Phytonutrients - Isoflavonoids

Question 1

Isoflavonoids

Answer 1

• Isoflavonoids are a group of flavonoids. The group includes:
  o Isoflavones
  o Isoflavonones
  o Isoflavans
  o Rotenoids.

Question 2

Food sources:

Answer 2

• Mostly soy, but also other legumes e.g. lentils, peas, chickpeas, peanuts.
• Alfalfa sprouts.
• Red clover.
• Brussel sprouts.

Question 3

Metabolism:

Answer 3

• 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 or 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.
• Eating isoflavones from a young age, being vegetarian, regularly consuming seaweeds and drinking green tea seem to favour equol production.
  Aglycones= a non-carbohydrate, combined with a sugar to form a glycoside

Genistin, daidzin and glycitin are the glycosides.
Genistein, dadzein and glycitein are the aglycones.

Question 4

Functions / Therapeutic uses

Answer 4

• Oestrogenic activity
• Cardiovascular health
• Osteoporosis

Question 5

Oestrogenic activity:

Answer 5

Therapeutic uses:
* Isoflavones have weak oestrogenic activity.
* Bind to oestrogen receptors, mimicking the effects of oestrogen in some tissues and antagonising (blocking) the effects of oestrogen in others.
* 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.

Question 6

Cardiovascular health:

Answer 6

Therapeutic uses:
* Isoflavonoids have been shown to have antioxidant and LDL-lowering properties.
* May help to reduce arterial stiffness (i.e. atherosclerosis) and be beneficial in ischaemic heart disease.

Question 7

Osteoporosis:

Answer 7

Therapeutic uses:
* Soy isoflavones can increase bone mineral density (BMD), or slow BMD loss, and improve biochemical markers of bone turnover in peri-and postmenopausal women. This is through its oestrogenic effects on bone.

Question 8

Dosage:

Answer 8

• Soy protein isolates prepared by an ethanol wash process, generally lose most of their associated isoflavones, while those prepared by aqueous wash processes tend to retain them.
  o For cardiovascular health 25–30 g soy protein per day.
  o For menopausal symptoms such as hot flushes, soy protein providing 80–160 mg isoflavones.
  o For preventing osteoporosis, 40 g soy protein providing 80–90 mg isoflavones.

Question 9

Drug interactions:

Answer 9

• High intakes of soy protein may interfere with the efficacy of warfarin.
• Seven studies investigating the effect of soy in combination with tamoxifen have reported no significant differences with respect to treatment outcomes or rates of adverse effects associated with use of soy among women who were receiving tamoxifen therapy.
  o Note that this is usage of soy in its wholefood form, not as isolated isoflavones.

Question 10

Safety:

Answer 10

• The safety of high intakes of soy isoflavones and other phytoestrogens for breast cancer survivors is an area of considerable debate among scientists and clinicians.
• The Shanghai Breast Cancer Survival Study was a large, population-based cohort study of 5042 female breast cancer survivors in China.
  o Among women with breast cancer, soy food consumption was significantly associated with decreased risk of death and recurrence.
• However, all genetically modified sources of soy must be avoided.

Question 11

Soya to avoid

Answer 11

What types of soya are NOT to be recommended?
* Soy protein isolate (SPI) is highly processed, unfermented and may be GMO.
* A 2017 research project from the University of Illinois found that, the compounds in minimally processed soy flour stimulate genes that suppress cancer, whilst the highly-processed soy isoflavones stimulate genes that promote tumour growth.
* Concerns about the safety of soy products stem from the use of industrially-processed products, not its whole form.
* Also remember that soy is generally difficult to digest.