There are two major types of bacteria in digestive tract that may play a role in weight control - the more Bacteroidetes you have, the more likely you are to be lean , the more Firmicutes you have, the more likely you are to be fat. • Rodent studies have confirmed this • These studies also showed that if the mice get the bacteria from an overweight mouse they would only become overweight if they were fed an inadequate diet, diet matters!! - = bacteria has a role to play ONLY in the presence of a poor diet - Average American consumes half a litre of soft drinks a day (200 extra calories) - cutting this out can lead to a loss of two pounds a month Topic 9: DIET AND DISEASE Lesson 1: Diet and cancer VIDEO 1 CAUSES OF CANCER : - Environment: 90% • Diet and obesity: 30-35% - Cancer is most frequent among those branches of the human race where carnivorous habits prevails • Tobacco: 25-30% • Infections: 15-20% • Radiation: 5-10% • Pollution: 3-5% • Alcohol/sexual: 3-5% - Genetics: 5-10% Study: environmental and heritable factors in causation of cancer (2000, Scandinavia) - 45,000 pairs of twins studied - 10,000 cancers occurred - Some cancers showed heritable factors • Stomach cancer - Environmental — Shared = 10% // Environmental — Non shared = 62% 22 of 66
- Heritable = 28% • Cervical cancer - Environmental: high - Heritable: low • Absolute risks (risks are averaged over a range) - Monozygotic twins (identical): 15% - Dizygotic twins (fraternal): 6% • Conclusion: - Unmistakable heredity: 1% - Major component heredity: 15% Another study on Norwegian Twins: heritability and familial risk of cancer (2013) • Monozygotic and dizygotic pairs: 133,689 • Prostate cancer heritability (2013)= 58%, whereas prior study (2000) = 42% • Other cancer rates lower and varied - CONCLUSION : even with twins, environmental factors strongly dominate VIDEO 2 - The term cancer comes from the Latin for "crab", because originally tumours and their blood vessels seemed to look like crabs with all of their legs - More than half a million people in the United States die of cancer every year • About 1,500 Americans a day - Mortality of cancer is decreasing, rate of cancer has increased a bit because of increased ways of detecting it, but overall there is no cancer epidemic • Some cancers are falling and some are increasing, but the general cancer rate is about the same • Varies with location (environment and diets) • Childhood cancer seems to be increasing, but we don’t know why - Breast cancer rates decreased when estrogen supplements stopped being given to menopausal women — these estrogen supplements were a main cause - There are very significant variations of cancer rates around the world • In some areas, some cancers are more frequent than others • suggests that environment influences the development of cancer • When people migrate from one country to the other, they tend to take on the cancer patterns of their new domicile 23 of 66
- 30-40% of cancers in the world, some 4 million cases a year, can be prevented by paying attention to environmental factors such a diet • Five or more servings of fruit a day lowered the risk of prostate cancer by 50% • 2,000 mg a day of calcium
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- Spring '11