Cancer Prevention Through Diet

A radio broadcast on this topic aired on August 21, 2008.

On September 4, 2008 we explored cruciferous vegetables (with a focus on broccoli) and their effects on cancer in more detail.

Cancer is a complex disease process with many contributing factors. At this point in time, there is lots of information about what causes or contributes to cancer, and there is lots of information about risk factors and trends. Yet despite the pouring of money into cancer research, pharmaceutical drugs, radiation and surgery, and even despite many novel theories and treatment methods, no single treatment has been shown beyond a shadow of a doubt to result in a 100% cure for cancer. By exploring some details about cancer and how it develops, we can discover some dietary habits that will support us in preventing this unfortunate disease from occuring in the first place.



Cancer Statistics

Each year the American Cancer Society estimates cancer incidence and mortality rates by collecting data from the National Cancer Institute, CDCP, North American Association of Central Cancer Registries, and National Center for Health Statistics. The following projections for 2008 are based on statistics collected through 2005.

According to American Cancer Society estimates, the top 10 deadliest cancers in 2008 will be:

Men

• lung
• prostate
• colon
• pancreas
• liver
• leukemia
• esophagus
• bladder
• non-Hodgkin lymphoma
• kidney

Women

• lung
• breast
• colon
• pancreas
• ovary
• non-Hodgkin lymphoma
• leukemia
• uterine
• liver
• nervous system

Other new cases of cancer that are expected to develop in large numbers though they may not result in death include cancers of the skin, mouth, thyroid, and ovary.

With the exception of lung cancer in women, overall cancer rates seem to be declining or reaching a plateau. Despite this trend, cancer, which accounts for 25% of all U.S. deaths, is the leading cause of death in women between 40-79 years old, and in men between 60-79 years old. It is the leading cause of death for both men and women under 85 years old. In 2005, deaths due to cancer exceeded deaths due to heart disease by approximately 67,000. 1



How Does Cancer Start?

Although genetics does play a role in some cases of cancer, environmental factors may play an even larger one. 2 As the number of carcinogenic compounds in our environment grows steadily, it becomes even more important to understand how cancer develops so that we can then strengthen our resistance to this disease.

Cancer starts from a single cell with damaged DNA. In normal circumstances, a cell replicates by making an identical copy of itself. If the copy is not made exactly, then the resulting changes in the DNA in the new cell are called mutations. Mutations aren't by definition harmful. For example, mutations are what allow species to adapt to new environments. If, however, the mutation in the DNA results in genetic damage, then the mutation can be problematic and result in the development of a cancer cell.

In the course of a cell's life, its genes dictate and regulate its growth, function, reproduction, and death. There are genes that are responsible for telling the cell how and when to grow, when to make a copy of itself, how to copy its DNA when its time to make that copy, and when its time to die. If due to genetic damage any of these processes isn't handled properly, then it is possible that the resultant cell will be cancerous.

Three features distinguish cancer cells from normal cells and from benign tumor cells. First, whereas the normal growth of cells is limited, cancer cells will grow uncontrollably. Second, as part of this uncontrolled growth, cancer cells will invade their surroundings to the point of damaging healthy tissues. Third, cancer cells can metastasize, or spread to other parts of the body and initiate similar destructive growths elsewhere. For example, it is relatively common for breast cancer to metastasize to the lungs if given the opportunity.

The first stage of cancer development is called initiation. This is the point at which the cell's DNA becomes damaged and produces a pre-cancerous cell. Ideally, cancerous cells are supposed to self-regulate and die. If they fail to die on their own, then the immune system is supposed to recognize them as cancerous and destroy them. It appears, however, that sometimes the immune system fails to recognize cancerous cells and so they remain to go through the stages of promotion and progression. In the promotion stage, cells slowly multiply and become pre-neoplastic or pre-tumor cells. In the progression stage, the cells become neoplastic and form tumors. 3 (Except leukemia, which is a cancer of the blood and does not form tumors.) It is at this point that the cells can metastasize and spread to other parts of the body.



