Fiber intakes, stool frequency, and stool weights of subjects consuming self-selected diets.

Neutral detergent fiber (NDF) contents of duplicate collections of food consumed by 29 men and women were determined for 7 days four times during the year. The ratio of analyzed NDF to calculated crude fiber intakes was approximately 2. Although mean NDF intake was 7.7 g/day for females and 9.5 g/day for males, the majority of the subjects had NDF intakes of from 4 to 9 g/day. Fiber-containing foods consumed with the greatest frequency were vegetables. NDF intakes were greater in the winter than in the spring and summer. Caloric and total carbohydrate intakes, number of stools, and fecal weights were greater for the males than for the females. Fecal weights were significantly correlated with caloric intake, NDF intake, and number of stools. It is suggested that the insoluble fiber measured by the NDF method is likely to be better correlated with fecal weight than the total dietary fiber which includes soluble fibers.

Mineral balances of human subjects consuming spinach in a low-fiber diet and in a diet containing fruits and vegetables.

The effects of spinach in the diet on mineral balances were examined in 12 men who consumed three controlled diets for 4 wk each. Diet 1, a low-fiber diet, contained spinach, which is high in oxalic acid, every other day. Diet 2 contained fiber in fruits and vegetables, including spinach every other day. Diet 3 was the same as diet 2 except that cauliflower, which is low in oxalic acid, replaced the spinach. During wk 4, mean balances of calcium, magnesium, and zinc on diet 2 were negative and significantly lower than those on diet 1. Magnesium and zinc balances during wk 4 were also significantly lower on diet 2 than on diet 3. Mean balances of these minerals were not significantly lower on diet 2 during wk 3, nor were there any significant differences among mineral balances when wk 3 and 4 were considered together. Fecal oxalic acid was significantly greater on diet 2 than on diet 1 during both wk 3 and 4.

Effect of fiber from fruits and vegetables on metabolic responses of human subjects I. Bowel transit time, number of defecations, fecal weight, urinary excretions of energy and nitrogen and apparent digestibilities of energy, nitrogen, and fat.

Twelve men 37 to 58 years of age consumed two diets for a period of 26 days each in a cross-over design. The high fiber diet contained fruits and vegetables and the lower fiber diet contained fruit and vegetable juices. Neither diet contained whole grain cereals or nuts. Some nutrients were added to the low fiber diet in order to make the diets equivalent insofar as possible in all respects except fiber. The inclusion of fruits and vegetables in the diet decreased bowel transit time, increased fecal weight, increased number of defecations, increased fecal excretions and decreased apparent digestibilities of energy, nitrogen, and fat. Six of the 12 subjects had diastolic blood pressure of 80 or more when consuming the low fiber diet. The diastolic blood pressures of these six men were significantly lower when the high fiber diet was consumed.

Effect of fiber from fruits and vegetables on metabolic responses of human subjects. III. Zinc, copper, and phosphorus balances.

Intakes and excretions of zinc, copper, and phosphorus were determined for 12 men when they consumed a diet low in fiber and when they consumed a diet containing fiber from fruits and vegetables (high-fiber diet). All subjects consumed both diets for 26 days each. The low-fiber diet was supplemented with copper so that it was equivalent to the high-fiber diet in this respect. Mean daily intakes on the low- and high-fiber diets, respectively, were: zinc, 13.2 and 12.6 mg; copper, 1.8 and 1.6 mg; phosphorus, 1.639 and 1.690 g. Mean daily balances on the low- and high-fiber diets, respectively, were: zinc, +3.5 and -0.9 mg; copper, +0.2 and -0.4 mg; phosphorus, +0.361 and +0.292 g. Zinc and copper balances differed significantly on the two diets (P less than 0.001 and P less than 0.005, respectively, but phosphorus balances did not. The fiber supplied by the fruits and vegetables contained more lignin and cellulose and less hemicellulose than would an equivalent amount of fiber from bran. The bran would supply more magnesium, zinc, and copper than this particular diet containing fruits and vegetables.

