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Biomedical subjects

G Block

Publications and source records attributed to G Block.

At least 91 records · Page 5Linked to original sources
PubMed1990

Dietary vitamin B-6 intake and food sources in the US population: NHANES II, 1976-1980.

Dietary vitamin B-6 intake and food sources were estimated from the Second National Health and Nutrition Examination Survey (NHANES II) dietary data for 11,658 adults aged 19-74 y. The average daily intake of vitamin B-6 was 1.48 +/- 0.01 mg (mean +/- SEM) for the total population, 1.85 +/- 0.02 for males and 1.14 +/- 0.01 for females. Seventy-one percent of males and 90% of females consumed less than the 1980 recommended dietary allowance (RDA) of vitamin B-6. Sixty-four percent of all survey respondents reported a ratio of vitamin B-6 to dietary protein of less than 0.02 (expressed as mg/g protein). Foods from animal and plant sources provided 48% and 52% of the total vitamin B-6, respectively. Vitamin B-6 intake decreased (P less than 0.0001) with increasing age and decreasing education and income status. Beef steaks and roasts, alcoholic beverages, potatoes, ready-to-eat cereals, and milk were important dietary sources of vitamin B-6.

Adult↗
PubMed1990

Use of vitamin and mineral supplements: demographics and amounts of nutrients consumed. The 1987 Health Interview Survey.

Data from the 1987 National Health Interview Survey show that 51.1% of the adults aged 18-99 years in the United States consumed a vitamin/mineral supplement in the past year, but that only 23.1% did so daily. Whites, women, and older individuals were more likely than blacks, men, and younger individuals to consume supplements regularly. Multivitamins were the most commonly consumed supplement, followed by vitamin C, calcium, vitamin E, and vitamin A. Results suggest that supplementation practices have changed little since the 1970s. Results regarding the amounts of nutrients obtained from supplements show that a food frequency type of methodology collects reasonably accurate data reflecting intake of supplements over the past year. Few, if any, individuals were consuming nutrients in amounts considered toxic. Although vitamin and mineral supplementation is a common health habit, it appears not to pose a significant health risk for most of the population.

Adolescent↗
PubMed1990

A reduced dietary questionnaire: development and validation.

A reduced questionnaire was developed by successively omitting segments of the full (98-item) Block questionnaire and calculating the correlations between nutrient estimates produced by the full and reduced versions. The reduced version contains 60 food items and requires 17 minutes to administer by an interviewer. It is intended to capture all nutrients in the diet, as is the full version. The reduced version was validated against three four-day records in a group of middle-aged women, and against two seven-day records collected 10-15 years ago in a group of older men. The absolute value of macronutrients estimated by the reduced questionnaire was lower than food-record estimates, but most micronutrients were not underestimated. For macronutrients correlations with food records were slightly lower with the reduced questionnaire, but for micronutrients there was only slight or no reduction in correlations as a result of using the reduced version. The brief version may be useful in studies that cannot allow the 30-35 minutes required for the full-length questionnaire.

Aged↗
PubMed1990

Use of adjustment factors with a brief food frequency questionnaire to obtain nutrient values.

The 100-item National Cancer Institute (Block) Food Frequency Questionnaire was created to measure an individual's relative nutrient intake as well as absolute nutrient values. A 60-item, brief questionnaire was then developed; its results correlate well with results from the 100-item questionnaire and with food record data. Adjustment factors, presented here, were developed that allow investigators to use the shorter questionnaire while obtaining nutrient values nearer the correct absolute values than those from the brief questionnaire alone. Data from the National Health and Nutrition Examination Survey II (1976-1980) and the first quarter of the National Health Interview Survey (1987) were used in developing the adjustment factors. The brief questionnaire was administered to approximately 22,000 subjects in the National Health Interview Survey. When the adjustment factors were applied to data from the second, third, and fourth quarters of the National Health Interview Survey, the adjusted values of 17 micro- and macronutrients were on average within 0.51% and 1.17% of estimates obtained by 24-hour recall in the National Health and Nutrition Examination Survey II, for men and women, respectively. Correlations between the adjusted nutrient values and absolute nutrient consumption, as measured by diet diaries in three smaller studies, were nearly the same or somewhat better than correlations with the unadjusted brief questionnaire.

