Cruciferous Vegetables
Cruciferous vegetables are extremely good for us. They fight disease and provide a mega-array of nutrients. Their cardiovascular disease and cancer fighting properties are mostly due to their strong showing of antioxidant, anti-inflammatory, and phytonutrient content. Many of the cruciferous vegetables, such as broccoli and Brussels sprouts, have been studied extensively, while others are just now grabbing the attention of researchers.
One of the things I like most about this group of vegetables is that it provides a variety of textures and tastes while providing strong disease-fighting power no matter which of those flavors and textures you enjoy.
The cruciferous vegetable family includes the following:
- Arugula
- Bok Choy
- Broccoli
- Brussels Sprouts
- Cabbage
- Chinese Cabbage
- Collard Greens
- Diakon
- Horse Raddish
- Kale
- Kohlrabi
- Mustard Greens
- Radishes
- Rutabaga
- Turnips
- Wasabi
- Watercress
Nutrients in Cruciferous Vegetables
The nutrients in cruciferous vegetables vary slightly from one to another, but they are exceptionally high in the viamins K and C. One cup of cooked broccoli contains about 245 percent of the Daily Recommended Intake (DRI) of Vitamin K, and 135 percent of the DRI of Vitamin C. They also contain significant amounts of chromium, folate, fiber, choline, B vitamins B2 and B6, vitamin E, vitamin A, panothenic acid, phosphorus, mangenese, and choline. Most also contain the flavonoids isorhamnetin, kaempferol and quercitin, along with the carotenoids lutein, zeaxanthin, beta-carotene, and even some very rare antioxidants not often found in foods. One cup of broccoli has as much protein as a cup of rice or corn, but only half the calories. (3)
Cancer
Numerous animal and in vitro studies have shown that cruciferous vegetables prevent cancer and kill cancer cells. While they provide several different functions that are known to prevent cancer, most of the research has targeted their phytonutrients, glucosinolates. In the body, glucosinolates are transformed into isothiocyanates (ITCs), which have been shown to prevent cancer.
However, human studies have shown mixed results. Often, studies researching the cancer-fighting properties of glucosinolates in the human body have failed to demonstrate significant positive differences between the control group and the group consuming cruciferous vegetables.
Researchers believe the mixed results may be caused by genetic differences in humans. According to the Linus Pauling Institute at Oregon State University,
“There is increasing evidence that genetic differences in humans may influence the effects of cruciferous vegetable intake on cancer risk (64). Isothiocyanates are glucosinolate hydrolysis products, which are thought to play a role in the cancer-preventive effects associated with cruciferous vegetable consumption. Glutathione S-transferases (GSTs) are a family of enzymes that metabolize a variety of compounds, including isothiocyanates, in a way that promotes their elimination from the body. Genetic variations (polymorphisms) that affect the activity of GST enzymes have been identified in humans. Null variants of the GSTM1 gene and GSTT1 gene contain large deletions, and individuals who inherit two copies of the GSTM1-null or GSTT1- null gene cannot produce the corresponding GST enzyme (65). Lower GST activity in such individuals could result in slower elimination and longer exposure to isothiocyanates after cruciferous vegetable consumption (66). In support of this idea, several epidemiological studies have found that inverse associations between isothiocyanate intake from cruciferous vegetables and risk of lung cancer (16-19) or colon cancer (34-36) were more pronounced in GSTM1-null and/or GSTT1-null individuals. These findings suggest that the protective effects of high intakes of cruciferous vegetables may be enhanced in individuals who more slowly eliminate potentially protective compounds like isothiocyanates. Alternatively, these same GSTs play a major role in detoxication of carcinogens and individuals with the null gene would be expected to be more susceptible to cancer; thus, the cruciferous vegetables may exhibit significant protection in this population if their protective effect is increasingly important at high carcinogen levels.” (3)
What this means is that according to some researchers, cruciferous vegetables may be lifesavers for some of us. For others, eating cruciferous vegetables simply may not make much difference as far as cancer is concerned.
