Researchers warn that the compound found in cocoa exists in small amounts in the average chocolate bar. (Dayna Smith for The Washington Post)

In case anyone needed another reason to love chocolate, a new study suggests that a natural compound found in cocoa, tea and some vegetables can reverse age-related memory loss.

The findings suggest that the compound increases connectivity and, subsequently, blood flow in a region of the brain critical to memory, the researchers said.

The study — published online Sunday in Nature Neuroscience and partly financed by a chocolate company — found that flavanols reverse mild memory loss in older adults. Using brain scans and memory tests, the latest study built on previous work showing that flavanols extracted from cocoa beans had improved neuronal connections in mice’s dentate gyrus, a part of the brain involved in memory formation.

But hold that chocolate bar. The researchers also warn that the compound found in cocoa exists only in minuscule amounts in the average chocolate bar compared with the amount used in the study, so gorging on chocolate in the name of health and improving one’s memory could backfire.

“It would make a lot of people happy, but it would also make them unhealthy,” Scott A. Small, a professor of neurology and director of the Alzheimer’s Disease Research Center at the Taub Institute at Columbia University Medical Center, said Friday.

Small said that even more important, the new study offers the first direct evidence that memory deteriorates with age because of changes in the dentate gyrus, a region of the hippocampus. Previous studies had shown a link between changes in this region of the brain and normal, age-related memory loss, but the Columbia University study asserts a causal link.

“It more firmly establishes that this is the anatomical source of age-related memory loss,” Small, the study’s senior author, said. He said the study also offered yet more evidence that diet and healthy lifestyles that increase blood flow to the brain can slow or reverse age-related cognitive decline.

The study involved 37 healthy subjects who ranged in age from 50 to 69. On a random basis, they were given either a high-flavanol diet, consuming 900 milligrams a day, or a low flavanol diet, consuming 10mg per day. Brain scans, which measure blood volume in the dentate gyrus, and memory tests were used to evaluate the effect of the diet. Small said the typical candy bar contains about 40mg of flavanols.

Researchers said that if a person had the memory of a typical 60-year-old at the beginning of the study, after three months, on average, that person’s memory would function more like a 30- or 40-year-old’s. The researchers also cautioned that more work is needed because of the study’s small sample size.

The compounds appear to enhance connectivity and metabolic activity in the dentate gyrus. Aging appears to reduce the synapses, or connections, between neurons in that part of the brain. That decline, however, is not related to severe memory loss and cell death in Alzheimer’s disease or other dementias, Small said.

Most cocoa-processing methods in use today remove many of the flavanols found in cocoa. But the chocolate maker Mars produced a cocoa flavanol test drink specifically designed for the research, which the company also subsidized.