Folate deficiency during pregnancy leads to neonates being born with neural tube defects. This knowledge led to the introduction of folic-acid fortification of wheat flour in the United States in 1996 and in Canada in 1997. This became mandatory in both countries in 1998. The government of Chile introduced a mandatory programme of folic-acid fortification of wheat flour in 2000 to reduce the incidence of neural tube defects in newborns. Indeed, this has been achieved with stunning results but a recent report from Chile showed that the rate of colorectal cancer in Chile has increased since 2000.  

Researchers from the University of Chile analyzed hospital discharge data for two 4-year periods – before folic-acid fortification (1992 – 1996) and after fortification (2001 – 2004). They found a significant increase in the number of cases of colon cancer in the second period. Among people aged 45 – 64 years, the increase in the rate ratio was 2.6 times while the increase was 2.9 times in people aged 65 – 79 years. While some would argue that the increased rate of obesity (from 19.7% in 1997 to 22% in 2003) in the population may have contributed to the increased rate of colorectal cancer, the lack of consistent patterns of change in other diseases such as cardiovascular diseases would argue against this (Eur J Gastroenterol Hepatol 2009; 21: 436 – 439).

Indeed, similar findings were published by researchers from the Tufts University in Boston 2 years earlier (Cancer Epidemiol Biomarkers Prev 2007; 16: 1325 – 1329). The authors noted that both United States and Canada experienced an abrupt reversal of the downward trend in the colorectal cancer (CRC) incidence seen in the preceding decade. The absolute rate of CRC in the United States began to rise in 1996 and peaked in 1998 and in Canada it rose in 1998 and peaked in 2000. The rates have continued to exceed the pre-1996 / 1997 trends by 4 – 6 additional cases per 100,000 individuals. While this observation did not prove a causal link, it was worrying.

In order to gain some information on the association between folate status and the risk of prostate cancers, researchers studied the occurrence of prostate cancer among the participants in the Aspirin / Folate Polyp Prevention Study (J Natl Cancer Inst 2009; 101: 432 – 435). This study is a placebo-controlled randomized trial of aspirin and folic acid supplementation for the chemoprevention of colorectal adenomas conducted between 6/7/1994 and 31/12/2006. These participants were followed for up to 10.8 years. Among the 643 men who were randomly assigned to placebo or folic acid supplementation, the estimated probability of being diagnosed with prostate cancer over a 10-year period was 9.7% in the folic acid group and 3.3% in the placebo group. Aspirin alone had no effect on prostate cancer incidence. Interestingly, in non-multivitamin users, the baseline dietary folate intake and plasma folate level were inversely associated with the risk of prostate cancer. However, this association did not reach statistical significance.

Is natural folate handled differently in our body? Does the folic acid in multivitamin preparations or that used in fortification act differently on our cells? In our quest to build up our body, are we taking too much folic acid as supplements? All these questions are awaiting the definitive answers. For those of us who are not pregnant or suffering from folate deficiency, perhaps we might be better off sticking to natural sources of folate than popping the daily multivitamin pill.

Indeed, natural might be better.

A long lost friend visited me with his daughter recently and over lunch he lamented that his children dislike vegetables - most probably because he has set a bad example by not liking vegetables and not eating any himself! How important are vegetables and fruits in our diet?

A recent study from the University of Hawaii investigated the association of vegetable, fruit and grain intakes with colorectal cancer risk in the Multiethnic Cohort Study (Am J Clin Nutr 2008; 88: 730 – 737). A total of 85,903 men and 105,108 women, living in Hawaii and Los Angeles County, California, completed a 26-page-long quantitative food-frequency questionnaire, over the period 1993 and 1996. The 5 ethnic groups studied were Afro-American, Japanese American, Latino, Native Hawaiian and Caucasian. They were then followed up for an average of 7.3 years. The median intake of vegetables and fruits combined was higher for Latinos and Native Hawaiians and lower for Afro-Americans, Japanese Americans and Caucasians. The risk of developing colorectal cancer in men who took the highest amount of vegetables and fruits was 26% lower than in those who consumed the least. If you only eat fruits but no vegetables, the risk reduction is only 20%. If you only eat vegetables but no fruits, then the risk reduction is 15%. When the analysis was performed for colon and rectal cancer separately in men, the associated risk reduction was stronger for colon than for rectal cancer. In women, the association between colorectal cancer risk and vegetable and fruit consumption was observed but this trend did not reach statistical significance.

In a separate publication, researchers from the University of Florence performed a meta-analysis of the effect of adherence to a Mediterranean diet on mortality and the incidence of chronic diseases [(BMJ 2008; 337: a1344); a free copy of the publication can be obtained at http://www.bmj.com/cgi/content/full/337/sep11_2/a1344] . The analysis was performed on 12 studies involving a total of 1,574,299 individuals. The analysis showed that greater adherence to a Mediterranean diet is associated with a significant reduction in overall mortality (9%), mortality from cardiovascular diseases (9%), incidence of or mortality from cancer (6%) and incidence of Parkinson’s disease and Alzheimer’s disease (13%).

The key components of the Mediterranean diet include generous amounts of fruits and vegetables, consumption of healthy fats such as olive and canola oils, eating small portion of nuts, consuming little red meat but eating fish on a regular basis and, for some, drinking red wine in moderation. From these two recent studies it can be seen that vegetables and fruits are important for maintaining a healthy body and warding off diseases. If you have a family, start them off young with the habit of eating fruits and vegetables. If eating vegetables wasn’t your cup of tea while growing up, perhaps you should start for yours and your children’s sake.

Being overweight and obese [body mass index (BMI) > 25] has been shown to be associated with increased risk of colon cancer, especially among men. Even when you are not overweight / obese, will weight change in adulthood have an influence on your subsequent colon cancer risk?

Researchers from the Harvard School of Public Health examined this question by studying 46,349 men, aged 40 – 75, who were participating in the Health Professionals Follow-up Study (Int J Cancer 2008; 123: 1160 – 1165). All men were cancer free at baseline and were followed up for an 18 – year period, from 1986 to 2004. A cumulative mean BMI > 22.5 was found to be associated with an increased risk of colon cancer. A short term weight gain of 10 pounds (4.54 kg) in the prior 2 – 4 years was significantly associated with increased risk of colon cancer. For every 10 pounds gained, the risk is increased by 14%. The risk of colon cancer is increased by 33% for every 10 pounds of weight gained per 10 years since age 21.

The above study involved men only. What happens in women? Will weight loss affect cancer risk in women? A study from the University of Minnesota looked at the influence of voluntary weight loss on the incidence of cancer in post-menopausal women (Int J Obes Relat Metab Disord 2003; 27; 1447 – 1452). The research studied 21,707 women, cancer free at baseline, over the period 1993 to 2000. Compared to women who never had voluntary weight loss of ≥ 20 pounds during adulthood, the incidence rates for all obesity – related cancer was lowered by 14% in those women who had voluntary weight loss. For specific cancers, voluntary weight loss led to a 19%, 9% and 4% reduction in the incidence rate of breast, colon and endometrial cancers respectively.

Putting on weight is associated with increased cancer risk. In addition it is also associated with increased cardiovascular and metabolic health risks. I am sure that the intention of these and other studies on the ill effects of weight gain is certainly not to scare you away from enjoying your food. If you eat healthily, consume moderately, exercise and watch your weight, you can still enjoy your food without exposing yourself to the added risk of developing cancers, ischaemic heart disease and diabetes.