Phytoestrogens

What are phytoestrogens?

Phytoestrogens are substances found in plant-based foods that have a similar chemical structure to oestrogen in a woman’s own body and have oestrogen-like properties. They bind to the same receptors that our own oestrogen does. However, they don’t bind as strongly to those receptors as our body’s own oestrogen does, so their effects are not as strong.

Since oestrogen is one of the hormones that declines during menopause, these phytoestrogen- containing plant-based foods are considered to assist with replenishing some of the oestrogen loss. These foods may not be enough to replenish oestrogen levels once menopause is reached, but they may help during the oestrogen swings of menopause.

The two types of phytoestrogens are isoflavones (found in soybeans) and lignans (found in flaxseed, whole grains, legumes, fruits and vegetables).

Benefits

Phytoestrogens also have a range of potential benefits, including:

• Relieving hot flushes

Phytoestrogens may help to relieve uncomfortable hot flashes. A 2014 study found that phytoestrogens reduced the frequency of hot flashes in menopausal women without any serious side effects (1). A meta-analysis in 2015 concluded that phytoestrogens appear to improve hot flushes without serious side effects (2).

• Assisting in prevention of osteoporosis

Estrogen deficiency after menopause can affect bone health and cause conditions such as osteoporosis. Phytoestrogens may be a natural alternative to menopausal hormone therapy.

While studies have found that phytoestrogens may help to combat postmenopausal osteoporosis, researchers noted that there were some potential side effects. It is not recommended that phytoestrogens are used alone to prevent osteoporosis (1).

• Combatting menstrual issues

When a woman’s estrogen levels drop during their menstrual cycle, it can affect mood and energy levels. Eating foods rich in phytoestrogens during this time may help to balance hormone levels and relieve symptoms (1).

More research is needed to support using phytoestrogens in this way.

• Treating acne

When women get acne, the cause may be a rise in male hormones (androgens) in their bodies. Phytoestrogens may help to combat acne by rebalancing hormone levels. More research is needed in this area to determine if phytoestrogens are an effective acne treatment (1).

• Promoting heart health

Phytoestrogens may support heart health. A 2016 study found that phytoestrogens helped to treat atherosclerosis and improve heart health in postmenopausal women (1).

Phytoestrogens and Cancer

There has been much research into the use of phytoestrogens and different types of cancer.

The World Cancer Research Fund (WCRF) have reviewed the available evidence on the association between the intake of foods containing isoflavones and the risk of cancer. The 2017 review concluded that there was not enough evidence on the link between the consumption of foods containing isoflavones and risk of pre- and post-menopausal breast cancer to make an evidence statement.  In studies on dietary intake there was limited evidence to suggest that foods containing isoflavones decreased the risk of lung cancer in people who have never smoked, but they did not find sufficient evidence to make a recommendation. (3)

A 2014 review of the available evidence by the WCRF found that breast cancer survivors who ate more soy foods after diagnosis may have a lower risk of dying, however the evidence is listed as limited suggestive and not sufficient to make a recommendation. (3)

The available evidence suggests that soy and other isoflavone-containing foods are unlikely to increase cancer risk and may in fact decrease the risk of developing some cancer types, although the evidence is not strong enough at this stage. Australia’s Cancer Council recommends that people who already consume soy foods as part of their normal diet, including those who have been diagnosed with breast cancer, should continue to do so. (3)

Food sources

Phytoestrogens occur naturally in plant-based foods. Some examples are:

• Soy products – tempeh, soybeans, tofu, miso, whole soybean soy milk, soy drinks
• Grains – oats, rice, barley, quinoa, rice bran, rye, wheat germ
• Seeds and nuts – flaxseed, sesame seeds, sunflower seeds, pistachios, almonds
• Legumes – chickpeas, lentils, red kidney beans, alfalfa, mung beans, split peas

You can simply increase your intake of phytoestrogens by including more plant-based foods in your diet. Try to avoid highly processed soy foods (including plant-based meat alternatives) and soy-based supplements, as they work differently to soy that is found in nature. Examples of ways to include phytoestrogens in your diet include:

• Baked beans on soy-linseed toast
• Glass low-fat soy milk
• Soy linseed bread sandwich with salmon, cucumber and rocket
• Vegetable and soybean soup
• Stir-fried noodles with Asian vegetables, tofu cubes and chicken
• Tempeh burger and salad
• Soy linseed crackers with hummus dip
• Nut and seed bar
• Soy smoothie with banana and 1-2 tablespoons wheat germ or ground flax seed
• 1 slice of dark rye toast with spread and lentil dip
• Miso soup (4)

Soy may not be right for everyone, so consult your healthcare practitioner before adding it to your diet regularly.

References

1. 1. Burgess L & Wilson D, 2018, ‘What are Phytoestrogens? Benefits and Foods’, Medical News Today, viewed on 16 October 2022, https://www.medicalnewstoday.com/articles/320630#benefits
   2. Chen M-N, Lin C-C & Liu C-F, 2015, ‘Efficacy of phytoestrogens for menopausal symptoms: a meta-analysis and systematic review’, Climacteric, 18(2): 260–269, viewed on 16 October 2022, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389700/
   3. Cancer Council, ‘Information Sheet: Soy & Isoflavones’, viewed on 16 October 2022, https://www.cancer.org.au/information-sheet-soy-isoflavones
   4. Jean Hailes for Women’s Health, ‘Phytoestrogens’, viewed on 16 October 2022, Phytoestrogens | Jean Hailes