Introduction
Mental function often declines particularly under conditions of stress or fatigue. In addition, most people age forty and older experience some memory loss, technically known as age-related cognitive decline or age-associated memory impairment. It is not known what causes this normal experience, and there is no conventional treatment available for it. A few natural treatments might be helpful.
Principal Proposed Natural Treatments
Statistically speaking, it is easier to demonstrate a big improvement than a small
one, and for that reason, it is more difficult to prove the effectiveness of a
treatment in a mild condition than in a severe one. Because of this, there is far
more evidence supporting the use of natural supplements for treating
Alzheimer’s
disease than for improving mental function in healthy people.
Nonetheless, there is some evidence for the latter.
Ginkgo biloba. An extract made from the herb Ginkgo
biloba is a well-established herbal treatment for Alzheimer’s disease.
Ginkgo may also be helpful for improving normal age-related
memory loss and even for enhancing mental function in younger people.
Age-related mental decline. In six of nine double-blind studies, the use of Ginkgo biloba extract significantly improved age-related mental decline compared with placebo. For example, in a double-blind, placebo-controlled trial, 241 elderly people complaining of mildly impaired memory were given either placebo or ginkgo for twenty-four weeks. The results showed that ginkgo produced modest improvements in certain types of memory.
Another double-blind, placebo-controlled trial examined the effects of ginkgo extract in forty men and women (age fifty-five to eighty-six years) who were not mentally impaired. In a six-week period, the results showed improvements in measurements of mental function. Benefits were seen in four other trials too, involving about 135 participants.
Set against these positive findings is a large (214 people) twenty-four-week study that found no benefit in ordinary age-related memory loss. It has been suggested that flaws in the trial’s design led to this negative outcome. However, three other studies enrolling about four hundred elderly persons also failed to find significant benefit with daily use of ginkgo. Another double-blind, placebo-controlled study used a one-time dose of ginkgo and found no benefits. Also, a small, double-blind, placebo-controlled study looking for immediate mind-stimulating effects did not find them.
Besides these negative trials, there is another weakness in the evidence. There are numerous measurable aspects of memory and mental function, and studies of ginkgo for improving memory and mental function have examined a great many of these. The exact areas of benefits seen vary widely. For example, in one positive study, ginkgo may speed up the ability to memorize letters but not expand the number of letters that can be retained, while in another positive study, the reverse may be true. This type of inconsistency tends to decrease the confidence one can place in these apparently positive studies, because if ginkgo were really working, one would expect its effects to be more reproducible. Ginkgo may help normal age-related memory loss, but more research is necessary to determine whether this is the case.
Improving memory and mental function in younger people. Several studies enrolling about 250 people have examined the effects of ginkgo on memory and mental function in younger people. However, the benefits seen in the positive trials were inconsistent, and the largest study failed to find any effect. One study hints that benefits may occur initially and then decline after several weeks.
Besides ginkgo alone, several double-blind, placebo-controlled studies evaluated
combined treatment with ginseng and ginkgo, or vinpocetine and ginkgo, for
enhancing mental function in young people, and most found some evidence of
benefit. Weak evidence suggests that combining phosphatidylserine with ginkgo
might increase its efficacy. However, in two studies, ginkgo combined with the
Ayurvedic herb brahmi failed to improve mental function.
Phosphatidylserine. Like ginkgo, the supplement phosphatidylserine (PS) is widely used in Europe to treat
various forms of dementia. There is some evidence that PS can also help people
with ordinary age-related memory loss.
In one double-blind study that enrolled 149 people with memory loss (but not dementia), PS provided significant benefits compared with placebo. Persons with the most severe memory loss showed the most improvement.
Another double-blind trial of 120 older people with memory complaints (but not dementia) found no benefits. This discrepancy may have to do with the type of PS used (the second trial used the more modern soy-derived form of the supplement). Phosphatidylserine might enhance the effectiveness of ginkgo.
Ginseng. Several studies have found indications that the herb
ginseng might enhance mental function. However, the specific
benefits seen have varied considerably from trial to trial, tending to make the
actual cognitive effects of ginseng (if there are any) difficult to discern.
For example, in a two-month, double-blind, placebo-controlled study of 112 healthy, middle-aged adults given either ginseng or placebo, results showed that ginseng improved abstract thinking ability. However, there was no significant change in reaction time, memory, concentration, or overall subjective experience between the two groups.
Another double-blind, placebo-controlled study of fifty men found that eight-week treatment with a ginseng extract improved ability to complete a detail-oriented editing task. A double-blind trial of sixteen healthy males found favorable changes in the ability to perform mental arithmetic in those given ginseng for twelve weeks.
More comprehensive benefits were seen in a double-blind, placebo-controlled trial of sixty elderly persons given fifty or one hundred days of treatment. The results showed that Panax ginseng produced improvements in numerous measures of mental function, including memory, attention, concentration, and ability to cope. Benefits were still evident at the fifty-day follow-up. However, virtually no improvement was seen in the placebo group, a result that is highly unusual and raises doubts about the accuracy of the study. Finally, four double-blind, placebo-controlled studies evaluated combined treatment with ginseng and ginkgo and found inconsistent evidence of improved mental function.
