Constance Kies

Green and black tea consumption by humans: Impact on polyphenol concentrations in feces, blood and urine

The objective of the study was to determine the effects of green tea, black tea and decaffeinated black tea consumption on urinary and fecal excretions and whole blood and blood serum concentrations of polyphenols. The 56 day study was divided into four randomly arranged experimental periods of 14 days each during which the 10 healthy adult subjects consumed a laboratory controlled, constant, measured diet based on ordinary foods. During separate periods, subjects received no tea, green tea, regular black tea or decaffeinated black tea beverages at the three daily meals. Subjects made complete collections of urine and stools throughout the study and fasting blood samples were drawn at the beginning of the study and at the end of each experimental period. Polyphenols contained in urine, feces, whole blood, blood serums, food and tea were analyzed by the spectrophotometry method of Wah Lau et al. (1989). Green tea consumption resulted in highest intakes in greatest fecal and urinary excretions, highest retentions, and high whole blood concentrations of polyphenols followed by effects of regular black tea, decaffeinated black tea and no tea treatments. These results indicate that polyphenols from tea are at least partly absorbable. Hence, both positive and negative effects of dietary polyphenol may occur internal to the body proper and not only as effects within the intestines.

Mineral balances in humans as affected by fructose, high fructose corn syrup and sucrose

The utilization of selected minerals when sugars were supplemented to basal diets was investigated in two separate, laboratory-controlled human feeding studies. Fructose-fed subjects had higher fecal excretions of iron and magnesium than did subjects fed sucrose. Apparent iron, magnesium, calcium, and zinc balances tended to be less positive during the fructose feeding period as compared to balances during the sucrose feeding period. Conversely, high fructose corn syrup (HFCS) did not affect the mineral balances when compared to sucrose feeding. Subjects fed fructose experienced diarrhea which possibly decreased absorption of minerals and thus increased fecal mineral losses. No such adverse effects were noticed when HFCS was fed.

Zinc bioavailability and tea consumption: studies in healthy humans consuming self-selected and laboratory-controlled diets

One self-selected study (study A) and one laboratory-controlled study (study B) were conducted to investigate the effect of tea consumption on zinc bioavailability in healthy humans. The 14-day study A consisted of two 7-day experimental periods, while the 28-day study B consisted of two 14-day experimental periods. In study A eight subjects and in study B ten subjects were participated. Subjects of study A consumed self-selected diets and kept a record of foods eaten. In study B, subjects ate a constant and weighed laboratory controlled diet. In both studies, subjects consumed 8 g of instant tea during tea supplementation periods. Complete urine and fecal collections were made by subjects of both studies. Zinc contents of urine, fecal and food samples were determined by using Atomic Absorption Spectrophotometer. Mean zinc intakes of humans consuming self-selected diets were below the RDA. Mean urinary zinc excretion, fecal zinc excretion and zinc balance were unaffected by the tea consumption. Negative zinc balances in study A and positive zinc balances in study B were observed in both tea and no tea dietary treatments. Tea consumption showed a small but not statistically significant adverse affect on zinc bioavailability in humans.

Niacin, thiamin, and pantothenic acid bioavailability to humans from maize bran as affected by milling and particle size.

The objective of the project was to determine the bioavailability of selected B vitamins (niacin, pantothenic acid and thiamin) to humans from wet and dry milled maize brans which were coarsely or finely ground. Using a double cross-over design, the nine subjects were fed laboratory controlled diets containing unsupplemented bread or bread supplemented with finely ground, wet milled maize bran; coarsely ground, wet milled maize bran; finely ground, dry milled corn bran; or coarsely ground, dry milled maize bran. Subjects made complete collections of urine throughout the study which were analyzed for contents of the test vitamins. Although varying somewhat among vitamins, in general, better apparent bioavailability was achieved with the finely ground, dry milled maize bran than with the other test brans.

Nitrate-nitrite levels in commercially processed and home processed beets and spinach.

Nitrate and nitrite content of commercially processed and home processed beets and spinach samples were analyzed using specific ion electrode and colorimetric methods. The home processed beets were found to be significantly higher in nitrate content than the commercially processed beets. This difference was attributed to differences in processing methods. Pickled and Harvard beets contained significantly lower amounts of nitrate/nitrite on a dry weight basis than the other types of processed beets, evidently due to the diluting effect of added sucrose. Home frozen spinach showed a trend toward lower nitrate content than commercially frozen spinach, although the difference was not significant. Length of storage of home processed beets and spinach did not appear to affect nitrate or nitrite content.

