Aspartame vs Partially Hydrogenated Oils: which is worse?

What is Aspartame?

Aspartame is a low-calorie synthetic dipeptide sweetener composed of two amino acids — phenylalanine and aspartic acid — bonded with methanol. When metabolized, it breaks down into these three components. It is approximately 200 times sweeter than sucrose, so tiny amounts provide significant sweetness with almost no calories.

What is Partially Hydrogenated Oils?

Partially hydrogenated oils (PHOs) are vegetable oils that have been treated with hydrogen gas in the presence of a catalyst to make them semi-solid at room temperature. This process creates artificial trans fatty acids (trans fats) as a byproduct. They were developed in the early 20th century as a cheaper, longer-lasting alternative to lard and butter.

Documented risks

Aspartame: Aspartame has been one of the most studied food additives in history, with over 200 regulatory studies reviewed by multiple agencies. The FDA and EFSA have repeatedly reaffirmed its safety at permitted levels for the general population. IARC classification controversy (2023): In July 2023, IARC classified aspartame as Group 2B (possibly carcinogenic to humans), based primarily on limited evidence from human epidemiological studies associating aspartame intake with hepatocellular carcinoma (liver cancer) in some observational studies. Notably, the WHO Joint Expert Committee on Food Additives (JECFA) simultaneously re-evaluated aspartame and maintained the ADI at 40 mg/kg/day, concluding that the evidence does not establish that aspartame causes cancer at typical intake levels. This rare split between IARC (hazard identification) and JECFA (risk assessment) created significant public confusion. Phenylketonuria (PKU): Aspartame is definitively harmful for individuals with phenylketonuria — a genetic disorder affecting phenylalanine metabolism. People with PKU cannot process phenylalanine normally, and aspartame consumption can cause severe neurological damage. This is why all aspartame-containing products must carry a PKU warning on US and EU labels. Methanol release: aspartame metabolism releases methanol (~10% by weight). Critics including independent researcher Woodrow Monte have argued that methanol from aspartame is harmful, citing methanol's conversion to formaldehyde and formic acid in the body. However, methanol released from aspartame is a fraction of the methanol obtained from fresh fruit juices, and regulatory agencies consider the amounts released too small to be clinically significant. Gut microbiome concerns: a 2021 Cell study found that aspartame and other sweeteners altered gut microbiome composition and glucose tolerance in humans. These microbiome effects are an emerging area of research.

Partially Hydrogenated Oils: Artificial trans fats (from PHOs) have the most well-established cardiovascular harm of any food ingredient ever banned. Multiple large meta-analyses have confirmed that trans fat consumption increases LDL ('bad') cholesterol, decreases HDL ('good') cholesterol, increases inflammatory markers, and significantly raises cardiovascular disease risk. The Harvard Nurses' Health Study and other landmark prospective studies in the 1990s identified trans fat as uniquely harmful — worse than saturated fat in its cardiovascular effects. A 2006 NEJM meta-analysis by Mozaffarian et al. estimated that eliminating artificial trans fats from the US diet could prevent 72,000 to 228,000 heart attacks per year and 30,000 to 100,000 coronary heart disease deaths annually. The WHO estimates that industrially produced trans fats cause over 500,000 cardiovascular deaths per year globally. The FDA revoked PHOs' GRAS status in 2015 based on this evidence, with compliance by 2018. Denmark banned artificial trans fats in 2003, the first country to do so, and observed a dramatic reduction in cardiovascular mortality in subsequent years.