Did you know herbal medicine can help prevent breast cancer? — Confirmed by a 14-year study of over 180,000 women

Three-line summary. In a large study that followed more than 180,000 women in Taiwan for 14 years, women who had been taking herbal medicine had a 43% lower risk of developing invasive breast cancer. The more consistently and heavily herbal medicine was taken, the greater the preventive effect (up to a 70% reduction), and with Si-wu-tang (四物湯), a leading gynecological formula, the risk was lower by as much as 64%.

“Beyond helping people who already have breast cancer, is there any way to prevent the disease in the first place?” This is a question often raised in the clinic by people with a family history of breast cancer or other risk factors. Today we offer one answer to that question, drawn from a large study that followed more than 180,000 people.

Can herbal medicine really reduce the ‘onset’ of breast cancer?

A study published in 2017 in the international journal Medicine addressed this question head-on. The researchers selected 184,386 women aged 20–79 from Taiwan’s National Health Insurance Research Database (NHIRD) and followed them for 14 years, from 1999 to 2012. About 78% of them had been prescribed a Chinese herbal product (CHP) at some point, and 1,853 new cases of invasive breast cancer were diagnosed during the follow-up period.

The result was clear. After adjusting for various risk factors, women who took herbal medicine had a 43% lower risk of developing breast cancer than those who did not (hazard ratio 0.57, 95% confidence interval 0.50–0.65). In terms of actual incidence as well, breast cancer occurrence per 10,000 person-years fell from 1.73 cases in the non-user group to 0.85 in the user group — about half.

The Sandol Korean Medicine Clinic column has introduced a number of studies on herbal cancer care, and although they were carried out by different researchers on different cancer types and topics, their conclusions always point in the same direction. Regardless of the cancer type, adding herbal medicine consistently converges toward preventing onset, reducing mortality, increasing survival, reducing the side effects of standard treatment, and improving quality of life. Today’s study illustrates the ‘preventing onset’ part of that picture.

How much do you need to take for it to work?

What makes this study especially persuasive is that it showed a clear dose-response relationship. The more herbal medicine was taken, the more the risk fell in a stepwise manner.

• Cumulative dose of 300 g or less: risk reduced by 35% (hazard ratio 0.65)
• 300–1,800 g: risk reduced by 51% (hazard ratio 0.49)
• More than 1,800 g: risk reduced by 70% (hazard ratio 0.30)

Even a small dose brought benefit, but the more consistently and heavily it was taken, the greater the preventive effect. It may look like a maze of numbers, but the key point is a single one: the longer a woman had been taking herbal medicine, the less breast cancer arose in the first place.

Was there a formula whose effect stood out in particular?

There was. Women who took Si-wu-tang (四物湯) — the leading gynecological formula for tonifying qi and blood — had a 64% lower risk of developing breast cancer (hazard ratio 0.36, 95% confidence interval 0.28–0.46). This protective effect appeared consistently across nearly all age groups, from women in their 20s to their 70s.

Si-wu-tang is a basic gynecological formula for tonifying a deficiency of qi and blood, composed of four herbs: Bai-shao (白芍, Paeonia lactiflora), Dang-gui (當歸, Angelica sinensis), Chuan-xiong (川芎, Ligusticum striatum), and Shu-di-huang (熟地黃, Rehmannia glutinosa). In laboratory studies, Si-wu-tang has been reported to inhibit the growth of breast cancer cells (such as MCF-7) and to show phytoestrogen activity.

I’m on hormone therapy — is it all right to use herbal medicine as well?

There is one more intriguing point in the same study. Women who were receiving hormone therapy (HT) in fact had roughly a 3.5-fold higher risk of breast cancer. Yet women who took herbal medicine while receiving hormone therapy had a lower risk than those who received hormone therapy alone. In other words, a treatment that raises risk and a treatment that lowers it were laid side by side within a single study. That said, whether to combine the two must always be decided in consultation with your treating physician.

How does herbal medicine prevent cancer ‘in advance’?

The clue lies in the character of the prescriptions. Notably, these women did not deliberately take herbal medicine in order to prevent breast cancer; most took it for gynecological concerns such as menstrual irregularity or premenstrual syndrome. A Korean-medicine doctor uses the four diagnostic methods (望聞問切) — observation, listening/smelling, questioning, and pulse-taking — to assess the state of the body, such as menstrual irregularity, insomnia, or menopausal symptoms, then determines a pattern diagnosis (辨證) and adjusts the prescription accordingly. The researchers interpret this early correction of subtle imbalances in the body — the so-called subhealth state — as a way of reducing the very soil in which breast cancer might take root.

Here we see the long-held perspective of Korean medicine known as “treating disease before it arises” (治未病). Just as, in a field where weeds keep growing back, one does not merely pull the weeds but changes the soil itself, herbal medicine seeks to restore the body to a balanced state in which breast cancer is less likely to develop.

So can I take herbal medicine instead of screening?

No. It is essential to keep a balanced perspective at all times. Although a strong association between herbal medicine and a breast-cancer prevention effect has been confirmed, herbal medicine is, above all, not a replacement for regular breast screening (mammography). Regular screening should be received on schedule as usual, while herbal medicine should also be taken consistently for preventive purposes at the same time.

If you have a family history of breast cancer or carry risk factors, we recommend discussing thoroughly with a specialist Korean-medicine doctor whether preventive herbal medicine — which helps restore the body’s balance — is right for you, alongside regular screening.