Herbal Medicine, Phytotherapy and Cancer Prevention – Dream or Reality?

Historyof cancer is older even than human history, and cancer remains a leading health problem worldwide today. Primarily rising obesity rates, followed by increasing average life expectancyand the resulting aging of society, appear to be the two most important reasons we have been unable to reduce cancer incidence. A study whose results were announced in December 2017, examining 631 thousand people, suggested that obesity or excess weight was the underlying cause in %40 of people diagnosed with cancer. In other words, obesity has now become a more important cause of cancer than smoking…

Because of its long history and the lack of any meaningful treatment until the past 1 century, cancer holds a deep place in our subconscious fears. The question of how we can prevent it occupies almost everyone’s mind. In fact, we now know that more than half of cancers can be prevented: if we protect ourselves from obesity, smoking, alcohol, harmful sunlight and certain carcinogenic microbes (for example, HPV and HBV), we can prevent half of all cancers. But these are not easy prescriptions for any of us. So we look for seemingly easy ways to protect ourselves from cancer, and traditional and complementary medicine methods are among the first things that come to mind. The most appealing of these, because it carries the label “natural” , is trying treatment with herbal medicines, or phytotherapy.

We Have Long Since Moved Beyond the Era of Obtaining Therapeutic Products from Natural Molecules

Although there are many reasons for the popularity of herbal medicines, their advocates frequently emphasize one point: a significant proportion of modern drugs are synthesized from natural products. However, although partly true 20 years ago, this claim is incorrect today, as we can readily state. We have long since moved beyond the era of obtaining therapeutic products from natural molecules. Today, targets in diseases are identified at the cellular level, and highly specialized drugs directed at those targets are produced using advanced biotechnology. To illustrate, let us compare old weapons of war with today’s weapons. Weapons referred to as ballistic, capable of reaching a specific target, are now preferred. Nobody considers fighting with arrows simply because they are natural…

Two other methods proven effective in protecting against cancer are being physically active and eating a diet rich in vegetables and fruit. This benefit of vegetables and fruit is one reason we look for benefits in herbal products and the substances they contain. Some examples are green tea, lycopene and selenium. This article discusses the role of herbal medicines in cancer prevention.

Can Herbal Medicines Prevent Cancer?

In recent years, traditional and complementary approaches, particularly herbal medicines, have regained popularity. Herbal medicines are very common in much of the world. The use of herbal medicines, including dietary supplements, is becoming increasingly popular even among healthy people. Moreover, approximately % 25 of existing drugs are of plant origin; however, the role of inspiration from herbal products is gradually declining.

As the figure above shows, most modern drugs today are synthetic drugs prepared in laboratories against molecular targets at the cellular level.

Nevertheless, various plant species are used in many parts of the world for disease prevention or treatment. Many countries conduct research to find promising medicinal herbal products. These are widespread not only in Asian countries but also in Europe and the United States.

Cancer is one area in which herbal product use is very common. Research in cancer is very expensive. Patients, relatives and some scientists show considerable interest in phytotherapy because it is easier to administer and cheaper than some cancer treatments. Numerous studies continue to seek the best solution for preventing cancer. These studies have examined ways to prevent cancer. Apart from a healthier lifestyle (an ideal weight, avoiding smoking and alcohol, protecting against sunlight, eating mainly vegetables and fruit, remaining physically active, etc.) no effective solutions for preventing cancer have been found. Very few drug treatments have been proven to prevent cancer; examples include vaccines for hepatitis B-related liver cancer and HPV-related cervical cancer, and the use of aspirin for colon cancer. Can plants play a protective role against cancer while promising fewer side effects?

Herbal Medicine: Back to the Future?

The World Health Organization defines traditional medicine (including herbal medicines) as therapeutic methods that existed hundreds of years before modern medical developments emerged and spread, and that are still used today.

Herbal medicine is one of the biologically based practices of complementary and alternative therapies and is also called phytotherapy.

Many people choose herbal medicine because they fear the side effects of conventional drugs, considering herbs harmless; many also expect healing effects from herbal medicines. However, we must acknowledge that herbal medicines have disadvantages as well as advantages. Despite numerous studies, some questions remain. Another problem with herbal medicines is standardization: the composition of even the same plant can vary across geographical areas and growing methods, and this problem currently appears unresolved.

Is Preventing Cancer with Plants a Dream?

Cancer is a major health problem and a leading cause of death worldwide. It is estimated that one-third of the world’s population will encounter this disease at some point in life and that one-fifth of all deaths are due to cancer.

At least % 40 of all cancer deaths appear preventable. Cancer prevention is very important, and this aim should form the foundation of cancer control programs.