It is important to note here that very few clinical studies have been done testing the cancer-fighting properties of cruciferous vegetables on humans. Most of the studies are prospective cohort studies
or case-control studies. Prospective cohort studies are studies in which a group of people are interviewed or tested for risk factors and then observed over time to determine their status with respect to a disease or health outcome. Case-control studies compare various risk factors, cruciferous vegetable consumption for example, between people who have a disease and people who don’t. Both of thesenstudy types lend themselves to error for several reasons. The most common of which is that people don’t always report accurately. There is also lots of room for manipulation, and too many variables to control. If you consider the first study in the list below, you will understand why I don’t have much faith in prospective cohort or case-control research. I’m sure most of the studies used did not control how people cooked their foods or what herbs they ate them with.
It isn’t news that our bodies don’t easily absorb some phytonutrients. Many phytonutrients are oil soluble, and our bodies don’t easily absorb them. Some phytonutrients are easier to absorb if we eat them with an oil containing omega-3 fats, as explained in my article about avocados. Also, the glucosinolates aren’t the only phytonutrients in cruciferous vegetables, and what about the antioxidants and anti-inflammatory nutrients. Are we unable to absorb those when they are in cruciferous vetetables, too? It probably is true that some of us absorb more of the glucosinolates than others, but I’m betting that it is eventually discovered that when eaten with the proper other foods, we absorb enough to protect us from cancer. In fact, there has already been some progress in that area:
- A study by University of Illinois researcher Elizabeth Jeffery, and published in the British Journal of nutrition revealed that cooking broccoli just right made more of the cancer-fighting glucosinolate, surforaphane, more available to our bodies. Jeffery states that sulphorphane is one of the most powerful anticarcinogens found in food. Jeffery found that there is an enzyme in broccoli that reacts with the sulforaphane and forms a molecule that we can’t absorb. When you cook broccoli at about 140 degrees, the enzyme is destroyed and the sulforphane becomes available for absorbpion. Since we don’t have the ability to control temperature as closely as the researchers had in their lab, they went on to determine that steaming broccoli at temperatures just hot enough to create steam for about four or five minutes achieved pretty close to the same goals.
Jeffery also showed that combining broccoli with a spicy food containing the enzyme myrosinase enhanced broccoli’s cancer-fighting benefits.”To get this effect, spice up your broccoli with broccoli sprouts, mustard, horseradish, or wasabi,” Jeffery said. (6)
- A study by Paul Talalay, M.D. and J.J. Abel, Distinguished Service Professor of Pharmacology at John Hopkins Medical School compared the phytochemical content of adult broccoli with that of broccoli sprouts. He determined that three-day-old sprouts contain 20 to 50 times more cancer protective chemicals than adult broccoli. “In animals and human cells (in vitro), we have demonstrated, unequivocally, that this compound (sulforaphane) can substantially reduce the incidence, rate of development, and size of tumors,” said Talalay. (7)
- Eating cruciferous vegetables with curcumin, a nutrient found in the herb turmeric, increases the body’s absorption of of the phytonutrient, phenethyl isothiocyanate, and kills prostate cancer cells. (9)
A 2011 in vitro cancer study involving the isothiocyanates (ITCs) in broccoli and other cruciferous vegetables and reported in the Journal of Medicinal Chemistry showed broccoli and its cousins can prevent cancer at the genetic level. Researcher Xiantao Wang and colleagues of Georgetown University analyzed the way ITCs interact with gene p53 in a variety of human cancer cells, including lung, breast, and colon cancer cells.
Gene p53 protects cells by keeping them healthy and suppressing cancer. When gene p53 mutates or suffers damage it stops working correctly and no longer suppresses cancer. According to the researchers, mutated or damaged p53 genes are found in fifty percent of human cancers. The study showed that ITCs remove defective p53 genes while leaving healthy genes alone.
As I mentioned in the introduction to this article, there are many more cancer studies involving the phytonutrients in cruciferous vegetables:
- A brand new study published in the journal Clinical Epigenetics showed that two mechanisms called DNA methylation and HDAC inhibition are influenced by sulforaphanes. These two mechanisms work together to maintain proper cell function. According to Emily Ho from the Linus Pauling Institue and the OSU college of Public Health and Human Sciences, “DNA methylation is a normal process of turning off genes, and it helps control what DNA material gets read as part of genetic communication within cells. In cancer, that process gets mixed up. (11) (12)
“It appears that DNA methylation and HDAC inhibition, both of which can be influenced by sulforaphanes, work in concert with each other to maintain proper cell function,” Ho said. “They sort of work as partners and talk to each other.”
