Question: Does the consumption of broccoli and/or other brassica vegetables as a daily staple increase the risk of cancer?
Answer: Yes, the regular consumption of brassica vegetables as a daily staple does indeed increase the risk of cancer, and even heart disease.
Read on to discover the evidence and exactly why BV's (brassica vegetables) actually increase the risk of cancer in humans.
The almost universal belief that broccoli fights cancer is simply wrong, and if anything the opposite is true. Even The American Cancer Society is hesitant about linking cancer prevention with broccoli:
"Broccoli contains certain chemicals that may reduce the risk of colorectal or other cancers, although it is not clear which individual compounds may be responsible for the protective effects. While research in this area continues, the best advice at this time to reduce cancer risk is to eat a wide variety of vegetables...." Source: The American Cancer Society, cancer.org.
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BV's are high in a variety of glucosinolates some of which are harmful. When you eat BV's such as broccoli or cabbage, some of their glucosinolates break down to indole-3-carbinol, and then some of the indole-3-carbonil breaks down to diindolymethane (DIM for short). In effect, the consumption of BV's gives you indole-3-carbinol and DIM.
In a laboratory, indole-3-carbinol and DIM can also be synthesised for testing to see if they fight cancer. Experiments on mice have tentatively shown that these synthesised compounds can prevent the formation of some kinds of cancer cells. Other studies on mice and on human lab samples have indicated that indole-3-carbinol and DIM may have applications in reducing the incidence of breast and cervical cancer.
But other studies have indicated that indole-3-carbinol may actually promote cancer. Here are four such studies:
1. Oganesian, A., et al., Potency of dietary indole-3-carbinol as a promoter of aflatoxin B1- initiated hepatocarcinogenesis: results from a 9000 animal tumor study. Carcinogenesis, 1999. 20(3): p. 453-458.
2. Kim, D.J., et al., Enhancement by indole-3-carbinol of liver and thyroid gland neoplastic development in a rat medium-term multiorgan carcinogenesis model. Carcinogenesis, 1997. 18(2): p. 377-381.
3. Dashwood, R.H., et al., Promotion of aflatoxin B1 carcinogenesis by the natural tumor modulator indole-3-carbinol: influence of dose, duration, and intermittent exposure on indole-3-carbinol promotional potency. Cancer Res, 1991. 51(9): p. 2362-2365.
4. Dashwood, R.H., et al., Tumor dose-response studies with aflatoxin B1 and the ambivalent modulator indole-3-carbinol: inhibitory versus promotional potency. Basic Life Sci, 1990. 52: p. 361-365.
So what is happening here?
"Apparently, there's some debate over whether or not these compounds fight cancer or promote cancer. The simple version of the story is that, taken before exposure to a carcinogen, these agents may actually reduce the risk of cancer. However, when taken after exposure to a carcinogen, the same agents may increase the risk for cancer. So while most studies report inhibitory or protective effects of indole-3-carbinol in vivo, a few provide evidence for the promotion or enhancement of carcinogenesis, depending upon the initiator (an agent that starts the process leading to cancer), exposure protocol, and species". Source: Dr. Thomas Incledon, more Fool's Gold, 2000 www.t-nation.com.
So the anti-cancer effects of indole-3-carbinol and DIM are ambivalent and research is still ongoing. Note: when we are talking about indole-3-carbinol, we are in effect talking about DIM which comes from indole-3-carbinol. Indole-3-carbinol itself has little effect on the body until it is broken down by digestion. But when it is broken down it produces DIM and other compounds which are being investigated for their anti-cancer effects.
Here is an abridged extract from the distinguished 'Linus Pauling Institute' in the USA:
"Oral indole-3-carbinol [pure synthesised indole-3-carbinol] has been found to inhibit the development of cancer in a variety of animal models and tissues, including cancers of the mammary gland, uterus, stomach, colon, lung, and liver. However, a number of studies have found that indole-3-carbinol actually promoted or enhanced the development of existing cancer. The cancer-promoting effects of indole-3-carbinol were first reported in a trout model of liver cancer. However, indole-3-carbinol has also been found to promote cancer of the liver, thyroid, colon, and uterus in rats....Although the long-term effects of indole-3-carbinol supplementation on cancer risk in humans are not known, the contradictory results of animal studies have led several experts to caution against the widespread use of I3C and DIM supplements in humans until their potential risks and benefits are better understood". Source: Victoria J. Drake, Ph.D., David E. Williams, Ph.D., Indole-3-Carbinol, 2008, Linus Pauling Institute, Oregon State University, USA, http://lpi.oregonstate.edu.
