Cancer is the most dreaded of all diseases, and ever since a "war on cancer" was declared 40 years ago, massive research has made progress, although the battle is far from won. Very little of this research has been directed at prevention. Advanced medicine, like the person on the street, has tended to think of cancer as something we have no control over: It happens to us or it doesn't.
The reason for thinking this way can be seen under a microscope, which reveals that malignant cells are misshapen compared to normal cells. Disastrous mutations at the genetic level lead to abnormal cell division, causing cancer cells to become rogues in the body, multiplying without check, crowding out normal cells, and in general wreaking havoc by losing communication with the body's fine-tuned intelligence.
Yet we may be seeing a revolution in our whole approach to cancer. Some highly-placed researchers now believe that 90-95 percent of cancers are preventable with drastic lifestyle changes. This represents a total reversal from what used to be taught in medical school, which held that only 5 percent of cancers could be traced to environmental factors like diet or chemical toxins. If the new view is correct, then for the first time we may have found an open road to ridding society of its most dreaded scourge.
To begin with, the genetic trail hasn't led to a cure, only to greater and greater complications. A disease like breast cancer, when examined at the genetic level, isn't one disease but hundreds. Yet at the opposite extreme, genetic mutations may be playing a much smaller part than anyone ever thought. Craig Venter, who led a private effort to successfully map the human genome, neatly summarizes the situation:
"Human biology is actually far more complicated than we imagine. Everybody talks about the genes that they received from their mother and father, for this trait or the other. But in reality, those genes have very little impact on life outcomes. Our biology is far too complicated for that and deals with hundreds of thousands of independent factors. Genes are absolutely not our fate."
In some cancers, inheritance certainly plays a major factor. For example, childhood cancer, of which the most common is a form of leukemia, has a simpler genetic profile than adult cancers. By targeting specific mutations, doctors who treat childhood cancer have raised their success rate from 20 percent to 80 percent in the past 40 years. Children with cancer must undergo severe regimens of chemotherapy and radiation, but it's no longer a case, as it once was, of killing the tumor before the treatment killed the patient.
For a vast majority of oncologists, targeting a malignant cell with chemo and radiation, along with surgery to remove the tumor, remains the mainstream approach. The track of prevention is all but unknown to them. There is no doubt that a cell has to mutate in order to become cancerous. Yet an inherited mutation isn't the same as an acquired mutation, one that develops during the lifetime of the patient. Let's simplify the case and divide acquired mutations into two types: those that result from accident and errors on the part of a person's DNA, and those that are linked to lifestyle. The revolution that is looming in cancer is based on believing that the lifestyle link is so strong that it accounts for 90 percent or more of cancer occurrences.
Let's pursue this line of reasoning with the expectation that doing everything you can to prevent cancer is clearly the best choice.
What medicine refers to as environmental and lifestyle factors include some familiar culprits: overweight, lack of exercise, poor diet, smoking, overuse of alcohol and overexposure to UV and other forms of radiation. Of all cancer-related deaths, it's thought that 25-30 percent are due to tobacco; 30-35 percent are linked to diet; and about 15-20 percent are due to infections, many of them preventable.
What is cancer?
Cells in adults normally have tightly-controlled patterns of growth. They divide in a regulated manner and have definite lifespans. Because of this, the number of cells in a healthy body remains roughly the same over time.
Cancer cells, however, display uncontrolled growth. The rate of division is faster in some cancers than in others, but in all cancers, the cells never stop dividing. In effect, they have infinite lifespans. Malignant tumors invade neighboring tissues and may metastasize, spreading to distant parts of the body. Cancerous tumors have the ability to produce activator molecules, such as vascular endothelial growth factor. Activator molecules induce the formation of new blood vessels to supply the tumor, allowing for cell reproduction and tumor growth.
Cancer is not one but hundreds of different diseases. Breast cancers, for instance, have individual characteristics and display different patterns of growth than lung cancers. That's why a cancer that originates in the breast and metastasizes to the lungs is referred to as metastatic breast cancer, not lung cancer.
How does cancer begin?
Cancer begins when a cell undergoes a mutation: one or more of its genes are damaged or lost. A number of different mutations have to happen before the cell becomes a cancer cell. If a cell carries a mutation, it usually either destroys itself or is recognized as being abnormal by the immune system and killed. This is why cancer usually occurs in older people: There has been more time for mutations to occur and for exposure to cancer-causing agents.
Genes may be damaged by:
- Free radicals produced in the normal process of metabolism
- Carcinogens, such as radiation, chemicals, tobacco, and infectious agents
- Random errors in DNA replication
- Inherited mutated genes
Almost from the time they first arise, cancerous tumors shed cells into the bloodstream. In fact, it's estimated that a 1-cm tumor sheds more than a million cells into the circulatory system in just 24 hours. Most of these cells are killed by cells of the immune system or die due to injury, but some may survive. Traveling cancer cells may become stuck in a capillary and adhere to its lining. From there they penetrate into surrounding tissues or organs, where they may generate secondary tumors. Cancer cells may also penetrate into the lymphatic vessel and travel in the circulating lymph fluid until it becomes lodged in the small channels inside a lymph node.
That the vast majority of cancers are not caused by genetic defects means that in most cases we have the power to modify or eliminate most of the factors that lead to it.