Adolescent↗
PubMed1990

Fruit and vegetables in the American diet: data from the NHANES II survey.

Twenty-four hour dietary recall data from the Second National Health and Nutrition Examination Survey (1976-80) were used to estimate the numbers of servings of fruit and vegetables consumed by Black and White adults, to examine the types of servings (e.g., potatoes, garden vegetables, fruit, and juice), and to estimate the mean intake of calories, fat, dietary fiber, and vitamins A and C by number of servings. An estimated 45 percent of the population had no servings of fruit or juice and 22 percent had no servings of a vegetable on the recall day. Only 27 percent consumed the three or more servings of vegetables and 29 percent had the two or more servings of fruit recommended by the US Departments of Agriculture and of Health and Human Services; 9 percent had both. Consumption was lower among Blacks than Whites. The choice of vegetables lacked variety. Diets including at least three servings of vegetables and two servings of fruit contained about 17 grams of dietary fiber. Although caloric and fat intake increased with increasing servings of fruit and vegetables, the percent of calories from fat remained relatively constant. Although these data are 10 years old, more recent surveys have shown similar results. The discrepancy between dietary guidelines and the actual diet suggests a need for extensive public education.

Adult↗
PubMed1990

The apparent validity of diet questionnaires is influenced by number of diet-record days used for comparison.

The effect of the number of diet records used as the reference data on the apparent validity of a diet history questionnaire was examined using data from 97 participants in the Women's Health Trial feasibility study. Pearson correlation coefficients were computed between the estimates of usual individual intake from the questionnaire and estimates from the mean of three 4-day records obtained over a 1-year period, the mean of the two most recent records, and the record obtained 1 year after the start of the study. The results illustrate that the apparent validity of a questionnaire increases when it is compared with a greater number of 4-day food records. The correlations increased for most nutrients when the baseline food record was included, despite the fact that it was completed at a time not targeted by the questionnaire. These findings suggest that greater effort should be given to obtaining more diet-record days when validating other dietary assessment instruments.

Aged↗
PubMed1989

Human dietary assessment: methods and issues.

It is possible that a "good" diet may enhance response to a chemopreventive agent, or that a diet deficient in some nutrients may weaken host defenses or host response to the agent. Thus, dietary intake should be assessed in chemoprevention as well as dietary studies. The advantages and disadvantages of several methods are presented. In addition, several principles and issues involved in dietary studies are discussed. Studies should attempt to assess the whole diet, not one or a few nutrients. Interpretation of the results of dietary studies can be seriously flawed and conclusions incorrect if only one or a few nutrients are assessed. Studies that ask about vegetable products but calculate only a fiber index are forced into drawing conclusions about fiber, when the true effective component may be elsewhere. Investigators should be cautious in the analysis and interpretation of results involving correlated nutrients. If two variables are quite highly correlated, either positively or negatively, a nutrient which has no effect may appear to have one, merely by being correlated with the other. Some examples are presented. Misclassification or measurement error is a serious problem for all dietary methods, although for different reasons. For most frequency or few-day-record methods, sample sizes must be multiplied several-fold over the sample size which standard formulas produce, to retain power in the face of measurement error.

Data Collection↗
PubMed1989

Folate intake and food sources in the US population.

Dietary data from 24-h recalls collected in the Second National Health and Nutrition Examination Survey (NHANES II) were analyzed to determine intake and food sources of folate in US adults between ages 19 and 74 y. Mean daily folate intake was 242 +/- 2.8 micrograms (means +/- SEM) for all adults, 281 +/- 3.6 micrograms for males, and 207 +/- 2.9 micrograms for females. Daily intake per 1000 kcal was 130 +/- 1.3 micrograms for all adults 122 +/- 1.3 micrograms for males, and 137 +/- 1.7 micrograms for females. Based on the Recommended Dietary Allowance of 400 micrograms/d, our results suggest that folate intake in the United States is low, particularly among women and blacks. Intake by age, education, and poverty index is discussed. Orange juice, white breads, dried beans, green salad, and ready-to-eat breakfast cereals are the major food sources of folate on a given day, contributing 37% of total folate intake.

