Isoflavones: What are they, properties, benefits, menopause, Do they make you gain weight? (2025)

Isoflavones or isoflavonoids can be from soy or soya, enriched with calcium, indicated for menopause or acting for their antioxidant effects as cardiovascular system protectors and skin aging blockers. There are different foods from which we can obtain them such as soy, citrus fruits, or from extracts of natural plants such as red clover in the form of a supplement.

Pills and capsules with isoflavones can help regulate estrogen, combat skin deterioration, as well as slow down damage from free radicals. Nowadays there are several types of flavonoids within the isoflavone class, each with its advantages and benefits, so we will explain what they are for and how you can rely on them to feel better without gaining weight, whether you are going to take them naturally or from other sources.

What are Isoflavones?

Isoflavones are natural chemical compounds derived from plants. They are secondary metabolites present in most vegetables such as fruits and vegetables, herbs, and legumes. They have antioxidant properties, benefit against free radicals…

An isoflavone is a compound derived from 3-phenyl-benzopyran-4-one and is somewhat different from other types of flavonoids that are called very similarly, flavones but in this case, they are derivatives of 2-phenyl-4H-1-benzopyr-4-one, that is, it is of the 1,2-diphenyl-propane type instead of 1,3-diphenyl-propane as would be the flavone.

This type of secondary metabolite is highly present in leguminous plants (Fabaceae). There are many vegetables that belong to this group such as trees, shrubs, perennial and deciduous herbs, as well as legumes. But the important thing about isoflavones is their properties and, of course, the benefits they can bring to the body. So let’s see what isoflavones are for and how you can benefit from them.

What are isoflavones used for?

• Regulate estrogen levels.
• Help increase bone density in menopause and osteoporosis.
• Protect the cardiovascular system.
• To block the damage of free radicals.
• To prevent cancer.
• Help lose weight.

Estrogen Regulation

Perhaps one of the most well-known and studied uses of isoflavones is to control the side effects of menopause, such as hot flashes, warmth, and discomfort experienced during menopausal transition in women. The estrogenic action of isoflavones makes them useful for menopause and some disorders in women’s reproductive system. They are considered as phytoestrogens.

Bone Strengthening

Another use and property of isoflavones is to promote the accumulation of bone material in postmenopausal osteoporosis.

It is known that some women lose bone density when they become infertile, which is a fairly common problem since fractures and musculoskeletal problems can occur. There are several studies demonstrating that in animals and humans, isoflavones help increase bone production, reducing bone resorption, a process carried out by osteoclasts, removing bone tissue and releasing minerals into the body.

Arteriosclerosis

Regarding the protection of the cardiovascular system and cardiac muscle, it is clear that they reduce the risk of developing arteriosclerosis in postmenopausal women. By acting as phytoestrogens, non-steroidal chemical compounds similar to human estrogens, isoflavones serve to reduce the amount of fat in the arteries, acting on LDL cholesterol that accumulates with age thanks to their hypolipidemic effect.

Another benefit or use that can be given to them is as an antioxidant protector. Isoflavones help prevent damage from free radicals, atoms that have been partially broken down and wander through the body causing deterioration of other molecules that are part of essential acids and substances for good health. Isoflavones are phenolic compounds that protect against the oxidation of LDL, inhibiting the formation of foam cells.

Cancer Protection

The antitumor action of isoflavonoids is known for their ability to inhibit various enzymes such as tyrosine kinase, aromatase, and topoisomerase II. These enzymes can trigger tumor cell duplication, establishing an anomaly in the epidermal growth factor, leading to skin cancer. A highly studied effect is the induction of cell apoptosis, thus preventing tumor formation.

They also protect the DNA of cells, and in the case of breast cancer, they can be a strong ally by preventing the formation of 17-beta-estradiol, which is formed from testosterone. Some tumors have their origin in hormones dependent on the mentioned estradiol.

Are they natural?

Yes. Isoflavones are natural phytoestrogens. They come from plants, fruits, herbs, and vegetables. Nature produces many types of plants that produce flavonoids of various classes, among which are isoflavonoids. Therefore, isoflavones are natural.

Types of Isoflavones (classification)

• Genistein

• Daidzein

• Glycitein

Foods with Isoflavones

Many vegetables and fruits are rich in phenolic compounds as they produce secondary metabolites that act as antioxidants, inflammation inhibitors, and regulators of female estrogens. Although it is true that not all contain the same proportions of isoflavonoids, in most foods with flavonoids, they can be found along with various types of polyphenols and healthy antioxidant substances for the human body.

As there are different vegetables that vary in their content, below are the foods with the highest amount of isoflavones:

• Soy.
• Red clover.
• Cherries.
• Oranges.
• Grapes.
• Black and green tea.
• Beer.
• Red and white wine.

Soy or Soya

They are chemical compounds present in the plant called Glycine Max, a species of the Fabaceae or legume family.
They are well known for their estrogenic effects, favoring the relief of menopausal discomfort. Soy isoflavones help reduce menopausal hot flashes, mood swings, and everything related to female climacteric.

