Are the proposed benefits of melatonin-rich foods too hard to swallow?

Melatonin has been proposed as a potent anti-oxidant and its presence in many plants and foods has been suggested to be beneficial for health. Indeed, the concentrations of melatonin in blood, and the melatonin metabolite 6 sulphatoxymelatonin in urine, have been found to increase significantly after ingestion of melatonin rich foods. In this review the studies have been critically evaluated in light of the reported plant melatonin concentrations and our knowledge of pharmacokinetics of orally administered pure melatonin. In the case of studies involving measurement of plasma melatonin following ingestion of beer or fruits the reported increases in melatonin are not consistent with the amount of melatonin ingested. Similarly the amount of melatonin metabolite excreted following ingestion of melatonin rich foods greatly exceed the amount ingested. It is concluded that studies reporting the appearance of melatonin in blood and its metabolites in urine following ingestion of melatonin rich foods are flawed. While there may be health benefits for certain foods it is difficult to accept that they are due to their low melatonin content.