Adult↗
PubMed1989

Issues in reproducibility and validity of dietary studies.

Numerous factors affect the reproducibility and validity of dietary assessment questionnaires. Although the respondents' abilities to respond accurately are most frequently discussed as the cause of apparently poor reproducibility and validity, many other factors are as important and perhaps more important. Most of these other factors are under the control of the investigator, and thus are amenable to improvement. Factors which may affect reproducibility included the degree of variability permitted by the instrument, the error-proneness of the response format, quality control of coding and keying and real dietary change in the time between the two administrations of the questionnaire. Factors affecting real or apparent validity include respondent characteristics, questionnaire design and quantification, quality control, and the adequacy of the reference data. The implications of inadequate reference data are illustrated and discussed.

Humans↗
PubMed1989

A dietary and risk factor questionnaire and analysis system for personal computers.

The authors report the adaptation of a dietary and risk factor questionnaire and analysis system for use with IBM (or compatible) personal computers. This system includes a flexible computer-assisted interview program which may be modified to suit investigator needs while preserving a standard output format. It also includes a nutrient analysis program for calculation of usual dietary intake. Each of these two major components has its own set of utilities and options, so that investigators may tailor the system to particular research areas. The nature and capabilities of the two main programs are described, as well as the development of the underlying system and the general flow of data in the system.

Data Collection↗
PubMed1989

Validation of a retrospective questionnaire assessing diet 10-15 years ago.

In 1985, 216 men, participants in the Baltimore Longitudinal Study of Aging, were asked to report on their usual diet during the period 1971-1975. The reference data for past diet consisted of multiple seven-day records collected between 1971 and 1975. The group was randomly assigned to complete the diet history either by personal interview or by mailed self-administered questionnaire. The items and response categories were identical in both cases. For both groups, the mean nutrient intake estimated by questionnaire was within +/- 10 per cent of the past diet record values for most nutrients. When the questionnaire was administered by an interviewer, correlations with past diet were approximately as good as those obtainable with present diet in other studies and indicate that useful studies of past diet can be performed with this questionnaire. Correlations for the mail group were considerably lower and suggest that assessment of past diet using this questionnaire format without personal instruction or callbacks may yield poor results. The effect of age was negligible, but response errors and change in diet since the target period had important effects on correlations with past diet in both interview and mail groups.

Aged↗
PubMed1988

Cancer morbidity and mortality in phosphate workers.

Phosphate ore mining and processing operations are associated with dusty conditions and potential exposure to gamma radiation and radon daughter products. Although most current measurements are within Occupational Safety and Health Administration (OSHA) guidelines, no measurements exist for the era preceding modern standards of industrial hygiene and workplace ventilation. All workers employed by the participating phosphate company between 1950 and 1979 were ascertained, and 3451 males employed for approximately 6 months or more comprise the study population. Statistically significant elevations in lung cancer (standardized mortality ratio = 1.62) and emphysema were observed in white but not in black workers, in relation to U.S. rates. Among workers for whom 20 years had elapsed since first employment, there was a dose-response trend of increasing lung cancer risk with increasing duration of employment (standardized mortality ratio = 2.48 with 20 years of employment). There was no evidence of excess lung cancer risk among employees hired after 1960. Multivariate analyses and internal comparisons of risk by job type are consistent with a hypothesis of occupationally related lung cancer, but small numbers prevent firm conclusions.

Chemical Industry↗
PubMed1988

Dietary factors in oral and pharyngeal cancer.

