[Read
Dr. Ryan’s article on current research and knowledge on companion animal cancer and nutrition.]
Metabolomics
is the identification and characterization of metabolic products in tissues and
body fluids and can also be applied to the study of small molecules found in
food. This mass spectrometry based approach has demonstrated robust and highly
sensitive capabilities of examining thousands of small molecules and peptides
that result from functional changes in the genome and transcriptome (Mensack et al., 2010; Heuberger et al., 2010).
Metabolomics
may be useful to not only identify biomarkers for companion animal cancer
detection and/or risk but also provides an immense opportunity to advance our
knowledge of the metabolic changes that occur following pets’ dietary intake of
bioactive food components. The utility of a metabolic signature modifiable by
diet is that it can be integrated with recent advances in nutrigenomics and intestinal
microbiome studies (Middelbos et al.,
2010).
Dietary
chemoprevention involves the use of chemicals, vitamins or other substances in
the diet or to prevent or decrease the incidence of cancer. Chemopreventive
agents have been broadly defined on the basis of their mechanisms of action and
can be grouped into two general classes: blocking agents and suppressing
agents.
Blocking
agents—such as flavonoids, oltipraz, indoles, isothiocyanates—prevent
carcinogenic compounds from reaching or reacting with critical target sites by
preventing the metabolic activation of carcinogens or tumor promoters by
enhancing detoxification systems and trapping reactive carcinogens. Suppressing
agents—such as vitamin D and related compounds, nonsteroidal anti-inflammatory
drugs, vitamin A and retinoids, DFMO, monoterpenes, calcium—prevent the
evolution of the neoplastic process in cells that would otherwise become
malignant.
We
postulate there is a combination of nutritional imbalances that may occur
during the lifetime of dogs or cats that ensue to favor the growth and
progression of cancer cells. To our knowledge, no long-term dietary
chemoprevention studies have been conducted in companion animals using evidence
based trial designs. Given the difficulties associated with conducting
companion animal studies on dietary supplements and cancer, the petfood
industry should be cautious of single-nutrient health claims in veterinary
oncology. One obvious reason is that nutrients do not function in isolation; rather,
they function in vast, complex networks (e.g., antioxidant feedback and
methylation pathways).
Another
promising area of research related to diet and nutrition of companion animals
with naturally occurring cancer is to study nutritional needs during the course
of cancer treatment, including surgery, radiation, chemotherapy and palliative
care (Ogilvie et al., 2000). Determining the efficacy of certain dietary
components during cancer treatment in companion animals adds another layer of
complexity to the already complicated set of interactions but may yield
important information on health outcomes in a shorter time frame. Balancing
host energetics, through adequate nutrition and physical activity, is
considered a practical means to improve the daily quality of life of companion animals
and may also translate to those animals with cancer or at high risk for
developing cancer.