A detailed examination of indole-3-carbinol and DIM is beyond the scope of this book and there is no intention to denigrate or dismiss the possible anti-cancer effects of these compounds in their pure synthesised form.
The amount of indole-3-carbinol and DIM derived from just the consumption of BV's is negligible and not enough to affect cancer. "Direct measurements of upward, beneficial shifts in estrogen metabolism indicate you would have to eat at least two pounds per day of raw or lightly cooked cruciferous vegetables to derive the same benefit as two capsules of specially formulated DIM. Benefits for cervical dysplasia, PMS, BPH, and other conditions have not been seen with the use of broccoli, cabbage juice, or dried powders or extracts from vegetables". Source: Thomas Stearns Lee, DIM (Di-Indoly Methane) For Natural Protection from Estrogen's Effects, Frequently Asked Questions, www.naturodoc.com.
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"Cell-culture studies and human clinical trials have shown that indole-3-carbinol at doses of 200400 mg/day can influence estrogen metabolism and promote formation of 2-OH-estrone, and therefore may be useful in breast cancer prevention. Current U.S. research studies are under way on indole-3-carbinol and women at increased risk for breast cancer". Source: Dan Lukaczer, N.D., Estrogen's Two-Way Street, the November 2001 Issue of Nutrition Science News.
With reference to the above quote, to derive 200-400 mg of indole-3-carbinol per day you would have to eat huge amounts of BV's daily. And if you were to do this, you would suffer malnutrition by having to exclude other foods. You would also significantly inhibit your thyroid and suffer health problems from the large amounts of antinutrients that come with BV's (phytates, oxalates and insoluble fiber).
Worst still, as explained in a moment, by consistently consuming large amounts of BV's you inhibit testosterone, and this greatly increases the risk of cancer plus a host of other health problems.
As already discussed in the previous section, most medicines are derived from plants. And many of these plants are inedible or even poisonous, yet they give us valuable and life-saving drugs and cures.
This is the case with BV's. The point here is that although certain compounds in BV's may fight cancer when purified and synthesised (and when carefully administered as a medicine) it does not mean that the consumption of BV's themselves will help fight cancer.
In what follows we will look at the link between BV's and cancer under the following four headings:
Consumption of brassica vegetables as a staple causes underactive thyroid.
Approximately 300,000 American die each year from the proper use of over-the-counter and prescriptions drugs made from plant-derived compounds. This exceeds deaths due to crack, handguns, and traffic accidents combined. Many millions more die each year worldwide from the improper use of drugs made from plant-derived compounds (just think of deaths related to drug-addiction).
They myth that consumption of BV's such as cabbage and broccoli fight cancer by virtue of having glucosinolates is just that, a myth. If anything, the research shows the opposite. Research shows that glucosinolates in BV's inhibit the thyroid from working properly and interfere with the synthesis of necessary thyroid hormones. The thyroid needs iodine to function, just like a car needs fuel to function.
Here is a technical explanation from the distinguished 'Linus Pauling Institute' in the USA:
"Two mechanisms have been identified to explain [the goitrogenic effect of glucosinolates]. The hydrolysis of some glucosinolates found in cruciferous vegetables (e.g., progoitrin) may yield a compound known as goitrin, which has been found to interfere with thyroid hormone synthesis. The hydrolysis of another class of glucosinolates, known as indole glucosinolates, results in the release of thiocyanate ions, which can compete with iodine for uptake by the thyroid gland. Increased exposure to thiocyanate ions from cruciferous vegetable consumption or, more commonly, from cigarette smoking, does not appear to increase the risk of hypothyroidism unless accompanied by iodine deficiency". Source: Jane Higdon, Ph.D., Victoria J. Drake, Ph.D., Linus Pauling Institute, 2008, Oregon State University, USA.
There are no long term human trials showing whether BV consumption causes an underactive thyroid in people with no iodine deficiency. Unfortunately, iodine deficiency and an underactive thyroid is very common throughout the world (more about this in a moment), and for such people it makes sense to not risk exacerbating one's state of health by consuming BV's.