What Causes Genetic Damage?

Some common causes of cancer include:

• Viruses (e.g. HPV can cause cervical cancer, Hepatitis B & C can cause liver cancer)
• toxins / carcinogens (e.g. asbestos can cause lung cancer, dioxins: lung, blood & lymph
• ionizing radiation (e.g. xrays, CATscans, nuclear radiation)
• hormonal imbalances (e.g. excess estrogen)
• free radicals/oxidation (e.g. oxidized cholesterol, rancid oils)
• genetics
• aging

How Can Diet Mediate Cancer?

There are three general ways that nutrients work to mediate the growth of cancer cells directly:

1) they can prevent genetic damage from occurring;
2) they can support proper cell reproduction; and
3) they can supply energy and nutrients needed for cells to die when appropriate.

Perhaps the most important stage is the initiation stage. In the initiation stage, nutrients called cancer-blockers work by preventing cells from becoming cancerous. They can prevent carcinogens from damaging the cell so no genetic damage occurs in the first place. Or, they can provide the ingredients necessary for proper DNA replication and healthy cellular reproduction. A recent study demonstrates that certain foods actually turn off cancer-promoting genes and turn on cancer-preveting genes. 4 During the promotion and progression stages, nutrients called cancer-supressors can facilitate the initiation of cell death in cancerous cells. They can also support the immune system in doing its job of recognizing and destroying the cancerous cells. 5

Besides affecting the growth of cancer cells directly, nutrients:

1) work to strengthen the immune system's response to cancer cells;
2) promote the detoxification of carcinogens in the liver; and
3) promote expedient elimination of potentially carcinogenic compounds.

The immune system is essentially of network of cells, tissues and organs that work together to maintain our health. For example, white blood cells don't just reside in lymph nodes, which get swollen when we have an infection, and the spleen, which filters blood. They also travel through blood to recognize and destroy cancer cells as well as pathogens. The thymus gland (located above the heart) regulates the development of particular immune cells, and mucous membranes all over function to keep out unwanted particles, chemicals, and pathogens. Nutrients in our diet ensure that all of these cells, tissues, glands and organs are able to function optimally.

If we breathe, eat, drink or even absorb through our skin substances that could be carcinogenic, it is the liver's job to break down these harmful chemicals into harmless ones. In the liver, there are two phases of detoxification. Phase I is responsible for breaking things down and cleaning them up, akin to the wash cycle in the washing machine. In Phase II, chemicals are repackaged to be removed from the body, similar to the rinse and spin cycle. Sometimes particular chemicals aren't inherently carcinogenic, but in the process of being broken down in Phase I they become carcinogenic. This is why it's very important to have a balance between Phase I and Phase II. If too many toxins are being created by Phase I while Phase II is unable keep up, then there's a potential for accumulating dangerous substances. Fortunately, many foods that promote liver function - especially the ones so well known for being anti-cancerous, such as broccoli, brussel sprouts, and cabbage - balance Phases I and II and therefore prevent these substances from causing genetic damage in the first place.

Lastly, once the substances have been packaged, the elimination pathways need to be open. For example, it's important that the colon is moving waste through at the proper speed. If the large intestine is sluggish, then potentially harmful substances can be reabsorbed and sent back through the liver again. Toxins can also be eliminated through urine or sweat. In this case the kidneys and skin need to be working properly. Many foods already that support detoxification in the liver also promote proper function and elimination through these routes.

The list of nutrients is long and varied, and there is a lot of disagreement about whether or not certain foods cause or prevent cancer. For example, red meat is often cited as being a cancer-causing food. However, studies of Argentinans who consume large quantities of red meat have demonstrated that an increased consumption of red meat does not necessarily result in an increased rate of colon cancer. 6 Furthermore, grassfed beef and dairy products from grassfed animals have been shown to contain conjugated linoleic acid (CLA), a fatty acid that has demonstrated to have very strong anti-tumor effects even at very low concentrations in the diet (.5 and 1.0%). 7 Meanwhile, vegetarians appear to be prone to cancers of the nervous and reproductive systems. 8 What follows is a brief overview of some nutrients and some of the ways they mediate cancer.