The importance of soy and its isoflavones is extremely high because, once we consume the food, the body cannot distinguish soy isoflavonoids from those naturally produced by the body.

This helps us modulate estrogen receptors, regulate systemic blood pressure, and strengthen blood vessels.

Red Clover

The other food or natural product that closely follows is red clover (Trifolium pratense L.). This plant is very rich in phytoestrogens, widely used to regulate menopausal side effects such as hot flashes, warmth, mood swings, and everything related to the period when a woman becomes infertile.
Red clover isoflavones are very effective for most menopausal symptoms. They help delay bone tissue loss and prevent the onset of osteoporosis, a very common condition after menopause.

Additionally, the content of isoflavone, a class of antioxidant flavonoid, reduces the influence of free radicals, protecting the cardiovascular system.

Another benefit of red clover and its isoflavones is that it helps remineralize the body, providing calcium and magnesium, trace elements necessary for the fertile period, during menstruation but also when the female climacteric arrives.

Other benefits of isoflavones

• Vasodilator properties.
• Antiplatelet aggregation.

Soy isoflavones and those from Cimicifuga racemosa reduce the amount of free calcium in smooth muscle. They are also capable of stimulating greater production of nitric oxide, which has vasodilator effects.

Another benefit of isoflavones is the prevention of thrombus formation. Their antiplatelet aggregation action modifies blood coagulation, reducing the percentage of cases with clots inside the arteries. This happens due to the inhibition of thromboxane A2 and also tyrosine kinase.

Isoflavones and Menopause

We have already mentioned some of the effects of this type of flavonoids on mature women who stop menstruating. However, the properties of isoflavones in menopause help regulate the deficiency of estrogen and progesterone.

The changes in the female body during climacteric are very important. There are hormonal changes, fluctuations in estrogen levels, which cause mood swings, hot flashes, and general discomfort.

Taking soy isoflavones during menopause and postmenopause helps regulate hormones. Remember that isoflavone has estrogenic action, something that in practice will make these natural chemical compounds restore balance in the body.

Dosage of Isoflavones for Menopause

• Between 40 and 80 mg of isoflavones per day.

It should be mentioned that not all foods will provide the same amount of isoflavones per gram of food, and neither do supplements rich in isoflavonoids contain the same proportions. Therefore, it is important to follow the doctor’s recommendations if consultation is necessary or follow the dosage on the product label.

The ideal and usual dosage is to start with one capsule a day, that is, 40 mg of isoflavones, and in case of strong or persistent symptoms, increase the dosage to 80 mg.

How to Take Them?

The best time of day is in the morning. You can take your dose of isoflavones for menopause with a glass of water.
This should only be done if you are taking isoflavones in pill form. If you take them from foods, you can take more in the morning or throughout the day.

Contraindications

• Pregnancy.
• Diabetes.
• Hypersensitivity to flavonoids.
• Hypothyroidism.
• Treatment for breast cancer and other oncological types.
• Gastrointestinal problems.
• Children.

Although isoflavones have not caused cases of insulin resistance, diabetic individuals should consult before taking them. There are some in vitro trials conducted on mice where a decrease in hepatic insulin receptors has been observed.

The isoflavone genistein can cross the placental barrier and reach the central nervous system, making it clear that a contraindication for isoflavones is pregnancy to prevent possible anomalies and malformations in the fetus. It could also lead to a lower than normal birth weight.

Side Effects

• Intestinal gas.
• Neutralization of the effects of breast cancer medications such as tamoxifen.
• Changes in menstrual period.

Although the side effects of soy isoflavones and those produced from other types of vegetables are not usually common, in some cases, flatulence and intestinal gas may occur. Individuals who frequently experience gas should monitor their consumption.

In the case of individuals undergoing cancer treatment, neutralization of the medicinal effects of the administered drugs may occur, so it is advisable to always consult with a doctor before starting to use them.

Young women may notice some imbalance or abnormality in their menstrual periods. This situation will correct itself upon discontinuing the intake of isoflavones. An increase in the duration of the menstrual period may occur as well as a decrease.

Isoflavones with Calcium

Ideal for improving bone health, isoflavones with calcium are a supplement to delay bone tissue loss, helping with the diet and regulating the deficiency in women during the menopausal period.

Calcium is essential for bone production, and isoflavones with their protective properties and stimulation of new bone formation participate in inhibition.

Vitamins, Soy Isoflavones, and Cimicifuga Racemosa

This is a suitable dietary supplement for menopausal women. Vitamins with soy isoflavones and Cimicifuga racemosa (Black Cohosh) help alleviate hot flashes and regulate mood swings in women reaching climacteric.

This supplement in the form of tablets with Cimicifuga racemosa extract is enriched with soy, available in health food stores and pharmacies, and distributed by various brands.

Do They Work in Men?

Yes. Isoflavones have properties for both men and women. They are natural substances that do not distinguish between individuals. However, because they simulate female estrogens, it is very common for women to use them when they enter menopause and during the postmenopausal period. However, due to their potent antioxidant effects and anti-inflammatory benefits, all adult individuals can use them.

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