Biomedical subjects

M L Neuhouser

Publications and source records attributed to M L Neuhouser.

24 records · Page 2Linked to original sources

PubMed1999

Validity of short food frequency questionnaires used in cancer chemoprevention trials: results from the Prostate Cancer Prevention Trial.

Here, we describe the measurement characteristics of a 13-item dietary screener used in the Prostate Cancer Prevention Trial. We used data from 10,913 men who completed the 13-item dietary screener, a food frequency questionnaire (FFQ), and questionnaires on demographic and health-related characteristics and from 146 men who also completed multiple 24-h dietary recalls in a substudy. The analyses in this report focused on percentage energy from fat and saturated fat and used the mean estimates from the dietary recalls as the criterion measures. Absolute nutrient estimates from the screener were about one-third of the estimates from the recalls and the FFQ. Validity was defined as the Pearson correlation of the criterion measures of fat with the corresponding measures from the FFQ and the screener. The FFQ was a statistically significantly more precise measure of percentage energy from fat (r = 0.71) and saturated fat (r = 0.72) than was the screener (r = 0.50 and 0.53, respectively). There were also statistically significant differences in how well these instruments could detect variation in dietary fat across various participant characteristics, suggesting that the screener may not perform as well as the FFQ across demographic strata such as education (P < 0.001). The results from this study suggest that the use of short dietary screeners as the sole assessment instrument may result in a serious loss of information regarding important exposures (e.g., fat intake) and lost opportunities to enhance our knowledge regarding dietary factors and cancer risk.

Aged↗

PubMed1998

Olestra Postmarketing Surveillance Study: design and baseline results from the sentinel site.

OBJECTIVE: To describe the design of the Olestra Postmarketing Surveillance Study (OPMSS) and to present baseline results from the sentinel site. The purpose of the OPMSS is to monitor consumption patterns of olestra-containing snacks and to determine whether consumption affects nutritional status. DESIGN: The OPMSS combines repeated cross-section, random-digit dial telephone surveys before and after the market release of olestra-containing foods as well as intensive dietary and clinical assessments on a subsample of survey participants. SUBJECTS: Data are from baseline telephone (n = 1,962) and clinical (n = 1,069) assessment of participants (aged 18 to 74 years) in the Marion County, Indiana, sentinel site. Mean age of participants in the telephone survey was 43.2 years; 19% of respondents were black and 29% had completed college. STATISTICAL ANALYSIS: Analyses examined associations among savory snack use, fruit and vegetable consumption, and demographic and health-related characteristics. Data from the telephone survey were adjusted to be representative of the Marion County population. RESULTS: Almost 96% of the population surveyed had eaten savory snacks in the month before the survey: 74% had eaten regular-fat, 26% fat-reduced, and 78% nonfat types. Total snack consumption did not differ by gender, education, or race. Residents younger than 35 years ate snacks 16 times a month compared with 12 times a month among older residents. Types of snacks consumed differed markedly by demographic characteristics. Male, younger, and less educated residents ate more regular-fat snacks; female, white, and college-educated residents ate more nonfat snacks. In general, residents practicing healthful behaviors, including not smoking, eating fruits and vegetables, and exercising, also ate fewer regular-fat and more nonfat snacks. Fat intake was also related linearly to use of snack foods, ranging from 33.2% of energy among those consuming 1 serving per month or less to 36.8% among those consuming 20 or more servings per month. APPLICATIONS/CONCLUSIONS: Procedures for recruitment and nutrition assessment appear adequate for evaluating the impact of olestra consumption on nutritional status. Nutritionists should be aware that there is potential for relatively high olestra consumption, given that almost 35% of Marion County residents eat snack foods at least 20 times a month. Consumers eating at least 20 servings of snacks per month derived more than 12% of their total energy and fat from snack foods, which suggests that substituting olestra snacks could substantially reduce intakes of fat and energy.

Adolescent↗

PubMed1998

Absorption of dietary and supplemental folate in women with prior pregnancies with neural tube defects and controls.

