Last month, in Part 1 of this article series, we visited the issues of:
In Part 2 of this series, we will review whether red meat and processed meats are safe, and whether eating a low-fat diet or a high-fiber diet can reduce your risk of cancer coming back.
To recap, we have based our discussion and recommendations on guidance by the American Cancer Society, the European Society of Medical Oncology, Cancer Australia and a few other large cancer societies.
Should I eat red meat? What about processed meats?
Firstly, what is red meat? Red meat includes beef, lamb, mutton, pork, veal, venison and goat. Processed meats refer to meat that has been preserved by smoking, curing, salting, or adding preservatives. These include sausages, bacon, ham, deli meats such as salami, pates, and canned meat such as SPAM and corned beef, and sliced luncheon meats.
Lean red meat is a good source of protein and iron. It can be included as part of the healthy diet. The association between red meat and cancer is unclear but some studies have linked eating large amounts of red meat and processed meats with increased risk of bowel, prostate and stomach cancers.
One of the potential ways through which red meat could increase the risk of bowel cancer is due to the heme iron found in red meat. This compound, which gives red meat its red colour, is thought to irritate the the bowel lining and may ultimately lead to carcinogenesis - which is the mutation of normal cells to cancer cells. Moreover, nitrate and nitrites, which are added as preservatives to processed meats, can form cancer-causing compounds that also increases your risk of cancer.
Some research suggests frying, broiling or grilling meat at very high temperatures creates chemicals that might increase the risk of some types of cancers.
For these reasons, the American Cancer Society and other cancer societies recommend limiting your intake of red meats to 500g a week and avoiding processed meats altogether. They also discourage cooking red meat at high temperatures.
Even though the research on safety of red meat and processed meats were not done in cancer survivors, this recommendation may also be applied to cancer survivors to encourage general good health and prevention of other cancers.
Should I eat a low-fat diet?
A low-fat diet is an eating plan that is low in total fat, unhealthy fat and cholesterol. Typically, a low-fat diet would include foods such as oats, lean meats, white fish, skimmed milk, vegetables, lentils and fruit.
A large study (The WINS study) looked at whether reducing fat intake after a diagnosis of early stage breast cancer affects the risk of cancer recurrence. On average, women who decreased their fat intake to 20% of their calorie intake had a 24% reduction in breast cancer recurrence. However, on average, these women also lost 2.7 kg over the course of the study. Therefore, it is unclear whether the reduction in breast cancer recurrence was due to eating less fat in their diet or from losing weight.
On the flip side, another large study, the Women's Healthy Eating and Living (WHELS) study did not find any survival difference between women with breast cancer who limited their fat intake and those who didn't.
Some studies suggest that omega-3 fatty acids, usually found in salmon, cod liver oil, walnuts and flaxseeds, have benefits for cancer survivors but these findings are not consistent and more research is needed. Regardless, including foods rich in omega-3 fatty acids in the diet is encouraged because it is associated with a lower risk of heart disease and longer lifespan.
Should I eat a high-fiber diet?
Fiber can be categorized into soluble and insoluble fiber. Soluble fiber is found in foods like oat bran, barley, nuts, seeds, beans, lentils, peas and some fruits and vegetables while insoluble fiber is found in foods like wheat bran, vegetables and whole grains.
Soluble fiber helps lower the risk of heart disease. Fiber is also linked to improved bowel function. Good sources of fiber are beans, vegetables, whole grains, nuts and fruits. Eating these foods is recommended because they also contain other good nutrients that may help reduce cancer risk and provide other health benefits.
Eating more vegetables and fruits has been associated with a lower risk of lung, mouth, oesophageal, stomach and colon cancers. Again, few studies exist on whether a diet high in vegetables and fruits can reduce the risk of cancer recurrence or improve survival for cancer patients although some studies suggest it may help prevent recurrence or increase survival for breast, prostate and ovarian cancer survivors.
Nonetheless, consistent with general dietary guidelines, cancer survivors are encouraged to aim for at least 5 servings of vegetables and 2 servings of fruit each day because of their health benefits. As it is not known which of the many compounds in vegetables and fruits may be most protective, the best advice is to eat plenty of a variety of colourful vegetables and fruits each day.
I hope this article has been helpful in clearing some of the confusion around food. Unfortunately, confusion exists when there is lack of solid evidence one way or the other. In this situation, I find it best to be guided by the large cancer societies.
In the next part of this article series, we will review if being vegetarian or vegan helps prevent cancer recurrence, whether we should be eating organic food, touch briefly on the alkaline diet, and discuss dietary supplements.
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Medical information disclaimer
The medical information provided is correct to the best of our knowledge, but no warranty as to accuracy is given. You must not rely on the information on our website as an alternative to medical advice from your doctor.
If you have any concerns about your health, you should seek immediate medical attention.