Most of the known risk factors for cancer have one thing in common: they create chronic (long-term) inflammation in the body. Inflammation is a normal part of your body's immune system response to injury. Problems arise when that inflammation becomes chronic. When that happens, levels of many potent inflammatory chemicals go up. These substances include cytokines (including TNF, IL-1, and IL-6), enzymes (such as COX-2 and 5-LOX), and adhesion molecules. All of these various chemicals have been linked to the development of cancerous tumors, and chronic inflammation precedes tumor growth in most types of cancer.
Obesity, smoking, alcohol, infectious agents and carcinogens in food and in the environment have been shown to cause chronic inflammation in the body. The longer the inflammation continues, the greater the risk of cancer.
Maintain a healthy weight
There's a clear link between obesity and cancer. It's thought that, in the U.S., excess weight or obesity cause 14 percent of cancer deaths in men and 20 percent of cancer deaths in women. Obesity is linked to many cancers, including cancers of the colon, breast, endometrium (uterine lining), esophagus, and kidneys.
Clearly, it's important to keep your weight at a healthy level to help prevent cancer. It's important for other reasons as well. You can also prevent the many co-morbidities of obesity, including diabetes, high blood pressure, cardiovascular disease, fatty liver disease and osteoarthritis.
Exercise to protect yourself against cancer
Numerous studies have shown that being physically active exerts a protective effect against cancer. Regular exercise lowers levels of IGF-1, a cytokine implicated in tumor growth, and other cytokines in the bloodstream. Interestingly, it does this even if the person who exercises is overweight and remains overweight. The lower levels of these cancer promoters are one possible explanation for the protective effect of regular exercise.
Exercising regularly reduces a woman's chances of getting breast cancer, possibly because doing so lowers blood levels of insulin and estrogen. Risk of colon cancer, too, is greatly reduced when you exercise, probably because being active decreases the amount of time it takes food to pass through the intestines. That means the colon is in contact with potential carcinogens for a shorter period of time.
Eat anti-cancer foods
It's estimated that diet causes about one-third of all cancer cases, almost as many as tobacco. Because cancer is so strongly associated with chronic inflammation, eating foods that fight inflammation can have a chemoprotective effect. Chief among cancer-protective foods are fruits and vegetables. They contain numerous cancer-preventing, anti-inflammatory chemicals, including:
- Carotenoids, especially lycopene, found in watermelon, guava, grapefruit, and tomatoes
- Resveratrol, found in grapes, peanuts, and berries
- Quercitin, found in red grapes, citrus fruits, tomatoes, broccoli, and leafy green vegetables as well as tea and wine
- Sulforane, found in cruciferous vegetables such as broccoli
Cancer-fighting chemicals are found in teas and many spices, including:
- Green tea
Whole grains contain potent antioxidants and are rich in fiber, which speeds the transit of food through the colon. Eating whole grains has been found to reduce the risk of colorectal cancer.
Don't smoke or use tobacco in any form.
In the U.S., 30 percent of cancer deaths are due to tobacco. That smoking causes lung cancer is well known; it's less known that tobacco use increases the risk for at least 14 different types of cancer. Smoking combined with drinking increases the risk of cancer synergistically. Smokeless tobacco, touted as a "safer" alternative, is responsible for 400,000 cases of oral cancer worldwide -- 4 percent of all cancers.
Drink alcohol only in moderation
If you drink alcohol, do so in moderation, if at all (two drinks a day for men, one a day for women). Chronic alcohol consumption is a risk factor for cancers of the upper respiratory and digestive tracts, including cancers of the mouth, throat, and esophagus, as well as for cancers of the liver, lung, and breast. Risk goes up with increasing consumption.
Avoid UV radiation
Skin cancer is extremely common and frequently fatal, if it isn't caught in time. Both sunlight and artificial sources of UV radiation (like tanning beds) are dangerous. Avoid peak radiation hours during the day (10 a.m.-4 p.m.) if possible. If you can't avoid being out in the sun, wear a hat and cover exposed areas. Use a broad-spectrum sunscreen with a sun protection factor (SPF) of at least 15. And don't use indoor tanning beds or sunlamps.
I realize that vaccination, once the pride of preventive medicine, has become a hot-button issue. There are popular movements that attribute many kinds of risks to being vaccinated. Let me simply give the accepted protocol here. Vaccination won't be a priority in cancer prevention, but a thorough approach, as dictated by some oncologists, would target specific cancers through being immunized against them. Human papillomavirus (HPV) is a sexually transmitted virus that can lead to cervical cancer. A protective vaccine is recommended for girls ages 11-12 and for girls and women ages 13-26 who haven't completed the full vaccine series. Hepatitis B can increase the risk of developing liver cancer. All babies and some high-risk adults should be vaccinated.
For many people, these lifestyle changes are so drastic that adopting them will take time, patience, and knowledge. The threat of heart attack, stroke, and diabetes hasn't been potent enough to cause wide swaths of the public from giving up bad lifestyle choices. Now we find that cancer can be added to the list, so far as some researchers are convinced of the link between cancer and environment.
You aren't called on to become a cancer expert. But weighing all the evidence, it's clear which way the wind is blowing. The likelihood that cancer is not enmeshed with lifestyle is diminishing year by year. Yes, cancer is immensely complicated, but everything you can do to support your body's innate intelligence is a positive step in allowing that intelligence to block the cellular changes that create malignancy. A decade from now, I expect that we will tune in and find that this ray of hope has become even brighter.
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