Effect of fiber from fruits and vegetables on metabolic responses of human subjects, II. Calcium, magnesium, iron, and silicon balances.

Intakes and excretions of calcium, magnesium, iron, and silicon were determined for 12 men consuming controlled diets containing fruits and vegetables (high fiber diet) or fruit and vegetable juices (low fiber diet) for periods of 26 days. Magnesium and iron were added to the low fiber diet to make the two diets as equivalent as possible in these respects. Mean daily intakes on the low and high fiber diets, respectively, were: calcium, 1070 and 1166 mg; magnesium, 355 and 322 mg; iron, 21.8 and 26.4 mg; silicon, 21.6 and 45.8 mg. Mean daily balances on the low and high fiber diets repectively, were: calcium +72 and -122 mg; magnesium, +28 and -32 mg; iron, +3.8 and +4.6 mg; silicon, -3.5 and -14.6 mg. Calcium magnesium, and silicon balances were significantly lower on the high than on the low fiber diet (P less than 0.01).

Variations in plasma fatty acid concentrations during a one-year self-selected dietary intake study.

A group of healthy volunteers, maintaining their usual lifestyle, was monitored as to their nutrient intake for a period of 1 yr. Diet records were kept daily and blood samples were collected at even intervals five times during the year. Plasma fatty acid levels were analyzed to determine any sex, age, or seasonal variations or if the plasma fatty acid levels could be correlated to dietary fat intake. In the population studied, there was a significant (p less than 0.0001) sex by age interaction, but no seasonal effect was observed. No major differences in plasma fatty acids related to diet were found. However, the younger men had the highest linoleic acid intake and the lowest plasma linoleic acid. Plasma linoleic acid levels for males older than 35 yr of age (87.0 +/- 3.1 mg/dl) were significantly greater than for males younger than 36 yr of age (67.9 +/- 1.8 mg/dl). The plasma linoleic acid levels of all the women were intermediate in value to the men but not different from each other (73.8 +/- 1.7 mg/dl for the younger women and 78.7 +/- 1.9 mg/dl for the older women). There was a significant (p less than 0.01) sex effect in the relative percentage of plasma linoleic acid (34.4 +/- 0.4% for the women and 32.4 +/- 0.6% for the men), but no age or seasonal effect was observed.

Sources of variation in energy intake by men and women as determined from one year's daily dietary records.

Data from a year-long study conducted by the US Department of Agriculture's Beltsville Human Nutrition Research Center were used to identify sources of variation in daily energy intakes. A specific hypothesis was that an inverse relationship exists between past body weight and future energy intake whereas a direct relationship exists between past energy intake and future weight. Daily energy intakes of 29 male (n = 13) and female (n = 16) adult subjects were related through linear-regression analysis to sex (+ for males), age (-), height (+), weight (- for past and present measurements, + for future measurement), data collection method (- for duplicate plate), day of week (+ for Friday and Saturday), and month (+ for May, July, August, December, and January). These relationships were statistically significant (p less than 0.05). The results confirmed the hypothesis and were in general agreement with previously published studies that used larger samples but fewer days of data.

Seasonal variation in plasma glucose and hormone levels in adult men and women.

Twenty-nine men and women collected diet records for 1 yr. Fasting blood samples were collected four times during the year so that each season of the year was represented. An oral glucose tolerance test was given in the spring and in the fall. Regardless of season men consumed significantly more kilocalories, carbohydrate, sugar, and starch than did the women. Men consumed more simple sugars in the fall than in the spring. No seasonal effect was observed for calories, total carbohydrate, or starch intake. Fasting glucose and insulin were higher in the fall than in the spring. Summed insulin levels after the oral glucose tolerance were significantly different by age and season. Summed insulin levels were significantly higher in older than younger subjects; men and older subjects had higher levels in the spring than in the fall. Fasting levels of thyroxine, free thyroxine, triiodothyronine, and glucagon varied significantly with the season. A significant sex by season interaction was observed in the thyroid hormones. It appears that seasonal variation as well as diurnal variation should be considered in evaluating hormone levels.

