People who want to have a sharp memory when they grow old might want to think twice before taking that next bug bite of doughnut. The sweet treat is not really to blame for poor memory but high levels of sugar in the blood, according to a new study.

Individuals with high levels of blood sugar are at a higher risk of having memory problems, based on the finding of a study published on the journal Neurology, the official journal of the  American Academy of Neurology. The study was conducted by German researchers, led by Dr. Agnes Floel from the Charite-University Medicine in Berlin.

"Our results indicate that even in the absence of manifest type 2 diabetes mellitus or impaired glucose tolerance, chronically higher blood glucose levels exert a negative influence on cognition, possibly mediated by structural changes in learning-relevant brain areas," the study said.

"Therefore, strategies aimed at lowering glucose levels even in the normal range may beneficially influence cognition in the older population, a hypothesis to be examined in future interventional trials," it added.

The research involved 140 healthy subjects aged between 50 and 80 years old who did not have any genetic predisposition to memory loss and no history of pre-diabetes or diabetic conditions. They were given memory tests where they were asked to read a list of words and asked to recall as many as they can.

The proponents found out that when an individual's hemoglobin A1C, a blood test that reflects the average blood sugar level of a patient in the last two or three months, climbed from five percent to 5.6 percent, the subjects tend to recall fewer words. The numbers represent the normal blood sugar level and what is considered as pre-diabetes by the medical community, respectively.

The effects may not be that huge, but are still significant.

"Elevated blood sugar levels damage small and large vessels in the brain, leading to decreased blood and nutrient flow to brain cells," explained Floel in a statement to the public radio site of the University of Tennessee-Chattanooga . The doctor also reiterated that high blood sugar levels "may impair the functioning of brain areas like the hippocampus, a structure particularly relevant for memory."

The hippocampus is the area of the human brain responsible for long-term and short-term memory. Damage to the hippocampus leads to problems in forming new or recalling old memories, both forms of amnesia.

"Consuming a diet rich in fiber, vegetables, fruit, fish, and whole-grain products," recommended Floel to control one's blood sugar level.