- A study published in the Journal Clinical Cancer Research in 2010 showed that sulforaphane was able to kill breast cancer stem cells in mice and in lab cultures It also prevented new tumor cells from growing. (15)
- Another glucosinolate in cruciferous vegetables, indole-3-carbinol (I3C), has been reported to controll the level of estrogen and raise levels of protective enzymes in the body, therefore reducing cancer risk.
Cruciferous vegetables protect us from cancer in one more important way. Researchers believe substances in these vegetables protect our DNA. In a recent study using Brussels sprouts, they found that white blood cells showed a 28 percnt decrease in DNA damage after test participants consumed 1¼ cups of Brussels sprouts every day for five weeks. Of course, DNA damage is a big risk factor for cancer. A similar study using watercress reported that short or long-term ingestion of watercress decreased exercise-induced DNA damage. (17)
Anti-inflammatory
Cruciferous vegetables help control chronic inflammation, which is a known risk factor for the development of cancer and heart desease. These vegetables contain a variety of anti-inflammatory nutrients. Several researchers have documented a group of nutrients called glucobrassicins. Glucobrassicins get converted to indole-3-carbinol (ITC), a special molecule that works to control inflammation at the genetic level, literally turning off the molecule that initiates inflammation before it gets started.
Cruciferous vegetables also contain relatively high values of omega-3 fatty acid. One cup of broccoli contains about 200 milligrams of alpha-linolenic acid (ALA), and Brussels sprouts contain nearly twice that amount. The two omega-3 fatty acids found in fish oil are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These two omega-3 fatty acids are used by the body to produce one of the most powerful anti-inflammatory messaging molecules in our bodies. Research has shown that alpha-linolenic acid is converted to DHA and EPA in the body, and therefore gives us the same anti-inflammatory and antioxidant benefits that eating oily fish provides. There isn’t a Recommended Daily Intake for omega-3 oils. However, recent research has shown that healthy individuals should have at least 500 milligrams, and anyone with cardiovascular or heart disease, or high risk factors for those diseases, should consume 800 to 1000 milligrams of omega-3 fats daily.
New research results published in the American Journal of Epidemiology found that vitamin K1 is an anti-infammatory. Scientists found that higher blood levels and increased intake of vitamin K1 correlated with lower levels of 14 inflammation biomarkers. Researchers also believe the body uses vitamin K to regulate inflammation and prevent chronic inflammatory responses. (16)
Antioxidant
Probably the best known antioxidant is vitamin C. As mentioned above, one cup of cooked broccoli contains 135 percent of the daily recommended intake of vitamin C. However, broccoli also contains a rich array of flavoniods, including kaempferol and quercitin, and the carotenoids lutein, zeaxanthin, and beta-carotene. The flavoniods work together with vitamin C and the carotenoids to provide long lasting antioxidant support. When you consider that broccoli also contains the antioxidants vitamin E, manganese, and zinc, its easy to understand why it protects the entire body from oxidative stress, preventing heart disease, cancer, diabetes, and many other threats to our health.
Detoxifying the body
The detoxification system is our body’s way of removing the toxins we get from our environment, lifestyle, bodily processes, and foods. Our detoxification system isn’t totally understood because it seems to be able to recognize toxins it has never encountered before. Scientists have, however, identified two phases of detoxification. Phase I uses oxidation to create a reactive molecule similar to a free radical. As you know,
unbridled oxidation is extremely damaging to our bodies. To protect us from the reactive molecules just formed, Phase II of the detoxification steps in.
