In 15 healthy adults, three weeks of daily mixed-nut consumption (30 g almonds, macadamias and pistachios) increased faecal lipid content and led to lipid-containing nut particles in stool, with only modest microbiota changes, suggesting that some nut cells reach the large intestine intact.
Lipid-containing nut particles were seen in faecal samples after nut consumption but not during nut abstinence.
Mixed nut consumption significantly increased total faecal lipid content compared with nut abstinence.
Faecal pH, dry matter, ash content, short-chain fatty acids and ammonium concentrations were not significantly altered by nut consumption.
Gut microbial community composition varied substantially between individuals, with only modest differences associated with nut consumption.
Predicted functional profiling suggested differences in lipid metabolism-related pathways between nut and abstinence periods.
The authors conclude that a portion of consumed nut cells likely reaches the large intestine intact, where encapsulated lipids may become available to colonic microbiota after cell wall degradation.
This study asked what happens to the fat in nuts once they are eaten, and whether it affects gut bacteria. Fifteen healthy adults ate 30 g of mixed nuts (almonds, macadamias and pistachios) daily for three weeks and avoided nuts for another three weeks, in a cross-over design, while otherwise eating as usual. During the nut period, stool samples contained visible fat-containing nut particles and had more total fat than during the nut-free period. This suggests that some nut fat is not fully digested or absorbed, probably because it stays inside intact nut cells that reach the large intestine. Other stool measures, including pH, dry matter, ash, short-chain fatty acids and ammonium, did not change significantly. Gut bacterial communities differed greatly from person to person, and nut eating was linked to only modest changes. Computer-based predictions hinted at differences in fat-related bacterial functions. This research suggests that nuts may deliver some fat to gut microbes, but the study was small, and the functional results were predicted rather than directly measured, so the health implications remain unclear.
Bermudez C, Horsman S, Flanagan B, Williams B, Yao H, Gidley M, et al.. (2026). Impact of mixed nut consumption on faecal lipid content and gut microbiota composition in healthy adults.. Food & function. https://doi.org/10.1039/d6fo00599c