Beta-carotene, which can be converted into vitamin A, is also anticancer. A Japanese study involving 265,000 people found a significant correlation between low beta-carotene intake and the incidence of lung cancer.31 In fact, the risk of lung cancer was the same for those who smoked and had good antioxidant levels as it was for nonsmokers with low antioxidant levels.
Beta-carotene—does it prevent or promote cancer?
While almost all studies involving dietary beta-carotene and cancer have proven its protective effect, and while the vast majority of studies involving using beta-carotene supplements have either proven it to be positive or ineffective, but not harmful, three studies have found an increased risk of cancer with beta-carotene. One study by the National Cancer Institute gave smokers beta-carotene and reported a 28 percent increase in the incidence of lung cancer.32 Confusing, isn’t it? A closer look at the figures shows that this “trend,” which sounded dramatic, represented the difference between five cases of cancer in a thousand people and six in a thousand people—people who had smoked for years and probably had undetected cancer before starting the trial. Hidden in the figures was an unreported finding. Among those who gave up smoking during the trial and took beta-carotene, there were 20 percent fewer cases of lung cancer. Does this mean that beta-carotene has moral powers and gives smokers cancer but protects those who give up smoking? In truth, what it shows is that giving one antioxidant on its own to smokers, ignoring the principle of synergy, could make matters slightly worse, not better.
The other study that found a trend toward increased risk gave male smokers vitamin E, vitamin E and beta-carotene, or beta-carotene on its own. The first two groups showed no significant change, but the beta-carotene-only group showed an increased risk.33 Why? A recent trial, published by the National Cancer Institute, may shed some light on this.
In this trial, people with a history of colorectal adenomas were given 7 IU of beta-carotene and/or both 100 mg of vitamin C and 600 IU of vitamin E, versus placebo. While there was less recurrence of colorectal adenomas in those who took either the beta-carotene or vitamins C and E or both, there was a modest increase in cancer recurrence among those who took only beta-carotene supplements and both smoked and drank alcohol every day.34
My instinct tells me that what these studies are showing is that the oxidants in cigarettes are oxidizing beta-carotene and, in the absence of other synergistic vitamins such as vitamins C and E, this does more harm than good. My advice is not to take beta-carotene on its own if you are a heavy smoker or drinker—and to stop smoking and drinking! Many other studies that have either given beta-carotene supplements with other antioxidants or provided it through beta-carotene-rich food, which naturally contains other antioxidants, show clear reduction of cancer risk. Even among smokers, a high dietary intake of beta-carotene is not associated with increased risk.35 So, keep eating the carrots!
Cancer patients live four times longer on vitamin C
Nobel laureate Dr. Linus Pauling and cancer expert Dr. Ewan Cameron first demonstrated vitamin Cs amazing anticancer properties in the 1960s. They gave terminally ill cancer patients 10 grams a day and showed that they lived four times longer than patients not on vitamin C.36 Many studies have since been performed.
A review of vitamin C research concluded that “evidence of a protective effect of vitamin C for nonhormone cancers is very strong. Of the forty-six studies in which a dietary vitamin C index was calculated, thirty-three found statistically significant protection.” These kinds of strong associations are being confirmed the world over. When Dr. Gladys Block, from the University of California, looked at a grand total of ninety studies, she came to the conclusion that the evidence was strong for a protective effect against cancers of the mouth, esophagus, stomach, and pancreas, and substantial for colorectal, breast, and lung cancers.37 The evidence for a protective effect against prostate cancer, however, is not strong.
As well as being an antioxidant and able to disarm free radicals, vitamin C can disarm a number of other carcinogens, such as nitrosamines. These can occur when chemicals called nitrates combine with amines. Nitrate levels are high in vegetables grown with nitrate-based fertilizers, as well as in water, owing to fertilizer residues leaching into water sources. Nitrates are also added to some cured meats such as ham, sausages, and bacon. About 70 percent of our intake comes from vegetables grown with artificial fertilizers, 21 percent from water, and 6 percent from meat. Vitamin C may be especially effective against cancers of the digestive tract because of its ability to disarm these carcinogens, as well as its proven immune-boosting properties.