Phase II of the detoxification system combines the reactive molecule created in Phase 1 with an atom that, after the chemical reaction, results in a water-soluble molecule that can be eliminated through the bile or urine. Sulfur is one of the atoms used to do this. Our bodies don’t produce sulfur, and our detoxification system can’t work without it. The sulfur compounds, glucosinolates, in cruciferous vegetables, are converted to Isothiocyanates (ITCs) by the body. ITC’s are well- documented modifiers of both the first and second phases of detoxification. They do this by changing the way enzymes involved in the process work so that an otherwise stressed system does it’s job as designed.
Cardiovascular Disease
The newest research involving cardiovascular problems and heart disease involves the role inflammation plays. Scientists have documented that chronic inflammation is at least partially responsible for the unhealthy oxidation of LDL cholesterol in our arteries. In addition, scientists now believe inflammation plays a role in the hardening of vessels and arteries. However, recent research into the cardiovascular benefits of cruciferous vegetables (broccoli) has shown that the isothiocyanate (ITC) sulforahpane triggers anti-inflammatory processes in our cardiovascular system. In addition, ongoing research shows it helps prevent and even repair damaged arteries and vessels.
Of course, the megapower antioxidants, vitamins C, k and E, flavoniods kaempferol and quercitin, and the carotenoids lutein, zeaxanthin, and beta-carotene, along with manganese and zinc help prevent heart disease just as the protect us from cancer.
Cruciferous vegetables not only help with the way our bodies deal with cholesterol, they also reduce the amount of cholesterol and fat that is available to circulate through our bodies. The fiber in broccoli forms molecules with cholesterol-containing bile acids that attach to fats and makes it impossible for our bodies to absorb them. The result is that the whole mess is passed out of the body via the bowel, reducing the amount of bile, and therefore cholesterol available to our liver. Because our bodies need cholesterol to make more bile, the liver pulls it out of the blood, reducing the amount that the blood contains.
Other Health Benefits
Cruciferous vegetables help us stay healthy in other ways:
- Xianglan Zhang, of the Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University School of Medicine, Nashville, TN and associates published a ten-year prospective cohort study in the American Journal of Clinical Nutrition. Zhang studied the relationship of vegetables, especially cruciferous vegetables, and fruit consumption to total and cardiovascular disease mortality in an Asian population (China). His conclusion: “Our findings support recommendations to increase consumption of vegetables, particularly cruciferous vegetables, and fruit to promote cardiovascular health and overall longevity.”
- Zhang’s study did not support the recommendation of either vegetables or fruit to prevent cancer.
- The kaempferol in cruciferous vegetables lessen the impact of allergy-related substances on our body.
- Cruciferous vegetables contain high levels of both calcium and vitamin K, both of which are important for bone health and prevention of osteoporosis.
- Cruciferous vegetables provide complex carbohydrates and are high in fiber, which aids in digestion, prevents constipation, maintains low blood sugar, and curbs overeating.
- The antioxidants in cruciferous vegetables may reduce your risk of cataracts and macular degeneration, support joint flexibility, reduce your risk of arthritis, and keep your skin and hair healthy and beautiful. Vitamin C may also support bone health.
- Vitamin B6 and folate are used to produce serotonin and dopamine, and may help prevent depression and memory loss. B vitamins also support scalp and hair health.
- Calcium supports your nervous system, bone health, muscle health and the immune system.
- Beta-carotene is used by the body to repair bodily tissues and protect skin from the sun.
- Cauliflower is a good source of choline, a B vitamin known for its role in brain development. Choline intake during pregnancy “super-charged” the brain activity of animals in utero, indicating that it may boost cognitive function, and improve learning and memory. It may even diminish age-related memory decline and your brain’s vulnerability to toxins during childhood, as well as conferring protection later in life.
Warning: Many people believe cruciferous vegetables cause a thyroid problem called goiter, which is caused by an enlarged thyroid. This just isn’t true. In fact, recent research suggests cruciferous vegetables support proper thyroid function in healthy people. Thiocyanates have been associated with thryroid problems in people who consistently consume excessive amounts of these nutrients, especially if they suffer from a lack of selenium or iodine. Selenium and iodine are used by the thyroid to function properly. Thyroid problems associated with thiocyanates are mostly restricted to areas of Africa and Asia where there isn’t enough selenium in the soil to provide adequate amounts of this nutrient. However, people who already have thyroid problems or who are concerned that they may not be getting enough selenium or iodine from their diet may want to discuss eating cruciferous vegetables with their health provider. Also, cruciferous vegetables may cause stomach issues for people with irritable bowl syndrome.
