More Lifestyle Choices for Cancer Prevention
To continue from the last blog on this topic, “What Does Eating Plants Do For Cancer? Part Four”, we’ll look at a few more steps you can take toward a long and healthy life.
Methionine is one of two sulfur-containing amino acids that are incorporated into proteins in humans. It is an essential amino acid because it cannot be produced by the human body; we must get it from our food. Foods that are the highest sources of methionine are animal-based, especially eggs and meat, particularly chicken and fish. There are lower amounts of methionine in plants.
Certain health disorders that affect methionine metabolism (such as elevated homocysteine) are treated by restricting methionine consumption. Lower methionine intake is also being studied for its benefit in chronic health conditions and to enhance longevity (8,9,10,11). Methionine restriction appears to slow the rate of growth of cancer cells and increase apoptosis (cell death) (12), improve sensitivity to insulin, improve lipid metabolism and decrease systemic inflammation (13).
Fighting cancer is difficult because cancer cells are our own cells gone rogue. This makes it difficult to destroy only the cancer cells and leave the healthy cells alone. Many human cancers, such as those of the colon, breast, ovary, prostate and skin, appear to have absolute methionine dependency. This means that they must have methionine to thrive. It follows that restricting methionine will decrease growth of these cancers. The added bonus is that normal cells can continue to thrive even when faced with low methionine levels. Lowering methionine also lowers the risk of cancer development in the first place. (12)
What about healthy aging and longevity. The less methionine in body tissues, the longer many mammals tend to live (14). It is theorized that lower methionine intake leads to less free radical production which in turn slows the rate of DNA damage and mutation and the rate of aging (15).
So how would one gain the benefits of lower cancer risk and longer life by lowering methionine? There are actually three ways to do this. The first is calorie restriction which in practical terms means to cut food intake in half, an almost impossible strategy to maintain for any length of time because of hunger. A second method is to practice protein restriction since methionine is high in certain proteins especially those of animal-based foods. This could be feasible, especially since our Western diet contains far more protein than we need. But there is a third way, one that not only lowers methionine but has a multitude of other health benefits. Plant proteins are low in methionine. The eating pattern that is lowest in methionine is a purely plant-based diet (11).
INCREASE INTAKE OF CANCER-FIGHTING FOLATES
Studies have shown that the relative risk of dying for women with breast cancer is 59% lower in those who have the highest blood folate levels compared to those with the lowest levels (16). High folate blood levels are also associated with reduced risk of cancer of the colon, pancreas and other parts of the gastrointestinal tract. The cancer preventative properties of folate are attributed to its function in DNA replication and repair (26).
Folates are not stored in the body so need to be eaten daily. Best sources are dark green vegetables such as broccoli and spinach and dried legumes such as chickpeas, beans and lentils (27).
FIGHT CANCER BY STARVING IT OF ITS BLOOD SUPPLY
Angiogenesis is the process used by our body to create new blood vessels. Most of our blood vessels form before we are even born but angiogenesis can also occur while healing from an injury or during pregnancy…or under more sinister circumstances. Cancers themselves are able to turn on angiogenesis. Cancers are only able to grow to a size of about 0.5 mm without a blood supply and, if you can prevent angiogenesis from ever supplying blood to a tumor, that tumor will wither and die. Conversely, if angiogenesis succeeds, cancer tumors can grow exponentially. Blood vessels formed by cancers are unlike regular healthy blood vessels; they are poorly constructed and somewhat vulnerable to assault from anti-angiogenic agents. Cancerous cells form regularly in our bodies. Our body’s immune system, through its use of prevention of angiogenesis along with other methods, is quite efficient at keeping cancer cells in check. (22,23)
Anti-angiogenic drugs have been available for a couple of decades now and do have the ability to prevent new blood vessel growth. However, some cancers, especially those of the lung, liver and brain, do not need new blood vessels; they are able to use existing vessels for their blood supply. This may be why anti-angiogenic drugs are proven to increase long-term survival in only some cancer types (18,19,20).
Some of the regular foods that we eat are naturally anti-angiogenic. These foods are all plant-based and include quite a long list (21). The following are some examples.
