Application of the method of triads to evaluate the performance of food frequency questionnaires and biomarkers as indicators of long-term dietary intake.

Little is documented about the performance of the food frequency questionnaire (FFQ) in US minority groups and in populations in developing countries. The authors applied a novel technique, the method of triads, to assess the validity and reproducibility of the FFQ among Hispanics. The subjects were men (n = 78) and women (n = 42) living in Costa Rica. Seven 24-hour dietary recalls and two FFQ interviews (12 months apart) were conducted between 1995 and 1998 to estimate dietary intake during the past year. Plasma and adipose tissue samples were collected from all subjects. Validity coefficients, which measure the correlation between observed and "true" dietary intake, were also estimated. The median validity coefficients for tocopherols and carotenoids estimated by dietary recall, the average of the two FFQs, and plasma were 0.71, 0.60, and 0.52, respectively. Compared with adipose tissue, plasma was a superior biomarker for carotenoids and tocopherols. Adipose tissue was a poor biomarker for saturated and monounsaturated fatty acids but performed well for polyunsaturated fatty acids (validity coefficients, 0.45-1.01) and lycopene (validity coefficient, 0.51). This study also showed that biomarkers did not perform better than the FFQ and that they should be used to complement the FFQ rather than substitute for it.

Population-based study of alpha- and gamma-tocopherol in plasma and adipose tissue as biomarkers of intake in Costa Rican adults.

BACKGROUND: gamma-Tocopherol is the most abundant form of vitamin E in the US diet, but alpha-tocopherol concentrations are the highest in plasma and tissues. Although plasma and adipose tissue concentrations of alpha-tocopherol have been used as biomarkers of intake, the relation between gamma-tocopherol intake and concentrations in plasma and adipose tissue is unknown. OBJECTIVE: Our goal was to investigate in a randomly selected population from Costa Rica whether plasma or adipose tissue concentrations of alpha- and gamma-tocopherol are suitable biomarkers of intake. DESIGN: A total of 361 men (x +/- SD age: 55 +/- 11 y) and 121 women (aged 59 +/- 10 y) completed a 135-item food-frequency questionnaire and provided a fasting blood sample and adipose tissue biopsy sample. RESULTS: Dietary gamma-tocopherol correlated with adipose tissue (r = 0.37, P < 0.001) and plasma (r = 0.42, P < 0.001) concentrations, regardless of supplement use. Dietary alpha-tocopherol correlated poorly with adipose tissue (r = 0.15, P < 0.01) and plasma (r = 0.16, P < 0.001) concentrations, and these correlations were even lower when users of vitamin supplements (n = 24) were excluded (adipose tissue: r = 0.10, P < 0.05; plasma: r = 0.09, P < 0.05). Compared with subjects who reported palm shortening (36%) as the major type of fat used for cooking, subjects using soybean oil (52%) had higher amounts of both alpha- and gamma-tocopherol in their diets. However, only gamma-tocopherol concentrations were higher in the plasma and adipose tissue of soybean oil users. CONCLUSIONS: Plasma and adipose tissue concentrations of gamma-tocopherol are equally good biomarkers of intake. The weak associations between alpha-tocopherol intake and plasma or adipose tissue concentrations suggest that these biomarkers are influenced more by factors other than alpha-tocopherol intake.

Vitamin A supplements and diarrheal and respiratory tract infections among children in Dar es Salaam, Tanzania.

OBJECTIVE: To determine the effect of vitamin A supplementation on the risk of diarrhea and of acute respiratory infection. DESIGN: Double-blind, randomized, placebo-controlled trial. SETTING: Dar-es-Salaam, Tanzania. SUBJECTS: Six hundred eighty-seven children, 6 to 60 months old, hospitalized with pneumonia, who received vitamin A or placebo at baseline and at 4 and 8 months after discharge from hospital. MAIN OUTCOME VARIABLES: Incidence and duration of episodes of diarrhea and respiratory tract infections during the year after discharge from the hospital. RESULTS: Relative to those receiving placebo, children receiving vitamin A had a significantly smaller risk of severe watery diarrhea (multivariate odds ratio = 0.56, 95% CI = 0.32-0.99, P =.04) but a higher risk of cough and rapid respiratory rate (multivariate odds ratio = 1.67, 95% CI = 1.17-2.36, P =.004). Vitamin A supplementation was also associated with increased risk of acute diarrhea among normally nourished children or children with stunted growth but was relatively protective among children with wasting disease (P value for interaction =.01). The apparently increased risk of respiratory tract infection was limited to children who were seronegative for human immunodeficiency virus (HIV) (P value for interaction =.07). CONCLUSIONS: Vitamin A supplements provide a low-cost intervention against morbidity in HIV-infected and undernourished children. Supplements may also have serious non-lethal adverse outcomes in well-nourished individuals. Whether these apparent detrimental effects of vitamin A are transient or long-term needs to be examined.

