United Sciences of America, Incorporated: an "optimal" diet?

The diet plan marketed by the United Sciences of America, Incorporated (USAI) claims to offer "optimal nutrition" for the health of Americans. This claim raises the question, what is an "optimal" diet? Analyses of the four diet products--a fiber energy bar, an omega-3 fatty-acid concentrate, a calorie-control formula, and a master formula of mixed ingredients--raise questions regarding safety and efficacy of this plan. Still further questions focus on endorsement of the USAI diet plan and the relation of endorsement to receiving "grants" from the producer.

Intestinal adaptation. Different growth responses to disaccharides compared with monosaccharides in rat small bowel.

Midgut infusions of sucrose and other disaccharides were compared with monosaccharides for their effects on intestinal mucosal growth in rats otherwise maintained on total parenteral nutrition for 7 days. Mucosal mass progressively increased in a proportional relationship to the concentration of infused sucrose. At equal concentrations by weight, disaccharide infusions stimulated mucosal growth more than monosaccharides. Disaccharide-induced mucosal adaptation was abolished when there was no hydrolysis of the disaccharide. The results suggest that the functional work load of absorbing epithelium, including the "work of hydrolysis," plays an important role in the stimulus for intestinal adaptation.

Relationship between enteral glucose load and adaptive mucosal growth in the small bowel.

Infusion of hyperosmolar glucose solutions into small bowel will prevent mucosal atrophy or stimulate mucosal growth in rats otherwise maintained on total parenteral nutrition (TPN). It is not certain whether this growth effect is related to the osmolarity of the solution or its total molecular load. Therefore, various concentrations of glucose and sodium salt solutions were studied for comparative effects on growth of small bowel mucosa. Male Sprague-Dawley rats (240 g) were maintained on TPN and infused continuously with either glucose or sodium chloride (2 and 0.6 ml/hr) or sodium sulfate (0.6 ml/hr) via a catheter placed in the mid-small intestine. Concentrations of infusion solutions ranged in osmotic pressure from 300 to 1500 mosmol/liter. Controls were TPN rats without infusion of any solution. Over a seven-day period, TPN rats receiving mid-gut infusions of 300 mosM saline gained 18.4 g in body weight. In TPN rats receiving mid-gut infusions of progressively greater concentrations of glucose, the additional total kilocalories per day resulted in greater body weight gain compared with the saline controls. After seven days, rats were killed, the small bowel removed, and divided into eight equal segments (segment 1, duodenum; segment 8, terminal ileum). Segment weight, mucosal weight, DNA, and protein concentration per segment were measured. Mid-gut infusions of 900 and 1500 mosM glucose solutions progressively increased mucosal mass in segments downstream from the site of infusion compared with 300 mosM glucose in water or 600 mosM glucose in saline which did not differ from any of the salt solutions or TPN alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiography of ileal adaptation in the rat following jejunectomy.

Six Sprague-Dawley rats were evaluated radiographically and histologically for adaptive changes in the ileum following total jejunal resection. Additionally, six rats were used as controls and six rats had sham operations. Marked hypertrophy of the ileum and hyperplasia of the mucosa with thickening of the ileal wall were documented in all six of the jejunectomized rats, compared with sham and unoperated controls. Radiographic changes were demonstrated in the bowel wall in three of six resected animals. These consisted of an irregular, serrated lumen that was normal to narrowed in caliber. No radiographic or histologic changes were seen in the control or sham rats. These results correlate radiographic changes with adaptive morphology of rat ileum after jejunal resection and resemble changes of adaptation seen in humans who have had jejunal-ileal bypass, jejunal resection, or nontropical sprue.

Adaptation of the ileum in nontropical sprue: reversal of the jejunoileal fold pattern.

Seven cases of nontropical sprue (gluten enteropathy) are described in which there was an increase in the ileal fold pattern depicted on barium examination of the small bowel. In five of these patients there was a decrease in the jejunal fold pattern. This combination created a reversed appearance of the normal small-bowel radiographic pattern. This is a distinctive pattern for nontropical sprue and reflects the chronic inflammation and atrophy of the jejunum and compensatory hypertrophy (adaptation) of the ileum. This usually indicates long standing disease and should heighten awareness to potential malignant complications.

Development of core competencies in clinical nutrition.

A nationwide survey of core competencies of nutrition knowledge and skills that primary care physicians should know and/or be able to do has been completed. Nutrition competencies were synthesized from a review of clinical nutrition practices as reported in the medical literature and by medical school faculty group discussions. A nutrition competency questionnaire was sent to 445 practicing physicians and to 752 department chairpersons in every US medical school in the disciplines of family practice, medicine, obstetrics and gynecology, pediatrics, psychiatry, and surgery. The overall response rate for practitioners and faculty combined was 46.03%. Of the 55 nutrition competencies, 28 items received very strong support (greater than 90% of respondents marked agree or completely agree). Twenty-two competencies received strong support (80 to 89% of respondents marked agree or completely agree), and five items received mixed support (40 to 79% of respondents marked agree or completely agree). Statistical comparisons of the item responses between practitioners and faculty were significantly different (p less than 0.05) on 19 (35%) of the items. It is anticipated that the 50 nutrition competencies that have received strong or very strong agreement among the 551 physicians representing primary care disciplines across the US will serve as guidelines for continued development of medical school curriculum and continuing medical education in clinical nutrition.

Scanning electron microscopy of intestinal metaplasia of the human stomach.