Berries – blueberries, strawberries, blackberries, raspberries,
Other fruits – apples, oranges, grapefruit, lemons, pineapple, cherries, peaches, grapes
Vegetables – onions, garlic, tomatoes, cauliflower, carrots, sweet potatoes, pumpkin, kale, bok choy, sea cucumber, broccoli, wine, spinach, artichokes, ginseng, maitake mushroom
Beans and legumes – chick peas, soy beans, lentils
Grains and seeds – whole grains, brown rice, oats
Herbs and spices – turmeric, nutmeg, parsley, lavender, licorice
Harvard School of Public Health studied angiogenesis by following 49,000 men for over twenty years. Those who consumed 2 to 3 servings of cooked tomatoes per week had a 40 to 50% reduced risk for developing prostate cancer and, in those who did develop prostate cancer, fewer blood vessels were found to be feeding their tumours (17).
If you need one more reason to increase the amount of these delicious foods in your daily diet this could be it.
INCREASE INTAKE OF ANTI-CANCER PLANT STEROLS
There are specific components of food that are uniquely beneficial in lowering the risk of some cancers. Plant sterols (phytosterols) are known to lower blood cholesterol levels. Phytosterols are molecules that are very similar to other molecules already familiar to the body; so similar in fact that the body treats the two molecules the same way. Enterocytes in the digestive tract, the cells lining the intestine that absorb nutrients from food, are deceived by the similarity of phytosterol and cholesterol and pick up both of them to deliver to the blood stream. Because the phytosterol uses some of the enterocyte machinery, less cholesterol is collected and absorbed and ends up being expelled from the body as waste. Cholesterol levels fall. (2,3).
Plant sterols are now being studied for their inhibitory effect on cancer (1). It has been observed that their cholesterol modulating effects may overlap with anti-cancer actions. Considerable research is discovering inhibitory actions of phytosterols on cancers. The mechanisms of this effect are multiple and include promoting cell death due to the decrease in cholesterol levels, discouraging the production of carcinogens, impeding angiogenesis and reducing cancer cell growth, invasion and metastases (4). Further research is underway to discover the full potential of phytosterols to obstruct lung, stomach, ovarian and breast cancer (4,5,6) as well as colon and prostate cancer (7).
Phytosterols are found in all plant foods but the best sources are whole grains, nuts, seeds, legumes and unrefined vegetable, nut and olive oils (24,25).
Randomized controlled studies, observational studies and long-term cancer follow-up trials have all shown that regular ingestion of acetylsalicyclic acid (ASA or Aspirin) can prevent cancer. An analysis of eight different studies and 25,000 people showed a 20% decrease in risk of death from cancer among those taking daily aspirin (31). A follow-up on this showed a reduction in cancer metastases by about one-third (32). The mechanism for this is thought to be the prevention by salicylic acid of the conversion of arachidonic acid to potentially tumour-producing prostaglandins (28). The cancer reduction effect occurs within 2 to 3 years of starting ASA and, because cancer takes many years to develop, the benefit appears to be not in the production of cancer but in the cutting of the risk of metastases. The downside to ASA use is that it increases the risk for stomach irritation, stomach ulcers and major bleeding, even at low doses.
Plants produce salicylates naturally in response to stress and a plant-rich diet contains substantial levels of salicylates (29). Salicylic acid levels have been shown to be significantly increased in vegetarians as compared to non-vegetarians (30) and can be as high as those of someone taking ASA every day. Perhaps not so surprisingly, eating food sources of salicylic acid do not cause the side effects that taking aspirin does. In plants the salicylic acid comes naturally pre-packaged with gut-protective nutrients such as the nitric oxide from dietary nitrates that protect the stomach by increasing blood flow and mucous production in the stomach lining.
Salicyclic acid is found in all fruits and vegetables but the richest sources are herbs and spices. Chili powder, paprika and turmeric have remarkably high concentrations but at the top of the heap is cumin which is about 1% salicylic acid by weight. If you consume one teaspoonful of cumin you are getting the same amount of salicyclic acid as that found in a baby aspirin. Meat, fish, dairy and cereals contain negligible amounts of salicylic acid or none at all. (33)
This is a case where eating organic may be better. Plants that are covered in pesticides do not experience as much stress from insects as do organically grown plants. Plants grown organically must create their own defenses and so they increase their production of salicylic acid. (34)
Researcher have shown that regularly donating blood results in a 37% reduction in cancer incidence and a significantly reduced risk of death in those who have cancer. Benefits can be seen only six months after giving blood once. Conversely, there is a spike in cancer rate within six months of receiving a blood transfusion (37). It is believed that this effect is due to the effects of iron being removed from the body while donating blood and being added to the body through blood transfusion (35,36). See “What Does Eating Plants do For Cancer? Part Two” for more information.
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