Science News - February 26, 2011

test scores and mood contained just 4 to 9 milligrams of caffeine. “That’s only about a tenth as much as you’d find in a cup of coffee,” Kennedy points out. “So guarana was doing something that wasn’t attributable to its caffeine” — although his team doesn’t yet know what.

He and colleagues have also been investigating other natural products that might elevate energy, attention and mental performance. Among these: Chinese ginseng (Panax ginseng). Young adults scored better on a battery of mental tests— including serial subtraction of numbers in their heads— and exhibited less mental fatigue after getting this herbal supplement rather than a placebo.

How Chinese ginseng may improve performance is unknown, but Kennedy suspects the effect might have to do with ginseng’s ability to moderate blood sugar levels. At least at the 200-milligram dose used by his group, this supplement caused a drop in blood-glucose levels one hour after consumption.

Researchers report that American ginseng (P. quinquefolius) also shows promise. Compared with a placebo, all doses improved some aspect of cognition, Swinburne’s Andrew Scholey and colleagues report in October in Psychopharmacology. One difference: This herbal supplement had no effect on blood glucose.

The Northumbria researchers are also exploring the idea that some natural products bolster brain function by affecting blood flow. For instance, if they dilate vessels, the products might allow more fuel — glucose — in to power brain activities. Kennedy and colleagues tested the idea by giving 30 students a cup of cocoa on three mornings. Each day’s formulation contained a different amount — 46, 520 or 994 milligrams per serving — of cocoa flavanols, natural agents that have antioxidant and sometimes heart-healthy properties.

The cocoa packages used in the study were prepared by Mars, a candy company that has been exploring health attributes of some chocolate products.

Both higher-dose formulations,
especially the middle one, improved
performance during mentally challeng-
ing tests involving math and the visual
processing of information, the scientists
report. At the same time, the college stu-
dents receiving the middle dose reported
a reduction in mental fatigue. Maxi-
mum benefits showed up two hours into
testing, which roughly corre-
sponds to the expected peaks
in concentrations of flavanols
in the blood and in blood flow
to the brain, Kennedy’s team
reported in the October Jour-
nal of Psychopharmacology.