An underactive thyroid can cause serious health problems such as stunted body growth, muscle loss, weight gain, memory loss and many other health problems. It is sad to see parents often berating their children for not eating their cabbage or broccoli, when in fact such consumption may well inhibit good body growth.
The scary thing about an underactive thyroid is that it is very insidious - you don't notice it until the harm is done because the effects are gradual. Regular consumption of BV's may not shut down the thyroid or cause full hypothyroidism. But such consumption can make the thyroid slow down enough to cause on-going health problems that may not be apparent to the person affected.
Many people who regularly consume BV's as a staple go for years putting on weight, losing muscle, feeling under-par and weak, and generally suffering poor health. They wonder why they are like this since they 'eat well', don't smoke and lead an active life. The cause is often a regular diet high in BV's that keeps their thyroid from working properly.
Note for women wanting to conceive: a mild or subclinical underactive thyroid has been associated with impaired fertility and an increased risk of miscarriage.
The following image shows the serious health problems caused by an underactive thyroid or by hypothyroidism (the symptoms are similar) and it strikes both genders although it is less common in men:
Ask yourself whether you may be suffering from any of these symptoms and reflect on your diet. Do you eat BV's several times a week?
Some may argue that the goitrogenic effect of BV's is too mild to affect people, and that in any event there is no shortage of iodine in the human diet. But you would be wrong to think this. Whether or not your diet gives you enough iodine, the consumption of BV's as a staple will cause an on-going effect on your thyroid because glucosinolate compounds in BV's will inhibit the thyroid from using what little iodine you receive from the diet. Without sufficient iodine, the thyroid cannot function properly and you're into hypothyroidism territory.
If you are healthy and you have enough iodine in your diet, the goitrogenic effect of eating BV's as a staple will be insidious and not obviously perceptible. Even a medical test may show your thyroid to be OK. But the continuous, albeit mild, goitrogenic effect will have an adverse effect on just about every aspect of your health, giving you an under-par quality of life.
But if you are at all iodine deficient it is particularly important to avoid BV's. The reality is that iodine deficiency is rampant throughout the world.
"Iodine deficiency resulting in goiter occurs in 187 million people globally as of 2010 (2.7% of the world population)". Source: Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013, Lancet 385: 117–171.
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"[In the USA] low thyroid function affects approximately 20-25 percent of the female population and about 10 percent of males. An additional 30 percent of persons over the age of 35 may also have sub-clinical or mild hypothyroidism whereby their thyroid stimulating hormone is within normal range, but they have many of the symptoms of low thyroid. The thyroid secretes two hormones - T3 and T4 - that are crucial for controlling our metabolism. Because thyroid hormones affect every cell in the body, a deficiency will result in many symptoms". Source: Lorna Vanderhaeghe, Thyroid (Hypothyroidism), Women helping Women, www.healthyimmunity.com.
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"In the US, it’s estimated that one in seven women suffers from iodine deficiency". Source: Caldwell KL, et al, Urinary iodine concentration: United States National Health and Nutrition Examination Survey 2001-2002, Thyroid, 2005 Jul; 15(7):692-9.
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"Approximately 40% of the world’s population remains at risk for iodine deficiency". Source: Iodine Deficiency, American Thyroid Association, 2012, www.thyroid.org.
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"In the developed world, iodine deficiency has increased more than fourfold over the past 40 years. Nearly 74% of normal, 'healthy' adults may no longer consume enough iodine". Sources: 1. Gunton JE, et al, Iodine deficiency in ambulatory participants at a Sydney teaching hospital: is Australia truly iodine replete? Med J Aust., 1999 Nov 1; 171(9):467-70. 2. Hoption Cann SA., Hypothesis: dietary iodine intake in the etiology of cardiovascular disease. J Am Coll Nutr. 2006 Fe 25(1):1-11.
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An underactive thyroid is one of the most common chronic disorders throughout the world. In the United States alone roughly 11 million American adults and children have underactive thyroids. It is most common in older women; at least 10 percent of older women in the USA are affected by an underactive thyroid or by hypothyroidism.
Put simply, many millions of people have iodine deficiency or underactive thyroids, or some combination of both without even knowing it. It is therefore disingenuous to argue that a fit and healthy body can withstand any goitrogenic effect from such food. Why take the risk?
