Journal of the National Cancer Institute: Colorectal cancer is the third most commonly diagnosed malignancy in the US, with nearly 150,000 new cases anticipated in 2005. Colorectal cancer is also the second most common cause of cancer-related death, and more than 55,000 people are expected to die of this disease this year. Several large epidemiological studies have previously linked a high intake of red meat and processed meat products with an increased risk of developing colorectal cancer. Recent studies have also linked diets rich in fish (and, in some studies, poultry) with a decreased risk of colorectal cancer. (The conventional medical wisdom regarding the benefits of a high-fiber diet in the prevention of colorectal cancer, however, is less clear, as there is clinical data that both supports and contradicts this association.)

An enormous prospective study from Europe, the European Prospective Investigation into Cancer and Nutrition, has just reported results encompassing a minimum of 5 years of follow-up of 478,040 men and women who were clinically free of cancer when they first entered the study (1992 to 1998). An interesting feature of this study, compared with most other studies based upon dietary surveys, was the use of smaller subset of study volunteers (36,994 subjects) to carefully analyze and correct for diet measurement errors. This subset analysis, combined with the prospective observational design of this study (and the huge number of study participants), sets a new standard for this common method of epidemiological research.

Study subjects who consumed an average of more than 160 grams (about five-and-a-half ounces) of red and processed meat per day, when compared with people who consumed less than 20 grams (seven-tenths of an ounce) per day, experienced a 35% relative increase in the risk of developing colorectal cancer. Conversely, eating more than an average of 80 grams (a bit less than 3 ounces) of fish per day, as compared to eating less than 10 grams (about one-third of an ounce) per day, resulted in a 31% reduction in the risk of developing colorectal cancer.

When the study’s authors applied their error-correction data to all study subjects, the association between red and processed meat intake and colorectal cancer became even more compelling. With each additional 100 gram (3.5 ounces) increase in average daily intake of red and processed meat, the risk of colorectal cancer increased by 55%. Likewise, the apparent reduction in colorectal cancer risk with increasing fish intake became more powerful following statistical data correction. Each 100 gram increase in average daily fish intake was associated with a 46% reduction in the risk of developing colorectal cancer. These values are relative increases and decreases in the incidence of colorectal cancer which, of course, translate into considerably smaller absolute changes in incidence. In terms of absolute risks, however, study subjects with the highest average daily intake of red and processed meat had a 1.71% 10-year absolute risk of developing colorectal cancer, while those with the lowest intake had a 1.28% absolute risk. With respect to average daily fish intake, study subjects with the highest levels of average daily fish consumption had a 1.28% absolute 10-year risk of colorectal cancer, while those who consumed the least amount of fish in their diets had a 1.86% absolute 10-year risk of developing colorectal cancer. A key finding of this study, compared to recent—as well as smaller and less rigorous—studies, was that the risk of colorectal cancer was unrelated to the amount of poultry consumed.

Taken as a whole, this huge study sets a new standard in scientific rigor for epidemiological research. The findings of this study comport well with smaller and less rigorous prior studies that have associated red meat and processed meat intake with an increase in the risk of developing colorectal cancer (and with pancreatic cancer as well), and a diet rich in fish with a reduced risk of this disease. I have come to believe that the data on the influence of diet upon colorectal cancer risk is so compelling that, over the past year or so, I have significantly modified my own diet to include far less red meat, virtually no processed meats, and a lot more fish and poultry (and calcium supplements too). My forthcoming second book, What You Don’t Know Can Kill You: A Clinically Proven Plan to Reduce Your Risk of Dying from Cancer! will delve into much greater detail about this—and other—approaches to cancer risk reduction based, as always, upon the most credible and powerful clinical and scientific research data available.

VITAMIN B6, ALCOHOL & COLORECTAL CANCER

Gastroenterology : While I am on the subject of colorectal cancer prevention, another interesting study has just been published on this topic. Vitamin B6 plays an important role in the synthesis and function of our cells’ DNA, and has thus been postulated as having possible anti-cancer activities. At the same time, increased alcohol intake often results in a diet that is inadequate in vitamin B6, and alcohol, itself, is capable of depleting the body’s stores of this important vitamin.

