LabDoor analyzed 74 best-selling protein supplements in the United States. Our analysis quantified protein, fat, sugar, cholesterol, calcium, sodium, lead, cadmium, arsenic, and mercury content and recorded presence/absence data for 63 inactive ingredients.
Our scientists recorded 17 variations of protein sources, featuring the fast-digesting whey varieties (indicated for exercise recovery), protein blends (indicated for meal replacement), soy and casein sources (indicated for sustained protein supplementation), and several forms of plant-based proteins, including hemp seed, pea, and brown rice (typically appropriate for those sensitive to dairy/soy or for those observing a vegan/vegetarian diet).
In a surprising find, over 52% of products recorded measurable amounts of free-form amino acids, which spike protein content in standard laboratory tests but add little nutritional benefit (beyond physiologically appropriate proportions). Asparagine was the most commonly spiked amino acid (15/74 products), followed by alanine (11/74), glycine (8/74), taurine (8/74), and leucine (7/74). Histidine, glutamine, alanine, cysteine, and taurine were the highest-risk amino acids, recording the most severe spikes in our batch analysis, respectively.
All protein powders tested in this batch passed our heavy metals screens for arsenic, lead, cadmium, bismuth, antimony, and silver (below 1 part per million). However, controversial artificial sweeteners, including Aspartame and Acesulfame Potassium, preservatives (Benzoic Acid), and artificial colors (FD&C Yellow 5, FD&C Blue 1, and FD&C Red 40) were commonly found in tested protein supplements.