The use of herbal mixtures and medicines is very common among people with chronic diseases, including cancer. Some attribute lower cancer rates in Asian countries, where traditional medicine is much more widespread, than in Western countries to herbal medicine use. Globally, however, cancer rates appear more closely related to obesity rates. The video below shows obesity rates worldwide by year and country.

The public considers proper nutrition the most important lifestyle factor for reducing cancer risk. Natural foods such as fruits, vegetables and spices have therefore attracted scientific and public attention for their cancer-preventive properties. Fruits and vegetables provide fiber and vitamins, along with substances such as polyphenols and alkaloids. Many studies are being conducted to demonstrate that micronutrients in fruits and vegetables reduce cancer incidence. Some population-based (epidemiological) studies have shown an inverse relationship between the risk of many types of cancer and fruit and vegetable consumption. However, the most important point to remember is that most trials of herbal medicines remain at the laboratory-study stage.

Vitamins, minerals and medicinal plant components are widely tested as whole foods or dietary supplements in an effort to demonstrate benefits of nutritional supplements in cancer prevention and treatment. However, scientific evidence does not support recommending specific nutritional supplements to prevent cancer; indeed, beta-carotene and selenium supplements have been shown to increase the risk of certain cancers.

Plant foods have an advantage because they contain abundant fiber and nutrients while being low in calories. Non-starchy vegetables, such as broccoli, carrots and turnips, are also recommended to protect against certain cancers and support weight control. Despite the pros and cons in the scientific literature, evidence-based guidelines do not recommend specific nutritional “supplements” for cancer prevention. Dietary supplements, including vitamins and minerals, are also recommended to be assessed in terms of their harm-benefit balance, side effects and drug interactions.

Some Examples of Anticancer Plants and Their Derivatives

Many plants and their derivatives are being evaluated for their effects on cancer prevention. These include biologically active substances such as curcumin, lycopene, capsaicin, zingerol, catechins, isothiocyanates, isoflavones, vitamins E and C, and selenium. These agents are thought to have anti-inflammatory effects that could influence carcinogenesis (cancer formation). The fact that some anticancer drugs were historically made from or inspired by natural products—many of which we still use as chemotherapy—keeps interest in herbal medicines alive.

Tannins are natural components of green tea thought to prevent cancer at certain doses by promoting cell death in cancer cells. Isoprenoids have been shown to suppress the proliferation of leukemia cells. Phytosterols have been studied as potential agents protecting against cardiovascular diseases and cancer progression.

For example, a supplement that could prevent lung cancer has been sought for decades. These studies found no evidence suggesting that supplements of vitamins A, C, E and selenium reduce lung cancer risk. On the contrary, beta-carotene intake was associated with increased lung cancer risk among people who smoke or have been exposed to asbestos.

Daily 1g calcium supplementation was found to have a moderately protective effect against colon polyps, but no protective effect against colon and rectal cancer. Another large randomized clinical trial found no protective effect of antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E and selenium, compared with placebo) against digestive system cancers. These supplements were even found to increase mortality (the risk of death). Although selenium alone has been reported to protect against certain cancers, this effect needs confirmation through further new studies. In addition, no clear relationship has been found between low selenium intake and increased cancer risk, despite the extensive claims made today. In conclusion, these supplements are not recommended for cancer prevention in men, women or children.

Green tea is another product under investigation because it provides catechins. Green tea may appear safe when consumed as a normal habit and may reduce certain treatment-related side effects in cancer patients, but there is no convincing evidence that it prevents cancer. However, severe liver damage has been reported at high doses, and patients receiving bortezomib treatment should not use it.

Lycopene, another popular supplement, has been investigated for its effects on prostate and head and neck cancers, but no benefit has been reported to date.

Laboratory research has observed some favorable effects of cumin and saffron components on tumor cells, but there is no evidence supporting their use for cancer prevention.

Flavonoids are very widespread. According to the literature, they are considered to have antibacterial, antiviral, anti-inflammatory, anticancer and antiallergic properties. However, study results on preventing colorectal (large bowel) cancers are conflicting and unproven.

Aloe verahas been investigated for an anticancer effect through activation of the immune system. Ginkgo biloba, a type of tree, has demonstrated antioxidant properties in laboratory settings. The potential chemopreventive (cancer-preventive) properties of broccoli and other cruciferous vegetables have been investigated.

In conclusion, none of these supplements has been found to have a significant effect in preventing any cancer. However, the many chemicals and fiber contained in vegetables and fruit may work together to reduce cancer risk. Although a healthy diet rich in fruit and vegetables is very important for cancer prevention, no evidence to date has shown that herbal approaches and specific dietary supplements prevent cancer. Future research should address standardization, possible side effects, drug interactions and individual characteristics.