Assessment of the electromagnetic field exposure due to wireless communication technologies in two university campuses of medellin, Colombia

Exposure to radiofrequency electromagnetic fields (RF-EMFs) is considered an area of significant importance in the medical and scientific community. However, the availability of exposure data for indoor and outdoor locations in universities is limited and currently inconsiderate in Latin America. The aim of this work was to evaluate the electric field levels due to mobile telecommunication technologies and Wi-Fi to which students and faculty staff from two campuses of a higher education institution are exposed. Using a portable spectrum analyzer, we carried out 516 short-term measurements in the 800-3000 MHz frequency range at both indoor and outdoor locations. These locations were chosen to cover all areas of the assessed buildings. The electric field differences between floors and buildings are discussed. Finally, we compared the electric field levels with exposure limits. The highest electric field level measured was 13.97 V/m at the 850 MHz band. However, the average electric field values were below 2 V/m. The greatest contribution to the total electric field was due to sources using the 850 MHz and 1900 MHz bands (98%), while the contribution of the Wi-Fi network was low (1.0%). The results show that all the electric field levels measured were lower than the ICNIRP reference levels for radio-frequency exposure.

Nutritional supplements used in weight-reduction programs increase intestinal gas in persons who malabsorb lactose

OBJECTIVE

To determine if ingestion of 2 doses of milk-based dietary supplements produce gaseous symptoms in subjects who malabsorb lactose.

DESIGN

Randomized, controlled, crossover trial.

SUBJECTS/SETTING

Ten community-based subjects who malabsorb lactose.

INTERVENTION

Ingestion of 2 standard servings of milk-based supplements (a powder reconstituted in fat-free milk or a ready-to-drink preparation) or low-lactose control preparations.

MAIN OUTCOME MEASURES

Frequency of flatus passage and subjective impression of bloating, flatulence, and abdominal discomfort.

STATISTICAL ANALYSIS

Wilcoxon signed-rank test.

RESULTS

The high lactose content (27 g) of 2 servings of the powder-based supplement ingested without other food resulted in a marked increase in daily flatus passages from the basal level of 9.7+/-8.2 to 30+/-14 (mean+/-SD), and a significant increase in the subjects' perception of gas. In contrast, the lower lactose content (18.4 g) of 2 servings of a ready-to-drink supplement resulted in a flatus frequency of 17+/-10 (P=.14 vs baseline) and no significant increase in the perception of increased gas. Neither supplement resulted in a significant increase in bloating, abdominal pain, or diarrhea. The lactose content of the liquid supplement was reduced by 80% following overnight incubation with an over-the-counter lactase preparation.

APPLICATIONS/CONCLUSIONS

Persons who malabsorb lactose should be aware that sizable increases in rectal gas commonly occur when milk-based powders reconstituted in milk are used as meal replacements. In contrast, gas problems probably will be minor following ingestion of 2 doses of a ready-to-drink, milk-based supplement. The lactose content of these supplements can be markedly reduced by overnight incubation with over-the-counter lactase preparations, and this manipulation should be beneficial for subjects troubled by the increased gas caused by the consumption of lactose-containing supplements.

Spontaneous fluctuations in the concentrations of oral sulfur-containing gases

Breath hydrogen sulfide (H2S) and methyl-mercaptan (CH3SH) concentrations are used as quantitative indicators of halitosis. However, measurements of these gases in duplicate oral samplings often show poor reproducibility. To determine if this poor reproducibility is an artifact of the collection/analytical procedure or a true biological phenomenon, we used a standardized technique to collect from 20 to 30 oral gas samples at two-minute intervals from 11 healthy subjects. The samples were analyzed for sulfur gases and CO2. Sizable variations in H2S and CH3SH concentrations were not associated with alterations in CO2, indicating that the variations did not reflect variable contamination with atmospheric or pulmonary gas. In addition, fluctuations in H2S and CH3SH were not identical and often were not random. We conclude that minute-to-minute variability in oral sulfur gas concentrations is a true biological phenomenon. This fluctuation complicates experimental studies designed to show that interventions alter halitosis.

Gas production by feces of infants

BACKGROUND

Intestinal gas is thought to be the cause abdominal discomfort in infants. Little is known about the type and amount of gas produced by the infant's colonic microflora and whether diet influences gas formation.

METHODS

Fresh stool specimens were collected from 10 breast-fed infants, 5 infants fed a soy-based formula, and 3 infants fed a milk-based formula at approximately 1, 2, and 3 months of age. Feces were incubated anaerobically for 4 hours at 37 degrees C followed by quantitation of hydrogen (H2), methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), methanethiol (CH3SH), and dimethyl sulfide (CH3SCH3) in the head-space.

