Ginkgo biloba is one of the most widely used natural compounds for the prevention and treatment of Alzheimer’s disease. [Photo: Bigstock]

Promising botanicals for fighting cognitive decline

30 May, 2018

Preventing and treating cognitive decline is a major challenge of the modern age.

All humans will develop some degree of decline in their cognitive capacity as they age. This decline doesn’t affect everyone in the same way or to the same degree and there are a variety of factors that are influential.

These include oxidative stress and free radical damage, chronic low-level inflammation, declines in hormone levels, inefficient circulation, excess body weight, poor nutrition as well as a variety of lifestyle and social factors.

Many of these are within the individual’s control, to a greater or lesser extent. In addition, a battery of conventional drugs exists to treat or delay the onset and progression of neurodegenerative and other age-related decline

But according to a recent review some herbal remedies have ‘very promising’ evidence behind them for combating cognitive decline.

Promising data

Quick summary

» While some cognitive decline is natural with age, it is not inevitable and some risk factors are modifiable.

» Polish and Italian researchers reviewed 47 years of data of herbal remedies and their active constituents to see if some of these could help lower the risk of age-related cognitive decline and dementia.

» Among the seven herbs they focussed on, four – Ginkgo biloba, Vitis vinifera, Camellia sinensis, Theobroma cacao – showed promise based on available data.

Researchers from Poland and Italy explored how herbs and their active components may affect cognitive declines.

“As it emerges from this systematic review, the use of some phytochemicals and botanicals seems to be very promising in order to delay the onset and progression of neurodegenerative and other age-related diseases”, ​according to their report, published​​ in the journal Pharmacological Research​.

The researchers collected English language reports that spanned a period of 47 years, from 1970 to 2017.

“A number of studies have investigated the possible action on cognitive decline of different botanicals and phytochemicals, most of which are well-known anti-inflammatory or antioxidant agents with a good tolerability and safety profile,”​ the researchers write.

Their search focused on seven botanicals that have a body of science demonstrating activity on the central nervous system and other clinically-relevant effects in modulating cognitive decline in humans. These were: Ginkgo biloba, Vitis vinifera, Camellia sinensis, Theobroma cacao, Bacopa monnieri, Crocus sativus ​and Curcuma longa. ​

Among these, the four popular herbals below seemed to be the best researched and most promising for helping to maintain healthy brain and neurological function.

Ginkgo (Ginkgo biloba)​​

Ginkgo biloba is one of the most widely used natural compounds for the prevention and treatment of Alzheimer’s disease. The extract derived from the leaves is high in antioxidant proanthocyanidins which help fight free radical damage. But it has also been shown to help increase cerebral blood flow by enhancing nitric oxide production in vessels.

They cite numerous studies including a 2016 meta-analysis of 21 clinical trials by researchers in China​​, which reported that ginkgo ​supplementation in combination with conventional medicine was superior to conventional medicine alone in improving mild cognitive impairment scores.

They concluded that Ginkgo biloba ​is “potentially beneficial for the improvement of cognitive function, daily life activities, and global clinical assessment in patients ​[who had] just suffered from mild cognitive impairment.” ​

Tea (Camellia sinensis)

Daily tea intake might be associated to a significant reduction in the risk to develop cognitive disorders due to its two main active components epigallocatechin-3-gallate (EGCG) and L-theanine

EGCG is the main polyphenol compound extracted from Camellia sinensis and has been shown to inhibit a large number of proteins that are involved in protein misfolding diseases, like Alzheimer’s.  It has anti-inflammatory activity and has the ability to cross the blood-brain barrier.

It is also a potent antioxidant, capable of neutralising the effects or free radicals, for instance those generated iron ions and copper, in the brain. By protecting against oxidative stress it also decreases cellular and animal neuronal death.

In spite of all this, clinical data to support the use of EGCG as a cognitive function improver in clinical practice is mixed and the authors suggest that the benefits of botanicals like green tea on human cognitive performance may be related to other compounds present in tea.

L-theanine, for instance, is a major amino acid found in green tea, which has been shown to enhance cognitive functions and to have a positive effect on relaxing, emotional status and on quality sleep. It has also been shown to improve focus and concentration during difficult or complex tasks.

The authors note that the caffeine component in tea can work synergistically with L-theanine and that in humans, regular consumption of caffeine is related to a significant lower risk of developing cognitive impairment/decline.

Cocoa (Theobroma cacao​​)

“In the recent years, a great attention has been given to the potential positive cognitive effects of flavanols contained in Theobroma cacao”,​ according to the researchers.

The research they cite suggests that cocoa flavanols can improve insulin sensitivity but also improve circulation to the brain through mechanisms involving nitrous oxide.

“Short-term interventions with flavanol-rich cocoa in elderly volunteers reported improvements in cerebral blood flow and neurovascular coupling”, ​the researchers note.

However, getting the right dose may be crucial.

In another cited study from 2013, researchers gave study participants one of two drinks containing cacao flavanols; one with a high dose (494 mg) and another was low (23 mg). They measured arterial cerebral blood flow before and after drinking.

Those taking the higher dose saw significantly better circulation to the brain in particular in the anterior cingulate cortex (involved in higher-level functions such as attention, decision making and impulse control) and the central opercular cortex of the parietal lobe (involved in interpreting sensory information, mathematical thinking and the ability to manipulate objects).

Reviewing this and other studies the authors say Theobroma cacao could be associated to improvement in cognitive performance.

Resveratrol (Vitis vinifera)

​​Resveratrol is an antioxidant found naturally in grape skins. Apart from its antioxidant effect it also has a beneficial effect on circulation and has also been shown to improve glucose metabolism.

The authors looked at 34 studies that looked at resveratrol’s potential cognitive benefits.

They note that, overall, “Cognitive deficits were demonstrated to correlate with higher reactive oxygen (ROS) levels and nitrogen species: in effect, the oxidative stress seems to precede the senile plaques formation. In this regard, resveratrol exerts potent antioxidant activity that could be useful in preventing neurodegeneration in Alzheimer’s disease.”​

They also note that taking resveratrol with quercetin can help increase its bioavailability.