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MAASTRICHT, THE NETHERLANDS. People who are constantly exposed to stress tend to experience a
decline in their ability to learn and memorize things (cognitive performance). It is believed that this effect is
caused by the fact that chronic stress reduces brain serotonin levels. Serotonin is formed from tryptophan
supplied by the diet. Tryptophan competes with other large amino acids for entry to the brain so a diet high
in protein may actually lead to lower tryptophan concentrations. Researchers at Maastricht University now
report that consuming a meal containing alpha-lactalbumin, a whey protein with a high tryptophan content,
increases the ratio of tryptophan to other large amino acids in the blood stream and improves cognitive
performance in stress-vulnerable people.
Their double-blind, placebo-controlled, crossover study included 23 students who were highly vulnerable to
stress and 29 who were not. The participants consumed a diet (breakfast, snack and brunch) containing
either whey protein or sodium caseinate (control). One and a half hours after brunch they had a blood
sample taken and were then seated in front of a computer and exposed to a cognitive performance test.
Blood analysis showed that the ratio of tryptophan to other large amino acids was 43 per cent greater after
the whey diet than after the control diet. It was also clear that stress-vulnerable participants on the whey
diet performed much better on the cognitive tests than did those on the control diet. No difference in
performance was noted for the low stress vulnerability group.
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