Potential Benefits of Sulforaphane

By Paul E. Lemanski, MD, MS, FACP

Editor’s Note: This is the 111th in a series on optimal diet and lifestyle to help prevent and treat disease. Any planned change in diet, exercise or treatment should be discussed with and approved by your personal physician before implementation. The help of a registered dietitian in the implementation of dietary changes is strongly recommended.

Medicines are a mainstay of American life and the healthcare system not only because they are perceived to work by the individuals taking them, but also because their benefit may be shown by the objective assessment of scientific study. Clinical research trials have shown that some of the medicines of Western science may reduce the risk of Type 2 diabetes, heart attacks, strokes, cardiovascular death, and even some cancers.

In the first 110 installments of the Non-Medicated Life, a healthy diet and lifestyle has been shown to accomplish naturally for the majority of individuals most of the benefits of medications in the prevention of the chronic medical conditions mentioned above. With respect to a healthy diet, certain foods may have a disproportionate benefit. This may be true for cruciferous vegetables and their most active and well-studied ingredient sulforaphane.

The cruciferous vegetables include arugula, bok choy, broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, radish and watercress. Epidemiological data suggests that cruciferous vegetables may reduce the risk of all-cause mortality and the risk for certain cancers. For example, while observed for some time, a study published in 2011 in the American Journal of Clinical Nutrition, showed individuals in the top 20% of vegetable consumption had a 16% reduction in all-cause mortality. Of interest, individuals in the top 20% of cruciferous vegetable consumption reduced all-cause mortality risk by 22%. 

In another study, men who consumed three-to-five servings a week of cruciferous vegetables had a 40% reduction in their risk for prostate cancer as compared to men eating less than one serving a week. In another study, smokers consuming four servings of cruciferous vegetables per month had a 55% reduction in lung cancer risk. Studies have also shown women consuming cruciferous vegetables once a week reduced risk for breast cancer by 17% and by up to 50% in those consuming cruciferous vegetables on a daily basis.

While such reductions are impressive, such epidemiological or population-based studies do not establish causality. For establishment of causality, randomized prospective clinical trials are needed, and finding the possible causative substance for the observed benefit would aid the design and completion of such trials.

Starting over 30 years ago Dr. Paul Talalay and the Johns Hopkins’ Cullman Chemoprotection Center attempted to identify the active ingredient responsible for the benefit seen in epidemiological studies. Ultimately, the lab identified a substance from broccoli called sulforaphane and set out to study it for efficacy and possible mechanisms. To date, thousands of research studies have been completed investigating sulforaphane and its potential benefit in human health.

Broccoli plants do not contain sulforaphane. Rather they contain the precursor of sulforaphane, called glucoraphanin, and an enzyme called myrosinase. The precursor and the enzyme are stored in small vesicles in close proximity to one another within the broccoli floret. When an animal or human chews the plant, the vesicles are broken and the glucoraphenin is acted upon by the myrosinase to produce sulforaphane. The sulforaphane has a disagreeable taste to many animals and some humans and the plant may use this property to protect itself from being eaten. While this may help the plant, what is its connection to possible cancer prevention in humans?

Cancer is a multistep process of damage to DNA ultimately resulting in uncontrolled cell division and dissemination called metastasis. Damage to DNA may come from a variety of sources including ionizing radiation, ultraviolet radiation, viruses such as HIV, HPV and Hepatitis B, as well as exposure to certain compounds called carcinogens. Carcinogens may be artificially made compounds but also may be naturally occurring. For example, a naturally occurring fungus growing on moldy peanuts and tree nuts produces a toxin called aflatoxin that increases the risk of liver cancer.

Thankfully, the liver which is the major detoxifying organ in the body, can act upon both ingested drugs and carcinogens to modify them and, when potentially unhealthy, help enhance their excretion and thus body cells’ exposure time. The liver has two enzymatic systems for drug and carcinogen processing: Phase 1 biotransformation enzymes and Phase 2 conjugation and detoxification enzymes. Phase 1 enzymes can actually take pro-drugs (and pro-carcinogens) and process them to active drugs or carcinogens. Phase 2 enzymes can combine carcinogens and cocarcinogens with substances that make them water soluble and thus able to be eliminated from the body via urine. 

Sulforaphane appears to influence both Phase 1 and 2 enzymatic systems. It decreases activity of Phase 1 enzymes and increases activity of the Phase 2 enzymes, thus reducing the formation of carcinogens and cocarcinogens and increasing their elimination from the body. Reducing carcinogen exposure in this way, may thus help prevent the development of cancer.

In addition, sulforaphane may have a direct effect on DNA by protecting tumor suppressor genes, portions of DNA that help control cell growth. In a study of men with diagnosed prostate cancer who showed evidence of recurrence after prostate surgery, 60 milligrams of sulforaphane a day (equivalent to what results from ingesting approximately 140 grams of broccoli sprouts) slowed the rate of rise of tumor marker Prostate Specific Antigen (PSA) by 86%. (Please note: although safe in moderate dosing, the adjunctive use of high-dose sulforaphane described above in cancer patients as with all patients should first be discussed with your oncologist, urologist, or primary care physician to determine any possible contraindications to use). While slowing the rise of this tumor-marker would seem to indicate a slowing of cancer growth, further studies are needed.

In summary, vegetables in general and cruciferous vegetables particular appear to lower all-cause mortality including cancer. One of the mediators of this benefit appears to be sulforaphane, a substance derived from the mastication of multiple cruciferous vegetables, but especially broccoli florets and broccoli sprouts. Sulforaphane activates enzymes in the liver that deactivate carcinogens and increase their elimination from the body. It may also have direct effects on protecting DNA. 

Sulforaphane is representative of a number of naturally occurring substances that may lower cancer risk and be used adjunctively with traditional Western medical treatments to potentially improve outcome once cancer is diagnosed.

Paul E. Lemanski, MD, MS, FACP (plemanski3@gmail.com) is a board-certified internist practicing internal medicine and lifestyle medicine in Albany. Paul has a master’s degree in human nutrition, he’s an assistant clinical professor of medicine at Albany Medical College, and a fellow of the American College of Physicians.