Cholesterol, Beneficial Fats and Fat-Soluble Vitamins

The first items listed are fats or fat-soluble nutrients. This may seem unlikely because so much bad press has been given to meat and other animal products such as meat and whole-fat dairy products. However, despite their negative reputation during the last 60 years or so, historically these foods have sustained and nourished many people around the world. In fact, in the 1930's and 1940's, Dr. Weston A. Price, DDS determined that traditional diets contained ten times more fat-soluble vitamins than our modern diet. 9

• Cholesterol - eggs, pastured animal foods (antioxidant, cancer suppressor)
• CLA - pastured animal foods (beef, lamb, veal, esp. dairy products (antioxidant, cancer blocker & suppressor)
• Vitamin A - liver, fish (liver) oil, eggs (cancer blocker, immune enhancer)

Note: Often carrots and other vegetables are referred to as containing Vitamin A. In these cases, what is being referred to is beta-carotene, a carotenoid which is a precursor to the true, biologically active Vitamin A. Beta-carotene must be converted in order to be utilized as Vitamin A. The biologically active Vitamin A is known as retinol or retinoic acid and is found in animal sources only. Also, it should be mentioned that the use of beta-carotene as a supplement (rather than coming from food) has been associated with an increase in lung cancer in smokers. 10 (What plant and animal sources of A have in common are their characteristic yellow color. For example, eating too many carrots can cause your skin to turn orange. Similarly, when cows eat spring grass their butter has a rich, yellow color, as do the yolks of eggs that come from chickens eating grass.)

• Vitamin D - cod liver oil, lard, sardines, mackerel, salmon, roe, eggs (cancer blocker)
• Vitamin E - whole cereal grains (antioxidant, cancer inhibitor, suppressor)
• Essential Fatty Acids - cod liver oil, salmon (cancer suppressor, immune enhancer)
• Saturated Fat - butter and other dairy fats, animal fats (immune enhancer)
• CoQ10 - mackerel, herring, liver, heart, kidney, whole grain germ (immune enhancer, antioxidant, cancer blocker & suppressor)

The B Vitamins

The following three B vitamins are important for a number of reasons. First, they play an important role in the function of DNA and RNA in the cells. Second, they are necessary for the proper metabolism of methionine, which is metabolized into homocysteine. While a certain amount of homocysteine may be beneficial to our health, elevated homocysteine levels are well known for their association with cardiovascular disease. They are also associated with increased cancer rates. How much we need of these vitamins depends on our age, genetics, hormones, and lifestyle.

Interestingly, homocysteine may have anti-cancer and anti-tumor properties when it combines with vitamin A (retinoic acid) and vitamin B12, vitamins that. 11, 12 The reputed success of raw liver in anti-cancer dietary therapies may be due in part to its high content of Vitamins B6, B9, B19 and Vitamin A. Also, note that two of these three vitamins occur in whole grains. A diet that is devoid of whole grains (and rich in refined grains and flours) may very easily cause a deficiency in these vitamins.

• Vitamin B6 (pyridoxine) - meats esp. liver, whole grains (cancer blocker, immune enhancer)
• Vitamin B9 (folic acid) - liver, whole grains, green vegetables (cancer blocker)
• Vitamin B12 (cobalamin) - liver, clams, milk (cancer blocker)