The effect of kind of carbohydrate in the diet and use of oral contraceptives on metabolism of young women. III. Serum glucose, insulin, and glucagon.

Responses of glucose, insulin, and glucagon in serum to a sucrose load dose of young women taking oral contraceptives (OC) were compared to responses to the load dose of women who had never taken OC. Two experimental diets contained about 13% of the calories from protein, 36% from fat, and 51% from carbohydrate. Of the carbohydrate 84% was either sucrose of wheat starch. The diets were fed in a crossover design. Subjects were fed a sucrose load (1 g/kg) before and after weeks 1 and 3 of each dietary period. Parameters were measured in blood drawn before and 30, 60, 120, and 180 min after the meal. Levels of serum glucagon and responses of serum glucose and insulin to sucrose load were significantly higher in OC users than in controls. Glucose and insulin rose significantly after the sucrose load. Time significantly affected glucose and insulin. The OC-time interaction also was significant for glucose and insulin levels. The OC users generally had higher peak levels of glucose and insulin and took longer to return to fasting levels than did the controls. After 3 weeks on the diet, the glucose and insulin responses of the OC users, but not of the controls, were significantly greater on the sucrose than on the starch diet. The response of the insulin/glucagon ratio to the sucrose load was not significantly affected by the OC use.

PIP: The effect of the kind, rather than the amount, of carbohydrate in the diet of young women using oral contraceptives (OCs) was determined by studying serum glucose, insulin, and glucagon alterations after a loading dose of sucrose in women receiving their carbohydrate from primarily sucrose or from primarily wheat starch; these results were compared with those from a group of matched women never using OCs. 12 women (aged 19-25 years) were studied; half had used OCs and half had not. The 2 experimental diets were fed 4 weeks each in a crossover design with 4 weeks between the 2 test diets. Subjects were fed a sucrose load before and after Week 1 and 3 of each dietary period. Blood was drawn before and 30, 60, 120, and 180 minutes after each meal for measuring the various parameters. Overall, levels of serum glucagon and responses of serum glucose and insulin to sucrose load were significantly higher (P. 05-.005) in OC users than in controls. Glucose and insulin rose significantly after the sucrose load. Time also significantly affected glucose and insulin levels. The OC-time interaction was significant for glucose and insulin levels too. The OC users generally had higher peak levels of glucose and insulin and took longer to return to fasting levels than did the controls. By 3 weeks of the diet, the glucose and insulin responses of the OC users, vs. the controls, were significantly greater on the sucrose than on the starch diet. The response of the insulin/glucagon ratio to the sucrose load was not significantly affected by OC use.

Relationships among dietary constituents and specific serum clinical components of subjects eating self-selected diets.

Sex- and age-related differences in dietary and blood chemistry factors were investigated in subjects adhering to their usual lifestyles. Diet records were examined daily and blood chemistry profiles were monitored five times during the 1-yr study. As expected, high-density lipoprotein cholesterol was significantly higher in women than in men. Values of creatine phosphokinase, aspartic aminotransferase, alanine aminotransferase, glucose, triglycerides, urea nitrogen, uric acid, and total bilirubin were higher in men than in women. Glucose was lower while high-density lipoprotein cholesterol, albumin, and total protein were higher in the younger women than in older women. Alcohol consumption by men correlated positively with aspartic aminotransferase and alanine aminotransferase but not with high-density lipoprotein cholesterol. Alcohol consumption by women did correlate positively with high-density lipoprotein cholesterol but not with the aminotransferase enzymes. Correlations between serum high-density lipoprotein cholesterol and vitamin C intake were positive and significant in women. In men, high levels of high-density lipoprotein cholesterol seems to be associated with very high vitamin C intakes, but no associations were apparent at normal levels of these parameters. Serum cholesterol did not correlate significantly with dietary cholesterol, saturated fat, linoleic acid, or P/S in men or women.

Magnesium intakes, balances, and blood levels of adults consuming self-selected diets.

