Lignans and Resveratrol Flashcards
Lignans
Lignans can be metabolised by intestinal bacteria to form the phytoestrogen compounds enterodiol and enterolactone:
* They are said to be the ‘Western equivalent’ of phytoestrogens and are a soy alternative.
* It is thought that variations in the intestinal bacteria mean that in Western populations tend to tolerate lignans more than soy.
Lignans: Food Sources
- Flaxseeds (most abundant 1 oz, 85.5mg)
- Sesame seeds (1 oz, 11.2mg), beans and pulses, cruciferous vegetables.
Lignans: Function
Oestrogen Modulation
Anti-cancer
Lignans: Oestrogen modulation
- Bind to oestrogen receptors exerting an oestrogenic
effect that is milder than endogenous oestrogens. - Where oestrogen levels are low the net effect is
to ↑ oestrogenic activity - Where oestrogen levels are high, lignans
antagonise endogenous oestrogens.
Lignans: Oestrogen modulation - Therapeutic Uses
- Menstrual irregularities Dosage: 2 tbsp whole
flaxseed per day (i.e. seed cycling) - Menopause support ↓ frequency and intensity of hot flushes; improves vaginal atrophy and cognitive function; supporting bone density, ↓ osteoporosis risk.
Dosage: 2 tbsp flax per day.
Lignans: Anti-cancer
- Lignans anti-cancer properties especially in hormonally driven breast and prostate cancer. There is also evidence for a role in endometrial and ovarian cancer.
- The following anti-cancer mechanisms have been found:
– Modulation of oestrogen metabolism and receptor
signalling pathways leading to decreased cell proliferation and angiogenesis.
– Strong anti oxidant properties.
– Reduces 5α reductase activity, thereby reducing the more biologically potent DHT (prostate). - Dosage: 25 g / day (providing 50 mg lignans).
Lignans: Intake and dosage
- Consume 25g flaxseed (approximately 50 mg lignans) daily.
- Lignans are not associated with the oil fraction of foods so intake of whole flaxseeds (ground) are needed to obtain benefits.
- Flaxseeds contain polyunsaturated fatty acids that are unstable and oxidise readily if exposed to oxygen, light and heat (avoid cooking use to garnish).
- Best consumed from flaxseeds that are freshly
ground . Ground flaxseeds also oxidise easily so do not purchase them ground.
Lignans: Safety
- Lignan precursors in foods are not known to have any adverse effects.
- Flaxseed may lower blood glucose levels and might have additive effects when used with anti diabetic drugs
- The safety of lignan supplements in pregnant
or lactating women has not been established.
Resveratrol
Resveratrol is the most studied stilbenoid . It is a
powerful antioxidant produced by some plants to protect them against environmental stresses:
Resveratrol: Food Sources
- Red grapes (skins(
- Blueberries, mulberries, raspberries, cranberries.
- Peanuts with red skins on, pistachios.
- Cocoa.
Resveratrol: Functions
Anti-oxidant
Insulin sensitivity
Oestrogen modulation
Resveratrol: Anti-oxidant
It is a potent antioxidant that can:
* Prevent LDL oxidation.
* Support fertility (e.g. sperm
* Provide anti cancer properties (also suppresses cell proliferation(
Resveratrol: Anti-oxidant - Therapeutic uses
- Cardiovascular health.
- Anti ageing / skin health / fertility.
- Diabetic neuropathy
Resveratrol: Insulin sensitivity
- It can improve insulin sensitivity especially in those with obesity. It also reduces fat accumulation.
Resveratrol: Insulin sensitivity - Therapeutic uses
- Type 2 diabetes
Dosage: 150 mg / day
Resveratrol: Oestrogen modulation
- A ‘phytoestrogen’. It can inhibit aromatase (reducing testosterone to oestrogen conversation).
Used in:
*
Oestrogen dominance (e.g. breast cancer(
Resveratrol: Dosage
- Trials looking at the effects of resveratrol in both
healthy subjects and those with medical conditions
have used dosages ranging from 10 mg -1 g per day. - Most supplements on the market are derived from
Japanese knotweed because this plant has one of
the highest concentrations of resveratrol in nature. - Resveratrol is very expensive so doses above
about 100 mg per day will likely be cost prohibitive. - The concentration of resveratrol in the blood is more bioavailable in the morning (due to diurnal variations in its metabolic pathway)
Resveratrol: Safety
- There is currently no evidence that resveratrol can be toxic or cause adverse effects in humans.
- The safety of resveratrol containing supplements during pregnancy and lactation has not been established.
- Avoid recommending alcohol consumption as a source ofresveratrol red grape juice is just as rich a source!
Resveratrol: Interactions
- High intakes of resveratrol (e.g. supplements) could increase the risk of bleeding when taken with anticoagulant drugs.
- Resveratrol inhibits the activity of cytochrome P450; thus high intakes of resveratrol (e.g. from supplements) could theoretically increase the bioavailability and toxicity of drugs that undergo extensive first pass metabolism by CYP450 (statins, immune suppressants, calcium channel blockers, etc)
