C4 Whey Protein Powder (Reese's Peanut Butter & Chocolate)

Carboxymethylcellulose was the second emulsifier (with polysorbate 80) in Chassaing et al. 2015 (Nature, PMID 25731162), which showed mucus-barrier thinning, a microbiota shift toward pro-inflammatory species, low-grade inflammation, and metabolic syndrome in mice. Chassaing 2022 (Gastroenterology, PMID 34774538) tested CMC directly in a randomized controlled human feeding trial and found reduced microbial diversity and bacterial encroachment into the normally sterile mucus layer in a susceptible subset of participants. EFSA's 2018 re-evaluation could not establish a safe level due to data gaps. For a purely textural excipient, the gut-barrier risk profile is unfavorable when safer thickeners are widely available.

Dose context matters. As a trace excipient in a tablet coating or capsule, the amount is minimal and not a meaningful concern. The evidence below applies to the gram-level intakes typical of sweetened protein powders, pre-workouts, and drink mixes: a 2022 human trial (Suez et al., Cell) showed sucralose disrupts gut bacteria and worsens blood sugar control in healthy adults, and a 2023 study (Schiffman et al.) found that sucralose-6-acetate — a compound formed when sucralose is digested — was genotoxic to human cells in vitro. It remains an artificial sweetener with no nutritional purpose.

Older NTP rodent studies (1980s, contested) reported lymphoma and leukemia at very high chronic doses; modern reviews (FDA 2003, EFSA 2000) concluded no cancer risk at human exposure levels but the issue is not fully resolved (Mishra 2020 review). Animal evidence suggests gut microbiome disruption (Bian 2017 — male mice on Ace-K showed altered microbiota and metabolic markers). Manufacturing uses methylene chloride, with potential residue concerns. Purely cosmetic additive — risk:benefit unfavorable for supplements.

Basic food-grade salt used for taste in supplements

Non-GMO, non-allergenic emulsifier derived from sunflower seeds

Natural thickener from fermented carbohydrates