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Oestrogens
Oestrogen hormonal replacement therapy in postmenopausal women has shown some benefits. It protects against decline in verbal memory and decreases the risk of developing Alzheimer’s disease. However, research studies have shown inconsistent results and currently this is not a widely recommended strategy for cognitive preservation. A recent study has shown that hormone replacement therapy, together with habitual exercise, improves cardiovascular function. This study indicated that the walls of arteries were thinner which led to improved circulation. This may be helpful in vascular conditions of the brain.
Ginkgo biloba
Ginkgo biloba shows promising evidence for improvement of cognition, but larger research trials are needed. Ginkgo has shown an improvement of age associated memory decline and some improvement of memory and other cognitive functions in dementia. The drug has also shown benefits in intermittent claudication. This is a condition of painful lower legs after exercise and is due to poor blood supply in the lower limbs. Ginkgo has also shown possible benefits for cardiovascular disease. Patients who also take warfarin and aspirin are advised to discuss their treatment with their doctor, as Ginkgo increases bleeding times. The dose of Ginkgo required for cognitive benefits are varied. Studies with dosages below 200 mg/day and above, have proven beneficial.
Arginine
Arginine is a precursor in the synthesis of nitric oxide. This biosynthetic pathway is involved in memory function. Some studies have evaluated Arginine in dementia, but no conclusive proof exists that Arginine has any beneficial effect.
Brahmi
An extract of Bacopa monnieri (Brahmi) has been examined for its possible beneficial effects on cognitive function in humans and animals. Preliminary results suggest that Brahmi may improve higher order cognitive processes, which include learning and memory. Brahmi seems to decrease the rate of forgetting newly required information.
Carnitine
L-acetylcarnitine (carnitine) has been studied in older adults with mild cognitive decline. A single blind study showed significant improvement of memory and psychological symptoms during treatment with carnitine. Other reports indicate that this medication may be useful in the treatment of dementia, but conclusive results are still awaited.
Choline
Lecithin is a major dietary source of choline. Choline has been examined for its possible benefits on cognitive performance. A study in healthy men, did not show any enhancement of cognitive ability following treatment with choline. Some studies have shown that decreased choline levels are associated with memory dysfunction. Choline supplementation may be beneficial in some conditions, but conclusive evidence is still lacking.
DHEA
Several studies have shown that a decline in dehydroepiandrosterone (DHEA) may contribute to Alzheimer’s disease. However, double blind studies with DHEA replacement have not shown significant improvement of cognition. Some of these studies have shown preliminary evidence for mood enhancing and antidepressant effects for DHEA. Long-term studies, in which DHEA is taken for longer than a year are still lacking, and may provide some benefits.
DMAE
Dimethylaminoethanol (DMAE) has been examined as a possible memory enhancer. Studies done on rats have shown significant improvements in working memory performance. Robust studies on humans are still lacking.
Ginseng
Ginseng has been studied for its possible beneficial effects on cognition. Short-term administration of ginseng has shown some improvement in memory performance. A Chinese study used Chinese ginseng for treatment of dementia after stroke and found some improvement. Some researchers have concluded that even well conducted clinical trials do not support the efficacy of ginseng for the treatment of impaired cognition.
Garlic
Aged garlic extract has shown some antioxidant health effects. Long-term extraction of garlic for up to 20 months ages the extract and creates more pronounced antioxidant properties. This may protect against the development of Alzheimer’s disease. Additional research is required, but aged garlic seems to decrease the risk of developing Alzheimer’s disease.
Glutathione
A metabolic pathway called the glutathione cycle has been examined as a possible cause for Alzheimer’s disease. This pathway is involved in oxidative stress. No conclusive evidence exists for the use of glutathione in Alzheimer’s disease.
Taurine
Taurine has been examined for its possible cognitive enhancement effect. Taurine and caffeine are ingredients of the Red Bull energy drink. Significant improvements have been shown in healthy volunteers for reaction time, concentration and memory. These improvements reflect the effects of a combination of ingredients. Taurine on its own has not shown any clear benefits in cognitive disorders.
Zinc
Zinc deficiencies may affect cognitive development. It appears that zinc is essential for the formation of new brain cells and new brain cell connections. However, zinc supplementation has not shown any real benefits in dementia conditions.
Vitamin C & E
Oxygen stress injury is caused by activated oxygen that is released in metabolic reactions. These chemicals destroy membranes of mitochondria and the genome of the cell. This leads to cell death. Vitamin C, vitamin E and Beta-carotene are considered antioxidants. Dietary supplementation of these vitamins in laboratory animals prolongs mean lifespan, but does not affect maximum lifespan. Various human studies have shown beneficial effects of these antioxidants. Vitamin C and E preserve health in old age. It seems to protect against artherosclerosis. Vitamin E and C also seem to have some beneficial effect on immune dysfunction. Vitamin E and C supplements may protect against vascular dementia and may improve cognitive function in late life.
A 1997 study examined the effectiveness of Vitamin E in patients with moderate to severe Alzheimer’s disease. In these patients, Vitamin E delayed the progression of the illness and it also preserved functioning in activities of daily living. The dosage of Vitamin E in the study was 1000 IU twice daily. For persons without Alzheimer’s disease a dose of 400 IU is recommended. People taking “blood thinners” like Warfarin should take care when they start taking Vitamin E. Vitamin E may lead to a prolongation of bleeding time.
B vitamins
A number of B vitamins have shown beneficial effects on memory. Deficiencies of thiamine (vitamin B1) are associated with poor memory, but supplements in healthy persons have not shown benefits. Niacin (vitamin B3) may have some benefits. Vitamin B6 (pyridoxine) and vitamin B12 are involved in metabolic processes that are important for memory, but supplementation has not proven beneficial.
Folate
Folate supplementation during pregnancy is important to prevent brain and spinal cord defects in the newborn baby. In healthy adults, supplementation has shown no significant benefits.
Anti-inflammatory substances
The use of anti-inflammatories such as non-steroidal anti-inflammatory drugs and aspirin seems to protect against Alzheimer’s disease. This protective effect is present at a low or high dose. Anti-inflammatories and aspirin do not seem to protect against vascular dementia.
Grape seed proanthocyanidin extract
The grape seed extract, proanthocyanidin, has shown antioxidant properties and some researchers believe that this is more pronounced than vitamin E and C and beta-carotene. Proanthocyanidin is also present in grape skins. These extracts may show some benefit in artherosclerosis. No evidence exists for any effects on memory.
Omega-3
Docosahexaenoic acid (DHA, an Omega-3 fatty acid) and arachidonic acid (AA, an Omega-6 fatty acid) are long-chain polyunsaturated fatty acids that are important for cognitive development and brain function. Omega-3 may play a role in mental well-being and may have mood-stabilising effects. In some studies, preparations with omega-3 to omega-6 ratios ranging from 1:4, produced significant favourable effects on learning performance.
Written by Dr Frans Hugo, MBChB, M.Med Psychiatry and Dr L. Van Wyk, MBChB, M. Med (Psych) from the Panorama Memory Clinic.
For more information visit: Dementia SA: http://www.dementiasa.org/ or Alzheimer’s South Africa: http://www.alzheimers.org.za
