Do Aspergillus fungi produce aflatoxins that enter the diet?

Aflatoxins are foodborne fungal toxins of major health relevance because aflatoxin B1 (AFB1) is among the most potent genotoxic carcinogens. The claim is strongly supported, with important species-, strain-, and commodity-specific qualifications.

Fungal production and mechanisms

• Aflatoxigenic Aspergillus produce AFB1; most toxin-producing A. flavus strains produce B-type aflatoxins, while A. parasiticus is well documented to produce both B- and G-type aflatoxins, including AFB1 and aflatoxin G2 (AFG2).
• AFG2 is not formed by conversion of AFB1. These compounds arise from divergent late biosynthetic branches: dihydro-O-methylsterigmatocystin is a precursor of AFG2, whereas O-methylsterigmatocystin is associated with AFB1 formation.
• The G-aflatoxin branch requires the cytochrome-P450 enzyme CypA. cypA disruption abolishes G-aflatoxin production while retaining B-aflatoxin production. Many A. flavus isolates have norB/cypA alterations that limit effective G-aflatoxin synthesis; toxin output also depends on isolate, growth medium, and temperature.

Dietary exposure and health relevance

• Consumption of contaminated cereals/grains, groundnuts and tree nuts, and spices is an established human exposure route recognized by EFSA, WHO, and JECFA. AFB1 is the most common aflatoxin detected in foods.
• Exposure is not uniform: concentrations and prevalence vary substantially by region, commodity, and lot. Nuts have particularly developed occurrence data, while cereal and spice contamination is also documented.
• Regulatory limits for AFB1 and total aflatoxins in cereals and specified spices reflect the controllable dietary nature of this exposure. Reliable testing requires representative sampling, grinding, and homogenization because contamination is highly heterogeneous.
• Aflatoxin–albumin adducts are validated biomarkers that can indicate human exposure alongside dietary assessment.

Bottom line

• The statement is accurate: aflatoxigenic Aspergillus, especially A. flavus and A. parasiticus, produce AFB1 and, particularly for A. parasiticus, AFG2; contaminated grains, nuts, and spices are recognized dietary sources of human aflatoxin exposure.