Phytoestrogens Are Not Estrogen

Not all women are able to have oestrogen, depending upon their hormone history. However phytoestrogens are quite different.


Australian naturopath Lara Briden is an expert in the field of female hormones and I thought it would be helpful to have her views on what is a common misconception – that is the difference between oestrogen and phytoestrogens.

What are they?

Phytoestrogens are a special group of phytonutrients that occur naturally in almost all plant foods. The two major classes are isoflavones in soy, and lignans in seeds, whole grains, legumes, fruits, and vegetables.

They’re called phytoestrogens because they interact with estrogen receptors but they’re not estrogen. In fact, they bind so weakly to estrogen receptors that they effectively block estradiol and are therefore better classified as ANTI-estrogen.

What effect can they have?

It’s long been observed that isoflavone crops such as red clover suppress the estrogen and fertility of livestock and it’s even been proposed that plants evolved phytoestrogens to reduce the fertility of female herbivores and prevent overgrazing.

In a chapter called “Agriculture and Selection for High Levels of Estrogen,” evolutionary biologist Grazyna Jasienska makes the case that ancient humans adapted to agriculture and phytoestrogen-rich plant food by upregulating endogenous levels of estrogen.

Those of us with agrarian ancestors are, therefore, probably “hormonally calibrated” to a relatively high intake of food-based phytoestrogens to shelter us from our own high estrogen.

How might phytoestrogens affect you?

So, what does this mean for period health? Well, for one thing, it’s fine to eat phytoestrogens like legumes and seeds. They’ve long been part of our traditional diet, and our hormonal system is adapted to them.

How phytoestrogens affect women’s hormones

During the reproductive years, when estrogen is high, phytoestrogens have a beneficial anti-estrogen effect and can help to promote the healthy metabolism or detoxification of estrogen.

Hormone-sensitive cancer prevention may even be helped by food-based phytoestrogens

Heavy periods. By reducing estrogen, phytoestrogens generally make periods lighter. However, if the dose is high enough to suppress ovulation and progesterone (the hormone that lightens periods), the result can be a heavier period.

Endometriosis. In general, phytoestrogens should be neutral for endometriosis, or even slightly beneficial. Some women with endometriosis report a worsening of symptoms with soy which is probably due to an immune reaction.

PCOS. Phytoestrogens can improve insulin resistance and have been found to have a beneficial effect on the hormonal condition polycystic ovary syndrome.

Hypothalamic amenorrhea. Phytoestrogens cannot correct the estrogen deficiency of hypothalamic amenorrhea. The treatment for hypothalamic amenorrhea is to promote ovulation by eating more. Read my blog post about estrogen deficiency.

Menopause. During menopause, when estrogen is low, phytoestrogens can have a mild pro-estrogen effect. That has led to a great deal of research into the use of phytoestrogen supplements such as soy as an alternative to menopausal hormone therapy.

From hundreds of studies and a few meta-analyses, it appears that isoflavones may help hot flushes, but don’t do much, if anything, for other symptoms of menopause.

Thyroid disease. Concentrated extracts of soy isoflavones may suppress thyroid function. Food-based soy is probably okay as long as you also have enough iodine.

In conclusion

Phytoestrogens generally have a beneficial anti-estrogen effect in women.

They have a mild pro-estrogen effect in menopausal women, which may be beneficial, and a pro-estrogen effect in men and children, which may be detrimental at a high dose.

Helpful information: 

Oestrogen has had a bad press, but it is an essential hormone for women. The problem arises when it is in excess and when unopposed by Progesterone, the hormone designed to balance it, known as oestrogen dominance.

Women who have a history of breast cancer risk for example generally can’t have oestrogen, but phytoestrogens are generally accepted.

Wellsprings Serenity cream and Menopause Capsules provide help with hormonal symptoms such as hot flushes, sleep and tiredness. Women with more severe symptoms who can have a little oestrogen can use 20-1 which has the majority ingredient of progesterone and two natural oestrogens derived from soy.

Lara Briden has written extensively about hormone health and you will find articles on her website at