People who eat BV's as a staple, whether raw or cooked, are likely to be much more health-conscious compared to the population at large. This is so because a person who consciously eats unpalatable food (i.e. BV's) in the belief that it is healthy is more likely to be adopting healthy lifestyles such as not smoking, being physically and following a highly nutritious diet.
When you hear of fit and healthy people who regularly eat BV's, they are fit and healthy in spite of eating BV's; they are fit and healthy because of other healthy lifestyle factors, not because of BV consumption.
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Broccoli is often lauded as a good vegetable to eat if you want to lose weight because it is claimed to fill you up 'without being fattening'. But nothing could be further from the truth. By causing an underactive thyroid, this results in less thyroid hormones being produced. This in turn impacts on the adrenal glands.
"Thyroid function influences and is influenced by the pituitary, adrenals, parathyroid, and sex glands, all of which work together". Source: Hoption Cann SA., Hypothesis: dietary iodine intake in the etiology of cardiovascular disease. J Am Coll Nutr. 2006 Feb; 25(1):1-11.
The strong link between an underactive thyroid and weight gain is well established. Basically, an underactive thyroid inhibits the adrenal glands from producing certain hormones that switch on 'lipolysis'.
When lipolysis is inhibited, fat cells cannot lose fat, and weight gain is inevitable. For optimum health you want to be in a state of lipolysis as often as possible. The regular consumption of BV's will indirectly inhibit lipolysis, thus promoting weight gain. Lipolysis is the body's own powerful weight loss weapon; once you understand how to switch on and exploit lipolysis you will be able to lose weight easily and maintain a healthy slim body. For more information about lipolysis, see our sister book 'The Lipo diet' (DeliveredOnline.com).
"[When] these goitrogenic compounds [brassica vegetables] are consumed, the glycosinolates are hydrolyzed to isothiocyanates in the gut, and they can have powerful anti-thyroid effects and interfere with the synthesis of necessary thyroid hormones....They inhibit thyroid function by blocking the incorporation of iodine into thyroxine precursors and by suppressing thyroxine secretion from the thyroid." Source: Glucosinolates (Goitrogenic Glycosides), Department of Animal Science - Plants Poisonous to Livestock, Cornell University College of Agriculture and Life Sciences.
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"Following these nutritional tips may help reduce symptoms of hypothyroidism: Avoid foods that interfere with thyroid function, including broccoli, cabbage, Brussels sprouts, cauliflower, kale, spinach...." Source: Hypothyroidism, University of Maryland Medical Center http://umm.edu/health.
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"Some glucosinolates have been shown to have toxic effects, mainly as goitrogens" (Wikipedia).
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"Very high intakes of cruciferous vegetables, such as cabbage and turnips, have been found to cause hypothyroidism (insufficient thyroid hormone) in animals". Source: Fenwick GR, et al, Glucosinolates and their breakdown products in food and food plants, Crit Rev Food Sci Nutr. 1983; 18(2):123-201.
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Do not think that by just taking an iodine supplement you can neutralize the anti-iodine effect of BV's, thus giving you license to consume such vegetables. This won't work for two reasons:
1. Certain glucosinolates in BV's (known as goitrogens) inhibit the thyroid from producing thyroid hormones. For the technically minded, these goitrogens actually block the incorporation of iodine into thyroxine precursors thus preventing the thyroid from working properly, so ingesting more iodine won't help. Put another way, goitrogens in food interfere with thyroid peroxidise (TPO), the enzyme responsible for adding iodine during production of thyroid hormones.
Clearly, if the hypothyroidism is caused by an acute lack of dietary iodine (a common form of hypothyroidism in some parts of the world), then taking more iodine will indeed help mitigate hypothyroidism. But if an underactive thyroid is caused by consuming goitrogens, then iodine supplements won't help; the solution is to give up ingesting such goitrogens.
2. A person consuming BV's may not be lacking in dietary iodine from other food sources. So taking iodine supplements may risk overdosing the body with iodine. To recover from an underactive thyroid deficiency is not a quick fix. The road to recovery will be slow and gradual over a period of several weeks once you give up BV's. You should be very cautious about taking iodine supplements so as to not risk overdosing with iodine and causing hyperthyroidism; this is as bad as hypothyroidism, but for other reasons.
Underactive thyroid inhibits testosterone.