Calcium, copper, iron, magnesium and zinc utilization of humans as affected by consumption of black, decaffeinated black and green teas☆

The objective of the study was to compare effects of black, decaffeinated black and green teas on the utilization of calcium, copper, iron, magnesium and zinc in young adults. Minerals were quantitated using atomic absorption techniques. A 56-d metabolic balance study was divided into four experimental treatments arranged in a randomized crossover design during which no black, decaffeinated black or green tea was consumed. Subjects (five females and four males) consumed a laboratory controlled diet low in the above minerals. The subjects received the same diet, except for the teas, during all treatments. Initial hematologic measurements indicated that subjects had normal iron status. For calcium, copper, magnesium and zinc, no significant differences were found in intake, fecal, urinary and balance values by gender, treatment or gender-by-treatment. Some small, but significant differences were observed by gender for urinary iron values. Iron balance values of both genders were significantly more negative (P < .05) in the green tea treatment than other treatments; no differences were observed by gender. No differences occurred in intake and fecal iron values by gender, treatment or gender-by-treatment. Overall, with few exceptions, these teas did not affect the calcium, copper, iron, magnesium and zinc balances of young adults fed diets low in these minerals.

Mineral utilization of vegetarians: impact of variation in fat intake.

One of the benefits associated with consumption of vegetarian diets is that these diets usually have lower contents of total fat and cholesterol and have more favorable polyunsaturated-to-saturated fatty acid ratios. Thus, use of vegetarian diets tends to fit recommendations relative to decreasing risk of cardiovascular disease. However, changes in level and kind of dietary fat may result in alterations in utilization of essential minerals. In studies carried out at the University of Nebraska using healthy human subjects, low-fat diets were found to inhibit the absorption of iron, zinc, manganese, and calcium. Further research indicated that both increase in fatty acid chain length and increase in saturation of fatty acids resulted in a decrease in Ca bioavailability. However, increased dietary cholesterol levels tended to increase Ca bioavailability.

Inhibitors of Copper Bioutilization: Fiber, Lead, Phytate and Tannins

Considerable evidence suggests that copper intakes of Americans have declined in recent years to levels that might be considered seriously low. Under such conditions, other dietary factors which inhibit copper utilization might be of concern since otherwise marginally adequate copper diets might be made copper deficient. A large number of mineral nutrients have been found to interact with copper. Non-nutrient substances in food also may affect copper utilization. Evidence suggesting that lead, certain kinds of dietary fiber, phytates and tannins inhibit copper utilization are reviewed in this paper.

Copper Absorption as Affected by Supplemental Calcium, Magnesium, Manganese, Selenium and Potassium

Effects of feeding supplements of calcium, magnesium, manganese, selenium and potassium on dietary copper bioavailability of humans were investigated. Results indicated that the calcium supplements depressed fecal copper losses and improved body copper retention as did potassium supplements. Magnesium and selenium supplementation of diets resulted in increased apparent fecal losses of copper while no effect of manganese supplementation was found. It may be that the unexpected positive effect of calcium on copper utilization was due to its neutralizing effect on the relatively high level of ascorbic acid provided by the constant background diet. Ascorbic acid is known to inhibit the absorption of copper.

Comparison of palm and mixtures of refined palm and soybean oils on serum lipids and fecal fat and fatty acid excretions of adult humans

The effects of palm (P) and mixtures of palmand soybean (PS), palmolein and soybean (POS),palmstearin and soybean (PSS) oils on serum lipids andfecal fat and fatty acid excretions of humans werestudied. Each oil was the dominant fat in dietsconsumed by ten normolipidemic live-in individuals.Test diets were assigned by randomization. All fourdiets had a similar influence on total cholesterol (TC),low density lipoprotein (LDL), high densitylipoprotein (HDL), very low density lipoprotein(VLDL), triglycerides (TG) and phospholipids (PL). Fecalfat excretion was higher (1.81, 1.80 g/d) with PS andPSS and lower (1.78, 1.42 g/d) with P and POS diets.Excretions of palmitic (C16: 0), oleic (C18: 1), andlinoleic (C18: 2) acids were similar for all diets.Excretions of stearic acid (C18: 0) were higher whenfeeding POS and PSS, and lower with feeding P and PS;the changes were statistically significant atp < 0.05. More linolenic acid (C18: 3) was excretedwhen P was fed compared to the feeding of PS, POS, andPSS. Changes in linolenic acid excretion between P andPOS were statistically significant at p < 0.05. It wasconcluded that there were no significant differencesin serum lipid concentrations due to feeding palm orany of the refined palm and soybean oil mixtures.However, a significant difference was found in C18: 0excretions with feeding POS and PSS compared to whenP and PS were fed. Similarly, significant C18: 3excretion was found with feeding P compared to whenPOS was fed.