Isothiocyanates
Isothiocyanates are sulphur containing chemicals that we get from certain vegetables with a strong taste and smell. These vegetables don't actually contain the chemical up front, but they do have a precursor that is made into isothiocyanate during the digestive process.
Cruciferous vegetables such as broccoli, brussel sprouts and cabbage have sulfur-containing chemicals called glucosinolates. When these vegetables are chewed or chopped, the cell membranes break down and they come in contact with an enzyme (also in the vegetable, and in smaller amounts in our intestinal tract) called myrosinase. Myrosinase hydrolizes the glucosinolates, and turns them into the phytonutrient isothiocyanates.
There are several different types of glucosinolates, which each produce a different variety of isothiocyanate. For example, glucoraphanin is hydrolized into the isothiocyanate sulforaphane, gluconasturtin becomes phenethylisothiocyanate, and sinigrin is turned into allyl isothiocyanate. You may find several of these chemicals in a single type of vegetable, and as a group they all exhibit cancer-fighting properties.
Brussel sprouts are an excellent source of glucosinolates. Some other foods that are high in glucosinolates, which are then changed to isothiocyanates, are watercress, mustard greens, turnip greens, cabbage, kale, kohlrabi, broccoli, horseradish, cauliflower and bok choi.
You can get the most benefits from this cancer-fighting phytonutrient if you eat these vegetables raw, or as lightly cooked as possible. Glucosinolates are water soluble, so they can be lost in your cooking water. Cooking at high heats can deactivate the enzyme myrosinase which is needed to hydrolize these chemicals into isothiocyanates.
There are a number of ways that these phytonutrients help the body fight cancer. They can inhibit the activation of carcinogenic substances and speed up the removal of these substances from the body. They increase the activity of enzymes that protect cells from DNA damage, and decrease inflammation in the cells. They induce apoptosis, which is the cell death signal that "turns off" cancer cells. They also inhibit growth of helicobacter pylori, a bacteria which is associated with gastric cancer.
While scientists can prove that isothiocyanates do all this in a test tube or animal studies, the real test is in human studies. Epidemiological studies have shown that people who eat more cruciferous vegetables have lower cancer rates, but it is hard to isolate this particular chemical as the protector, and not some other chemical found in the foods. Studies now focus on urinary excretion of isothiocyanates, rather than intake of glucosinolates. This tells how much of the phytonutrient was actually absorbed into the system. A study published in The Lancet in 2000 followed a group of 18,244 men in Shanghai, China for 11 years. The conclusions showed that men with detectable levels of isothiocyanates in the urine were at decreased risk of lung cancer.
The information on this page is not meant to be used in treatment of medical conditions. Please seek the advice of a physician about any medical condition or symptom. Those with medical conditions should consult a medical professional about the appropriateness of taking dietary supplements or diet therapy, and how these methods will interact with their medications.
Phytochemical Society of North America
Phytochemical Society of Europe
For detailed information about the chemical structure, formula, and molecular weight of various phytonutrients, visit
The US Dept of Agriculture.
Phytochemicals also gives detailed information on specific phytochemicals.
Search for herbs at the Sloan Kettering Memorial Cancer Center website.