Other Nutrients

As research into cancer-fighting compounds has progressed, a whole new class of nutrients called phytonutrients has been identified. These are compounds that aren't classified as vitamins, a category that has been reserved for compounds considered essential for life. And while research has only begun in this field, they have been shown to have numerous health benefits, of which offering protection from cancer is only one. The phytonutrients can be classified generally into three main categories (nitrogen compounds, polyphenols, and sulfur compounds) and then further subcategorized, though there appears to be some discrepancies concerning their categorizations. The number and complexity of these chemicals are dizzying, and is reflected by the varied roles they have within the plants in which they are found and the myriad of ways they support health in humans and animals. For example, besides contributing to a plant's smell, taste or color, some of their functions include: defending one plant from being overgrown by another; defending a plant from being eaten by insects and animals; defending a plant from physical damage or disease; facilitating reproduction; and facilitating decomposition and recycling of nutrients back into the soil. 13 In animals and humans they have anti-inflammatory, anti-cancerous, immune-supporting, and detoxifying functions, to name a few.

What is most striking about these chemicals is that they often have multiple anti-cancerous functions, and the foods in which they are found usually have several beneficial phytochemicals. This is why cruciferous vegetables (broccoli, brussel sprouts, kale, cabbage, and cauliflower, for example) have gained such a strong reputation. Isothiocyanate-derived components such as indole-3-carbinol (I3C) and sulphoraphane support both phases of liver detoxification. I3C has also been shown to work against cancer in both the initiation and promotion. 14,15 Sulforaphane has been tested in mice and has been demonstrated to improve the immune systems of older mice. In fact, their immune response was so improved that after treatment, their immune response equaled that of younger mice. 16

Spices have also gained a lot of attention due to their terpenoid content. Terpenoids can be found in basil, cinnamon, cloves and ginger, for example. In these plants they play a role in scent, while in humans they function to promote the death of cancer cells. 17

Some other anti-cancerous compounds follow:

• ellagitannins (ellagic acid) - strawberries, cranberries, grapes, pomegranates (antioxidant, cancer blocker and cancer suppressor)
• catechins and tannins - tea (green, white, black, and oolong teas), chocolate/cocoa (antioxidant, cancer suppressor)
• anthocyanins - black & red raspberries, blueberries, cranberries, blackberries, cherries, red cabbage (antioxidants, cancer blockers & cancer supressors)
• phenols (e.g. resveratrol) - commonly known in the skin of red grapes and peanut (cancer blocker & cancer suppressor)
• liminoids - citrus fruit peels (detoxification support)
• lipoic acid - kidney, heart, liver, spinach, broccoli, potatoes (potent antioxidant)
• capsaicin - chile peppers (cancer blocker & cancer suppressor)
• curcumin - tumeric (antioxidant, cancer blocker & cancer suppressor, detoxification support)
• allyl sulfides - onions , garlic, leeks (cancer blocker, cancer suppressor, detoxification support)
• beta-glucans - maitake, shiitake, reishi, hiratake (oyster) musthrooms (cancer suppressor, immune enhancer)
• cyanogenic glycosides - almonds, apples, pears, peaches, apricots and raspberries (cancer suppressor)

  Note: These compounds are highly controversial. Sometimes referred to as Vitamin B17 and found in bitter foods that aren't commonly eaten, we no longer consume this nutrient regularly in our diet. It used to be found in grasses that were fed to livestock, but that practice has been discontinued. It can still be found in the kernels of apricot, peach, and plum pits, and also in cassava, millet, alfalfa leaves, and bamboo shoots.
  
  Discovered by Dr. Ernst T. Krebs, Jr., Vitamin B17, also known as laetrile, nitriloside or amygdalin, owes the source of its controversy is due to its cyanide content. This vitamin has been shown clearly to cause the death of cancer cells without damaging healthy cells. But because of fear around its potential side-effects (which may include death) it is illegal as a cancer treatment in the United States. Though research shows that in limited amounts this vitamin is safe while still effectively reversing cancer, toxicity is yet to be determined. 18,19

Fiber

When it comes to colon health, everyone has heard about fiber. There are some interesting features to note about the health benefits this apparently simple compound provides. Fiber can promote bowel movements and therefore keeps any toxins moving through our system and prevents them from being reabsorbed. This is one of the most common theories for why a diet high in fiber is associated with a decreased risk of cancer. However, fiber also helps support beneficial bacteria in our digestive system by providing them a food source as well as a structure to which they can attach for survival in our intestines. (As we will see below, beneficial bacteria also play a role in cancer prevention.) Fiber is found in all fruits and vegetables. Apples are particularly well known for their pectin content, for example.