Magnesium balances and plasma and blood cell concentrations were determined in 34 men and women, 20 to 53 yr of age, during each season for 1 yr while they were consuming their customary diets. Dietary records were maintained 365 days. Analysis of variance indicated no seasonal variation in intake or balance. Blood cell magnesium correlated with magnesium intake (r2 = 0.203; p less than 0.04). Daily magnesium intakes of the men (323 mg) were significantly higher (p less than 0.01) than of the women (234 mg), and reflected greater calorie consumption for their greater body weights. Daily magnesium balances for the men and women were -32 and -25 mg, respectively. Multiple regression analysis showed that magnesium balance was associated not only with magnesium intake but also with the intake of other nutrients such as fiber, protein, calcium, and phosphorus. Moreover, the effect of these nutrients on magnesium balance varied with age and sex.

The effect of kind of carbohydrate in the diet and use of oral contraceptives on metabolism of young women. II. Serum lipid levels.

The response of lipids in the blood between two groups of six young women was compared. Group 1 took oral contraceptives and group 2 had never taken oral contraceptives. Two experimental diets supplied about 13% of the calories from protein, 36% from fat, and 51% from carbohydrate. Of the carbohydrate, 84% was either sucrose or wheat starch. Each diet was fed for 4 weeks in a cross-over design. In the portion of the research presented here, subjects were fed a high sucrose meal before each dietary period and after weeks 1 and 3 of each dietary period. Blood lipids were measured before and 30, 60, 120, and 180 min after each meal. Cholesterol and lipoproteins were not affected by the sucrose meal, but free fatty acid levels decreased significantly in both groups. The serum levels of triglycerides, beta-lipoproteins, and cholesterol were significantly higher in users than in nonusers of oral contraceptives. Free fatty acid levels were affected by an interaction between diet and time, and the decrease in response was greater after the sucrose than after the wheat starch diet. Triglycerides, cholesterol, and total lipids were not significantly different after the two carbohydrate diets.

PIP: The response of lipids in the blood between 2 groups of 6 young women, ages 19-25, was compared. Group 1 took (OCS) oral contraceptives and group 2 had never taken OCS. 2 experimental diets supplied about 13% of the calories from protein, 36% from fat, and 51% from carbohydrates. Of the carbohydrate, 84% was either sucrose or wheat starch. Each diet was administered for 4 weeks in a cross-over design. In a portion of the research here presented, subjects were fed a high sucrose meal before each dietary period and after weeks 1 and 3 of each dietary period. Blood lipids were measured before and 30, 60, 120, and 180 minutes after each meal. Cholesterol and lipoproteins were not affected by the sucrose meal, but free fatty acid levels decreased significantly in both groups. The serum levels of triglycerides, beta-lipoproteins, and cholesterol were significantly higher in users of OCS than in non-users. Free fatty acid levels were affected by an interaction between diet and time, and the decrease in response was geater after the sucrose than after the wheat starch diet. Triglycerides, cholesterol, and total lipids were not significantly different after the 2 carbohydrate diets.

Effect of fiber from fruits and vegetables on metabolic responses of human subjects: fiber intakes, fecal excretions, and apparent digestibilities.

Intakes and excretions of fiber were determined for 12 men consuming controlled diets containing fruits and vegetables (high fiber diet) or fruit and vegetable juices (low fiber diet) for periods of 26 days. The fiber in the low fiber diet appeared to be mostly hemicellulose, with an apparent digestibility of 95%. Apparent digestibilities of hemicellulose, cellulose, and lignin in the high fiber diet were 88, 42, and 18%, respectively. Small amounts of uronic acids were detected in the feces, but there is no certainty that they were derived from pectin. Linear regressions indicate that fiber intakes, rather than fiber disappearance, influenced the fecal volume.

The effect of kind of carbohydrate in the diet and use of oral contraceptives on metabolism of young women. I. Blood and urinary lactate, uric acid, and phosphorus.