BACKGROUND: The Public Health Service of the United States recommends that all women capable of childbearing consume .4 mg (400 microg) folic acid per day to decrease the risk of having a pregnancy affected by a neural tube defect such as spina bifida or anencephaly. Three strategies are available to women to achieve this goal: use of dietary supplements; use of fortified foods; and/or increased intake of naturally occurring folate from foods. Identification of the most effective vehicle for delivery of folate to all women is critical in order to prevent these devastating congenital defects. OBJECTIVE: To investigate the difference in response to an oral load of folate both from naturally occurring food sources and synthetic supplements among women with prior pregnancies affected by neural tube defects and controls. METHODS: We compared the absorption of test doses of 400 microg pteroylglutamic acid (unconjugated or synthetic folic acid found in supplements) and 400 microg pteroylpolyglutamic acid (conjugated or food folate) in 10 women with a history of neural tube defect affected pregnancies and eight controls with normal birth outcomes. The folate test dose was given as either 32 fluid ounces of orange juice or a folic acid single supplement pill. All participants received each test dose at separate clinic visits. The response to each test dose was measured by constructing an area under the curve (AUC) from the serum folate levels at 1, 2 and 3 hours post dose and applying a t-test to compare within and between cases and controls. We also compared red cell folate, vitamin B12, zinc and homocysteine between cases and controls. RESULTS: Within group comparisons showed that the area under the curve was significantly greater for the pteroylglutamic acid dose compared to the pteroylpolyglutamic acid dose for both cases and controls (p=0.02 and p=0.03, respectively). In a between group comparison, control women had a greater serum folate response to both forms of the vitamin compared to the case women, but the difference reached statistical significance only for the pteroylglutamic acid dose (p=0.02). Other measured nutrients differed between cases and controls, but did not reach statistical significance. CONCLUSION: We conclude that for all women synthetic folic acid as supplements or fortified foods may be the best way to increase acute folate levels in the blood, and thus delivery to the developing embryo. Further, since case women had a diminished response to both forms of the vitamin, and some case women had almost no response, we speculate that women with prior affected pregnancies may need a larger dose of folate to elicit a plasma response equivalent to the general population.

Absorption↗

PubMed1998

Cancer-related behavior of vitamin supplement users.

Epidemiological studies suggest that certain vitamin supplements may reduce the risk of some cancers. However, observational studies can be compromised by confounding, because supplement use is related to other factors that affect cancer risk. The purpose of this paper is to identify cancer-related behaviors that could confound studies of the associations between vitamin supplement use and cancer risk. Data are from a random digit dial survey to monitor cancer risk behavior in adults in Washington State (n = 1449). Unconditional logistic regression was used to examine whether regular supplement users were more likely to practice other cancer-related behaviors than nonusers, after adjustment for age, education, and smoking. Among women, supplement users were more likely to have had a sigmoidoscopy [odds ratio (OR), 2.3; 95% confidence interval (CI), 1.2-4.5], hemoccult (OR, 2.3; CI, 1.5-3.5), or mammogram (OR, 1.5; CI, 1.0-2.1) in the past 2 years. Among men, supplement users were twice as likely to have had a prostate-specific antigen test (OR, 2.2; CI, 1.3-3.7) and to regularly take aspirin (OR, 1.7; CI, 1.1-2.6). Supplement users were statistically significantly more likely to exercise regularly, eat four or more servings of fruits and vegetables per day, follow a low-fat diet pattern, and believe in a connection between diet and cancer. The association was especially strong for fruits and vegetables (women, OR, 1.9; and CI, 1.3-2.6; men, OR, 2.4; CI, 1.6-3.8). Those investigating the benefits and risks of vitamin and mineral supplements need to be aware of the lifestyle characteristics of supplement users to assess the potential for bias in their studies.

Adult↗

PubMed1998

Measurement error from assessing use of vitamin supplements at one point in time.

Although many epidemiologic studies ask about current use of vitamin supplements, long-term use is usually the exposure of etiologic interest. We conducted a mailed survey to investigate the relation between current and long-term (10-year) supplement use (N = 325 adults). Estimates of current daily intake for supplemental micronutrients were roughly twice that of average daily intake over the past 10 years. Correlations between current intake and long-term intake from supplements alone were 0.77, 0.75, and 0.65 for vitamin C, vitamin E, and calcium, respectively. A measure of supplement use at one point in time incorporates measurement error that will attenuate measures of association.

Aged↗

PubMed1997

Vitamin supplements and cancer risk: the epidemiologic evidence.

This report reviews published epidemiologic research on the associations of vitamin and mineral supplementation with cancer risk. Although the literature on nutrition and cancer is vast, few reports to date have addressed supplemental nutrients directly (seven clinical trials, 16 cohort, and 36 case-control studies). These studies offer insight into effects of nutrients that are distinguishable from effects of other biologically active compounds in foods. Randomized clinical trials have not shown significant protective effects of beta-carotene, but have found protective effects of: alpha-tocopherol against prostate cancer; mixtures of retinol/zinc and beta-carotene/alpha-tocopherol/selenium against stomach cancer; and selenium against total, lung, and prostate cancers. Cohort studies provide little evidence that vitamin supplements are associated with cancer. Case-control studies have reported an inverse association between bladder cancer and vitamin C; oral/pharyngeal cancer and several supplemental vitamins; and several cancers and vitamin E. A randomized clinical trial, a cohort study, and a case-control study have all found inverse associations between colon cancer and vitamin E. Overall, there is modest evidence for protective effects of nutrients from supplements against several cancers. Future studies of supplement use and cancer appear warranted; however, methodologic problems that impair ability to assess supplement use and statistical modeling of the relation between cancer risk and supplement use need attention.

Case-Control Studies↗