Lack of adverse effects in a subchronic 90-day oral toxicity study of almond hull powder in Sprague-Dawley rats

Almond hulls (AH) are a by-product of almond production, contain bioactive compounds with potential health benefits. This study evaluated the subchronic toxicity of AH in a 90-day oral toxicity study following OECD Guideline 408. Sprague-Dawley rats (96 total, 48 per sex) were assigned into four groups and fed diets containing AH at concentrations of 0 %, 0.625 %, 1.25 %, and 2.5 %, equivalent to doses of 0, 500, 1000, and 2000 mg/kg body weight/day. Rats were observed daily for clinical signs, with body weight and food consumption were recorded weekly. At the end of the study, hematology, clinical biochemistry, organ weights, and histopathology were assessed. No treatment-related adverse effects were observed in any group, including no changes in clinical signs, body weight, food consumption, or motor activity. Hematology and biochemical parameters were within normal ranges, and histopathology showed no abnormalities. The no-observed-adverse-effect level (NOAEL) for AH was determined to be 2.5 %, the highest dose tested, equivalent to 2000 mg/kg body weight/day. These findings confirm the safety of AH as a functional food ingredient. Combined with previous evidence showing no genotoxicity at doses up to 5000 mg/kg, AH is considered safe for human consumption at levels exceeding 322.58 mg/kg/day based on body weight.