Spotlight on Polyphenols for brain health

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So when I typed in Polyphenols into Pubmed there were 30,750 matches: Wow!  This is a huge and actually surprisingly well researched area so I decided to concentrate on the area which most concerns me the most – my brain.

My father died of Alzheimers and I have the APOE4 gene which predisposes me to the disease.   As a Naturopathic Nutritional Therapist I know I am luckier than most i.e. I have the knowledge to stay healthy but I don’t half batter my brain with a work, research, multitasking and sometimes a few G and T’s.  As a busy working mother I sometimes think my brain will burst with the amount of stuff I have to remember to do.

So how can Polyphenols help and what exactly are they?

Polyphenols are phytochemicals which means compounds found in natural plant food sources that have antioxidant properties.  There are alleged to be over 8,000 and it’s the Polyphenols which give fruits, berries, and vegetables their vibrant colours, contribute to the tartness, aroma and also oxidative stability of the food. In the plant, they are there to protect against ultraviolet radiation, pathogens and harsh climatic conditions.

Common polyphenols in the diet are flavanols (cocoa, tea, apples, broad beans), flavanones (hesperidin in citrus fruit), hydroxycinnamates (coffee, many fruits), flavonols (quercetin in onions, apples and tea) and anthocyanins (berries).

As a general rule, foods contain complex mixtures of polyphenols, with higher levels found in the outer layers of the plants than the inner parts (5)

This is a link to a useful diagram showing the main polyphenol classes with structure, name of representative compounds and examples of food sources.

As we all know just because we ingest does not mean we absorb. I am sure it’s no surprise that the for optimal absorption and metabolism of these compounds the gut microbiota play a critical role in absorption; (1)

The beneficial effects resulting from polyphenol intake have been extensively studied in regard to the Mediterranean Diet which is characterised by a high consumption of fruits, vegetables, sea-fish (modest amounts wine) and olive oil as the principal source of fat, both highly enriched in polyphenols. (3)

Furthermore, epidemiologic studies over the last decades have supported the positive correlation between Mediterranean eating patterns and a large number of health benefits including improved cognitive function (4)

 So what foods should we eat?

We are all aware of the nutritional value of vegetables so eating a wide variety is a given but fruit should in my opinion be eaten in moderation. I chose to have a closer look at berries because they can actually be grown them here in the UK. (16)

Polyphenols are abundant in for example blackcurrants and have been shown to inhibit the formation and extension of β-Amyloid fibres and to destabilise preformed Aβ fibres in vitro as well as inhibit Aβ-induced reactive oxygen species i.e. good for our brain (7).

Three published peer-reviewed intervention studies have shown beneficial effects of berry consumption on human behaviour, affecting verbal memory and spatial memory after supplementation (6,7)and in adults with age related memory decline (8).

A randomised, double-blind, placebo-controlled, crossover study was conducted in 2015 using 36 healthy young participants (18–35 years). Findings from the intervention illustrate several cognitive benefits of blackcurrantsupplementation (9). Additionally, there was a significant on plasma concentrations of dihydroxyphenylglycine (DHPG) compared to control (9). Recent investigations suggested possible beneficial effectsin the treatment of neuronal injury, such as Alzheimer’s and for cognitive enhancement.(10)

Resveratrol, found in grape skins and red wine, has been found to have neuroprotective effects. (17) Other studies have demonstrated a reduction in the progression of dementia when polyphenols were included in the daily diet, by reducing two changes in the neurological system leading to dementia. (18)

The European Journal of Clinical Nutritionhas published a list of the 100 richest dietary sources of polyphenols, based on milligrams (mg) per 100 grams (g) or 100 mg of food. Here are the top 20 (19)

Cloves Peppermint Star anise Raw cacao
Mexican oregano Celery seeds Dark chocolate Flaxseed meal
Black elderberry Chestnut seeds Dried sage Rosemary
Spearmint Thyme Blueberries Blackcurrant
Capers Black olive Hazel nuts Pecans

Eating a diet rich in healthy fats will help the amount of polyphenols your body can absorb. In addition one of the interesting facts about polyphenols is that they are fat soluble. This means that you should try to take them with fats in your diet to help absorption. (11)

Just a final word of caution though to say Polyphenols are not all created equal and some polyphenol-rich foods may also affect the absorption of certain nutrients, as is the case with tea and iron from plant foods and also Grapefruit juice is known to interact with multiple medications so make sure its right for your or your clisnts own individual set of circumstances.

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