Phyto-oestrogens are plant chemicals, flavonoids, that behave like oestrogen in humans. These plant oestrogens are about 300 times weaker than human oestrogen, which can augment the oestrogenic effect in the body by weakening regular oestrogen (in case of excess) or increasing from low oestrogen (say in menopause)1.
We can use phyto-oestrogens for a weak and strong relative effect depending on the person’s need. We would also be cautious in using phyto-oestrogens in men, babies, children and those without oestrogen imbalances.
Some Sciencey Stuff Most phyto-oestrogens are flavonoids, with the most potent being coumestans and isoflavones (genistein and daidzein). Most research has been done on isoflavones, which are found in soy and red clover. Lignan - not a flavonoid - is also a phyto-oestrogen. These are phenolic phyto-oestrogens. Some other molecules, plant steroids and terpenoids, may also have an oestrogenic effect.
Sources of phyto-oestrogens
While many plants contain phyto-oestrogens, only some contain enough that we’d use them medicinally.
Foods with phyto-oestrogens include:2,3
- Flax seeds (high in lignans)
- Legume seeds (soy, beans, peas, high in isoflavones)
- Soy products (tofu, tempeh, soy milk, soybeans, high isoflavones)
- Sesame seeds
- Wheat
- Berries
- Oats
- Barley
- Dried beans
- Lentils
- Rice
- Alfalfa
- Mung beans
- Apples
- Carrots
- Wheat germ
- Ricebran
- Soy-linseed bread
The amount of phyto-oestrogens in a particular food varies depending on processing. An intake of 45mg of phyto-oestrogens daily may have a stabilising effect on hormones.
Searchable phyto-oestrogens food list
| Plant species (Common name) | μg/100 g dry weight | Levels |
|---|---|---|
| Plum | 5 | Very Low |
| Wheat (white meal) | 8 | Very Low |
| Banana | 10 | Very Low |
| Apple | 12 | Very Low |
| Oatmeal | 13 | Very Low |
| Potato (peeled) | 16 | Very Low |
| Lentil | 23 | Very Low |
| Pea | 27 | Very Low |
| Cabbage | 33 | Very Low |
| Tritacle (meal) | 35 | Very Low |
| Wheat (wholegrain) | 36 | Very Low |
| Cabbage, Turnip-rooted | 43 | Very Low |
| Poppy seed | 51 | Very Low |
| Tritacle (wholegrain, wheat variant) | 52 | Very Low |
| Barley (wholegrain) | 80 | Low |
| Barley bran | 85 | Low |
| Onion | 91 | Low |
| Pistachio nut | 96 | Low |
| Beetroot | 100 | Low |
| Almond | 111 | Low |
| Cauliflower | 111 | Low |
| Rye meal (wholegrain) | 112 | Low |
| Wheat bran | 121 | Low |
| Hazelnut | 123 | Low |
| Paprika | 124 | Low |
| Rasberry | 139 | Low |
| Sharon | 145 | Low |
| Cabbage, Red | 160 | Low |
| Red currant | 165 | Low |
| Walnut | 173 | Low |
| Oat bran | 179 | Low |
| Witloof/Endive | 190 | Low |
| Cloudberry | 203 | Moderate |
| Caraway seed | 235 | Moderate |
| Chickpea/Garbanzo bean | 250 | Moderate |
| Black-eyed pea/Cow pea | 255 | Moderate |
| Cashew nut | 261 | Moderate |
| Rye bran | 299 | Moderate |
| Black gram bean | 361 | Moderate |
| Carrot (skin on) | 370 | Moderate |
| Garlic | 380 | Moderate |
| Kidney bean | 396 | Moderate |
| Black currant | 398 | Moderate |
| Peanut | 420 | Moderate |
| Broccoli | 451 | Moderate |
| American groundnut (potato bean) | 511 | Moderate |
| Pigeon pea | 517 | High |
| Clover seed | 518 | High |
| Zuccini (skin on) | 817 | High |
| Blueberry | 835 | High |
| Sesame seed | 852 | High |
| Cranberry | 1054 | High |
| Strawberry | 1210 | High |
| Lingonberry | 1510 | High |
| Tea, Yellow label tea-bag | 2591 | Very High |
| Sunflower seed | 2600 | Very High |
| Tea, Earl Grey tea (Oriental tea mixture) | 3212 | Very High |
| Kudzu leaf | 3371 | Very High |
| Tea, Pure Lapsang Souchong tea (China) | 3520 | Very High |
| Tea, China Gunpowder | 3672 | Very High |
| Pumpkin (peeled) | 3874 | Very High |
| Tea, Japan Sencha Green tea | 4075 | Very High |
| Tea, Nippon Sencha Green tea | 5565 | Very High |
| Tea, Prince of Wales, tea-bag | 5768 | Very High |
| Tea, China Green tea | 5965 | Very High |
| Tea, Green | 8000 | Very High |
| Black tea | 8500 | Very High |
| Soy bean | 88843 | Extremely High |
| Kudzu root | 197631 | Extremely High |
| Flaxseed | 370987 | Extremely High |
| Flaxseed (crushed) | 547300 | Extremely High |
Herbal medicines with phyto-oestrogens include:
- Red clover
- Alfalfa
- Hops (what beer is made from)
- Liquorice
- Turmeric
How plant oestrogens work in the human body
Phyto-oestrogens bind to certain oestrogen receptors in select tissue, activating or down-regulating the response of cells.
