19. PHYTONUTRIENTS Flashcards
This module covers: • What phytonutrients are and their classifications. • The following key phytonutrients: - Catechins and epicatechins, quercetin, naringin, isoflavonoids, lignans, proanthocyanidins, anthocyanins, resveratrol, phytosterols, isothiocyanates, indole-3-carbinol, carotenoids.
What are phytonutrients?
Phytonutrients (phytochemicals) are chemical compounds produced by plants which are beneficial to human health and help prevent various diseases.
They are found in fruits, vegetables, tea, nuts, grains, beans, herbs and spices and give foods taste, fragrance, colour and other characteristics.
Phytonutrients are normally a by-product of glycolysis or photosynthesis. What is the difference between primary and secondary metabolites formed this way.
Primary metabolites:
* Are compounds necessary for plant survival such as proteins, carbohydrates, lipids, enzymes and chlorophyll.
Secondary metabolites:
* Are synthesised by the plant in reaction to its environment — an adaptive response.
* Evolve to facilitate the survival of the plant.
* Deter predators and protect from infection.
Outline the roles of secondary metabolites in plants
- Protection against herbivores, plant pathogens and against other plants.
- Protection against physical stressors such as ultraviolet light.
- Signals for communication and to attract pollinators.
What is the role of secondary metabolites in the human body?
Secondary plant metabolites in the human body have the potential to:
* Function as antioxidants (e.g. quercetin, abundant in red onions).
* Regulate the cell cycle.
* Increase detoxification of carcinogenic and other toxic compounds.
* Reduce DNA damage (e.g. lycopene in tomatoes).
* Mimic or interact with hormones and other body chemistry (e.g. lignans in flaxseeds can support oestrogen levels when low).
Why do organic plants have higher phytonutrient levels?
They have to protect themselves in their environment as they don’t get ‘support’ from pesticides, fertilisers and ‘perfect’ conditions.
What factors can determine the levels of phytonutrients in plants?
Difference in phytonutrients in plants can be due to:
* Chemotype of plant.
* Soil and water conditions.
* Fungi and mycorrhizae.
* Insect friends and foes.
* Climate.
* Seasonal cycles.
* Variability of plant part.
* Bacteria, virus and pathogens.
* Humans and other animals around them.
True or False:
All phytonutrients are beneficial to the human body
False.
Some phytochemicals are dangerous or toxic to the body.
Which class of phytonutrients include morphine, vinblastine and digoxin and can be very poisonous?
Alkaloids
Which phytonutrients found in beans, grains and legumes may prevent the absorption of minerals?
Phytates
What benefits do the following colours of phytonutrients confer. Give examples of foods containing each:
1. Blue, black, purple
2. Green
3. Red
4. Orange, yellow
5. White, brown
- Antioxidant to fight free radicals, support heart health, circulation and vision. Blueberries, blackberries, red cabbage, aubergines, black olives.
- High in chlorophyll and nutrients, supports liver detoxification, binds with toxins in the gut preventing absorption into the body. Kale, spinach, collard, broccoli, brussels sprouts, parsley, lettuce, avocado, watercress, cucumber.
- Reduces inflammation, high in vitamin C and supports the prostate. Tomatoes, guava, watermelon.
- Improves immune system, vision and joint health. Carrot, squash, sweet potatoes, orange, papaya, corn, melon, peppers, pumpkin, turmeric.
- Supports heart, circulation and liver detox. Garlic, onions, leeks, ginger, white cabbage, mushrooms, parsnips.
Phytonutrients are classified according to different chemical compounds and their properties.
Name the five main classes.
- Phenols and polyphenols
- Terpenes
- Phytosterols
- Organosulphur compounds
- Alkaloids
Flavonoids belong to the polyphenol family and has six subgroups. List three of these with one example each.
- Flavonols (e.g. kaempferol - in kale, spinach; quercetin - in red onions and apples).
- Flavones (e.g. apigenin - in parsley, celery, chamomile).
- Isoflavones (e.g. genistein and daidzein - in soybeans).
- Flavanones (e.g. naringin - in grapefruit).
- Anthocyanins (e.g. cyanidin - in red grapes, blackberry, blueberry).
- Flavanols or catechins (e.g. epicatechin - in green tea, cocoa).
Name three classes of phytonutrients in the polyphenols category
- Flavonoids
- phenolic acids
- lignans
- stilbenes
Also:
- quinones
- tannins
Which flavonoid can be found most notably in green tea? Outline three functions and the associated therapeutic uses for this substance.
(Also to be found in oolong tea, black tea, cocoa, black grapes, berries, apples, pears, plums, vinegar.)
Catechins & epicatechins
Anti- inflammatory:
* Asthma / eczema.
* Urticaria / hay fever.
* Anti-cancer.
