Oestrogen: What It Does, Menopause, Bone and the Evidence on Soy

Oestrogen is not one hormone but a family of three, of which oestradiol, made mostly in the ovaries, does the main work in the years between puberty and menopause. It builds the lining of the uterus each month and also supports bone, cholesterol handling and brain function in women and men. Levels fall at menopause, which WHO says most women reach between 45 and 55 years. A survey by the Indian Menopause Society found the average age of natural menopause in India to be 46.2 years. This entry sits in NNWA's handbook of hormones.

What is oestrogen and where is it made?

It is a group of related hormones produced chiefly by the ovaries, with smaller amounts from body fat, the adrenal glands and, in pregnancy, the placenta. The US National Library of Medicine notes that many types exist but only three are commonly tested, and each has its own source and its own stage of life. Men make oestrogen too: small amounts of oestradiol come from the testicles, and their levels do not change much through life.

What does oestrogen do through life?

It rises at puberty, cycles every month for three or four decades, peaks in pregnancy and declines after menopause. In each menstrual cycle oestradiol helps an egg to be released and thickens the lining of the uterus during the first half; the second half belongs to its partner hormone, covered in the entry on progesterone. The same source lists work well outside reproduction: healthy cholesterol and blood sugar levels, bone and muscle strength, and brain functions such as the ability to focus.

That wider list explains why the end of ovarian oestrogen shows up in places far from the uterus. Bone turnover, the place where fat is stored and the pattern of blood fats all shift during the same few years, and each is taken in turn below. None of these changes is a disease in itself, and they differ a great deal from one woman to the next.

What changes at menopause?

The ovaries stop releasing eggs and the oestrogen circulating in the blood declines. WHO defines natural menopause as 12 consecutive months without a period with no other cause, and calls the years of irregular cycles before it, plus the year after the final period, perimenopause. It lists hot flushes and night sweats, vaginal dryness, difficulty sleeping and changes in mood among the symptoms, and stresses that some women have few if any. Pregnancy is still possible during perimenopause, a point that is often missed.

Age at menopause in India: the survey figures

The Indian Menopause Society surveyed women through 21 of its chapters across the north, south, east, west and centre of the country. Natural menopause arrived at an average of 46.2 years, against the 51 years the paper quotes for Western women, and irregular periods began at about 44.7 years. Regional averages ran from 45.5 years in the north to 47.8 years in the central region. Age also rose with money: 46.1 years among women from poor economic backgrounds and 48.1 years among the rich.

NFHS-5 asked a broader question. It counts a woman aged 30 to 49 as menopausal if she is not pregnant or recently delivered and has had no period for six months, or if she reports menopause or a hysterectomy. On that definition 17 per cent of women in the age band are menopausal. The same survey found that 3 per cent of women had undergone a hysterectomy, which is one reason the younger rows of the table are not zero.

Researchers who removed hysterectomy from the NFHS-5 data estimated that 2.2 per cent of women had reached menopause before 40, which is called premature, and 16.2 per cent of those aged 40 to 44 had reached it early. An analysis of NFHS-4 put premature menopause at 3.7 per cent of women aged 25 to 39, of which 2.1 per cent was natural and 1.7 per cent surgical. The Society's guideline draws the consequence: it reports osteoporotic fractures occurring 10 to 20 years earlier in Indians than in Caucasians.

How does falling oestrogen affect bone?

Bone is lost fastest in the few years around the final period. The American SWAN cohort followed 862 women with repeated scans: loss began one year before the last period and slowed, without stopping, two years after it. Over ten years the lumbar spine lost 10.6 per cent of its density, 7.38 points of that inside the three-year window, and the neck of the thigh bone lost 9.1 per cent. Women with a higher body mass index lost bone more slowly. WHO names this loss a significant contributor to osteoporosis and fractures.

Food cannot replace the hormone, but it supplies what bone is made from. ICMR-NIN's 2020 report sets calcium at 1,000 mg a day for an adult woman and 1,200 mg a day after menopause, with vitamin D at 600 IU. The handbook entries on calcium requirements and vitamin D give the detail, and the calcium table for Indian foods ranks the sources. Because Indian women reach menopause early, the years spent with low oestrogen are long, and the case for building the habit before 45 is strong.

Does menopause cause weight gain, and what about the heart?

Weight, on the SWAN data, does not jump at menopause, but body composition does change. Among 1,246 women measured by body scan, weight climbed in a straight line through the forties with no acceleration at the transition. Underneath, the yearly rate of fat gain nearly doubled, from 1.0 to 1.7 per cent, and lean mass began to fall. Across a transition lasting about 3.5 years that came to a 6 per cent rise in fat mass, an average of 1.6 kg, and both trends flattened roughly two years after the final period.