RESULTS

H2 was produced in greater amounts by breast-fed infants than by infants in either formula group, presumably the consequence of incomplete absorption of breast milk oligosaccharides. CH4 was produced in greater amounts by infants fed soy formula than by infants on other diets. CO2 was produced in similar amounts by infants in all feeding groups. Production of CH3SH was conspicuously low by feces of breast-fed infants and production of H2S was high by soy-formula-fed infants. CH3SCH3 was not detected. Only modest changes with age were observed and there was no relation between gas production and stool consistency, although stools were more likely to be malodorous when concentrations of H2S and/or CH3SH were high.

CONCLUSIONS

Gas release by infant feces is strongly influenced by an infant's diet. Of particular interest are differences in production of the highly toxic sulfur gases, H2S and CH3SH, because of the role that these gases may play in certain intestinal disorders of infants.

Morning breath odor: influence of treatments on sulfur gases

We assessed the effects of several treatments on the concentrations of oral sulfur-containing gases, compounds thought to be responsible for morning breath. Upon awakening in the morning, healthy volunteers collected oral gas samples before and for eight hours after the following treatments: no treatment, brushing the teeth with toothpaste, brushing the tongue, rinsing with 5 mL of 3% hydrogen peroxide, breakfast ingestion, or swallowing two BreathAsure capsules. The gas samples were analyzed for sulfur-containing volatiles via gas chromatography. Baseline collections usually contained three sulfur gases: hydrogen sulfide, methanethiol, and dimethylsulfide. The effectiveness of a treatment was determined via comparison of the areas under gas concentrations-time curves with and without treatment. Brushing the teeth or ingestion of BreathAsure had no apparent influence on the sulfur gases. Ingestion of breakfast and tongue brushing resulted in strong trends toward decreased sulfur gases. Hydrogen peroxide significantly reduced the sulfur gas concentrations for eight hours.

An understanding of excessive intestinal gas

Complaints of "excessive gas" from patients are very common but are difficult, if not impossible, for the physician to document. This review addresses the pathophysiology and management of such complaints, looking at the sources and routes of elimination, excessive eructation, bloating, and distention. In addition, common flatulence problems are summarized, including excessive flatus volume and noxious flatus.

Binding of hydrogen sulfide by bismuth does not prevent dextran sulfate-induced colitis in rats

Several lines of evidence suggest that ulcerative colitis could be caused by excessive bacterial production of H2S in the colon. A rodent model of colitis involves the feeding of nonabsorbable, carbohydrate-bound sulfate in the form of dextran sulfate or carrageenan. The observation that metronidazole blocks the development of this colitis suggested that the injurious agent could be a sulfur-containing compound (such as H2S) that is released during the bacterial metabolism of the nonabsorbed sulfate. We tested this possibility by feeding rats dextran sulfate, with or without bismuth subsalicylate, a compound that avidly binds H2S. Bismuth subsalicylate reduced the fecal release of H2S in dextran sulfate-treated rats to values well below that of controls. Nevertheless, all the animals developed colitis. We conclude that excessive H2S production does not play a role in the dextran sulfate model of colitis.

Site of bismuth absorption from bismuth subsalicylate: implications for treatment of colonic conditions

Poorly absorbed bismuth preparations may benefit a variety of chronic colonic conditions including ulcerative colitis. Bismuth-induced neurotoxicity is a potential complication of the chronic use of these preparations, and a less-absorbable form of bismuth is needed. If bismuth absorption occurs primarily in the upper gut, a delayed-release bismuth preparation could reduce absorption. We studied the site of bismuth absorption from bismuth subsalicylate (BSS) in rats. For 15 days, BSS (50 mg/day) was ingested or infused directly into the cecum via a chronically implanted cannula. Oral BSS resulted in serum and urine bismuth levels many times higher (3.5 +/- 0.3 microg/liter and 1,570 +/- 286 microg/g creatinine, respectively) than with cecal administration (undetectable (<1.5 microg/liter) and 75 +/- 25 microg/g creatinine). Thus, bismuth absorption from BSS occurred almost entirely in the upper gut. These findings provide a rationale for a similar study of delayed-release bismuth preparations in humans.

Failure of activated charcoal to reduce the release of gases produced by the colonic flora

OBJECTIVE

Activated charcoal is used to treat excessive volume or malodor of intestinal gas. Our previous studies demonstrated that activated charcoal failed to bind appreciable quantities of the volumetrically important gut gases. However, the odor of feces and flatus derives primarily from trace quantities of sulfur-containing gases, primarily H2S and methanethiol, which should avidly bind to activated charcoal. The goal of this study was to determine if ingestion of activated charcoal reduces the fecal release of sulfur gases.

