The Benefits of Cruciferous Vegetables

By Paul E. Lemanski, MD, MS, FACP

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 heart attacks, strokes and cardiovascular death while others may reduce certain types of cancer.

In the first 88 installments of the Non-Medicated Life, certain dietary practices and a healthy lifestyle have been shown to accomplish naturally for the majority of individuals most of the benefits of medications in the treatment of chronic medical conditions such as hypertension, high cholesterol, pre-diabetes, diabetes and heart disease. As a medical intervention, certain dietary practices and a healthy lifestyle may accomplish such benefits with fewer side effects, may reduce the number and amount of medication, and may allow actual discontinuation of medication. And while medications such as tamoxifen and raloxifene (selective estrogen receptor modulators) have been shown to decrease breast cancer risk, and low-dose aspirin may reduce cancers of the gastrointestinal tract, such medications have side effects and other associated risks. 

In contrast, the consumption of cruciferous vegetables may reduce cancer risk more broadly and more powerfully than medications, and offers little to no risk. Cruciferous vegetables should be viewed as an integral part of an effective plant-based diet.

Cruciferous vegetables include broccoli, broccoli rabe, cauliflower, kale, Brussels sprouts, cabbage, turnip greens, mustard and Bok Choy. They are members of the genus Brassica, and are commonly referred to as cruciferous because their flowers resemble a crucifer or cross. Although not members of the genus Brassica, arugula, watercress, radish, horseradish and wasabi are also considered cruciferous.

Vegetables and fruits have been associated in epidemiological or population-based studies with lower rates of cancer. Currently, the National Cancer Institute is recommending the consumption of nine servings of vegetables and fruits per day. Apart from this, specific recommendations for the consumption of cruciferous vegetables have not been made to date. Nevertheless, in epidemiological studies, a high intake of cruciferous vegetables has been associated with lower risk of lung and colorectal cancers. There is also some evidence of a reduction in breast and prostate cancers. Additionally, in some studies consumption of cruciferous vegetable intake, specifically cabbage, was associated with lower risk of pancreatic cancer. 

Cruciferous vegetables are an extremely rich source of a group of phytonutrients called glucosinolates, including glucoraphanin that under the proper circumstances break down to sulforaphane and indol-3-carbimol, both of which have been extensively studied in animal models and human tissue culture as natural substances – with potent anti-cancer properties.

For example, sulforaphane is a potent inducer of the phase 2 enzyme system in the liver, which is responsible for breaking down carcinogens consumed in the diet or inhaled. Both sulforaphane and indol-3-carbimol have been shown to induce cell cycle death (apoptosis) in cells with DNA damage that could progress to cancer, thereby inhibiting proliferation of damaged cells for a number of cancers. Finally, there is some evidence in human trials and tissue culture that sulforaphane and indol-3-carbimol can inhibit metastasis of cancer cells into normal tissue, as well as inhibit the development of new blood vessels (angiogenesis) that cancer cells need to proliferate. 

Unfortunately, the consumption of cruciferous vegetables by any means may not be sufficient to obtain maximal potential benefit. In nature, glucosinolates including glucoraphanin, are stored in small vesicles in the flesh of the plant. In close proximity, other vesicles contain the enzyme myrosinase. When the raw plant is chewed the vesicles break and myrosinase acts on the glucoraphanin to form sulforaphane. However, cooking or steaming the plant for more than four minutes may inactivate most of the myrosinase, and significantly diminish the amount of sulforaphane produced. This inactivation of myrosinase also occurs with frozen broccoli that is first flash boiled to improve shelf life. 

One strategy that may allow maximal sulforaphane production, despite cooking, would be to add ground mustard seed after cooking. As part of a cruciferous vegetable, ground mustard seed contains myrosinase that because it an enzyme (biological catalyst), need be present in only very small amounts to maximize production of sulforaphane. Or, eating a small amount of raw red cabbage in your salad would also add to your stomach contents the myrosinase needed to utilize the glucoraphinin of cooked cruciferous vegetables, such as broccoli or Brussels sprouts. Alternatively, if veggies are cut up 30-40 minutes prior to steaming or cooking, the myrosinase will convert the glucoraphinin to sulforaphane – and once produced, the sulforaphane is heat stable.

Another strategy for those not interested in eating raw broccoli (that may be difficult to chew), is to consume raw broccoli sprouts. Added to a salad or a sandwich, broccoli sprouts are easy to chew, lend a fresh spicy flavor, and result in 10 to 100 times the sulforaphane production of raw broccoli florets. Adding broccoli sprouts to a smoothie in the morning is another way to maximize your daily dose of sulforaphane and its anticancer benefits. 

In summary, cruciferous vegetables have been shown in epidemiological studies to reduce cancer risk in lung, colon, breast, prostate, and possibly pancreatic cancers.  The mechanism appears to be an ability of sulforaphane and indol-3-carbimol to induce enzymes in the liver to break down ingested carcinogens, as well as direct effects on inducing cancer cell death, and reducing the risk of metastasis by reducing blood vessel formation within tumors. Animal models, and human tissue culture seem to confirm these mechanisms. 

From a practical perspective, maximizing sulforaphane from cruciferous vegetables requires consuming them raw or minimally cooked or cutting up the vegetables 30-40 minutes before cooking. With proper preparation of the cruciferous vegetables as part of an effective plant-based diet plan, cancer risk may be minimized, and the non-medicated life more likely result. 

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.