Lunar variations in the nutrient intakes and the meal patterns of humans were investigated by reanalyzing the data previously collected by paying 694 adult humans to maintain a 7-day diary of everything they ate, when they ate it, and their subjective state of hunger. A small but significant lunar rhythm of nutrient intake was observed with an 8% increase in meal size and a 26% decrease in alcohol intake at the time of the full moon relative to the new moon. This effect was present for meals ingested either during the daytime or the evening, indicating that nocturnal illumination level was not the critical variable. The results suggest that there is a true internal lunar rhythm which influences nutrient intakes of normal humans free-living in their natural environments.