* IBD
Neurological health:
* Parkinson’s (neuroprotective).
* Depression.
* Cognitive disorders.
Cardiovascular health:
* Lowers BP & LDL-cholesterol.
* Increased NO prod. (vasodilation).
* ↓ insulin resistance.
Joint health:
* ↓ joint degeneration in OA & RA
* Protects cartilage by inhibiting proteoglycan and collagen breakdown.
Which abundant flavonoid would you expect to find in red onions? Outline how this substance can benefit cardiovascular and immune health.
Quercetin
Cardiovascular health:
- Powerful antioxidant - protects vascular endothelium, inhibits LDL oxidation.
- Vasodilatory effects (via NO release), reduces platelet aggregation, ↓ BP (in hypertensives) via ACE-inhibiting properties.
- Supports endurance by ↑ blood circulation.
* Dosage: 150 mg‒1000 mg per day.
Immune health:
- Anti-inflammatory — inhibits LOX & COX, potent down-regulator of NF-κB.
- Anti-histamine —inhibits mast cell degranulation.
- Reduces inflammation in the brain (protective against Alzheimer’s and Parkinson’s).
How can increasing food sources of quercetin be beneficial for gout sufferers?
Quercetin can inhibit xanthine oxidase (normally converts purines → uric acid)
How can the absorption of quercetin into the blood be enhanced?
- Onions and shallots contain quercetin in its unbound (aglycone) form, which may make absorption easier.
- Quercetin is hydrophobic, so is best absorbed with fats, emulsifiers or apple pectin.
Which flavonoid contained in grapefruit inhibits intestinal CYP3A4 and is therefore contraindicated with numerous medications?
Naringin
How can naringin reduce acceleration and complications of diabetes?
Naringin inhibits ‘aldose reductase’ (an enzyme associated with diabetic complications by directing glucose into pathways producing inflammatory metabolites).
It reduces diabetic retinopathy and neuropathy.
List three therapeutic uses for Naringin.
- Atherosclerosis (incl. prevention).
- Hyperlipidaemia.
- Cancer prevention.
- Reduces acceleration and complications of diabetes.
Name four good food sources of isoflavonoids
- Mostly soy, but also other legumes e.g. lentils, peas, chickpeas, peanuts.
- Alfalfa sprouts.
- Red clover.
- Brussel sprouts.
What is the difference between a glycone and an aglycone?
glycone = attached to a sugar molecule
aglycones = compound without a sugar group attached.
Discuss how compromised digestive capacity affects the absorption of isoflavones from soybeans?
- In soybeans, isoflavones are present as glycosides (bound to a sugar molecule) and need to be split apart to render them active.
- Digestion or fermentation of soybeans / soy products results in the release / splitting of the sugar molecule from the isoflavone glycoside, leaving an aglycone.
- Health benefits of soy isoflavones depend on one’s capacity to convert isoflavones to metabolites during digestion.
- Specifically, some colonic bacteria can convert the soy isoflavone daidzein to equol, a metabolite that has greater oestrogenic activity than daidzein. Equol production depends on the gut flora and is therefore influenced by diet.
Recommend FOUR phytonutrients that could be useful for a client wanting to lower their LDL-cholesterol
Consume foods rich in:
1. Catechins / epicatechins: green tea, oolong tea and black tea, cocoa, black grapes, berries, apples, pears, plums, vinegar.
2. Naringin: Citrus fruits (esp. grapefruit), tomato paste.
3. Isoflavonoids: Soy, lentils, peas, chickpeas, peanuts, alfalfa sprouts, red clover, brussel sprouts.
4. Phytosterols: Unrefined vegetable oils, nuts, seeds, whole grains and legumes.
Discuss the interplay between isoflavones and oestrogen.
- Isoflavones have weak oestrogenic activity.
- They bind to oestrogen receptors, mimicking the effects of oestrogen in some tissues and antagonising (blocking) the effects of oestrogen in others.
- Their anti-oestrogenic effects in reproductive tissue could help reduce the risk of hormone-associated cancers (breast, uterine and prostate), while oestrogenic effects in other tissues can help maintain bone density.
- Reduce menopausal symptoms and support those who have condition of low oestrogen (e.g. amenorrhoea).
- Consider isoflavones as selective oestrogen modulators.
List FIVE dietary recommendations for a client in order to support their bone mineral density.
Increase the following foods in the daily diet:
1. Green tea (catechins)
2. Fermented soy products eg. tempeh (isoflavones, lysine), natto (isoflavones, vitamin K2)
3. Ground flax seed and sesame seed (lignans)
4. Dark green leafy vegetables (Magnesium, vitamin K1)
5. Oily fish / fish oil (Vitamin D & A)
Also: Adequate protein, eliminate junk food, lower caffeine and red meat, use himalayan rock salt or celtic sea salt instead of table salt.
