Which plants help brain function and protect us from dementia?

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Professor Robert Thomas explains how the best way to avoid dementia is to start approaches before symptoms develop

Once noticeable memory loss and other signs of dementia have developed, a lot of the brain cells have already been killed but it’s never too late to make positive dietary and lifestyle changes. Many well conducted scientific studies have confirmed that dietary strategies, particularly those which boost plant intake can slow the rate of damage and ensure the remaining brain cells, as well as delicate neuronal connections are running as efficiently as possible.

Obviously, the best way to avoid dementia is to start these approaches before symptoms develop - as early in life as possible. Distinctive types of dementia are influenced by different lifestyle factors although there is considerable overlap. Vascular dementia is mainly caused by untreated high blood pressure, high cholesterol, smoking and lack of exercise whereas Alzheimer’s is linked to chronic inflammation caused by an ageing, ailing immune system, accelerated by unhealthy dietary habits and a sedentary lifestyle. Both types of dementia are strongly influenced by the phytochemicals, fats and micronutrients found in many edible plants we should all be eating more of, on a daily basis.

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Before we delve into the fascinating complexities of phytochemicals (the natural chemicals which give plants their colour, smell and taste) it is important to summarise, and provide links for, the evidence and advice for the multiple factors which together can help us improve our memory, avoid dementia and other chronic degenerative disease:

  • Exercise 3 hours a week
  • Eat plenty of colourful phytochemical rich plants
  • Reduce intake of processed sugar
  • Avoid Vitamin D deficiency
  • Keep your weight down
  • Avoid mineral deficiencies
  • Ensure an adequate intake of iodine
  • Quit smoking
  • Try to achieve a regular sleep pattern
  • Reduced processed meat intake
  • Ensure adequate intake of omega fats
  • Moderate your alcohol intake
  • Control or treat raised cholesterol
  • Control or treat raised blood pressure

Why and how are plant phytochemicals so important for brain function

These wonderful gifts from nature have been studied extensively for their ability to enhance alertness, mood, motivation and memory and in the long term a reduced the risk of dementia or slow of its progression. Many phytochemicals have more than one mechanism of action and the whole foods, from which they originate, also have other healthy ingredients such as healthy oils, fibre, vitamins, minerals and proteins. The majority of edible plants have some healthy properties but here is a description of phytochemical rich foods which have particular benefits for the brain:

Pomegranate contains many polyphenols including Ellagic acid which has been shown to block accumulation of amyloid plaques in the brain preventing age-related decline in cognition, improved learning and memory performance.

Cranberries, blueberries, beetroot, spinach and celery are rich in nitrates which, following interaction with other phytochemicals, are converted by the body to nitric oxide (NO). This relaxes muscles around arteries, improving blood flow resulting in improved oxygenation and removal of toxic metabolites in tissues such as muscles, improving recovery after exercise and brain improving alertness and cognitive function. Participants, in clinical trials, given cranberry extract significantly improved memory, neural functioning and delivery of blood to the brain compared to placebo.

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Cocoa, fruits, other berries and leafy green vegetables are rich in flavonoids which have antioxidant enhancing and anti-inflammatory properties. It is established that their higher intake over time is associated with a lower risk of developing dementia.  A recent small study found that people taking a flavonoid rich cocoa had improved memory and cognitive function compared to those taking placebo.

Green tea contains epigallocatechin gallate (EGCG) found to help untangle fibres called tau and protect the brain. In Alzheimer’s, excess tau abnormally sticks together in fibrous tangles that spread between brain cells, leading to amyloid formation and cell death.

Curcumin (turmeric) helps reduce inflammation and improves anti-oxidative pathways but also has direct neuroprotective properties. A study  published in the American Journal of Geriatric Psychiatry found that curcumin supplementation improved memory and attention in older adults with cognitive impairment.

Ginger also has potent anti-inflammatory and anti-oxidative properties but also helps with the absorption and bioavailability of other phytochemicals which is why it’s called a bioenhancer. Like many of these foods mentioned, so far, it is rich in soluble fermentable fibres which act as prebiotics that help to feed healthy gut bacteria and improve gut integrity.

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Broccoli and other cruciferous vegetables are rich in Isothiocyanates (ITCs) such as sulforaphane (SFN) which have been shown to decrease levels of pro-inflammatory chemicals, reverse amyloid formation and hence reduce damage to brain cells. SFN also has a peculiar capacity to activate antioxidative defence against toxins which can trigger brain cell death. Unsurprisingly, over 20 clinical studies have been published linking a higher intake of cruciferous vegetables with a lower risk of dementia.

How to boost phytochemical rich food intake

Asian and Mediterranean diets are typically abundant in phytochemical-rich fruits, mushrooms, vegetables, salads, herbs, spices, teas, nuts, berries, seeds and legumes. Typical western diets, on the other hand, are dreadfully deficient in phytochemicals, meaning we need to eat a lot more of them, preferably some with every meal of the day.  A lot of emphasis is placed on exotic, rare fruits (superfoods) but they are easily available in the average supermarket in the UK. Less obvious sources include dark chocolate, chilli, red wine, coffee and tea so you don’t have to have a boring diet to enjoy them.

