A case-control study of colorectal adenomatous polyps and consumption of foods containing partially hydrogenated oils.

The trans fatty acids produced by partially hydrogenating vegetable oils may cause colorectal neoplasia by interfering with cell membrane function or eicosanoid synthesis. This possibility provides a rationale for looking at the relation between colorectal adenomatous polyps and consumption of foods containing partially hydrogenated vegetable oils (PHVOs). A total of 516 cases and 551 controls who underwent screening sigmoidoscopy from 1991-1993 were recruited from a prepaid Los Angeles health plan. Subjects were interviewed and given a self-administered food frequency questionnaire. Food items containing PHVOs were divided into four groups characterized by principal ingredients and preparation methods: sweetened baked goods, candy bars, oils and condiments, and french fries and chips. After adjusting for age, sex, physical activity, body mass index, smoking, total energy, and red meat and vegetable intake, there was a positive association between polyps and sweetened baked goods [350+ versus <50 kcal/day (odds ratio, 2.1; 95% confidence interval, 1.3-3.5)]. No association was found with the other food groups after adjustment for dietary and nondietary covariates. Neither was total dietary trans fatty acid associated with adenomas after adjustment for sweetened baked goods and other covariates. These results do not support the hypothesis that eating foods containing PHVOs increases the risk of colorectal adenomas, but they are consistent with the hypothesis that foods high in fat and sugar and low in fiber and correlated micronutrients increase the risk of adenomas.

Intake of carrots, spinach, and supplements containing vitamin A in relation to risk of breast cancer.

Intake of fruits, vegetables, vitamin A, and related compounds are associated with a decreased risk of breast cancer in some studies, but additional data are needed. To estimate intake of beta-carotene and vitamin A, the authors included nine questions on food and supplement use in a population-based case-control study of breast cancer risk conducted in Maine, Massachusetts, New Hampshire, and Wisconsin in 1988-1991. Multivariate-adjusted models were fit to data for 3543 cases and 9406 controls. Eating carrots or spinach more than twice weekly, compared with no intake, was associated with an odds ratio of 0.56 (95% confidence interval 0.34-0.91). Estimated intake of preformed vitamin A from all evaluated foods and supplements showed no trend or monotonic decrease in risk across categories of intake. These data do not allow us to distinguish among several potential explanations for the protective association observed between intake of carrots and spinach and risk of breast cancer. The findings are, however, consistent with a diet rich in these foods having a modest protective effect.

Use of selenium concentration in whole blood, serum, toenails, or urine as a surrogate measure of selenium intake.

We examined the validity of using the selenium level in a single biological specimen as a surrogate measure of usual intake. We used data from 77 free-living adults from South Dakota and Wyoming. Subjects provided multiple 1-day duplicate-plate food composites, repeated specimens of blood and toenails, and 24-hour urine collections. We developed a statistical calibration method that incorporated measurement error correction to analyze the data. The Pearson correlation coefficients between selenium intake and a single selenium status measure, after deattenuation to adjust for the effect of within-person variation in intake, were: 0.78 for whole blood, 0.74 for serum, 0.67 for toenails, and 0.86 for urine. We present formulas to estimate the intake of individuals, based on selenium levels in a single specimen of blood, toenails, or urine. In these data, the concentration of selenium in a single specimen of whole blood, serum, or toenails served reasonably well as a measure for ranking subjects according to long-term selenium intake but provided only a rough estimate of intake for each subject.

Dietary intake of specific carotenoids and vitamins A, C, and E, and prevalence of colorectal adenomas.

