Recently the wife of a patient of mine asked “Can he eat beef?”  It transpires that the daughter and son-in-law have told the patient that he is not allowed to eat beef as it will make his cancer worst and beef causes cancer. I have been asked the same question by quite a number of patients. Is cancer caused by eating beef?

A recent study from the National Cancer Institute examined the associations between meat consumption (type of meat, cooking methods and related mutagens), heme iron, nitrite / nitrate and prostate cancer in 175,343 US men aged between 50 and 71 years of age (Am J Epidemiol 2009; 170: 1165 – 1177). These men were followed up for 9 years. The study showed that men who ate the most versus those who ate the least amount of red meat had a 12% higher risk of developing prostate cancer. For processed meat, the risk was 7%. The study also found that heme iron, barbequed/ grilled meat and benzo[a]pyrene were all associated with increased risk of prostate cancer. Nitrite and nitrate intakes were associated with increased risk of advanced prostate cancer.

In certain parts of China, the incidence of cancers of the oesophagus and stomach are much higher than the national average. Detailed studies finally showed that this was related to the pickled vegetables in their diet. The pickled vegetables contained significant amounts of nitrite and nitrate which are known to be carcinogenic. Recent studies have also shown that individuals who drink very hot tea have a higher incidence of cancer of the oesophagus. The likely mechanism here is related to the heat rather than the tea itself.

Cooking certain meats at high temperatures creates chemicals that are not present in uncooked meats. Heterocyclic amines (HCAs) are a group of chemical compounds formed from the cooking of muscle meats such as beef, pork, fowl and fish. HCAs form when amino acids (the building blocks of proteins) and creatine (a chemical in muscles) react at high temperatures during cooking. HCAs are potent compounds that can cause cells to mutate and in experimental animal models HCAs have been shown to induce tumours. Temperature is the most important factor in the formation of HCAs. Frying, barbecuing and broiling involve cooking at very high temperatures and thus produce the largest amounts of HCAs. Baking and oven roasting lead to lower levels of HCAs as the cooking temperature is lower. Poaching, stewing and boiling produce negligible amounts of HCAs. When meat is microwaved for 2 minutes before cooking, the HCA content is reduced by 90%.

From the examples given above, would it be correct to stop drinking tea because drinking hot tea has been shown to be associated with an increased risk of developing oesophageal cancer? Similarly, should one stop eating vegetables because pickled vegetables have been associated with increased risk of developing oesophageal and stomach cancers?

Association is not causation. Furthermore, the reasons behind an association may be due to factors other than the starting ingredient, such as beef. The reason for the association may be because of what you have done to the ingredient.

“Cancer: shock breakthrough” was the headline on the 20^th June of The Independent newspaper in England. It was referring to a news release by Mayo Clinic researchers on 2 patients with advanced prostate cancer who had been given the human antibody called ipilimumab. (Ipilimumab binds to the cytotoxic T lymphocyte-associated antigen 4, a molecule on T cells that plays a critical role in regulating immune responses.)

These 2 patients had been participating in a clinical trial of over a hundred patients with advanced prostate cancer. In addition to receiving androgen-ablative therapy (treatment to remove testosterone availability in the body), these two patients were randomized to receive a single dose of ipilimumab intravenously. Their advanced prostate cancer responded dramatically to the treatment and went from an inoperable stage to a stage where surgery could be considered. In the end,  both patients underwent surgery and when the prostate tissue was submitted for pathological examination, the pathologist had a tough time finding cancerous cells in the prostate tissue.

Ipilimumab has been used in clinical trials for patients with advanced prostate cancer before. At the recent 2009 annual meeting of the American Society of Clinical Oncologists (ASCO), a poster presentation from the Memorial Sloan-Kettering Cancer Center in New York City, reported their experience with ipilimumab in 45 patients with metastatic castration-resistant prostate cancer. Ten of the patients had ≥ 50% reduction in the PSA level. In one patient the PSA level normalized and his metastatic lesions showed complete response.

In the medical world, occasional exceptional response to a new drug can happen during preliminary study. However, with further clinical trials, the new drug may turn out to be less effective than existing drugs or to have unacceptable side-effects. Ipilimumab may turn out to be a very effective drug for prostate cancer; however, we must wait for further bigger clinical trials before we can pass final judgement.

New promising drugs for treating advanced cancers are always welcome news for patients, their families and doctors. However, sensational headlines can sometimes lead to unrealistic expectations. When the drug fails to deliver the sensational response, the patient and his family members feel let down and ‘cheated’. Sensational headlines sell newspapers while premature sensational medical headlines cause disappointment.

Some of us may find the constant reminder that one should eat healthily, exercise regularly and maintain a normal BMI annoying. The attitude is born out of either a sense of denial or belief: denying that the ill effects of having an unhealthy lifestyle will ever affect one’s health or believing that destiny and not lifestyle will determine if one gets seriously ill or not. Perhaps a recent report from the University of California might make these individuals reconsider.

Researchers studied changes in the prostate gene expression in men, with low-grade prostate cancer, who underwent intensive lifestyle and nutrition intervention over a period of 3 months (PAS 2008; 105: 8369 – 8374). Thirty one men with low-grade prostate cancer, who declined immediate surgery, hormonal therapy or radiation, participated in the study. They agreed to a comprehensive lifestyle change instead. A prostate biopsy was performed prior to initiation of the lifestyle change programme. The 3 month lifestyle modification comprised of a 3-day intensive residential retreat followed by weekly outpatient follow-up by a study nurse. The modifications included a low fat (10% of calories from fat), whole foods, plant-based diet; stress management 60 minutes / day (gentle yoga-based stretching, breathing, meditation, imagery and progressive relaxation), moderate aerobic exercise (walking 30 minutes / day for 6 days / week) and a one hour group support session per week. The diet was supplemented with soy (one daily serving of tofu plus 58 gm of a fortified soy protein powdered beverage), fish oil (3 gm daily), vitamin E (100 units daily) selenium (200 mg daily) and vitamin C (2 gm daily). Another prostate biopsy was performed at the end of the 3 months intervention. The gene expression from the normal prostate tissue obtained before and after the lifestyle changes was compared. At the end of 3 months, they found 48 genes up-regulated and 453 genes down-regulated (simplistically, up-regulation means switched on and down-regulation means switched off) in the prostate tissue. The pathways under the control of these genes were found to be involved in tumorigenesis (formation of tumours). For example, they found a set of down-regulated RAS family oncogenes (RAN, RAB14 and RAB8A). In the prostate, RAN may function as an androgen receptor coactivator and its expression is increased in tumour tissues. (Androgen stimulates prostate cancer to grow and oestrogen can suppress prostate cancer growth. Hence, one of the treatments for prostate cancer is to castrate the patient and remove testosterone, an androgen, from circulation. This manoeuvre will then deprive the prostate cancer its driving force, thus, slowing its growth.)

While this study involves only a small number of patients, if its findings are shown to be true in subsequent larger studies, it will make us sit up and take note. We can no longer blame it all on fate or parents for passing on ‘bad’ genes. In the meantime will you continue with your unhealthy lifestyle habits or might you, just to be on the safe side, adopt a more healthy lifestyle?