, since aging muscles require a stronger signal to start rebuilding.
Plant proteins can absolutely work, but they come with trade-offs worth knowing about. Pea protein contains eight of the nine essential amino acids but runs low in methionine. Hemp protein is low in both lysine and leucine. Soy protein does contain all essential amino acids, though research shows it produces a slightly weaker muscle-building response than whey, likely due to slower digestion and a less favorable amino acid ratio. The workaround: blends that combine pea and rice protein tend to fill in each other’s gaps and deliver a complete amino acid profile comparable to whey.
If you’re choosing plant-based protein for dietary or ethical reasons, look for a blend rather than a single-source powder, and check the label for at least 2 grams of leucine per serving.
How Much Protein You Actually Need
Revised dietary guidelines now recommend 1.2 to 1.6 grams of protein per kilogram of body weight daily, a notable increase from the older recommendation of 0.8 grams per kilogram. For a 70-kilogram (154-pound) person, that’s 84 to 112 grams per day. If you’re actively losing weight, especially on a weight-loss medication, aiming for the higher end (1.6 grams per kilogram) helps preserve lean muscle mass.
A protein powder serving typically delivers 20 to 30 grams, which means it’s filling a gap in your diet rather than replacing whole meals. When comparing products, check the protein-per-serving number against the total serving size in grams. A powder that lists 25 grams of protein in a 35-gram scoop is mostly protein. One that lists 20 grams in a 50-gram scoop is mostly filler. That ratio tells you more than almost anything else on the label.
Read the Ingredient List, Not Just the Label
Protein powders are allowed to contain a surprising amount of non-protein ingredients. Some are harmless. Others are worth avoiding depending on your health.
Maltodextrin is a cheap, highly processed starch filler that spikes blood sugar quickly. It’s broken down into glucose and absorbed rapidly in the gut. If you have prediabetes or diabetes, or you’re using protein powder to manage hunger between meals, maltodextrin works against you. Animal studies also suggest it can disrupt the gut microbiome and promote intestinal inflammation.
Guar gum and xanthan gum are thickeners that give protein shakes a smoother texture. Guar gum acts as a soluble fiber that can slow digestion and moderate blood sugar spikes, which sounds beneficial. But in higher amounts, both gums can cause gas, bloating, cramping, and diarrhea, particularly if you’re sensitive to dietary fiber. Xanthan gum can have a laxative effect in large quantities.
Cellulose gum passes through the body undigested, adding bulk to stool. Animal studies have linked it to increased intestinal inflammation and changes in the gut microbiome, raising concerns for people with inflammatory bowel conditions.
A shorter ingredient list is generally better. The core ingredients should be the protein source, maybe a natural sweetener, and minimal else. If you see a long list of gums, fillers, and additives you can’t pronounce, that’s a product optimized for texture and shelf life rather than nutrition.
Heavy Metals Are a Real Concern
Independent lab testing has consistently found measurable levels of lead, cadmium, and arsenic in protein powders. This isn’t a fringe worry. Plant-based protein powders contain roughly nine times the lead found in whey-based products, and about twice as much as beef-based options. The reason: plants absorb heavy metals from soil, and concentrating those plants into a powder concentrates the metals too.
Consumer Reports testing found that two out of 23 tested products exceeded safe daily limits for cadmium (4.1 micrograms per day by their standard), and one exceeded their arsenic threshold of 7 micrograms per day. The FDA sets slightly higher limits at 5 micrograms for cadmium and 15 for arsenic, but even at those thresholds, some products come uncomfortably close.
This doesn’t mean plant protein is dangerous, but it means brand choice matters more than usual. Look for products that publish third-party heavy metal testing results. If you use a plant-based powder daily, rotating brands periodically can reduce your cumulative exposure to any single contaminant source.
Third-Party Testing Certifications
Protein powders in the United States are classified as dietary supplements, which means they don’t require FDA approval before going to market. The manufacturer is responsible for safety and accuracy, with no one checking their work unless a problem surfaces. Third-party certifications fill that gap.
The two most recognized seals are NSF Certified for Sport and Informed Sport (sometimes labeled Informed Choice). Both programs test for banned substances flagged by the World Anti-Doping Agency, as well as contaminants and label accuracy. Informed Sport and Informed Choice use identical testing procedures through ISO 17025 accredited labs. NSF Certified for Sport follows a similar scope. If you’re a competitive athlete subject to drug testing, one of these seals is essentially non-negotiable.
Even if you’re not an athlete, these certifications confirm that what’s on the label matches what’s in the tub, and that contaminant levels fall within acceptable ranges. A product without any third-party seal isn’t necessarily bad, but you’re taking the manufacturer’s word for it.
Digestive Enzymes and Gut Comfort
If whey protein gives you gas, bloating, or cramps, you’re likely reacting to the lactose it contains. Some protein powders now include digestive enzymes to address this. The most relevant one splits lactose into two simpler sugars your body can absorb without fermentation in the gut. That fermentation is what causes the discomfort.
Some products go further and include enzymes that break down protein and fat molecules, supporting more complete digestion. This combination can improve amino acid absorption and reduce the heavy, sluggish feeling some people get after a protein shake. If you tolerate dairy well, these enzymes aren’t necessary. If you don’t, they can make the difference between a protein powder you can actually use daily and one that sits in your cabinet.
Whey isolate is another option for lactose-sensitive stomachs. The extra filtration step removes most of the lactose, leaving a higher percentage of pure protein per scoop. It costs more than whey concentrate but causes fewer digestive issues for most people.
Sweeteners and Flavor Additives
Most flavored protein powders use either sugar, artificial sweeteners like sucralose and acesulfame potassium, or sugar alcohols like erythritol and stevia. Each comes with a trade-off. Added sugar increases calories and can spike blood sugar. Artificial sweeteners are calorie-free but can cause bloating in some people, and their long-term gut health effects are still debated. Stevia and monk fruit extract are the most neutral options for most people, though they can have a bitter aftertaste at higher concentrations.
Unflavored protein powder avoids all of these issues and gives you control over taste by blending with fruit, cocoa, or other whole foods. It’s the cleanest option if you’re willing to experiment with your own recipes.
A Quick Checklist for Comparing Products
- Protein per scoop vs. scoop size: aim for at least 70% of the serving weight to be actual protein
- Complete amino acid profile: all nine essential amino acids, with at least 2 grams of leucine per serving
- Short ingredient list: protein source first, minimal gums and fillers, no maltodextrin
- Third-party certification: NSF Certified for Sport, Informed Sport, or Informed Choice
- Heavy metal transparency: published testing results, especially for plant-based powders
- Sweetener type: check whether the sweetener matches your preferences and tolerance
- Digestive enzymes: helpful if you’re lactose-sensitive and choosing whey