Six oral contraceptive (OC) users and six control subjects consumed diets in which 43% of the calories came from either sucrose or starch for 4 weeks in a cross-over design. Kind of carbohydrate in the diet had no effect on blood lactate response to a sucrose load, but lactate response of OC users was greater than that of control subjects. Kind of carbohydrate in the diet did not affect urinary lactate excretion after a sucrose load; however, OC users excreted more lactate than did controls and there was a significant interaction between dietary carbohydrate and OC use. Serum uric acid levels were significantly higher when the sucrose diet was consumed, but levels were not affected by OC use. Serum phosphorus levels were not affected by kind of carbohydrate in the diet but were higher in control subjects than in OC users and there was a significant interaction between diet and OC use. There were no significant differences in urinary uric acid and phosphorus excretions after sucrose loads or in 24-hr urinary excretions of uric acid, phosphorus, or urea due to kind of carbohydrate in the diet or OC use.

PIP: 6 oral contraceptive (OC) users and 6 control subjects aged 19-25 consumed prepared diets in which 43% of the calories came from either sucrose or starch for 4 weeks in a crossover design. OCs taken were Ovral (1), Ortho-Novum 1/50 (2), Ortho-Novum sequential (1), Oracon sequential (1), and Norlestrin (1). The kind of carbohydrate in the diet had no effect on blood lactate response to a sucrose load, but lactate response of OC users was greater than that of control subjects. Kind of carbohydrate in the diet did not affect urinary lactate excretion after a sucrose load; however, OC users excreted more lactate than did controls and there was a significant interaction between dietary carbohydrate and OC use. Serum uric acid levels were significantly higher when the sucrose diet was consumed, but levels were not affected by OC use. Serum phosphorus levels were not affected by kind of carbohydrate in the diet but were higher in control subjects than in OC users and there was a significant interaction between diet and OC use. There were no significant differences in urinary uric acid and phosphorus excretions after sucrose loads or in 24-hour urinary excretions of uric acid, phosphorus, or urea due to kind of carbohydrate in the diet or OC use.

Impact of variation in carbohydrate intake on mineral utilization by vegetarians.

Dietary intakes of two groups of vegetarians (of Asian Indian and of American origin) residing in the United States were compared with intakes of a group of nonvegetarians. Mineral intakes and balances were determined for all three groups for a 7-d period. The vegetarians had a significantly higher percent of energy intake from carbohydrate and significantly higher intakes of crude fiber (CF) and neutral detergent fiber (NDF) than did the nonvegetarians. The American vegetarians had significantly higher intakes of magnesium, iron, and copper than did the other groups. Manganese intakes were significantly higher for the two vegetarian groups than for the nonvegetarians. Calcium, iron, zinc, and copper balances were not significantly different among the groups. Magnesium and manganese balances were significantly more negative for the American vegetarians than for the other two groups. In general, the higher percent of carbohydrate intake or the higher level of fiber intake did not appear to affect mineral utilization by the vegetarians.

Sodium and potassium intake and balance in adults consuming self-selected diets.

Twenty eight adults, 12 men and 16 women, participated in a 1-yr study designed to assess daily nutrient intake accurately. All subjects lived at home, consumed self-chosen diets, and maintained a detailed daily dietary record throughout the year. During four 7-day balance studies, one in each season of the year, meals, beverages, urine, and feces were analyzed for sodium and potassium content by atomic absorption spectrometry. Total intakes averaged 3.4 g/day for sodium and 2.8 g/day for potassium. The Na:K ratio for all diets analyzed averaged 1.3. Nutrient densities of sodium and potassium were 1.8 and 1.5 g/1000 kcal, respectively. Apparent absorptions of sodium and potassium were 98 and 85%, respectively, and did not change significantly over the wide range of intakes. Average urinary excretions of sodium and potassium were 86 and 77% of total intake, respectively. Mean metabolic balances were positive for sodium, +0.47 g/day, and potassium, +0.28 g/day. The data of this study provide useful information concerning the dietary intakes, excretions, and balances of sodium and potassium for adults based on analytic determination.

Evaluation of long-term dietary intakes of adults consuming self-selected diets.

