School of Medical Sciences


Optimising dietary strategies for cancer prevention, using in vitro and in vivo models

Food components and extracts

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Herbal extracts

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Plant fibre

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The dietary fibre (DF) hypothesis suggested that DF, as plant cell walls, protected against colorectal cancer. The implicit assumption in much historic literature was that the readily analyzed and quantified nonstarch polysaccharide (NSP) component was critical in cancer protection. However, the presence of polymeric phenolic components such as lignin or suberin has profound effects on the physicochemical properties of the cell walls and largely determines their physiological properties in humans. In certain groups of food plants, degradation of cell walls that contain neither lignin nor suberin releases ferulic acid and other hydroxycinnamic acids. These acids have antioxidant, antimutagenic, and other anticancer effects, including modulation of gene expression and immune response.

Dietary fibres can also increase the population size and activity of beneficial gut bacteria following pre-biotic ingestion.

Vitamins and minerals

New Zealand National Nutrition Survey (1999) shows that our population is not reaching the current RDA’s of certain required micronutrients. Our goal is to study the effects of deficient/sufficient levels to make recommendations for the benefit of public health.

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These deficient nutrients can cause DNA instability through many mechanisms including defects in DNA methylation.

 

Gene nutrient interaction

We know that low levels of micronutrients such as selenium (Se) enhance the risk of cancer, and may be a particular problem in New Zealand, which has low Se in its soils. Recent work suggests that small changes in genes, called single nucleotide polymorphisms or SNPs, may affect the amount of Se required by individuals. There is reason to believe that there are a small number of individuals in New Zealand and other countries, who are cancer prone because they require a higher than normal intake of Se.

Currently we are screening a sample of the population (>500 healthy men) to establish how commonly these genotypes occurs, and consider whether supplementation with 200µg Se per day, in the form of selenised yeast, can help to overcome the associated deficiencies. The supplementation benefits are being measured through various biomarkers including DNA stability (through Comet Assay), activity of seleno enzymes, effects on DNA methylation and effects on androgen metabolism. Genotyping of our study group has been accomplished through Applied Biosystems TaqMan SNP genotyping procedure and Sequenome MassArray platform. Our nutregenomics approach in this assessment is aligned with similar approaches being carried out through our work in the Discipline of Nutrition.