Each year, as many as a quarter of a million women in the US utilize surgery to increase their breast size. Many other women purchase natural products touted to achieve the same goal without surgery. However, there is no meaningful evidence that any of these herbs and supplements actually have this effect, and no theoretical evidence to suppose that they would. In this article, we discuss the information that is available on this subject.


Many manufacturers of breast enhancement products claim that their treatments are clinically proven. A typical website may quote a study that says something like this: “One hundred women were given this product, and after 6 months their breast size increased by 10%!” However, while this may sound promising, it actually shows nothing at all.

The problem lies in a deeply rooted feature of human perception: When people expect to observe something, they usually do observe it, whether or not it actually occurred. In the hypothetical breast enhancement study just described, researchers would find it almost impossible not to “discover” an improvement. Measurement of breast size is an inexact art that allows for considerable leeway. Human nature would inevitably incline researchers to err on the side of finding improvement when they make their measurements at the end of the study. This would be the case even if the researchers were completely impartial, and it is even more of a problem if they are paid by the product’s manufacturer (which is usually the case). This is not to say that they’re lying, it’s just that they are human.

In order to get around this problem, medical researchers use a special type of study: the double-blind, placebo-controlled trial. In these trials, some participants receive real treatment, others receive fake treatment, and neither the participants nor the researchers know which is which (until the study is over). When performed correctly, double-blind, placebo-controlled studies eliminate the influence of bias (and other confounding factors), and for this reason they are the accepted source of reliable knowledge regarding medical treatments.

Unfortunately, there are no published double-blind, placebo-controlled studies of breast enhancement products at the time of this writing. Until breast enhancement products are subjected to this form of study, it is not possible to take any of them as evidence-based. (For more information on why double-blind trials are so essential, see Why Does This Database Rely on Double-Blind Studies?)

In lieu of clinical evidence, one might possibly be encouraged to try breast enhancement products if they had a reasonable theoretical likelihood of increasing breast size. But here, again, these products fall short.

There are three basic categories of herbs and supplements found in breast enhancement products: phytoestrogens, herbs and supplements said to raise progesterone levels, and miscellaneous herbs and supplements that have no real relationship to breast enhancement. We will discuss each one individually.


The hormone estrogen, if taken in high enough doses, increases breast size by stimulating growth of breast tissue. However, it is not safe to use estrogen in this way because when breast cells are stimulated to grow, they are more likely to turn cancerous. A woman who took enough estrogen to enlarge her breasts would greatly increase her risk of breast cancer.

Many herbs and supplements provided in breast enhancement products are included there because they act somewhat like estrogen in the body. These substances are called phytoestrogens, meaning “plant-based estrogens," and include the following:

Other herbs and supplements that are not phytoestrogens, but are widely promoted as if they were, are added to breast enhancement products. These include black cohosh, chasteberry, dong quai, ginseng, and Mexican yam. Black cohosh may have estrogen-like actions in some parts of the body, but probably not in breast tissue; the other herbs are probably not phytoestrogenic at all.

According to manufacturers of breast enhancement products, phytoestrogens can enlarge the breasts, like estrogen, but without incurring estrogen’s risks.

However, there are several problems with this hypothesis.

Perhaps the most important is that phytoestrogens generally act to decrease the estrogen-related functions of the body, rather than increase them. Here’s why: Natural human estrogen exerts its effects in the body by latching on to special sites on cells called estrogen receptors. Phytoestrogens also latch on to estrogen receptors. However, when they do so, they only produce a partial effect. In addition, they block the ability of real estrogen to bind to those receptors. The net effect in women of menstrual age is to reduce the action of estrogen. This may be a very useful effect because, in theory, it could decrease a woman’s chance of developing breast cancer. However, the same line of reasoning suggests that phytoestrogens should decrease breast size, not increase it.

Furthermore, studies indicate that many breast enhancement products do not even contain substantial amounts of phytoestrogens.1,2

In any case, if a breast enhancement product were to contain a powerful phytoestrogen in sufficient quantities to actually stimulate growth of breast cells (a very big if), it would also increase the risk of breast cancer! You can’t get one effect without the other. Measurement of estrogenic breast cell stimulation is, in fact, one way of determining the breast cancer risk posed by a substance under study, whether it is a supplement or an environmental contaminant.

Thus, there is no particular reason to believe that phytoestrogens can enhance breast size, nor, it they did, that they would produce such an effect safely.

Raising progesterone levels

Other constituents of breast enhancement products are used because of their supposed effect on the hormone progesterone. This approach does have a certain logic to it. When taken as a pill, progesterone does increase breast size, and is fairly safely. However, it does so by stimulating the growth and development of milk-producing cells, an effect that most non-nursing women would wish to avoid.

The herb chasteberry, added to breast enhancement products, might increase progesterone levels in some women.3 However, there is no evidence that it increases breast size.

Another herb widely added to breast enhancement products as a source of progesterone, Mexican yam, does not in fact raise levels of progesterone at all. The widespread belief that it does so is based on a misconception.

For more information, see the full Chasteberry and Mexican Yam articles.

Other herbs and supplements

Numerous herbs and supplements are added to breast enhancement formulas merely on the basis that they have been used for some condition that affects women. Some of the more commonly mentioned include damiana (an unproven herbal treatment for sexual dysfunction in women), saw palmetto (an unproven herbal treatment for problems with nursing), fish oil (possibly helpful for painful menstruation), and calcium (probably helpful for PMS), among literally hundreds of others. However, there is no reason whatsoever to believe that an herb or supplement used to treat an unrelated women’s health condition will enhance breast size.