Cooking Cruciferous Vegetables
Like garlic, chopping cruciferous vegetables breaks the cell walls and allows the plant’s natural defense mechanism to go to work. When the cell walls are broken, chemicals mix together and form the nutrients that makeup the plant’s immune system. To maximize the nutrients availabe to your body, chop all cruciferous vegetables in the smallest size your recipe will allow about ten minutes before you use them.
Also, cruciferous vegetables are best for you when they are slightly cooked. Steaming broccoli and Brussels sprouts for four to five minutes is just about right. Separate brocolli flowers from the stems. Slice the stems and steam them for a couple of minutes before you add the flowers. Then steam the whole works for no more than five minutes.
Brussels sprouts often smell and even taste like sulfur if they are over cooked. Most nutritionists recommend that you cut them in quarters to avoid over-cooking the outside layers.
Cabbage can be cut into large bite-sized pieces and steamed as well. Sometimes it is a little tough if you don’t cook it quite long enough, so test it before you take it out of the steamer. Boiling it destroys some of the nutrients.
Steam collard greens, mustard greens, and kale just until they are tender. Boiling them tends to deplete their nutrients.
Bok Choy is often cooked in a head, with the stocks still connected at the bottom. If you do this, you will have to cook the outside stalks too much in order to get the inside stocks tender. Further, there is the posibility that dirt will be stuck in the inside between the stocks, which could be a sanctuary for disease-causing microbes. It’s best to cut the stalks just above where they join, and then steam or stir-fry them, again for about five minutes.
I like to run a little stream of olive or coconut oil over the vegetables above, then sprinkle them with an aromatic herb, such as marjoram, dill, or basil—your favorite will work just fine. Add a little parmesan cheese and serve. The oil helps your body absorb the oil-soluble phytonutrients.
Rutabagas are often overlooked as a nutritious, and inexpensive vegetable. Their sweet, slightly spicy flavor can dress up a boring salad or soup. You must peel rutabagas. They are great raw in salads or raw-vegetable plates. They are also good cooked. Cut them into bite-sized chunks and bake them at a low temperature until they are tender, about 25 minutes, or slice them thinly and stir-fry them for about seven minutes. I like to put them and broccoli stalks in the wok with other slow-cooking vegetables (like celery, or carrots) before I add vegetables that cook quickly. This allows them to partially steam and helps keep them from getting too hot and losing their nutrients. You can also cut rutabagas into quarters or so and bake them for about thirty minutes, or add them to soups or stews.
Kohlrabi was once considered food fit for a king. They have a mild flavor and can be eaten cooked or raw, including the greens. The purple variety has a little more flavor than the green. Large kohlrabi have woody skin and must be peeled, but the skins of small kohlrabi, about an inch and a half or two inches in diameter, have tender skin that can be eaten. Use the greens in salad, or steam them as described above for collard or mustard greens. Steam sliced kohlrabi for about seven or eight minutes, or stir fry them as described for rutabagas.
Like its relatives, broccoli is exceptionally high in the viamins K and C. One cup of cooked broccoli contains about 245 percent of the Daily Recommended Intake (DRI) of Vitamin K, and 135 percent of the DRI of Vitamin C. It also contains significant amounts of chromium, folate, fiber, choline, B vitamins B2 and B6, vitamin E, vitamin A, panothenic acid, phosphorus, mangenese, and choline. Broccoli also contains the flavonoids kaempferol and quercitin, along with the carotenoids lutein, zeaxanthin, beta-carotene, and some lesser-known phytonutrients.
References
(1) Seow A, Shi CY, Chung FL, et al. Urinary total isothiocyanate (ITC) in a population-based sample of middle-aged and older Chinese in Singapore: relationship with dietary total ITC and glutathione S-transferase M1/T1/P1 genotypes. Cancer Epidemiol Biomarkers Prev. 1998;7(9):775-781. PubMed.