Is soy a safe alternative to HRT?

Most people who are going through menopause will have experienced some of the annoying (or, occasionally, debilitating) side effects that come with it. These unpleasant side effects, which can include hot flushes, mood swings, and vaginal dryness, are due to low levels of oestrogen.

A common treatment prescribed for the management of menopausal symptoms is hormone replacement therapy (HRT). This is normally oestrogen alone or combined with another hormone, progestin, given in the form of patches or as tablets.

However, HRT is not suitable for everyone. Those who have a history of breast cancer, heart disease, stroke, active liver disease, or blood clotting disorders should not have HRT. This is because HRT may make these conditions worse, or cause new complications. People who have diabetes, migraine, or risk factors for blood clots (like a family history of blood clots) may also be more at risk of complications if they take HRT.¹ Some people may therefore want to consider alternative treatments for managing their symptoms.

Why soy?

Soy contains isoflavones, which are plant-based compounds containing a plant oestrogen called phytoestrogen. These phytoestrogens bind to oestrogen receptors in the body and work like a weak form of oestrogen. Many people, therefore, believe that eating soy, and in doing so taking in more phytoestrogen, will provide the same effects as HRT in helping menopausal symptoms.

However, the amount of isoflavone that a soy product contains depends on how it is processed, and there is great variability in isoflavone content between different forms of soy.² The structure of the isoflavone is also important because, in its natural form, isoflavone is attached to a sugar molecule which must be removed before it can be absorbed by the gut.

The amount of isoflavone absorbed from a particular product varies between people, which means the effects of the soy consumed may also be different

The removal of this sugar molecule is done by intestinal enzymes which vary in quantity between different people. So, the amount of isoflavone absorbed from a particular product varies between people, which means the effects of the soy consumed may also be different.

If you want to increase isoflavone intake it is important to check food labels to see how much isoflavone each product contains. Examples of foods that contain soy include miso soup, tofu, soy milk, and edamame.

Does soy actually help control menopause symptoms?

There haven’t been many studies done to test whether increasing consumption of soy leads to definite health benefits, and the results of the ones that have been done are generally conflicting. At present it is not entirely clear whether soy is a good alternative to HRT or not, in terms of reduction of menopause symptoms.

In 2013, Cochrane – a research organisation which specialises in large analyses of data – published a review looking at whether phytoestrogen treatments reduced the number and severity of menopausal hot flushes.³ They collected the results from 43 trials of phytoestrogen (soy-based) treatments.

It’s difficult to make solid conclusions about whether soy-based treatments are effective

These trials were all randomised controlled trials, which means that some participants were given the treatment and others (“control participants”) were given no treatment or the standard treatment. The Cochrane review found that some trials showed a slight reduction in hot flushes and night sweats with soy-based treatments, but overall there was no indication that soy-based treatments work any better than no treatment.

Since the Cochrane review, more studies have been published. However, these often have conflicting results. In one study from 2022, 84 postmenopausal women were split into two groups, one making no dietary changes and the other following a low-fat vegan diet with daily cooked soybeans. The study found that women following the new diet had fewer menopausal symptoms such as hot flushes. However, this was a small study, and there is no way to tell whether it was the soybeans or the low-fat vegan diet that made the difference to the participants’ symptoms.⁴

Another study from 2021 gave 78 women either a soy and hop extract or a placebo tablet. The women taking the soy and hop extract reported a greater improvement in vaginal dryness and tiredness than those taking the placebo, but there was no difference between the two groups in hot flushes.⁵

As the Cochrane review found in 2013, many of the studies testing soy-based treatments for menopause are of poor quality and do not have many participants. They also use a range of soy-based treatments. This makes it difficult to make solid conclusions about whether soy-based treatments are effective.

Is taking soy safe?

In general, soy is well tolerated by most people. Some may experience minor stomach cramps and bloating because of the starches in the soy products. Although some human studies suggest that eating too much soy (more than 100 mg soy isoflavones a day) can affect the function of the ovaries and lead to lower hormone levels, evidence suggests that diets containing 1-2 servings of soy a day are considered safe and are not thought to cause any negative health consequences.

One-two servings of soy a day is about the level of soy found in a traditional Asian diet, and even twice this amount of soy has little effect on the functioning of the ovaries.⁶

The Cochrane review did not find any evidence that using soy-based treatments for menopause in clinical trials caused harmful effects.⁷

Is soy more beneficial than HRT?

There are no studies that compare soy to HRT in how well they treat hot flushes, so we do not know which is more effective. In general, we can expect the effects of soy to be deemed weaker than those of HRT, because soy contains weaker oestrogen. Whether or not you personally find soy beneficial, there is no harm in taking it, in moderation, as part of a healthy balanced diet.

If soy does not help with your menopausal symptoms and you are able to take HRT, it may be worthwhile trying HRT. There is less evidence for soy’s benefits compared with HRT for certain menopausal symptoms, which may mean you are at a higher risk of some side effects if soy is your sole alternative to HRT.

If HRT is not a suitable option, there are other therapies available, and soy is not the only alternative

For example, the evidence for soy’s use in preventing osteoporosis is limited, and it is still unclear whether or not it is helpful in preventing bone thinning.⁸ There is good evidence, however, that HRT helps reducing hip fractures,⁹ so a danger of substituting soy for HRT is that it could potentially leave you at higher risk of bone thinning.

If HRT is not a suitable option, there are other therapies available, and soy is not the only alternative. Lifestyle measures such as taking regular exercise, maintaining a balanced diet, cutting down on spicy foods, alcohol, and coffee, stopping smoking, and reducing stress levels may help with mood.

Vaginal lubricants or moisturisers can help with vaginal dryness, and prescription medications such as tibolone and clonidine may help with symptoms of hot flushes. Finally, antidepressants may be helpful if you are experiencing low mood and are unable to take HRT. It is worth discussing your options with your GP and they will be able to help you decide which treatment is best for you.

Featured image show two women in a kitchen pouring a pot of yoghurt or milk into a blender full of fruit. The image is cropped so you can only see their torsos

Last updated May 2023
Next update due 2026