This extremely large Swedish study, encompassing 61,433 women who are participating in a study of the benefits of mammography, looked at long-term dietary intake of vitamin B6 and alcohol as a function of the incidence of colorectal cancer. This large cohort of women, aged 40 to 76 years, was followed for an average of nearly 15 years prior to reporting the results of this study. Based upon serial dietary surveys and medical histories, and after controlling for the effects of age and other established risk factors for colorectal cancer, this study determined that women who consumed the highest levels of vitamin B6 in their diet experienced a 34% reduction in their risk of developing colorectal cancer when compared to women taking in the lowest amount of vitamin B6. This protective effect of vitamin B6 against colorectal cancer was even more pronounced in the subset of women who reported moderate-to-high levels of alcohol intake. Among those women who consumed at least 2 alcoholic drinks per week, high dietary levels of vitamin B6 reduced the incidence of colorectal cancer by 72%, when compared to women with similar alcohol intake and low levels of dietary vitamin B6. The results of this study suggest two important factors related to the risk of colorectal cancer, alcohol intake and vitamin B6 intake. First, low levels of dietary vitamin B6 are associated with a higher incidence of colorectal cancer than high dietary levels of this nutrient. Secondly, even rather moderate levels of alcohol intake may be associated with an increased risk of colorectal cancer, and a diet rich in vitamin B6 may substantially reverse this putative adverse effect of alcohol consumption. These results are intriguing, and build upon earlier research that has suggested similar links between colorectal cancer risk, and dietary levels of vitamin B6 and alcohol.

AGE, OBESITY, TESTOSTERONE & ERECTILE DYSFUNCTION

Journal of Urology: For men, approaching middle age is cause for apprehension about a number of potential age-related health problems. For many men, if not the majority, fears about declining sexual potency are very close to the top of the list. The recent advent of medications to treat erectile dysfunction (ED) has significantly ameliorated the fear of age-related impotence, but questions remain about the safety of long-term use of these medications.

It has been known, for decades, that cardiovascular disease (and smoking, which remains the number one cause of preventable cardiovascular disease) is a significant risk factor for ED. Other proposed risk factors have included serum testosterone levels (which gradually decline as men age) and obesity (which is associated with increasing blood levels of estrogen, the dominant female sex-hormone). However, the relative contributions of each of these factors, in addition to advancing age, remain unclear at this time.

This new study evaluated 675 men, ranging in age from 45 to 60 years, and evaluated their age, serum testosterone levels and body mass index (BMI). All study subjects completed a detailed and previously validated questionnaire related to erectile function. With increasing age, blood levels of testosterone declined significantly, as previously observed in other studies. Increasing age was also, again not surprisingly, associated with decreasing levels of erectile function. Interestingly, increasing BMI, irrespective of age, was associated with decreasing erectile dysfunction to about the same extent as increases in age. Statistically, each year of increasing age in this population of middle-aged men was associated with an 8.2% increase in the risk of developing ED, while each kilogram per meter-squared increase in BMI was also associated with a 7.6% increase in the risk of ED. Low levels of testosterone in the blood were, likewise, associated with an increased risk of ED. The take-home message from this study is that there are at least 3 factors known to increase a man’s risk of ED, one of which (age) is not currently modifiable. Obesity, which was confirmed by this study to be a risk factor for ED, is, however, both modifiable and preventable. Likewise, although still controversial, the hormone testosterone can be supplemented in men with extremely low blood levels of this dominant male sex-hormone. As an aside, when I am see young male smokers in my surgical clinic, I find virtually all of them to be nonplussed when I describe for them the increased risk of lung disease (including the number one cause of cancer-related death, lung cancer), cardiovascular disease and stroke associated with smoking. However, when I tell them that their likelihood of becoming impotent is markedly increased by smoking, they tend to pay a little closer attention to what I am telling them….

Dr. Robert A. Wascher