A population-based case-control study of oral and pharyngeal cancer conducted in four areas of the United States provided information on a number of risk factors, including diet. Interviews were obtained from 871 oral cancer patients and 979 controls among whites, frequency matched for age and sex. Consumption frequency of 61 food items was assessed in the questionnaire; attention was given to foods that are sources of vitamins A and C and carotene. The major finding was an inverse relationship between fruit intake and risk of oral and pharyngeal cancer; individuals in the highest quartile of intake had about half the risk of those in the lowest quartile. Vitamin C, carotene, or fiber in fruit did not appear to account completely for this relationship, since these nutrients in vegetables did not provide similar protection. This finding suggests the influence of other constituents in fruits, although it is possible that cooking vegetables may have a nutrient-diminishing effect. Dietary intake of other nutrients, such as the B vitamins, vitamin E, folate, and iron, showed no consistent relationship to risk of oral and pharyngeal cancer. Coffee or other hot beverage consumption did not increase risk; intake of nitrite-containing meats or cooking practices, such as smoking, pickling, or charcoal grilling, also did not increase risk. All analyses were adjusted for the effects of tobacco and alcohol, strong risk factors for oral and pharyngeal cancer. Dietary findings among the few subjects who did not use tobacco or alcohol were similar to those for all subjects.

Adult↗
PubMed1988

Relation of changes in amount and type of dietary fat to fecapentaenes in premenopausal women.

Correlation studies suggest that fecal mutagenicity is increased in groups eating high-fat diets, the same groups who are often found to have high colorectal cancer incidence and mortality. The fecapentaenes are the best characterized class of fecal mutagens, but the relationship of dietary fat intake to the excretion of these potent genotoxins is unknown. We studied the effect of changes in amount and type of dietary fat on fecapentaene levels in 31 premenopausal women 20-40 years of age who participated in a controlled feeding study. After a pre-diet free-living period lasting 1 menstrual cycle, women were placed on a high-fat (40% energy from fat) diet for 4 menstrual cycles and then switched to a low-fat (20% energy from fat) diet for an additional 4 menstrual cycles. One-half the subjects were maintained throughout the study at a ratio of polyunsaturated-to-saturated fatty acids (P/S ratio) of 1.0, the other half at 0.3; body weight was constant. All meals during the controlled diet periods were prepared at the Human Study Facility of the Beltsville Human Nutrition Research Center. Fecapentaene and fecapentaene precursor levels were measured in acetone extracts from 3-day pooled stool samples collected during the study. No differences in fecapentaene or precursor levels were observed between the high- and low-fat diets at either P/S ratio. Fecapentaene and precursor levels were higher while on controlled diets than during the pre-diet free-living period, and levels declined again in the post-diet free-living period. We conclude that dietary fat has no significant effect on fecapentaene or precursor levels in acetone extracts of stool in premenopausal women. The effect of other dietary or non-dietary factors on fecapentaenes remains unknown.

Adult↗
PubMed1988

Vitamin supplement use, by demographic characteristics.

Detailed data on vitamin supplement use are presented for nine specific vitamins and minerals by a wide range of demographic and behavioral characteristics. Previously recorded but uncoded data from the first National Health and Nutrition Examination Survey (1971-1974) have been coded and analyzed, providing the only detailed vitamin use data in a representative sample large enough to examine joint distributions and multivariate analyses of numerous characteristics. Significantly fewer black persons than white persons consume vitamins regularly, and the difference is especially pronounced for specific vitamins: fourfold for vitamin E, sixfold for vitamin A, and 10-fold for vitamin C. Significant differences were also seen for age, sex, geographic region, education, poverty, type of alcoholic beverage consumed, and Quetelet index. Data are presented indicating that supplement use has not increased notably between the time of the survey and 1983, and thus the supplement use data are considered to be reasonably representative of current patterns of supplementation practice in the United States.

Adult↗
PubMed1988

Food choices and the cancer guidelines.

Twenty-four hour dietary recall data from 11,658 adult respondents in the second National Health and Nutrition Examination Survey (NHANES II) (1976-80) were used to examine the American diet in relation to certain of the cancer dietary guidelines from the National Academy of Sciences and the American Cancer Society. The per cent who reported consuming any food in those food groups considered protective was small: cruciferous vegetables (18 per cent); fruits and vegetables high in vitamin A (21 per cent); high fiber breads and cereals (16 per cent). The per cent consuming foods potentially increasing cancer risk was high: red meat (55 per cent); bacon and lunch meats (43 per cent). Proportions of persons eating fruits and vegetables increased with income. Diets were closer to the guidelines for females than males, for Blacks than Whites, and for older than younger Americans.

Adult↗