The scale can therefore stay almost still while the waist grows, which makes the waist to hip ratio calculator a better check than weight in these years. On the heart, WHO states that women's advantage over men in cardiovascular disease gradually disappears after menopause. A 2020 scientific statement from the American Heart Association describes the transition as a time of accelerating risk, with adverse changes in body composition, blood fats and blood vessels, and calls midlife a window for early prevention.

Phytoestrogens and soy: the trial evidence

Phytoestrogens are plant compounds, the best studied being the isoflavones of the soya bean. They have been tested mainly as extracts in capsules, less often as food. The table gathers what four pooled analyses reported. The amounts mentioned describe what the trials used and are not a recommendation.

Read these as modest effects from uneven evidence. The JAMA authors judged 74 per cent of their trials to be at high risk of bias, and results varied widely between studies. One fewer hot flush a day matters to a woman having ten and hardly at all to a woman having two. The Indian Menopause Society advises awareness of phytoestrogen-rich foods in the Indian diet, a Grade C recommendation, and its 2020 guideline warns that India has no regulations ensuring the content or quality of herbal and isoflavone products.

As a food, soya stands on other merits. IFCT 2017 lists the brown soya bean at 35.6 g of protein and 239 mg of calcium per 100 g, which is why soya chunks, tofu and the whole bean suit a vegetarian plate at any age. NNWA's note on the protein in soya chunks covers portions.

A worked example: calcium on a Kolkata plate after menopause

This case is illustrative and describes no real person. A 52-year-old vegetarian schoolteacher in Kolkata had her final period two years ago, so ICMR-NIN's figure for her is 1,200 mg of calcium a day. She wants to know whether food alone can get close. The amounts below use IFCT 2017 values per 100 g of raw food.

Which tests measure oestrogen, and who reads them?

An oestrogen test measures one or more of the three types in blood, urine or saliva; on a report it usually appears as oestradiol or E2. Doctors order it for early or late puberty, absent or abnormal periods, difficulty conceiving, menopausal symptoms and bleeding after menopause, and to monitor hormone therapy. In pregnancy an oestriol test between weeks 15 and 20 may form part of a screening panel. A healthy level depends on age, sex, the type measured and the reason for testing, and the test is often repeated.

Menopause itself rarely needs a hormone test. The Indian Menopause Society's guideline says it is diagnosed in retrospect from the history of periods, and that markers such as follicle-stimulating hormone (FSH) and anti-Mullerian hormone (AMH) are best kept for special situations and fertility questions. Oestrogen levels change so often in these years that one reading may settle nothing. The number belongs with the doctor who ordered it.

Common myths and mistakes

A second mistake is to believe that a diet, a tea or a seed mixture can restore oestrogen after menopause. Nothing in the trials above shows a food raising the hormone; the most that isoflavone extracts achieved was a modest easing of hot flushes. A third is to blame every kilo gained in the forties on hormones. The SWAN data show weight rising at the same pace before and during the transition, so appetite, sleep and activity deserve the same attention they did at 35.

Hormone therapy, supplements and safety: when to see a doctor

Oestrogen is also a prescribed medicine, on its own or with a progestogen, in menopausal hormone therapy and in many contraceptives. WHO notes that both hormonal and non-hormonal options exist and that the choice should be made with a health-care provider in light of medical history and preference. Nothing on this page is advice to start, stop or change any of them, and no food or supplement stands in for a prescription.

Isoflavone capsules deserve particular caution in anyone treated for breast cancer. A 2024 pooled analysis of observational studies linked soy isoflavones with a 26 per cent lower risk of recurrence among survivors, but its authors added that evidence is still needed on starting or sharply increasing intake after diagnosis. Observational data cannot settle the question for one patient, so the decision belongs to the oncologist.

Is a low oestrogen level always a problem?

No. After menopause a low oestradiol level is the expected state, and the body goes on making oestrone in fat tissue and the adrenal glands. In men oestrogen stays low throughout life, and it is a high level that prompts a doctor to look further. A low reading matters when it arrives early, before 40, or alongside missed periods at a younger age, and that is a question for a gynaecologist. NNWA's guide to the menopause diet in India covers everyday eating once the transition is under way.

Learning this with NNWA

NNWA, a private skill academy based in Kolkata, runs its classes online in English and in Hindi. Its courses, including the Women's Health and PCOS course, train people to coach healthy clients on food and habits through midlife and to send medical questions to a doctor. None of them is a degree or a dietitian qualification.