The synergy of vitamins C and E and selenium
A ten-year study on over eleven thousand people, completed in 1996, found that those who supplemented both the antioxidants vitamin C and vitamin E halved their overall risk of death from all cancers and heart disease.38 Vitamin C is water soluble, while vitamin E is fat soluble. Together they can protect the tissues and fluids in the body. What is more, when vitamin C has disarmed a carcinogen, it can be reloaded by vitamin E, and vice versa, so their combined presence in diet and in the body has a synergistic effect. Vitamin E is a powerful anticancer agent, especially in combination with selenium. While high blood levels of vitamin E alone are associated with a significant reduction in cancer risk, studies in Finland by Dr. Jukka Salonen found that combined low levels of vitamin E and selenium increase cancer risk more than ten times.39
The mineral selenium has long been known to protect against cancer. Studies in the region of Quidong in China, where liver cancer rates are among the highest in the world, have found a strong correlation between low selenium intake and cancer risk, with other risk factors being hepatitis B infection, exposure to the dietary carcinogen aflatoxin, and a genetic predisposition.40 The researchers then began a large-scale selenium study in which an entire village of twenty thousand people took a selenium supplement, which was added to their salt. In the following years, there was a significant drop in the incidence of both hepatitis B and liver cancer. Professor Gerhard Schrauzer, an expert on selenium and cancer, recommends a supplement of 200 to 300 mcg of selenium for those who want optimal protection.
WHICH NUTRIENT FOR WHICH TYPE OF CANCER?
The following antioxidant vitamins and minerals have so far been proved effective in medical research against the types of cancer indicated.
As you might expect, supplementing all these cancer-protective nutrients reduces risk. French researchers at the Scientific and Technical Institute for Nutrition and Diet in Paris carried out a large study involving thirteen thousand men and women between the ages of thirty-five and sixty to investigate the effects of a pill containing a number of antioxidant vitamins and minerals.
Half the study volunteers were given a placebo pill and the other half were given a supplement pill containing beta-carotene (20,000 IU), vitamin C (120 mg), vitamin E (45 IU), selenium (100 mcg), and zinc (20 mg). The participants were followed over a seven-and-a-half-year period. Over the course of the follow-up, 103 men and 71 women died. Cancer affected 562 people and was the major cause of death. There was a highly significant 31 percent reduction in the risk of all cancers in men, plus the overall death rate in men was 37 percent lower in those taking the supplement. Surprisingly, the results weren’t statistically significant for women. It isn’t clear exactly why only men seemed to benefit from the supplements, although it’s suggested that perhaps they had a poorer diet to start with. Another explanation is that cancer in women (they were affected primarily by breast cancer) may not be so responsive to antioxidant intake.41
Hormone-related cancers
While antioxidant nutrients have a protective effect in many cancers, free radical damage is unlikely to be the major cause in all of them. Evidence is accumulating that the high incidence of cancer of the breast and ovaries in women, and of the prostate and testes in men, may be related to disturbed hormone signals in the body. All of these body tissues are sensitive to hormones and hormone-di
srupting chemicals, and excess estrogen, a hormone that stimulates cell growth, may play a key role in these cancers.