Practical tips to boost phytochemical rich food intake

There are many healthy dishes which include tasty phytochemical rich foods made from readily available, low-cost ingredients, so you don't have to seek rare delicacies from far flung places. In addition to whole meals, there are many other practical ways to  boost phytochemical intake on a daily basis.

Juices and smoothies – Many of the fruit juices available on the market today aren’t actually ‘real’ fruit juices. They consist of water mixed with concentrate and extra sugar. Even real fruit juice has a high concentration of fructose as so many fruits are used to make them. There is also little chewing resistance to slow down consumption, making it very easy to drink a large amount of sugar in a short period of time. Juicing, which entails the whole fruit being put in the blender, is more effective at maintaining the pulp and fibre, yet still often involves a high fructose content. To overcome this, smoothie aficionados add avocado, vegetables such as kale or spices such as ginger, lowering the sugar content while improving the polyphenol intake.

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Soups – Most phytochemicals survive a degree of cooking, making soups an ideal way to guarantee an effective intake. Tomato soup significantly increases lycopene intake, making it perfect for those not keen on raw tomatoes. A vegetable broth flavoured with extra spices and herbs and consumed before a meal tends to fill the stomach, helping with weight loss regimens, while broccoli, onion and pea soup, with a sprinkle of turmeric and a generous twist of fresh ground pepper, constitutes the perfect superfood mix. To get the most out of soups, eat them with a fresh salad containing raw onions, lettuce or radish, all of which contain the enzyme myrosinase which is required to convert the sulforaphane in cooked cruciferous vegetables into the bioactive antioxidant enzyme glutathione. Also add ginger and pepper liberally, they are known to increase the bioavailability of polyphenols in the vegetables and spices.

Shots – Some, more health-orientated, food outlets are offering short blends of phytochemical rich foods such as ginger, turmeric and chilli diluted with apple or orange juice. These provide a quick boost but are usually not cheap. It is possible to make your own shot by grating fresh ginger into a small apple juice and adding a twist of lemon. If you have the time, it is also possible to make ginger shots with a blender, a technique which gets much more out of the root. For a green shot, try combining a length of fresh-scrubbed clean ginger with some green apple, some spinach leaves and half an avocado, before adding the juice from a lemon and a small pinch of cayenne pepper.

Grains and sprouting legumes – Although individual foods can be very healthy, mixing them together is a fantastic way to provide your body with a great variety of protein, omega fats, fibre and other essential nutrients. Soaking mixed whole grains overnight helps to remove some of the gluten and other proteins such as phytic acid which some people are sensitive to. Many health food and corner shops now sell mixed grain nuts and seeds, so should be easily available. Phytochemicals are naturally rich in pulses (seeds) such as chickpeas, lentils, peas, watercress but their levels significantly increase if they are added to water and left to sprout. Many people add sprouted seeds to salads and various sprouters are commercially available which make the process easier.

Nuts, pumpkin, chia and flax seeds - As well as being a rich source of protein, phytochemicals and prebiotics which help gut health, these are rich in healthy fats. All fats are energy-rich, meaning too high can lead to obesity which is why they have had a bad press over the years. Eaten in moderation, however, they are an excellent slow release energy source. Polyunsaturated fatty acids (PUFA), in particular, have numerous healthy attributes including an ability to reduce inflammation and impact on cognitive performance at all stages of life. There are different types of omega 3 and 6 PUFAs including (Eicosapentaenoic acid - EPA, docosahexaenoic acid - DHA and alpha-linolenic acid - ALA) all of which are essential for brain functions. DHA, however, is the dominant omega-3 in the brain, which has a vital role in the healthy function of neurotransmitters and brain cell repair. Walnuts, other nuts and even unprocessed peanuts have good PUFA levels but make sure they are fresh as stale nuts can oxidise and contain toxins. Pumpkin seeds can be chewed whole but it's best to use crushed flaxseeds, to release the oils and soak chia seeds in water to make them more digestible.

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Phytochemical rich supplements - In the busy world we live in, it’s often difficult to prepare fresh healthy meals on a daily basis. A well-made supplement, for some people, is a convenient way to increase phytochemical intake and spread intake across the day. Nutritional supplements can also contain foods which are not commonly eaten in a typical UK diet such as turmeric, ginger and cranberries. The problem is, the quality of over the counter supplements can vary, contain too much of one particular food or worse still only contain single extracted chemicals from a single food. These miss out on the benefits of the whole plant, or combination of plants, which can work in synergy to enhance their favourable effects. Most of all, the vast majority have not been evaluated for effectiveness in robust medical trials. There are some exceptions, such as the blend developed by the scientific committee of the latest UK national nutritional intervention study. It contains most of the concentrated whole foods, mentioned above, which are known to have brain protective properties. Supplements designed for medical trials have to be scrutinised by ethical approval boards so have a much higher level of quality assurance and hence safety.

  • In summary of how phytochemicals help the brain:
  • Prevents build-up of amyloid or help reabsorb existing plaque
  • Dampens excess chronic inflammation
  • Improves oxidative pathways – reducing damage from free radicals and toxins
  • Enhances Nitric Oxide (NO) which improves brain oxygenation
  • Directly Inhibits brain cell death (apoptosis)
  • Supports gut health which can secondarily affect the brain  

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