|
|
|
|
|
|||
|
|||
|
Vertically
|
Nutrition
for Cancer and Aging page 1 2 3 Slide 14-11. The interconversions of sex hormones including estrogen and testosterone involved in breast and prostate cancer are modulated by nutritional effects on substrates and products as well as expression of enzymes such as aromatase. There are hormones such as insulin and glucocorticoids which are modulated by nutrition and in turn affect the expression of various enzymes such as aromatase (cytochrome p450 A19). Slide 14-12. The carcinogenesis process is often divided into neoplastic conversion and neoplastic development and progression. In humans the neoplastic conversion is estimated to occur 10 to 15 years prior to diagnosis for most human cancers. As diagnostic methods improve there is earlier diagnosis. However, nutrition can influence both phases of carcinogenesis in experimental studies in animals. Slide 14-13. The multistep process of carcinogenesis has been defined best in colon cancer where specific mutations have been related to each successive step in the development and progression of colon cancer. Nutrition can influence this process at every stage of carcinogenesis. Slide 14-14. The metabolic activation of potential carcinogens results from the action of metabolizing enzymes which are in turn affected by diet and the ingestion of a wide variety of phytochemicals. There are also genetic variations in the activity and distribution of these enzymes among different individuals. Slide 14-15. Once the ultimate carcinogen is formed, it binds to DNA forming an adduct which can then result in a mutation which activates oncogenes, inactivates tumor suppressor genes, or modifies gene expression so as to promote carcinogenesis.
Slide 14-16. In studies of patients with colon polyps the risk of developing cancer is increased twofold in those with a null mutation at the GSTM1 enzyme locus. However, if these patients eat cruciferous vegetables such as broccoli they obviate the effects of the GSTM1 mutation. Slide 14-17. The observed gene-nutrient interaction for colon cancer makes sense biochemically since broccoli constituents can inhibit the cytochrome p450 which forms the carcinogens typically deactivated by GSTM1. The susceptibility to carcinogenesis may depend on such mutations in enzymes involved in carcinogen metabolism. The Xenobiotic Hypothesis of Cancer posits that there are many such instances to be discovered which will enhance our ability to prevent cancer. Slide 14-18. Known or suspected dietary carcinogens include aflatoxin found in moldy foods, heterocyclic amines found in meat cooked at high temperatures, n-nitroso compounds found in spoiled foods, proteins, and endogenous sources, and polycyclic hydrocarbons found in cooked foods, and dark beer. Slide 14-19. Arachidonic acid metabolites promote breast and prostate cancer cell growth in culture. The PPAR-gamma receptor has been identified in both of these cell types and is believed to mediate the effects of the high levels of linoleic acid in the Western diet on carcinogenesis. Linoleic acid is efficiently converted to arachidonic acid, but eicosapentanoic acid found in fish oil competes and interferes with the metabolism and action of the eicosanoids from arachidonic acid. Slide 14-20. With age there is a reduction in lean body mass in both men and women. The decrease is associated with reduced calorie requirements and increased risk of developing common forms of cancer. The reduced muscle mass may be associated with increased insulin and reproductive hormone levels in some aging individuals.
|
|
||||
|
|
|
Nutrition
101 - Natural
Remedies - Weight
Management - Physician
Education |
||||