We determined whether intakes of the main dietary carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein plus zeaxanthin, and lycopene) and of vitamins A, C, and E were associated with the prevalence of colorectal adenomas among male and female members of a prepaid health plan in Los Angeles who underwent sigmoidoscopy (n = 488 matched pairs). Participants, ages 50-74 years, completed a 126-item semiquantitative food-frequency questionnaire and a non-dietary questionnaire from 1991 to 1993. In the univariate-matched analysis, alpha-carotene, beta-carotene (with and without supplements), beta-cryptoxanthin, lutein plus zeaxanthin, vitamin A (with and without supplements), and vitamin C (with and without supplements) were associated with a decreased prevalence of colorectal adenomas. After adjustment for intake of calories, saturated fat, folate, fiber, and alcohol, and for current smoking status, body mass index, race, physical activity, and use of nonsteroidal anti-inflammatory drugs, only beta-carotene including supplements was inversely associated with adenomas (odds ratio (OR), 0.6; 95% confidence interval (CI), 0.41.1; trend, P= 0.04; ORs compare highest to lowest quartiles0; vitamin C showed a weaker inverse association (OR, 0.8; 95% CI, 0.5-1.5; trend, P = 0.08); and the remaining compounds were no longer clearly associated with risk. After including beta-carotene with supplements and vitamin C simultaneously in the mutivariate model, the association of beta-carotene with supplements with adenomas was weakened (OR, 0.8; 95% CI, 0.5-1.3; trend P = 0.15), and vitamin C was no longer associated with risk. These data provide only modest support for a protective association of beta-carotene with colorectal adenomatous polyps.

A 1-y trial of the effect of high-selenium bread on selenium concentrations in blood and toenails.

The concentration of selenium in toenail clippings and blood reflects dietary intake better than does intake calculated from dietary data because of the highly variable selenium concentration in different samples of the same food. However, the time course of selenium intake in relation to subsequent concentrations in toenail clippings is unclear. Therefore, 12 males were fed high-dose (4.91 mumol Se/d), medium-dose (2.61 mumol Se/d), or control (0.41 mumol Se/d) whole-wheat-bread for 1 y and the concentration of selenium was measured in toenail clippings collected every 12 wk for 2 y. Toenail selenium concentration was unaffected by dietary intake in the previous 3 mo and appeared to provide a time-integrated measure of intake over a period of 26-52 wk. Use of selenium concentration in toenail clippings may be an alternative to blood when a measure of long-term average intake is desired. The absence of a short-term effect of diet on toenail selenium concentration also makes this a useful marker of intake in retrospective studies.

Selenium in diet, blood, and toenails in relation to human health in a seleniferous area.

To determine whether high dietary selenium intake was associated with adverse effects, selenium in diet, blood, and toenails was studied in relation to human health in adults residing in western South Dakota and eastern Wyoming. Over a 2-y period 142 subjects were recruited from households selected at random and from ranches where unusually high selenium intakes were suspected. Subjects completed health questionnaires, underwent physical examinations, provided blood samples for clinical assessment, and provided blood, urine, toenails, and duplicate-plate food collections for selenium analysis. About half of the 142 free-living subjects had selenium intakes greater than 2.54 mumol/d (200 micrograms/d) (range 0.86-9.20 mumol/d, or 68-724 micrograms/d). Physical findings characteristic of selenium toxicity were not present nor were clinically significant changes in laboratory tests or frequency of symptoms related to selenium in the blood, toenails, or diet. We found no evidence of toxicity from selenium in subjects whose intake was as high as 9.20 mumol/d (724 micrograms/d).

Selenium intake, age, gender, and smoking in relation to indices of selenium status of adults residing in a seleniferous area.

Duplicate meals, serum, whole blood, and toenails were collected every 3 mo for 1 y from a group of 44 free-living adults residing in high-selenium areas of South Dakota and Wyoming to assess the relation of selenium intake to indices of selenium status. The average selenium values for the group were as follows: dietary intake, 174 +/- 91 micrograms/d (mean +/- SD), 2.33 +/- 1.08 micrograms/kg body wt; serum, 2.10 +/- 0.38 mumol/L; whole blood, 3.22 +/- 0.79 mumol/L; and toenails, 15.2 +/- 3.0 nmol/g. Selenium intake (micrograms/kg body wt) was strongly correlated (all values, P less than 0.01) with selenium concentration of serum (r = 0.63), whole blood (r = 0.62), and toenails (r = 0.59). Men and women had similar mean values of serum, whole blood, and toenail selenium despite higher selenium intakes in men. Smokers had lower tissue selenium concentrations than did nonsmokers due, at least in part, to lower selenium intake. Age was not associated with tissue selenium content. Of the variables examined selenium intake was clearly the strongest predictor of tissue selenium concentration.