Buy pre-packaged cooking oil with an SC code; avoid bulk, unregulated homemade peanut oil

When peanuts get damp and moldy, they produce aflatoxin, a confirmed human carcinogen that primarily harms the liver. After Guangzhou tightened regulations on small-scale oil producers, the share of local residents who regularly consumed homemade peanut oil and had abnormal liver function fell by roughly 35%. In Guangxi, pregnant women who ate homemade peanut oil faced a nearly 90% higher risk of giving birth to babies with low birth weight, and an 80% higher risk of premature delivery.

The price difference isn’t huge if you shop elsewhere. Just check whether the packaging lists a food production licence number starting with “SC”. The real challenge is convincing older family members used to buying homemade oil.

Aflatoxin is a Group 1 carcinogen per the International Agency for Research on Cancer, meaning it definitely causes cancer, especially liver cancer. A Guangzhou study measured aflatoxin B1 levels in homemade peanut oil from small producers between 2010 and 2022. The median concentration was 1.29 μg/kg, with half of all samples falling between 0.12 and 6.58 μg/kg. After local rules for small producers took effect, toxin levels dropped by 2.865 μg/kg, then fell an additional 2.593 μg/kg each year. Concurrently, the proportion of local residents with abnormal liver function fell by 35% (PR 0.650, 95% CI 0.469–0.902). Another Guangxi study of 1,611 pregnant women found 81.7% ate homemade peanut oil; those women had a nearly 90% higher risk of bearing low birth weight babies (aOR 1.9, 95% CI 1.1–3.2) and an 80% higher risk of premature delivery (aOR 1.8, 95% CI 1.1–3.0).

Both studies were observational, non-randomised studies with no control groups. The Guangzhou study tracked liver function test results rather than incidence of liver cancer or mortality. The median aflatoxin level in homemade oil was actually below China’s legal limit of 20 μg/kg for peanut oil, so risk stems from long-term consumption and occasional batches with higher concentrations. This legal limit applies to all peanut oil, but pre-packaged oil must meet production licence and factory inspection requirements, while small producers are subject to far fewer routine checks under regional regulations. The main beneficiaries of this advice are you and your family members who eat with you.

Lei J, Li Y, Wang Y, 等 (2024). The impact of small food workshops management regulations on aflatoxin B1 in home-made peanut oil and the liver function of high-consumption area residents: an interrupted time series study in Guangzhou, China. Frontiers in Public Health, 12. https://doi.org/10.3389/fpubh.2024.1484414；Zhong Y, Lu H, Jiang Y, 等 (2024). Effect of homemade peanut oil consumption during pregnancy on low birth weight and preterm birth outcomes: a cohort study in Southwestern China. Global Health Action, 17. https://doi.org/10.1080/16549716.2024.2336312；IARC (2012). Chemical Agents and Related Occupations. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 100F. https://publications.iarc.fr/123；国家卫生计生委、国家食品药品监督管理总局 (2017). 食品安全国家标准 食品中真菌毒素限量（GB 2761-2017）