Breast and uterine tissue has the most ER-alpha oestrogen receptors, while metabolic processes for the cardiovascular system and bones tend towards ER-beta receptors.
With other factors in play, the impacts of oestrogens can be oestrogenic or anti-oestrogenic. In breast and uterine tissue, ER alpha receptors are downregulated by phyto-oestrogens, which may explain the possible anti-cancer benefits.
Phyto-oestrogens may also impact the balance of oestrogen metabolites (the end result of oestrogen metabolism), of which three are unfavourable to the body (16 alpha-hydroxy estrone, 4-hydroxy estradiol and 4-hydroxy estrone) and one favourable (2-hydroxy estrone).
Phyto-oestrogens may protect against cancer in the prostate4, breast and uterus (and others)5 and may offer protection against heart disease and osteoporosis. Soybeans contain multiple anticarcinogens, with isoflavones noteworthy due to soy being the only major dietary source.
Phyto-oestrogens and the thyroid
Isoflavones in soy and flavonoids from other plants inhibit thyroid peroxidase, an enzyme involved in thyroid hormone synthesis. High intake of phyto-oestrogens may result in worsening hypothyroidism or goitre in iodine-deficient or those with hypothyroidism.6
Iodine deficiency increases the thyroid-blocking impact of soy, with iodine reversing this process.
How to use soy products for their phyto-oestrogens
In menopause, phyto-oestrogens can play a role alongside the adrenals in adding to the overall oestrogenic effect on the body, helping to relieve symptoms of genitourinary symptoms of menopause (GSM) – dry, easily irritated or damaged vaginal and vulvar tissue, incontinence, etc.
We also use phyto-oestrogens in vaginal treatments such as Fennelope fennel pessaries for a local effect, which has been shown to thicken vaginal epithelial cells7. This thickening reduces the vulnerability of cells and can help provide much-needed glycogen in vaginal cells to support healthy vaginal flora.
Soy protein can be useful in some people as a source of complete protein, as soybeans contain all essential amino acids.
People with a history of hormone-related cancers (breast, ovarian, prostate) may benefit from a low animal fat diet and future protections from endogenous oestrogens. Regular intake of soy products can also decrease ‘bad’ cholesterol by as much as 10 per cent, with every one per cent equalling around a two per cent drop in heart disease risk.
As a result, soy products are a good substitute. The FDA determined that diets with four daily soy servings can reduce levels of low-density lipoproteins, the so-called bad cholesterol that builds up in blood vessels, by as much as 10%.
This number is significant because heart experts generally agree that a 1% drop in total cholesterol can equal a 2% drop in heart disease risk.
References
- 1.Setchell KDR. Soy Isoflavones—Benefits and Risks from Nature’s Selective Estrogen Receptor Modulators (SERMs). Journal of the American College of Nutrition. Published online October 2001:354S-362S. doi:10.1080/07315724.2001.10719168
- 2.Mazur W, Adlercreutz H. Naturally occurring oestrogens in food. Pure and Applied Chemistry. Published online September 1, 1998:1759-1776. doi:10.1351/pac199870091759
- 3.Thompson LU, Boucher BA, Liu Z, Cotterchio M, Kreiger N. Phytoestrogen Content of Foods Consumed in Canada, Including Isoflavones, Lignans, and Coumestan. Nutrition and Cancer. Published online July 2006:184-201. doi:10.1207/s15327914nc5402_5
- 4.Castle EP, Thrasher JB. The role of soy phytoestrogens in prostate cancer. Urologic Clinics of North America. Published online February 2002:71-81. doi:10.1016/s0094-0143(02)00019-8
- 5.Adlercreutz H. Phyto-oestrogens and cancer. The Lancet Oncology. Published online June 2002:364-373. doi:10.1016/s1470-2045(02)00777-5
- 6.Doerge DR, Sheehan DM. Goitrogenic and estrogenic activity of soy isoflavones. Environmental Health Perspectives. Published online June 2002:349-353. doi:10.1289/ehp.02110s3349
- 7.Yaralizadeh M, Abedi P, Najar S, Namjoyan F, Saki A. Effect of Foeniculum vulgare (fennel) vaginal cream on vaginal atrophy in postmenopausal women: A double-blind randomized placebo-controlled trial. Maturitas. Published online February 2016:75-80. doi:10.1016/j.maturitas.2015.11.005
Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.
Jessica is the owner and lead naturopath of My Vagina, and is a member of the:
- International Society for the Study of Vulvovaginal Disease (ISSVD)
- International Society for the Study of Women's Sexual Health (ISSWSH)
- National Vulvodynia Association (NVA) Australia
- New Zealand Vulvovaginal Society (ANZVS)
- Australian Traditional Medicine Society (ATMS)