At the vanguard in choline research, as in much other research on the relationship between diet and performance, both mental and physical, is the U.S. Army. Even Napoleon knew that an army marches on its stomach, although if he were alive today he might update his famous dictum by declaring that an army thinks on its stomach, too. Can choline enhance the mental and physical skills of troops?
In Food Components to Enhance Performance, a groundbreaking report produced for the army by the National Academy of Sciences in 1994, researchers pulled together what's known about food and behavior.
Choline supplementation, the report concludes, enhances memory and reaction time in animals, particularly aging animals. It also enhances memory in people, scant human studies show. The most concrete evidence of the benefits of choline supplementation concern physical performance. Choline supplementation minimizes fatigue. In one study cited in the report, choline given during a 20-mile run improved running time by five minutes.
Army researchers are also looking at the effects of supplemental tyrosine, the amino acid that is the precursor to the neurotransmitters dopamine, epinephrine (or adrenaline), and norepinephrine (noradrenaline). All three help regulate levels of arousal and anxiety, and are the major players in the brain's response to stress. Environmental stress depletes the blood of tyrosine, limiting the amount available for neurotransmitter manufacture. Performance flags. But when given tyrosine supplements, soldiers exposed to high altitudes or prolonged cold do not suffer the loss of memory, lightheadedness, headache, nausea, and general malaise such stresses normally bring on.
Before you make the synaptic leap from megadosing with neurotransmitter precursors to cognitive superiority, consider this: All effects so far depend on the context. Neurotransmitter supplementation improves cognitive performance only in the face of a deficit caused by environmental stress or aging. No one yet knows whether supplementation can improve performance in people who have normal levels of neurotransmitter precursors. "Whether or not you'll sustain a benefit depends on where you start off," says Strupp. "If you have a deficit of a certain neurotransmitter precursor, then you may benefit."
To complicate matters, precursor amino acids normally compete with each other to cross the blood-brain barrier. If you eat a protein-rich meal, amino acids are delivered to the brain in an acceptable pattern. But when you take supplements of individual amino acids, in attempts to bolster a specific neurotransmitter, you monopolize the transport system. That may be counterproductive, throwing off the balance of neurotransmitters needed for all-around mental performance and well-being. To date, the best way to get the right mix of neurotransmitter precursors, along with other nutrients that are turned into brain chemicals, "is the way they come in food," says Strupp.
Still, taking extra choline may not hurt. Since it's not an amino acid, choline has no competition crossing from blood to brain, and therefore it doesn't interfere with the absorption of other nutrients. It seems to be safe in the doses used in studies -- around 5 grams per day -- according to Strupp. If you don't regularly eat egg yolks, organ meats, and legumes, you can get choline from lecithin. But keep in mind that choline is a fat and thus adds calories.
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