This study will examine the risks and protective effects of dietary factors on temporary genetic damage to cells lining the gastrointestinal tract and to blood cells. Some foods, including very well done meat, may increase genetic damage in cells, while others, such as yogurt and vegetables, may reduce genetic damage. This study may provide new information on the influence of diet on increasing or decreasing the risk of developing cancer, particularly colorectal cancer. The study is conducted at the General Clinical Research Center (GCRC) of the University of North Carolina.
Nonsmoking, English-speaking, healthy adults between 18 and 45 years of age may be eligible for this 4-week study. Participants undergo the following tests and procedures:
- Interview: Participants complete questionnaires including information on their diets, habits, past and present health, and family histories.
- Diet: Participants adhere strictly to the diet provided by the dietician at the GCRC for all 4 weeks of the study. All meals are provided by the GCRC. All meals contain well-done meat and some contain yogurt, cruciferous vegetables, including broccoli and cabbage, and chlorophyllin tablets. Chlorophyllin is a compound in some foods that protects against genetic damage.
- Urine sampling: Participants collect a urine sample each morning except Saturday and Sunday.
- Stool sampling: Participants collect two stool samples during the study, one during the second week and another during the fourth week.
- Blood draw: About 2-1/2 tablespoons of blood are drawn once a week for research purposes. The blood is tested for the effects of eating foods in the different diets used in the study.
- Rectal biopsies: Four pinch biopsies, each about the size of a grain of rice, are taken from the rectum once a week for research purposes. For this procedure, forceps are inserted shallowly into the rectum to collect the tissue. The effects of the different diets on the colon cells are measured.
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Dietary exposures have been implicated as risk factors in colorectal cancer. Such agents may act by causing DNA damage or may be protective against DNA damage. The effect of dietary exposures in either causing or preventing damage has not been directly assessed in colon tissues. We are proposing a pilot study of dietary factors and DNA damage, involving 16 healthy volunteers in a four-week controlled feeding study. The primary focus of this study is to assess genetic damage to colonic epithelium and blood lymphocytes induced by pyrolysis products formed in cooked meat, as well as the putative protective effects of cruciferous vegetables, yogurt, and chlorophyllin against that damage. In the first phase of this pilot study, eight subjects will be fed either a baseline diet or a diet high in fried meat in two-week intervals. In the second phase, the remaining eight subjects will be fed either the fried meat diet or a diet containing fried meat along with putative inhibitors. In both phases of the study, blood will be drawn and rectal biopsies will be obtained from subjects each week during the four-week study periods. Damage in the lymphocytes and colon epithelium from the different dietary regimens will be evaluated using the single cell gel electrophoresis (comet) assay. Rectal biopsies used in this study are painless and generally without risk. In previous studies conducted by Dr. Robert Sandler, at UNC, over 2,000 rectal biopsies have been obtained without any adverse events. The goal of this study will be to determine the feasibility of conducting a larger study to examine the interaction of genotoxic components in fried meat with "protective" dietary factors on a molecular level.