METHODS

Five healthy human volunteers ingested 0.52 g of activated charcoal four times daily for 1 wk and the fecal liberation of intestinal gases was measured before and after the activated charcoal treatment. In an effort to explain the in vivo results, additional in vitro studies were performed to compare the binding capacity of charcoal to the sulfur gas released by feces.

RESULTS

Ingestion of activated charcoal produced no significant reduction in the fecal release of any of the sulfur-containing gases, nor was total fecal gas release or abdominal symptoms significantly influenced. In vitro studies suggested that the failure of ingested charcoal to reduce liberation of sulfur gases probably is explained by the saturation of charcoal binding sites during passage through the gut.

CONCLUSION

Commonly employed doses of activated charcoal do not appreciably influence the liberation of fecal gases.

Gas production in human ingesting a soybean flour derived from beans naturally low in oligosaccharides

BACKGROUND

Ingestion of soy products may cause excessive intestinal gas. This gas results from colonic bacterial fermentation of the indigestible oligosaccharides raffinose and stachyose, which are present in high concentrations in legumes.

OBJECTIVE

The objective of the study was to compare gas production and gaseous symptoms in healthy volunteers after ingestion of 34 and 80 g soy flour made from either conventional soybeans or soybeans naturally low in indigestible oligosaccharides.

DESIGN

In a double-blind, randomized, crossover protocol, breath hydrogen (an indicator of carbohydrate malabsorption), flatus frequency, and abdominal symptoms were assessed after subjects ingested the soy products and after 2 control meals (rice or lactose-hydrolyzed milk).

RESULTS

The sum of breath-hydrogen concentrations for 8 h was significantly greater (P < 0.005) after 34 g conventional soy (60.4+/-9.4 ppm) than after low-oligosaccharide soy (34.3+/-8.1 ppm). Greater differences were observed with 80-g doses: 157.9+/-19.4 ppm after conventional soy and 50.8+/-6.8 ppm after low-oligosaccharide soy (P < 0.001). Flatus frequency (7.5+/-1.9 times/12 h) was significantly greater (P = 0.039) after ingestion of 80 g conventional soy than after the control, rice meal (3.2+/-0.8 times/12 h), whereas flatus frequency after the low-oligosaccharide soy meal (3.9+/-0.7 times/12 h) was comparable with that after the rice meal. There were no significant differences in the severity of other abdominal symptoms.

CONCLUSION

Soy flour derived from low-oligosaccharide soybeans resulted in less gas production than that derived from conventional soybeans.

Evaluation of an extremely flatulent patient: case report and proposed diagnostic and therapeutic approach

We recently encountered a patient with severe flatulence who previously had been subjected to innumerable diagnostic tests and ineffective therapies based on the belief that his rectal gas was produced in the colon. Analysis of three flatus samples demonstrated that nitrogen (N2) was the predominant flatus gas whereas the three gases produced in the gut (CO2, H2 [hydrogen], and CH4 [methane]) comprised <16% of rectal gas. This result plus a series of other diagnostic tests clearly indicated that the patient's flatus was derived almost entirely from swallowed air. Based on this case, the present report summarizes available data on excessive flatulence and suggests a rational approach to the patient complaining of this problem. Particular emphasis is placed upon a sequential strategy consisting of: 1) a count of flatus passages to determine if the subject truly is abnormal (normal: <20 passages/day); 2) an analysis of flatus to determine if the flatus originates from swallowed air (predominantly nitrogen) or intraluminal production (predominantly CO2, H2, and CH4); and 3) treatment based upon the origin of the rectal gas.

Lactose maldigestion is not an impediment to the intake of 1500 mg calcium daily as dairy products

BACKGROUND

A National Institutes of Health consensus conference concluded that a daily calcium intake of 1500 mg reduces the severity of osteoporosis. Because dairy products are the main natural source of dietary calcium, a diet providing 1500 mg Ca must contain large quantities of dairy products. However, it is widely believed that the lactose content of these products will not be tolerated by persons with lactose maldigestion (approximately 30% of the adult US population).

OBJECTIVE

We evaluated the symptoms of lactose maldigestion and digestion when the diet was supplemented with dairy products providing 1300 mg Ca/d.

DESIGN

Sixty-two women (31 with lactose maldigestion and 31 without) were studied in a double-blind, randomized protocol. Symptoms were compared during 1-wk periods when the diet was supplemented with 480 mL (2 cups) milk, 56 g cheese, and 240 mL yogurt provided as conventional products (34 g lactose/d) or as lactose-hydrolyzed products (2 g lactose/d).