Human immunodeficiency virus infection in Mexico City. Rectal bleeding and anal warts as risk factors among men reporting sex with men.

The objectives of this study were to evaluate the frequency and determinants of rectal bleeding and the association between rectal bleeding and risk of human immunodeficiency virus (HIV) infection among homosexual/ bisexual men in Mexico City. Men who requested anonymous HIV testing at a public clinic in Mexico City and who reported engaging in any homosexual behavior were eligible to participate in this study. Trained staff collected information on demographic factors, sexual behavior, psychological states, and HIV serostatus from all consenting, eligible clients. Logistic regression modeling was used to investigate the independent effect of risk factors among 2,758 men who were tested between June 1991 and December 1992. Bleeding during anal intercourse was a common occurrence: More than one third of the men in the study reported some bleeding, and 8% reported bleeding in half or more of their intercourse episodes. The prevalence of HIV infection among bleeders was 42% as compared with 28% in nonbleeders (p < 0.0001), and the adjusted odds ratio was 1.8 (95% confidence interval (CI) 1.1-2.8) for men who bled in more than half of their anal intercourse episodes relative to nonbleeders. There was a trend of increasing HIV seroprevalence with increasing frequency of rectal bleeding (p = 0.001). Nine percent of all HIV infections and 42% of infections among frequent bleeders were attributable to rectal bleeding. Men who reported both rectal bleeding and anal warts were 3.5 (95% CI 2.1-5.8) times more likely to be HIV-infected in multivariate analysis than men reporting neither rectal bleeding nor anal warts. Determinants of rectal bleeding included older age, more education, more receptive anal intercourse than insertive intercourse, receptive digital-anal contact, anal warts, and genital ulcers. Among men reporting sex with men in Mexico City, rectal bleeding is common. It is an independent risk factor for HIV infection, and warrants attention in acquired immunodeficiency syndrome prevention efforts. Rectal bleeding that results from rupture of anal warts may be an especially effective portal of HIV transmission.

PIP: During June 1991 to December 1992, 68.8% of all men who gave informed consent for HIV testing at a public health clinic in Mexico City and for participation in this study had ever had sexual intercourse with men. The final sample size was 2758 men. The study examined the reported frequency of rectal bleeding, the determinants of rectal bleeding, and the interactions between rectal bleeding and other risk factors with HIV infection among homosexual/bisexual men. It also aimed to determine whether rectal bleeding is an independent risk factor for HIV transmission. 32.8% had HIV infection. 39% reported some rectal bleeding during anal intercourse. 8% experienced rectal bleeding during at least 50% of intercourse episodes. Overall, bleeders were more likely to be HIV infected than nonbleeders (42% vs. 28%; p 0.0001; adjusted odds ratio [AOR] = 1.8 for men who bled in more than 50% of anal intercourse episodes; AOR = 1.3 for men who sometimes bled). The odds ratios increased as the frequency of reported rectal bleeding increased (p = 0.001). Condom use during receptive anal intercourse did not affect the association between rectal bleeding and HIV infection. 9% of all HIV infections were attributable to rectal bleeding. 42% of HIV infections among bleeders were attributable to rectal bleeding. In the multivariate analysis, men with both rectal bleeding and anal warts were more likely to have HIV infection than men who had neither (67.9% vs. 27.2%; AOR = 3.5). Significant predictors of rectal bleeding were older age (i.e., =or 30) (AOR = 1.5), more education (AOR = 1.4-1.5), more receptive anal intercourse than insertive intercourse (AOR = 5.3-16.1), receptive digital-anal contact (AOR = 1.6), anal warts (AOR = 1.9), and genital ulcers (AOR = 2). These findings show that rectal bleeding is an independent risk factor for HIV infection. Rupture of anal warts is an especially effective portal of HIV transmission.