In a recent trial of people with dementia, 240 mg a day of ginkgo standardized extract improved memory and attention, as well as relieving some of the depression, anxiety and agitation that can complicate the disease. Reviews of the ginkgo research conclude the herb is significantly more effective than placebo in stabilizing or improving cognitive function in people with AD. Ginkgo has also been shown comparable to the drug Aricept.
The Ayurvedic herb bacopa (Bacopa monnieri) is also gaining a reputation as a brain aid. Stough, who has done much of the research on bacopa, says the herb has several anti-Alzheimer’s actions. “It removes beta-amyloid. And it is a strong anti-inflammatory, antioxidant and metal chelator.” He adds, “There is a growing consensus indicating that bacopa and particularly CDRI08 [a special standardized extract] improve memory and cognition in non-AD patients.”
In the largest and most recent study, 107 healthy adults took either a placebo or a standardized bacopa extract (two 150-mg tablets a day) for three months. Those who faithfully took the herb performed significantly better on memory tests. A 12-week study of healthy adults showed bacopa improved learning and memory and reduced anxiety. So far, one-time doses of bacopa do not seem to have an appreciable impact on cognitive function.
Ginkgo and bacopa combined may also improve mental function in healthy adults. While study results are mixed, outcomes may depend upon the dose and the duration of treatment.
Stough is excited about ongoing investigations into the effects of 12 months of bacopa extract (CDRI08) in healthy elderly people and of three to six months of bacopa in people with AD.
Ashwagandha (Withania somnifera) has a long history in Ayurvedic medicine as a rasayana, or rejuvenative tonic—a substance to promote longevity, sharpen the mind, protect against the ravages of stress, and reduce anxiety. (Click here to see an image of ashwagandha.) In test-tube studies, root extracts protect nerve cells from beta-amyloid, increase the healthy branching of nerve cells in the hippocampus (a brain area damaged by stress overload and AD), and improve memory in normal and demented mice. So far, no studies have investigated its potential benefits in preventing or treating dementia in humans.
Long used to enhance vitality, Asian ginseng (Panax ginseng) and American ginseng (P. quinquefolius) benefit the brain. Like ginkgo, Asian ginseng protects nerve cells from beta-amyloid and other toxins. Both species are adaptogens, substances that mitigate stress overload. Chronic stress, according to animal studies, atrophies brain areas involved in memory.
Alexander Panossian, Ph.D., head of research and development at the Swedish Herbal Institute, has published numerous articles on adaptogens such as ginseng and rhodiola (Rhodiola rosea). He believes both that stress overload is a risk factor for dementia and that “adaptogens might be very beneficial in preventing dementia.”
While research has yet to prove that theory, two preliminary studies found that Asian ginseng, as an add-on to drug treatment, improved cognitive function in people with Alzheimer’s disease. Both Asian and American ginseng (with or without ginkgo) have been shown to boost memory in healthy people.
Another promising adaptogen is rhodiola (Rhodiola rosea). The root of this Arctic plant has a long history in folk medicine. Research in the former Soviet Union revealed enhancement of physical and mental function during times of stress. In more recent research by Panossian and others, rhodiola extracts improve symptoms of anxiety, depression and stress burnout, and reduce mental fatigue. One study showed improvement in people with “cognitive deficiencies.” In rat studies, extracts increase key brain chemicals (including acetylcholine), protect nerves and reduce cognitive impairment in a condition like AD.
Rhodiola hasn’t yet been studied in people with dementia. Nevertheless, Richard P. Brown, M.D., and Patricia Gerbarg, M.D., authors of The Rhodiola Revolution (Rodale, 2005), have found that standardized extracts can enhance memory and cognitive function in their patients, including those with age-related memory decline and mild dementia. Even more effective, they say, is the combination of rhodiola with two other adaptogens—eleuthero (Eleutherococcus senticosus) and schisandra (Schisandra chinensis).
Gotu kola (Centella asiatica) is a ground cover native to India, Australia and Southeast Asia. The herb is an adaptogen, wound healer, circulatory stimulant and brain tonic. Scientific research only recently has begun to validate its ability to improve cognition. In a 2008 Thai study, a gotu kola extract enhanced working memory and improved mood in a group of 28 elderly adults.
Sage (Salvia lavandulaefolia, S. officinalis) has a tradition in European herbalism for improving memory. The leaf’s essential oils are anti-inflammatory, antioxidant, help preserve the brain’s acetylcholine (a neurotransmitter decreased in AD) and protect neurons from beta-amyloid’s toxic effects. Several studies demonstrated memory enhancement with oral consumption of dried leaf extracts or small amounts of diluted essential oil in healthy people, both old and young. At least one study has shown that inhalation of the essential oil improves memory and mood.
Chinese club moss (Huperzia serrata) contains huperzine A, a chemical that inhibits destruction of acetylcholine and protects nerve cells from beta-amyloid and other noxious agents. A half dozen preliminary human trials show huperzine A improves some measures of cognitive function and behavior in people with AD.
While huperzine A sells as a dietary supplement, it’s not something you’d take unless you had AD. Cott notes that this purified extract has a pharmaceutical effect much like the drug Aricept, though it may have fewer side effects. Brown and Gerbarg agree that that huperzine A is generally well tolerated, although some patients do report mild nausea, diarrhea and dizziness.
Another isolated plant chemical, curcumin, comes from the curry spice turmeric (Curcuma longa). A potent antioxidant and anti-inflammatory agent, curcumin also inhibits formation of beta-amyloid and improves its clearance from the body. Experiments suggest that vitamin D and curcumin may have an additive effect in clearing beta-amyloid. Studies investigating the potential benefits in AD have just begun.
Intestinal absorption of curcumin is poor, though once in the blood this chemical passes readily into the brain. Things that enhance absorption include cooking turmeric in oil (as is the case in Indian cooking), encapsulating curcumin with bromelain and piperine (from pepper) or binding it with phosphatidylcholine. Cott’s recipe is to heat a cup of full-fat milk, add a teaspoon of turmeric and a half teaspoon of pepper, and drink morning and evening.
Chemically speaking, curcumin is a polyphenol. Other polyphenol-rich plants include red grapes, berries, pomegranates, green and black tea, chocolate, and coffee. Berries are rich in a particular type of neuroprotective polyphenol called anthocyanins. People who regularly consume berries are less likely to develop Parkinson’s disease. Grape polyphenols reduce production of beta-amyloid, inhibit its tendency to clump, and protect the brain cells from its toxic effects. They also reduce activation of microglia, brain cells associated with inflammation. Lab experiments also show green tea (Camellia sinensis) polyphenols protect against beta-amyloid-induced nerve toxicity. Humans and lab animals who drink green tea have a reduced risk of dementia, including AD and Parkinson’s disease. Green tea drinkers also enjoy protection against cardiovascular disease, which is a risk factor for dementia.