Whole Grain

From The Experts

Cancer

Currently available research suggests that there is a strong protective relationship between the regular consumption of wholegrain cereal foods and cancer. Evidence for the protective role of wholegrain foods is strongest for colon cancer (a risk reduction of 30-40%), however findings from case-control studies suggest that wholegrain foods may also protect against several other types of cancers including gastric cancer, breast, endometrial and prostate cancers (McIntosh 2001).

A review of 40 different studies on wholegrain food consumption and cancer risk by Jacobs et al revealed a consistently protective effect from wholegrain foods for up to 20 different types of cancer when wholegrain foods were consumed 3-4 times a week (Jacobs et al, 1998).

A series of case control studies in Italy over a 13 year period examined the frequency of consumption of wholegrain foods and the risk of several cancers including oral, pharynx, oesophagus, stomach, colon, rectum, liver, gallbladder, pancreas, larynx, breast, endometrium, ovary, prostate, bladder, kidney, thyroid, Hodgkin's disease and multiple myelomas. It was found that high intakes of wholegrain foods were consistently associated with a reduced risk of cancer at all sites except for the thyroid (Chatenoud et al, 1998).

A recent study from Sweden examined the relationship between diet and cancer in a population of over 60,000 women who were followed over a 14-year period. It was found that those women who consumed a high intake of wholegrain foods experienced a lower risk of developing colon cancer (Larsson et al, 2005).

The evaluation of 19 case control studies demonstrated an inverse (protective) relationship between cereal food intake and colon cancer in 16 of the studies, the remaining 3 studies showed no relationship. This analysis was used by European cancer experts for a consensus statement that concluded, "A diet rich in high fibre cereal foods is associated with a reduced risk of colorectal cancer" (Hill 1998).

The evidence for wholegrain foods in the protection against gastric cancer is weaker than for colorectal cancer. Seven case control studies published between 1985 and 1993 were evaluated for the influence of wholegrain and wholemeal foods on gastric cancer, with six of the seven studies demonstrating an inverse relationship (Jacobs et al, 1995).

There is some evidence to suggest a role for wholegrain/wholemeal cereal foods in the protection against hormonally mediated cancers, such as breast and prostate cancer, however more research is required (McIntosh 2001).


Protective Mechanisms

Wholegrain foods are rich in a variety of protective compounds that are believed to work in combination to prevent cancer. Much focus has been given to the beneficial effects of dietary fibre and, more recently, resistant starch. These compounds work to positively alter the gut environment, through lowering faecal pH, altering bacterial fermentation and short chain fatty acid production and binding to carcinogens. Dietary fibre also helps to increase faecal bulk and promotes a rapid transit time.

Protective compounds such as trace minerals, phenolics, phytates and phyto-estrogens function as antioxidants. Phyto-estrogens may also provide potential hormonal effects.

Wholegrain foods play a role in modulating the glycemic response and may also play a role in the prevention of insulin resistance. Wholegrain foods have a beneficial effect on energy balance and body weight, which may also play a role in cancer prevention (McIntosh 2001, Slavin et al, 1997; Slavin et al, 1999).

References

  1. Chatenoud L et al. Whole grain foods and cancer risk. International Journal of Cancer 1998;77:24-8.
  2. Hill MJ. Cereals, cereal fibre and colorectal cancer risk: a review of the epidemiological literature. European Journal Cancer Prevention 1998;7:S5-S10
  3. Jacobs DR, Slavin J, Marquart L. Whole grain intake and cancer: a review of the literature. Nutrition and Cancer 1995;24:221-9
  4. Jacobs DR, Marquart L. Slavin J, Kushi LH. Whole-grain intake and cancer: an expanded review and meta-analysis. Nutrition and Cancer 1998;30:85-96.
  5. Larsson SC et al. Whole grain consumption and risk of colorectal cancer: a population-based cohort of 60,000 women. British Journal of Cancer 2005;92:1803-7.
  6. McIntosh G. Cereal Foods, fibre and the prevention of cancers. Australian Journal of Nutrition and Dietetics 2001;58:S35-S48.
  7. Slavin JL, Jacobs D, Marquart L. Whole-grain consumption and chronic disease: protective mechanism. Nutrition and Cancer 1997;27:14-21
  8. Slavin JL, Martini MC et al. Plausible mechanisms for the protectiveness of whole grains. American Journal of Clinical Nutrition 1999;70:459-463