But different fibers offer other benefits as well, depending on the individuals health and digestive system. For example, psyllium husk, though it's known to promote bowel movements, can actually cause constipation in some people, so it can help someone who is prone to loose stools. On the other hand, it's better for someone who is chronically constipated to consider fiber from ground flax seeds. Both flax seeds and psyllium husks can bind toxins, but flax seeds have a loosening effect on the bowels and are better for certain individuals for this reason.



Fermented foods

Naturally occuring in unpasteurized fermented foods and sold as supplements called probiotics, beneficial bacteria function both as cancer blockers and suppressors. This appears to be true in cases of fermented dairy products as well as fermented vegetables. Fermented foods also demonstrate antioxidant and immune-boosting properties. 13,20



Foods to avoid

Foods that damage tissues require the body to work more as the damage must be repaired just like an injury:

• Trans-fatty acids
• Rancid fats

Eating foods that deplete nutrients deprive your body of the resources it needs in order to keep your immune system and detoxification process working properly:

• Refined carbohydrates (e.g. white bread, pasta)
• Refined sweeteners (e.g. white sugar, brown sugar)

Food additives and preservatives are oftem chemicals that damage tissues and stress the immune system:

• MSG (sometimes simply called "natural flavor")
• Aspartame
• Food colorings

Conclusion

Rates of cancer are increasing and it's important to know what you can do to prevent cancer cells from taking hold in your body. Some estimate that approximately 50% of cancer cases and 35% of cancer deaths are related to diet. 21 And although this is just an estimate given that our understanding of cancer is still quite limited, it is clear that eating a healthy, balanced diet does help to prevent cancer. Eating whole foods that are nutrient-dense and organic when possible and avoiding highly processed and fast foods will provide a solid foundation for health in general as well protect against cancer. By eating well you will be getting what you need to stay healthy and reducing your intake of substances that may trigger the development of cancer in the first place.

Please note, however, that in excess quantities, some of the above nutrients can become toxic - more is not always better. Also, keep in mind that food sources always provide the best forms of these vitamins. Although there is still so much that is unknown about these nutrients and their cofactors (which occur naturally in foods), we do know that getting too much of one nutrient may cause a deficiency of another. Therefore, use caution with supplements that advertise their health benefits yet contain only isolated compounds. The best - and safest - way to get these nutrients is to get them from food sources rather than synthetic, concentrated pills.



References

1. 2008, American Cancer Society

2. July 2000, The New England Journal of Medicine

3. 1998, The Cancer Journal

4. June 2008, Proceedings of the National Academy of Sciences

5. October 2003, Nature Reviews Cancer

6. January 2003, Nutrition

7. November 1991, Cancer Research

8. Weston A. Price Foundation

9. Nutrition and Physical Degeneration by Weston A. Price, D.D.S.

10.December 2004, Journal of the National Cancer Institute

11. August 2002, The Homocysteine Revolution: An interview with Dr. Kilmer McCully

12. July 1999, Nutrition Science News

13. Edible Medicines: An Ethnopharmacology of Food by Nina L. Etkin

14. December 2006, Biochemical Pharmacology

15. December 2004, The Journal of Nutrition

16. May 2008, The Journal of Allergy and Clinical Immunology

17. June 2008, Cellular and Molecular Life Sciences

18. VitaminB17.org, Ed Griffin

19. University of Idaho, Dept. of Food Science and Toxicology

20. Probiotics: Nature's Internal Healers by Natasha Trenev

21. December 1999, Toxicological Sciences