Mean daily intakes of calories and 19 nutrients were calculated for 13 males and 16 females, ages 20 to 53 yr, who kept daily diet records for 1 yr. Mean daily caloric and 19 selected nutrient intakes of the subjects met or exceeded the 1980 recommended dietary allowances except for iron and calcium for females. Males had higher intakes than females for all nutrients studied except crude fiber, vitamin A, and vitamin C. However, nutrient density values were comparable for both sexes, except that the females had higher nutrient density values for vitamin A than did the males. The younger subjects had higher intakes of calories and saturated fat than the older ones. The younger males had higher intakes of total fat, saturated fat, and oleic acid than the older males. The consistency of reporting food intakes examined by applying a systematic sampling method designed for this study did not vary considerably when diet records kept over a long period of time were evaluated by four methods.

Effect of making duplicate food collections on nutrient intakes calculated from diet records.

In a 1-yr study in which food intakes were recorded daily, subjects were asked to make duplicate food collections for 1 wk during each of the four seasons. Mean calculated energy intake of the 29 subjects was 12.9% less during the food collection periods than the mean for the entire year (which included collection periods). There were also significant reductions in the reported intake of all nutrients during the collection periods. Protein, vitamin A, saturated fat, and cholesterol intakes were decreased to the greatest extent. The actual decrease in energy intake was greater for the males than for the females, but the percentage was the same (12.9%). The younger group of subjects (less than or equal to 35) decreased energy intake 16.8% and the older group (greater than 35) 8.8%. Comparison of intakes during collection periods with intakes the week before and the week after showed that 28 of the 29 subjects decreased their energy intake from 1.1 to 32.3%. These data suggest that intakes of subjects during food collection periods do not represent their habitual levels of intake reported throughout the year.

Zinc, copper, and manganese intake and balance for adults consuming self-selected diets.

Twenty-eight adult men and women participated in a year-long study designed to determine accurately the nutrient intake of adults who lived at home and consumed self-selected diets. During four metabolic balance periods, 7 days each, corresponding to the seasons (spring, summer, fall, winter), duplicates of the diet, and all urine and feces were collected. Daily mean intakes for zinc and copper were 9.9 and 1.2 mg, respectively. These levels were less than the recommended daily intakes of 15 mg for zinc and 2 to 3 mg for copper. In contrast, the mean dietary intake of manganese was 3.0 mg/day which is within the suggested safe and adequate range of 2.5 to 5.0 mg. Metabolic balances were negative for all three elements possibly due to a reduction in food intake during the collection periods compared to the noncollection intervals. The collection of the duplicate diets apparently influenced the food intake during the collection weeks.

Phytate:zinc and phytate X calcium:zinc millimolar ratios in self-selected diets of Americans, Asian Indians, and Nepalese.

The literature indicates that phytate:zinc and phytate X calcium:zinc millimolar ratios of a diet may provide useful indexes of the bioavailability of dietary zinc. However, there is little information on the phytate:zinc and phytate X calcium:zinc millimolar ratios for total human diets. We have therefore determined the phytate:zinc and phytate X calcium:zinc millimolar ratios of self-selected diets of 29 American omnivores, 23 American vegetarians, 30 Asian Indian immigrant vegetarians, and 26 Nepalese lactating vegetarians. Criteria for selection of subjects were: good health, no extreme dietary habits, and no intake of nutrient supplements. According to the limited literature, the suggested critical values for phytate:zinc and phytate X calcium:zinc millimolar ratios in animal diets and retrospective calculations from human diets are greater than 10 and greater than 200, respectively. The mean phytate:zinc and phytate X calcium:zinc millimolar ratios of American omnivorous diets in the present study were less than 10 and 200, respectively. Confirmation of the critical molar ratios as indexes of the bioavailability of zinc in human diets has not been established by experimentation. However, if the data from animal studies are applicable to human diets, the present study suggests that phytate has little influence on zinc bioavailability of most American diets. In contrast, the mean phytate:zinc and phytate X calcium:zinc millimolar ratios of all vegetarian diets were above the proposed critical levels. Those data, therefore, suggest that phytate might increase the risk of impaired zinc bioavailability for vegetarians consuming a relatively high level of calcium.