As mentioned, BV's contain many glucosinolates, some of which convert to indole-3-carbinol and DIM (diindolylmethane) once digested. Those who make or sell supplements that include indole-3-carbinol or DIM try hard to proclaim that such compounds increase testosterone. Their argument goes something like this:
"Most testosterone circulates in the blood, bound to SHBG (Sex hormone-binding globulin). Such testosterone cannot be freely used by the body. DIM breaks up some of the SHBG, thus freeing some of the testosterone which can then be used by the body".
This is mostly conjecture and the evidence is equivocal. There are no significant trials (i.e. long-term, peer-reviewed studies) to prove whether DIM does in fact increase the amount of free testosterone in the human body. Animal trials show that it depends on the species. For example, after treatment with indole-3-carbinol or DIM, rat liver enzymes respond differently than monkey liver enzymes. Source: Wortelboer, H.M., et al, Acid reaction products of indole-3-carbinol and their effects on cytochrome P450, and phase II enzymes in rat and monkey hepatocytes. Biochem Pharmacol, 1992. 43(7): p. 1439-1447.
Furthermore, even if it turns out that synthesised DIM does indeed help increase the amount of free testosterone in the blood, this is not the end of the story as far as BV's are concerned. Unlike pure synthesised DIM, BV's come with a host of unhealthy ingredients some of which inhibit testosterone.
Pure synthesised indole-3-carbinol and DIM do not contain goitrogens and do not cause an underactive thyroid. Hence, such medications will not inhibit free testosterone in the blood, although it is debatable (the research is not clear) whether they actually increase free testosterone.
But as mentioned, BV's contain goitrogens that can and do cause an underactive thyroid. And it is now well established that an underactive thyroid can inhibit testosterone, quite apart from the other health problems it causes.
"Testosterone is made in the testes and adrenal glands in a male, and in a woman, the ovaries and adrenal glands. Testosterone is very important for metabolism. It has been shown that a low thyroid results in low testosterone levels. When the thyroid gland returns to optimal function in individuals with challenged thyroids, their testosterone levels also return to normal". Source: Dr. Nikolas Hedberg, D.C., D.A.B.C.I., Hormone-Thyroid Connection, 2011, http://drhedberg.com.
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"Thyroid hormone deficiency affects all tissues of the body....Free testosterone concentrations are reduced in men with primary hypothyroidism and thyroid hormone replacement normalizes free testosterone concentrations". Source: Meikle AW, The interrelationships between thyroid dysfunction and hypogonadism in men and boys, Thyroid. 2004; 14 Suppl 1:S17-25.
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"The interest in iodine comes from the fact that hypothyroid patients have been found to have significantly lower testosterone - perhaps by as much as 36%". Source: J Androl, et al, Serum levels of total testosterone and sex hormone binding globulin in hypothyroid patients and normal subjects treated with incremental doses of L-T4 or L-T3, J Androl. 1988 May-Jun; 9(3):215-9.
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To summarize this point, an underactive thyroid affects the adrenal glands, thus inhibiting the adrenals from producing hormones. One of these hormones is testosterone. So an underactive thyroid indirectly inhibits the body's production of testosterone, and this can have a harmful feminizing effect on the body as explained in the following pages.
"The adrenal glands produce….sex hormones, or androgens….which are converted to more potent androgens such as testosterone and DHT or to estrogens (female sex hormones) in the gonads" (Wikipedia.org).
Less testosterone causes harmful feminizing effect.
We have seen that the regular consumption of BV's as a staple can inhibit iodine uptake by the thyroid, causing an underactive thyroid. We have also seen that an underactive thyroid inhibits testosterone, causing less free testosterone to be available to the body.
Does a reduction in free testosterone in the blood have a harmful feminizing effect on the body?
Absolutely! Many studies show that adequate levels of testosterone in both men and women are essential for good overall health. When testosterone is inhibited, all sorts of health problems ensue, ranging from cancer, infertility and stunted body growth to osteoporosis, dementia and heart disease.
More specifically, when it comes to women, the feminising effect of consuming BV's does not make a woman 'more feminine'. Rather, it has a devastating effect on a woman's health. Women need testosterone as much as men, albeit at a lower level. A healthy level of testosterone in women ensures good body growth and normal height, greater emotional stability and general well-being, healthy sex drive, better stamina, more energy, regular periods, a slim feminine body, firm muscles and much more. Testosterone does not make a woman more masculine; rather, testosterone makes a woman more feminine with all the curves in the right places!
Men also need healthy levels of te