Research shows that if estrogen levels are increased, the proliferation rate of breast cells increases by over 200 percent, more than twice the normal rate. On the other hand, if progesterone is given and the level in breast tissue is raised to normal levels, the rate of cell multiplication falls to 15 percent of that in untreated women.42
This study, undertaken on healthy, premenopausal women, shows that estrogen will promote the proliferation of breast cancers, while progesterone is protective. This may explain why the risk of breast cancer doubles for women who take estrogen HRT for five or more years and why the risk of ovarian cancer is 72 percent higher in women given estrogen HRT, according to a 1995 study by the Rollins School of Public Health at Emory University, which followed 240,000 women over eight years.43
On the basis of this and many other studies, I’ve been advising women for the past decade not to have HRT. However, it wasn’t until the Million Women Study, published in the British Medical Journal in 2002, confirmed a doubling of breast cancer risk that HRT was effectively banned for the treatment of osteoporosis. This study, involving 1,084,110 women in Britain, confirmed that the risk of invasive breast cancer among HRT users goes up by 66 percent and that the risk of death goes up by 22 percent. The biggest risk by far was seen in women on combined estrogen/progestin HRT preparations. In these women, the incidence of breast cancer doubled, compared with a 30 percent increase among those on estrogen-only HRT, which is generally given only to women who have had a hysterectomy since estrogen given on its own increases the risk of womb cancer. The researchers estimate that in Britain alone, the use of HRT by women aged fifty to sixty-four has resulted in an estimated twenty thousand extra cases of breast cancer in the last decade alone.44
The increased incidence of hormone-related cancers cannot, however, be attributed solely to estrogen dominance due to HRT, especially in men, for whom prostate cancer is the fifth-largest cause of death, affecting one in ten men. Hormone expert Dr. John Lee believes that many factors are contributing to estrogen dominance and progesterone deficiency, which in his opinion is the major cause of these cancers. “Stress, for example, raises Cortisol which competes with progesterone. Xenoestrogens from the environment have the ability to damage tissue and this leads to increased cancer in later life. There are also nutritional and genetic factors to consider.” He recommends a plant-based diet, excluding sources of estrogen such as meat and milk, high consumption of which is strongly associated with increased cancer incidence, particularly of the colon, breast, and prostate.
Countries that have low or no consumption of dairy products and the meat of dairy animals have remarkably low incidences of both breast and prostate cancer, as well as other hormone-related cancers. The fact that the incidence of breast cancer in China is one in one hundred thousand women, compared with our incidence of one in seven women, and that prostate cancer, which affects one in six men in the U.S., is virtually unheard of in China, points a strong finger at diet. The major difference between diets in Western countries and China is that the Chinese do not generally consume dairy products or meat from dairy animals, and they eat more fruit and vegetables and more beans, especially soy.
In case you are wondering whether there’s something inherently different in Asian people, their risk goes up when they immigrate to the United States or the United Kingdom. Within three generations their risk, and presumably their diet, becomes just as bad.
The other possible causes of cancer are hormone-disrupting chemicals. We’ve invented some one hundred thousand of them, thirty thousand of which are in use in foods, food packaging, household products, toiletries, and industry. Some of these damage DNA, some disrupt hormone signals, and some mimic estrogen. These xenoestrogens from the environment come from pesticide residues, industrial residues, and plastics, which contaminate water and get into the food chain. Even cosmetics, skin products, and your sofa may be a problem! A recent study found parabens, used in underarm deodorants, present in breast tumors and there is now clear evidence that widely used flame-retardants, called PBDEs (polybrominated diphenyl ethers), required on many fabric-covered furnitures, are carcinogenic. Research has shown that the combination of tiny amounts of these hormone-disrupting chemicals, equivalent to the levels found in human blood, are carcinogenic and trigger breast cells to proliferate.
The first step is to avoid sources of hormone-disrupting chemicals as much as possible. This means eating organic and drinking pure water (mineral water, filtered water, or distilled water). As far as diet is concerned, my advice is to also to avoid fried, browned, and burnt foods, which are sources of free radicals; to cut out or cut down on meat, especially beef, and milk, which are sources of natural estrogen and IGF-1, a hormone disruptor that is becoming strongly linked to both breast and prostate cancer.
Other possible steps are to avoid HRT containing either estrogens or synthetic progestins. Natural progesterone, however, helps counter the potentially damaging effects of estrogen. Under medical guidance, progesterone, which is given as a transdermal skin cream, can both help balance hormones and reverse cancer risk.45
Homocysteine and cancer
If oxidation is one of the principal ways in which DNA becomes damaged, high homocysteine and associated abnormal methylation is another (see chapter 16). DNA is always being damaged, often by oxidants, and therefore needs to be constantly repaired. It also needs to be copied, encoding new cells that we make at an extraordinary rate of tens of millions per minute. Methylation controls both the synthesis and the repair of DNA, putting homocysteine, and the key homocysteine-lowering nutrients such as B12, folate, vitamin B6, B2, and TMG smack in the middle of the whole cancer process. Any lack of these B vitamins is already well established to increase the risk of certain cancers.