Bacopa monniera (brahmi). The Ayurvedic herb Bacopa
monniera (brahmi) has a traditional reputation
for improving memory. However, a twelve-week, double-blind, placebo-controlled
trial of seventy-six persons that tested the potential memory-enhancing benefits
of brahmi generally failed to find much evidence of benefit. The only significant
improvement seen among all the many measures used was one that evaluated retention
of new information. A randomized trial involving forty-eight healthy elderly
persons found some memory-enhancing effects of B. monniera
compared with placebo, but the outcomes measured were too numerous to be
convincing.
In another double-blind, placebo-controlled study of thirty-eight persons, short-term use of brahmi failed to produce any measurable improvements in memory, while in a third double-blind, placebo-controlled study, the use of brahmi over a two-week period did produce some benefits, but in quite a different pattern. Finally, a study found that one-time combined treatment with ginkgo (120 milligrams [mg]) and brahmi (300 mg) failed to improve mental function.
Slightly more promising results have been seen in studies of a proprietary
Ayurvedic mixture containing brahmi and about thirty other
ingredients. However, these studies were generally not up to modern scientific
standards.
Other Proposed Natural Treatments
On the basis of one small double-blind study, a proprietary mixture of substances called neuropeptides has been extensively marketed for improving mental function. Radio, television, and Web advertisements state that this product has been shown to bring about “a reversal of ten years of short-term memory decline.” However, this claim is not founded in reliable evidence. Another single study suggests that the supplement nicotinamide adenine dinucleotide might help improve temporary mental impairment caused by jet lag.
Evidence conflicts on whether multivitamin-multimineral tablets may improve cognitive function in people of various age groups. In general, the best-designed studies have failed to find benefit. However, it is quite possible that multivitamin-multimineral supplements are helpful for people with marked vitamin or mineral malnutrition. Studies of isoflavone-rich soy or red clover for enhancing mental function in women have found little to no beneficial effects at best.
Huperzine
A is a potent chemical derived from a particular type of club
moss (Huperzia serrata). This substance is really more a drug
than an herb, but it is sold over the counter as a dietary supplement for memory
loss and mental impairment. Some evidence indicates that it may be helpful for
Alzheimer’s disease and related conditions; very weak evidence suggests benefit
for healthy people. Much the same can be said about the substance vinpocetine.
Creatine, best known for its use as a sports-performance
enhancer, may improve mental function in sleep-deprived, but not necessarily
well-rested, young persons. Sage and vitamin B17 have slight supporting
evidence from preliminary double-blind trials.
Mild vitamin B12 deficiency may impair mental function. Because such deficiency is relatively common in the elderly, it has been suggested that vitamin B12 supplements may be appropriate in this age group. However, in the two studies that tried it, no benefits were seen.
The elderly are also commonly deficient in vitamin B6, but a review of the literature failed to find meaningful evidence that vitamin B6 offers any benefits. One study failed to find folate helpful either; however, in another study, folate supplementation improved mental function in older persons with high levels of homocysteine. Combinations of B vitamins, including B12, B6, and folate, have proved ineffective.
One study failed to find any benefit with zinc. Other preliminary double-blind trials suggest that the amino acid tyrosine may improve memory and mental function under conditions of sleep deprivation or other forms of stress. Other double-blind trials suggest that a proprietary extract of the herb Rhodiola rosacea may offer a similar benefit.
Whey protein contains alpha-lactalbumin, a protein that in turn contains high levels of the amino acid tryptophan. Tryptophan is the body’s precursor for serotonin and is thought to affect mental function. In a small double-blind study, the use of alpha-lactalbumin in the evening improved morning alertness, perhaps by enhancing sleep quality. Another small double-blind study found weak evidence that alpha-lactalbumin improved mental function in people sensitive to stress. A third study failed to find that alpha-lactalbumin significantly improved memory in women experiencing premenstrual symptoms.
Herbs that contain caffeine would be expected to enhance
mental function in healthy people, at least temporarily. These herbs include green
tea, black tea, maté, and guarana. For example, in a double-blind,
placebo-controlled study of 129 healthy young adults, the one-time use of
guarana plus vitamins and minerals improved mental function
and reduced mental fatigue among those undergoing a battery of cognitive tests. In
another double-blind, placebo-controlled study, the use of guarana alone or
guarana plus ginseng appeared to improve mental function. However, these studies
had some design problems. In two other studies, no benefits were seen.
Some reports suggested that declining levels of the hormone dehydroepiandrosterone (DHEA) cause impaired mental function in the elderly. On this basis, DHEA has been promoted as a brain-boosting supplement. However, large studies have failed to find any correlation between DHEA levels and mental function, and there is no direct evidence that DHEA supplements provide any benefit in the elderly. One study did find potential benefits in younger people.
Weak evidence culled from a large, double-blind, placebo-controlled study hints that the use of beta-carotene over many years might enhance mental function. However, long-term use of beta-carotene might present safety risks.
