Propylene Glycol vs Neotame: which is worse?

What is Propylene Glycol?

Propylene glycol is a synthetic organic compound used as a humectant, solvent, and emulsifier in food, pharmaceuticals, cosmetics, and industrial applications. It is produced from propylene oxide (derived from petroleum). Its chemical formula is C3H8O2.

What is Neotame?

Neotame is a synthetic dipeptide sweetener — a derivative of aspartame with a 3,3-dimethylbutyl group added to block aspartame's metabolism, preventing the release of phenylalanine. This means it is safe for people with phenylketonuria (PKU), unlike aspartame. It is approximately 7,000-13,000 times sweeter than sucrose.

Documented risks

Propylene Glycol: Propylene glycol is generally considered safe by the FDA and is metabolized by the liver to lactic acid and pyruvate (normal metabolites). However, at high doses — particularly from intravenous pharmaceutical formulations — propylene glycol can accumulate and cause lactic acidosis, kidney toxicity, and CNS effects. These effects are seen in critically ill patients receiving high-dose PG-containing intravenous medications, not from food consumption. In children and people with impaired liver or kidney function, PG accumulation may occur at lower doses than in healthy adults. Animal studies have found reproductive and developmental effects at high doses. EFSA's 2018 re-evaluation found no concerns at typical food use levels but noted the EU limits PG use as a direct food additive, using it only as a carrier solvent for permitted additives.

Neotame: Neotame is one of the newer synthetic sweeteners with a shorter safety track record. A 2023 study published in Frontiers in Nutrition found that neotame damaged intestinal epithelial cells in vitro and disrupted the gut microbiome in mice — including reducing beneficial bacteria and increasing bacterial invasion of intestinal cells. The study observed effects at concentrations that could be achievable through high consumption of neotame-containing products. The FDA has set an ADI of 0.3 mg/kg/day, one of the lower sweetener ADIs, reflecting a conservative safety margin. Limited long-term human safety data exist compared to aspartame, acesulfame K, or saccharin, which have been used for decades. EFSA's 2010 opinion found no safety concern at permitted levels. The Frontiers in Nutrition 2023 gut study represents new concerning findings that warrant further investigation.