RESULTS

Women who digested lactose reported no significant difference in symptoms between the 2 treatment periods. Women with lactose maldigestion reported significantly increased flatus frequency and subjective impression of rectal gas during the period of high lactose intake; however, bloating, abdominal pain, diarrhea, and the global perception of overall symptom severity were not significantly different between the 2 treatment periods.

CONCLUSION

The symptoms resulting from lactose maldigestion are not a major impediment to the ingestion of a dairy-rich diet supplying approximately 1500 mg Ca/d.

Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour

BACKGROUND/AIMS

While the social significance of flatus derives mainly from its odour, previous studies have focused on the non-odoriferous components of rectal gas. The aims of the present study were to determine the role of sulphur-containing gases in flatus odour and test the efficacy of a device purported to reduce this odour.

METHODS

Flatus was quantitatively collected via rectal tube from 16 healthy subjects who ingested pinto beans and lactulose to enhance flatus output. The concentrations of sulphur-containing gases in each passage were correlated with odour intensity assessed by two judges. Odour intensity was also determined after treatment of flatus samples with zinc acetate, which binds sulphydryl compounds (hydrogen sulphide and methanethiol), or activated charcoal. Utilising gastight Mylar pantaloons, the ability of a charcoal lined cushion to adsorb sulphur-containing gases instilled at the anus of eight subjects was assessed.

RESULTS

The main sulphur-containing flatus component was hydrogen sulphide (1.06 (0.2) mumol/l), followed by methanethiol (0.21 (0.04) mumol/l) and dimethyl sulphide (0.08 (0.01) mumol/l) (means (SEM)). Malodour significantly correlated with hydrogen sulphide concentration (p < or = 0.001). Zinc acetate reduced sulphur gas content but did not totally eliminate odour, while activated charcoal removed virtually all odour. The cushion absorbed more than 90% of the sulphur gases.

CONCLUSION

Sulphur-containing gases are the major, but not the only, malodorous components of human flatus. The charcoal lined cushion effectively limits the escape of these sulphur-containing gases into the environment.

Bismuth subsalicylate markedly decreases hydrogen sulfide release in the human colon

BACKGROUND & AIMS

Hydrogen sulfide is one of the main malodorous compounds in human flatus. This toxic gas also has been implicated in the pathogenesis of ulcerative colitis. Therefore, a treatment that reduces colonic H2S levels could be clinically useful in the treatment of flatus odor and of ulcerative colitis. In this study the ability of bismuth subsalicylate, a compound that binds H2S, to reduce H2S release in the colon, was tested.

METHODS

Homogenates made from human and rat feces were incubated with and without bismuth subsalicylate, and gas production was measured. Fecal samples from 10 healthy subjects were analyzed before and after ingestion of bismuth subsalicylate (524 mg four times a day) for 3-7 days.

RESULTS

Fecal homogenates showed a dose-dependent relationship between the concentration of bismuth subsalicylate and H2S release. Treatment of subjects with bismuth subsalicylate produced a >95% reduction in fecal H2S release.

CONCLUSIONS

The ability of bismuth subsalicylate to dramatically reduce H2S could provide a clinically useful means of controlling fecal and/or flatus odor and of decreasing the putative injurious effects of H2S on the colonic mucosa.

Tolerance to the daily ingestion of two cups of milk by individuals claiming lactose intolerance

We reported previously that consumption of one cup of milk (240 mL) per day produced negligible symptoms in lactase-nonpersistent (LNP) individuals self-described as being severely lactose intolerant. We hypothesized that such LNP individuals could also tolerate two cups of milk per day if taken in two widely divided doses with food, and that psychologic factors play a role in perceptions of lactose intolerance. The Minnesota Multiphasic Personality Inventory 2 (MMPI-2) was administered to 19 LNP subjects self-described as markedly lactose intolerant (S-LNP), 13 LNP subjects who denied lactose intolerance (A-LNP), and 10 lactase-persistent individuals who believed they were lactose intolerant (S-LP). Symptoms were recorded when LNP subjects ingested 240 mL regular or lactose-hydrolyzed milk twice daily for 7 d in a double-blind crossover study. The results showed that neither LNP group had a significant increase in symptoms (P < 0.05) during the regular compared with the lactose-hydrolyzed milk periods. However, S-LNP subjects reported significantly greater gaseous symptoms than did the A-LNP subjects during both treatment periods. The MMPI-2 showed a high score on the "lie" validity scale for S-LNP subjects. We conclude that LNP subjects tolerate two cups of milk per day without appreciable symptoms. S-LNP subjects have underlying flatulence that is misattributed to lactose intolerance. MMPI-2 results were of questionable validity because of the high rate of dissimulation by LNP subjects.