Other herbs and supplements that have been proposed for enhancing memory and mental function, but that lack meaningful supporting evidence, include gotu kola, rosemary, saffron, muira puama, sage, and lobelia. In one small double-blind study, the supplement ribose failed to prove effective for enhancing mental function. However, the researchers suggested that the dose they used (2 grams daily) may have been insufficient.
A large study failed to find that the use of vitamin E helped maintain healthy mental function in women older than age sixty-five years. Also, women who are marginally deficient in iron may experience improved mental function when they correct this deficiency. Carnitine has shown some benefit for reducing mental fatigue and enhancing cognitive function in centenarians.
Bibliography
Ataka, S., et al. “Effects of Oral Administration of Caffeine and D-Ribose on Mental Fatigue.” Nutrition 24 (2008): 233-238.
Balk, E. M., et al. “Vitamin B6, B12, and Folic Acid Supplementation and Cognitive Function.” Archives of Internal Medicine 167 (2007): 21-30.
Calabrese, C., et al. “Effects of a Standardized Bacopa monnieri Extract on Cognitive Performance, Anxiety, and Depression in the Elderly.” Journal of Alternative and Complementary Medicine 14 (2008): 707-713.
Crews, W. D., et al. “A Double-Blinded, Placebo-Controlled, Randomized Trial of the Neuropsychologic Efficacy of Cranberry Juice in a Sample of Cognitively Intact Older Adults.” Journal of Alternative and Complementary Medicine 11 (2005): 305-309.
Durga, J., et al. “Effect of Three-Year Folic Acid Supplementation on Cognitive Function in Older Adults in the FACIT Trial.” The Lancet 369 (2007): 208-216.
Fournier, L. R., et al. “The Effects of Soy Milk and Isoflavone Supplements on Cognitive Performance in Healthy, Postmenopausal Women.” Journal of Nutrition, Health, and Aging 11 (2007): 155-164.
Grodstein, F., et al. “A Randomized Trial of Beta Carotene Supplementation and Cognitive Function in Men: The Physicians’ Health Study II.” Archives of Internal Medicine 167 (2007): 2184-2190.
Hvas, A. M., et al. “No Effect of Vitamin B-12 Treatment on Cognitive Function and Depression.” Journal of Affective Disorders 81 (2004): 269-273.
Kang, J. H., et al. “A Randomized Trial of Vitamin E Supplementation and Cognitive Function in Women.” Archives of Internal Medicine 166 (2006): 2462-2468.
Kennedy, D. O., C. F. Haskell, et al. “Improved Cognitive Performance and Mental Fatigue Following a Multi-vitamin and Mineral Supplement with Added Guarana (Paullinia cupana).” Appetite 50 (2008): 506-513.
Kennedy, D. O., P. A. Jackson, et al. “Modulation of Cognitive Performance Following Single Doses of 120 mg Ginkgo biloba Extract Administered to Healthy Young Volunteers.” Human Psychopharmacology 22 (2007): 559-566.
Kennedy, D. O., S. Pace, et al. “Effects of Cholinesterase Inhibiting Sage (Salvia officinalis) on Mood, Anxiety, and Performance on a Psychological Stressor Battery.” Neuropsychopharmacology 31 (2006): 845-852.
Kritz-Silverstein, D., et al. “Effects of Dehydroepiandrosterone Supplementation on Cognitive Function and Quality of Life.” Journal of the American Geriatrics Society 56 (2008): 1292-1298.
McNeill, G., et al. “Effect of Multivitamin and Multimineral Supplementation on Cognitive Function in Men and Women Aged Sixty-Five Years and Over.” Nutrition Journal 6 (2007): 10.
Malaguarnera, M., et al. “L-carnitine Treatment Reduces Severity of Physical and Mental Fatigue and Increases Cognitive Functions in Centenarians.” American Journal of Clinical Nutrition 86 (2007): 1738-1744.
Markus, C. R., et al. “Evening Intake of Alpha-lactalbumin Increases Plasma Tryptophan Availability and Improves Morning Alertness and Brain Measures of Attention.” American Journal of Clinical Nutrition 81 (2005): 1026-1033.
Maylor, E. A., et al. “Effects of Zinc Supplementation on Cognitive Function in Healthy Middle-aged and Older Adults.” British Journal of Nutrition 96 (2006): 752-760.
Murray-Kolb, L. E., and J. L. Beard. “Iron Treatment Normalizes Cognitive Functioning in Young Women.” American Journal of Clinical Nutrition 85 (2007): 778-787.
The NEMO Study Group. “Effect of a Twelve-mo Micronutrient Intervention on Learning and Memory in Well-Nourished and Marginally Nourished School-Aged Children.” American Journal of Clinical Nutrition 86 (2007): 1082-1093.
Rawson, E. S., et al. “Creatine Supplementation Does Not Improve Cognitive Function in Young Adults.” Physiology and Behavior 95 (2008): 130-134.
Van Uffelen, J. G., et al. “Walking or Vitamin B for Cognition in Older Adults with Mild Cognitive Impairment?” British Journal of Sports Medicine 42 (2008): 344-351.
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