Does a high hymocysteine score increase your risk for cancer? This is a key question and one that is only starting to be explored. As in the case of heart disease, having accurate markers for cancer helps in its diagnosis, prevention, and treatment. Such markers can not only identify someone at risk, but also encourage immediate preventive steps and even measure the success of a cancer treatment.
Dr. Lily L. Wu and colleagues at the University of Utah’s Health Science Center wondered whether homocysteine might act as a tumor marker, so they decided to measure homocysteine along with other known tumor markers in cancer patients undergoing treatment.46
They found that when the other tumor markers went up, the homocysteine went up, and when the tumor markers went down, the homocysteine went down. They also observed that homocysteine proved to be a better marker than the other more conventional indicators. Remarkably, homocysteine levels also reflected much more accurately whether cancer therapy was going successfully or not. If the cancer was growing larger and therefore not responding to therapy, homocysteine increased at the same time; if the cancer was becoming smaller with therapy, homocysteine levels also decreased. Among the tumor markers, only homocysteine revealed the success of cancer therapy in this way. Although it’s in the early days of research, this study certainly indicates that homocysteine levels may prove to be a very useful indicator of the existence of cancer as well as of the success or failure of cancer therapies.
To date, the cancers most associated with high homocysteine are skin cancer, leukemia, dysplasia, colon cancer, and, to a lesser extent, breast cancer. It is well-known that colon cancer risk is strongly linked to a poor diet—diets high in cooked, especially burnt, meat and low in fiber, fruit, and vegetables—but that taking in large amounts of folate, a key nutrient in vegetables, is highly protective.47 It is highly likely that, as the spotlight focuses in on homocysteine as the marker for methylation problems, and with methylation problems being seen as part of the root cause of many cancers, we will start to see an association between homocysteine and many different types of cancer.
For now, we can only say that ther
e is reasonable evidence that having a high homocysteine level increases cancer risk, especially of colon cancer, skin cancer, leukemia, and the dysplasias, including cervical dysplasia. For these cancers, and probably others, an optimal diet plus supplements may reduce risk.
Cancer-fighting foods
Eating certain kinds of foods is associated with a decreased risk of cancer. While the evidence accumulates, adding the following foods to your diet cannot hurt, and is likely to help.
Fruit and vegetables are the top anticancer foods. These are good sources of vitamins A and C. A study in Japan on 265,000 people found that those with a low intake of beta-carotene, which is found in fruit and vegetables, had a high risk of lung cancer.48 Other studies have produced the same result for colon, stomach, prostate, and cervical cancers. Beta-carotene is found in particularly large amounts in carrots, broccoli, sweet potatoes, cantaloupe melons, and apricots. There is lots of vitamin C in fresh vegetables and fruit.
Garlic, used liberally, may keep cancer away. A National Cancer Institute study carried out in China in 1989 discovered that provinces where garlic was used liberally in their cooking had the lowest rate of stomach cancer.49 Garlic contains sulfur compounds that help deal with toxins and free radicals.
Soybeans have been associated with a lower risk of breast cancer. In Japan and China, women who get most of their protein from soybean foods—tofu, soybeans themselves, and soy milk—have lower rates of breast cancer. These results have been confirmed in animal studies. A list of phytestrogen-rich foods is given in part 9.
Yogurt may protect against colon cancer. The bacterium Lactobacillus acidophilus, found in many live yogurts, slows down the development of colon tumors, and yogurt eaters have a lower incidence of colon cancer than those who do not eat yogurt, as do those whose calcium intake is high.50 Abnormal cell divisions in the colon have also been shown to slow right down when calcium intake is increased to 2,000 mg a day. Of course, nondairy yogurt would be best.
The New Optimum Nutrition Bible Page 30