Review article: the treatment of lactose intolerance

While about 50 million Americans malabsorb lactose, the colonic metabolism of this disaccharide may prevent the symptomatic state known as lactose intolerance. Elucidation of the clinical importance of lactose malabsorption requires comparison of symptoms after ingestion of lactose with those following an identical appearing lactose-free control. This paper reviews the extensive literature concerning lactose-induced symptoms and the value of lactose digestive aids. Poorly controlled studies have suggested that a cup of milk results in appreciable symptoms in the majority of lactase-deficient subjects. In contrast, controlled trials in unselected lactose malabsorbers of subjects claiming severe lactose intolerance indicate that symptoms from a cup of milk are no greater than that with a lactose-hydrolyzed control. An increasing fraction of subjects experience symptoms as the lactose load is increased, with the majority having symptoms when the equivalent of 1 L of milk is ingested as a single dose. Further studies are required to determine the tolerance to several cups of milk taken throughout the day. Available digestive aids include pre-hydrolyzed milk and lactase preparations that can be added to milk (which is then incubated) or ingested with milk. While these products are effective in reducing symptoms, it should be emphasized that there appears to be no need for these preparations when the dosage of milk is limited to one cup per day.

A comparison of symptoms after the consumption of milk or lactose-hydrolyzed milk by people with self-reported severe lactose intolerance

BACKGROUND

Ingestion of a large dose of the milk sugar lactose--for example, the 50-g load in 1 liter of milk--causes symptoms such as abdominal pain, diarrhea, bloating, and flatulence in the majority of people with lactose malabsorption. It is uncertain whether the ingestion of more common doses of lactose, such as the amount in 240 ml (8 oz) of milk, causes symptoms. Some people insist that even smaller quantities of milk, such as the amount used with cereal or coffee, cause severe gastrointestinal distress.

METHODS

In a randomized, double-blind, crossover trial, we evaluated gastrointestinal symptoms in 30 people (mean age, 29.4 years; range, 18 to 50) who reported severe lactose intolerance and said they consistently had symptoms after ingesting less than 240 ml of milk. The ability to digest lactose was assessed by measuring the subjects' end-alveolar hydrogen concentration after they ingested 15 g of lactose in 250 ml of water. Subjects then received either 240 ml of lactose-hydrolyzed milk containing 2 percent fat or 240 ml of milk containing 2 percent fat and sweetened with aspartame to approximate the taste of lactose-hydrolyzed milk; each type of milk was administered daily with breakfast for a one-week period. Using a standardized scale, subjects rated the occurrence and severity of bloating, abdominal pain, diarrhea, and flatus and recorded each passage of flatus.

RESULTS

Twenty-one participants were classified as having lactose malabsorption and nine as being able to absorb lactose. During the study periods, gastrointestinal symptoms were minimal (mean symptom-severity scores for bloating, abdominal pain, diarrhea, and flatus between 0.1 and 1.2 [1 indicated trivial symptoms; and 2, mild symptoms]). When the periods were compared, there were no statistically significant differences in the severity of these four gastrointestinal symptoms. For the lactose-malabsorption group, the mean (+/- SEM) difference in episodes of flatus per day was 2.5 +/- 1.1 (95 percent confidence interval, 0.2 to 4.8). Daily dietary records indicated a high degree of compliance, with no additional sources of lactose reported.

CONCLUSIONS

People who identify themselves as severely lactose-intolerant may mistakenly attribute a variety of abdominal symptoms to lactose intolerance. When lactose intake is limited to the equivalent of 240 ml of milk or less a day, symptoms are likely to be negligible and the use of lactose-digestive aids unnecessary.

Lactose digestion and tolerance in adult and elderly Asian-Americans

Twenty adult (20-40-y old) and 20 elderly (> or = 65-y old) Asian-Americans subjects were evaluated for baseline lactose consumption, fecal beta-galactosidase activity, and lactose maldigestion to determine whether there were differences in lactose metabolism and tolerance between these groups. Fasted subjects consumed a challenge dose of 0.5 g lactose/kg body wt. Breath-hydrogen production and symptoms were monitored. There were no statistically significant differences in total hydrogen production (P < 0.6), flatulence (P < 0.6), or fecal beta-galactosidase activity between the two groups. Fecal beta-galactosidase activity did not correlate with prior lactose consumption. The shape of the breath-hydrogen curves suggests a slightly delayed transit in the elderly subjects, but apparently this delay was insufficient to alter tolerance. Thus, the findings suggest that these two groups do not differ in their metabolism and tolerance of lactose.