1. Maintain a healthy weight and eat less fat meat
Being overweight, or obesity, is a condition in which a person has an abnormally high and unhealthy proportion of body fat. Obesity is associated with increased risks of certain cancers, including colon and rectum cancer (CRC). An American study estimated that in 2007 in US, about 34,000 new cases of cancer in men (4%) and 50,500 in women (7%) were due to obesity. In Europe, 11% of CRC cases have been attributed to overweight and obesity.
Does this mean we should eat less meat in general? Is this recommendation only for processed meat? What is classified as ‘fat meat’?
Red meat and processed meat are classified by the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) as causes of colorectal cancer. Haem iron (found in red meat) and animal fat are classified by WCRF/AICR as a possible cause of colorectal cancer, based on limited evidence.
An estimated 21% of bowel cancer cases in the UK are linked to eating red and processed meat. The effects of red meat have been examined in many studies. Most, though not all, associate an increase in colorectal cancer with greater intake of red meat.
Based on this evidence, you should limit the amount of red meat, especially processed meat intake. Examples of red meats are beef, pork, lamb and liver. Processed meats include hot dogs and some luncheon meats. Generally, the recommended daily intake of red or processed meat is 70gm or 500gm a week.
Several studies have found that the risk of colorectal cancer is specifically increased among meat eaters who consume meat with a heavily browned surface (frying) or meat that has been prepared at high temperatures for prolonged durations (grilling). It is believed that prolonged high temperature converts the fats in the meat to mutagenic (cancer-causing) chemicals.
2. Be physically active
Being physically active is beneficial to our overall health. Researchers have established that regular physical activity can improve health by:
- Helping to control weight
- Maintaining healthy bones, muscles, and joints
- Reducing the risk of developing high blood pressure and diabetes
- Promoting psychological well-being via endorphins released during exercise
- Reducing the risk of death from heart disease
- Shown to be associated with decreased risk of certain cancers including colorectal cancer
Researchers are learning that physical activity can affect the risk of cancer. There is convincing evidence that physical activity is associated with a reduced risk of colorectal cancer and breast cancer. Despite these health benefits, recent studies have shown that more than 50% of the population do not engage in enough regular physical activity.
How much physical activity do adults need?
The Centers for Disease Control and Prevention (CDC) recommend that adults should “engage in moderate-intensity physical activity for at least 30 minutes on 5 or more days of the week,” or “engage in vigorous-intensity physical activity for at least 20 minutes on 3 or more days of the week”.
Here are some examples of moderate-intensity and vigorous-intensity physical activities.
3. Get enough vitamin D
A healthy vitamin D intake reduces the risk of colorectal cancer and increases survival rates for those already affected by colorectal cancer.
Vitamin D could lower the risk of colorectal cancer through various mechanisms, including reducing spread of cancer cells, promoting cell differentiation, and stimulating apoptosis (the body’s way of getting rid of unneeded or abnormal cells).
Some of largest studies on the effect of vitamin D include those that showed how high levels of vitamin D concentration (at least 30ng/mL) are associated with reduced risk of colorectal cancer.
To achieve a vitamin D concentration of at least 30ng/mL in the blood, recommended daily intake of vitamin D ranges from 10 – 20mcg a day. Main sources of vitamin D come from sun exposure as well as foods with vitamin D (eg. fatty fish like tuna and salmon, orange juice, soy milk, beef liver, cheese and egg yolk).
4. Limit consumption of red meat, especially processed meat
The recommended daily intake of red meat is about 70gm per day or about 500gm per week. The way of cooking is also important. Avoid prolonged high temperature methods of cooking the red meats, like frying and grilling.
More truths about lowering cancer risk
There are risks and benefits to regular aspirin use. Low dose aspirin is given routinely to patients with increased cardiovascular and ischemia stroke risk to prevent heart attacks and strokes.
Aspirin has been shown to reduce colorectal cancer risk. This benefit is observed in some studies, but no long-term study has been conducted to observe the effects of aspirin taken over a minimum period of 10 years to determine the association of aspirin with lower colorectal cancer risk.
There are risks and adverse effects from taking aspirin regularly over a long period, such as bleeding in the gastrointestinal tract (eg. stomach) and brain. Presently, their routine use is not recommended for prevention of colorectal cancer in the general population due to concern about their associated toxicities.
Garlic is a vegetable (allium sativum) that belongs to the allium class of bulb-shaped plants, which also includes onions, chives, leeks, and scallions. Garlic is used for flavouring in cooking and is unique because of its high sulphur content. In addition to sulphur, garlic also contains nutrients such as arginine, oligosaccharides, flavonoids, and selenium, all of which may be beneficial to health.
Several population studies show an association between increased garlic consumption and reduced risk of certain cancers, including colorectal cancer. However, these studies use different preparation methods and dosage of garlic. A recent updated meta-analysis of prospective studies on consumption of garlic and risk of colorectal cancer states that ‘consumption of raw and cooked garlic or garlic supplements is not significantly associated with reduced colorectal cancer risk’.
The National Cancer Institute, part of the National Institutes of Health, does not recommend any dietary supplement for the prevention of cancer, but recognises garlic as one of several vegetables with potential anticancer properties.
As all garlic preparations are not the same, it is difficult to determine the exact amount of garlic that may be needed to reduce cancer risk. Furthermore, the active compounds present in garlic may lose their effectiveness with time, handling and processing. The World Health Organisation’s guidelines for general health promotion for adults is a daily dose of 2 – 5g of fresh garlic (approximately 1 clove), 0.4 – 1.2g of dried garlic powder, 2 – 5mg of garlic oil, 0.3 – 1g of garlic extract, or other formulations that are equal to 2 – 5mg of allicin.
Article contributed by Dr Dennis Koh, general surgeon at Mount Elizabeth Hospital