Biopsy samples of gastric mucosa were obtained at endoscopy from patients suspected of having intestinal metaplasia. These samples were prepared for light microscopy and scanning electron microscopy. Observations of the luminal surface of the gastric mucosa in the scanning electron microscope revealed distinct topographic differences in the intestinalized and nonintestinalized regions. The latter area showed features consistent with those described in chronic gastritis, i.e., the exaggeration of the "cobblestone relief" appearance of the luminal surface of the stomach and the presence of numerous short, stubby, bulbous microvilli which project from the free border of the surface mucous cells toward the lumen of the stomach. The intestinalized region revealed a plush microvillous (striated) border periodically interrupted by apical openings of goblet cells. The scanning electron microscope is a useful research aid for examination of cell membrane expressions of the surface cells of the gastric mucosa not totally appreciated by light microscopy and transmission electron microscopy.

Effect of diverting bile and pancreatic secretions into the ileum on small bowel mucosa in rats fed a liquid formula diet.

The long-term effects of diverting bile and pancreatic secretions directly into the ileum on small bowel mucosa was determined in rats fed a hydrolyzed liquid formula diet. Male Sprague-Dawley rats were divided into four experimental groups: duodenal papilla transplant-sham operation, transplantation of the duodenal papilla into the ileum, bile duct sham operation, and transplantation of the bile duct into the ileum. After 28 days, animals were killed, the same bowel removed, rinsed with cold isotonic saline, and divided into six segments (two jejunal segments and four ileal segments). The mucosa of each segment was weighed and assayed for DNA and protein concentration, and specific activity of sucrase and maltase. Bile and particularly pancreatic secretions diverted into the ileum stimulated local mucosal growth compared with their respective controls. The absence of pancreatic secretions from the jejunum also was associated with an increase in jejunal mucosal mass. Diverting pancreatic secretions into the ileum decreased ileal sucrase and maltase specific activity while the absence of both bile and pancreatic secretions from the jejunum increased jejunal sucrase specific activity. The results suggest that bile and pancreatic secretions entering the ileum are important factors in stimulating ileal mucosal hyperplasia while the absence of these secretions from the proximal intestine is associated with greater jejunal mucosal growth. The mechanisms regulating jejunal mucosal growth appear to be different than those influencing the ileum.

Permeability of adolescent rat intestine to pancreatic ribonuclease.

There are indications that exocrine pancreatic enzymes may undergo an enteric recirculation. Ribonuclease (RNase) is present in considerable quantities in pancreatic exocrine secretions. Therefore we studied the intestinal transport of pancreatic RNase using everted gut sacs from duodenum, midgut, and ileum of young rats. Gut sacs were incubated aerobically at 37 degrees C, 22 degrees C, and 0 degrees C, and anaerobically at 37 degrees C. Measurable amounts of RNase crossed the intestinal barrier, but neither duodenum, midgut nor ileum absorbed RNase preferentially. The experimental data favor simple diffusion of RNase across rat small bowel. However, the amounts of pancreatic RNase absorbed were small. Thus, while our data do not negate the concept of an enteropancreatic recirculation in the rat, only a minor quantity of luminal, pancreatic RNase could recirculate.

Non-hormonal regulation of intestinal adaptation.

Infusion of simple sugars and some amino acids into the lumen of the small bowel stimulates local mucosal growth where these substrates come into direct contact with the mucosa. This stimulation does not require active absorption or mucosal metabolism of the substrate and in the case of glucose can be inhibited by phlorizin. Infusion of sugars and some amino acids into ileal lumen results in mucosal growth of proximal bowel distant from the site of infusion. Diverting pancreatico-biliary secretions from proximal to distal small bowel lumen markedly stimulates growth in distal small bowel, while the absence of these secretions from the duodenojejunum paradoxically results in growth of the mucosa at this site. Such regional differences in adaptation suggest that regulation of mucosal growth is different in proximal and distal small bowel.

Effects of octapeptide-cholecystokinin, secretin, and glucagon on intestinal mucosal growth in parenterally nourished rats.

Nutrients in the lumen of the small intestine may cause the release of enteric hormones which directly or indirectly stimulate intestinal mucosal growth. Male Sprague-Dawley rats with either an intact small bowel or following jejunal resection were maintained on total parenteral nutrition (TPN). C-terminal octapeptide-cholecystokinin alone or combined with secretin, or glucagon alone were added to the intravenous nutrient solution and continuously infused. Control rats received only TPN or gastric infusion of isocaloric amounts of TPN solution. After 7 days, intestinal hypoplasia was noted in rats with an intact bowel maintained on TPN alone compared with the gastrically infused group. TPN did not maintain the proximal-distal gradient of mucosal mass. Continuous intravenous infusion of octapeptide-cholecystokinin alone and together with secretin in rats maintained on TPN significantly stimulated small bowel mucosal growth, partially restoring the proximal-distal gradient. Glucagon infusion did not stimulate mucosal growth. Rats with a jejunal resection and maintained on TPN for 7 or 14 days failed to develop mucosal hyperplasia of the ileum in contrast to rats given the TPN solution intragastrically. Continuous intravenous infusion of octapeptide-cholecystokinin in rats maintained on TPN after jejunal resection caused significant mucosal growth in the ileum compared with the rats maintained on TPN alone, but not to the extent seen in gastrically fed animals. Intravenous infusion of octapeptide-cholecystokinin stimulates small-bowel mucosal growth. Secretin appears to have an additional effect when given together with octapeptide-CCK. Although a direct trophic action by these hormones on the intestinal mucosa is possible, this effect is more likely mediated via stimulation of pancreaticobiliary secretions.

Stimulation of mucosal growth by gastric and ileal infusion of single amino acids in parenterally nourished rats.

The effect on the intestinal mucosa of continuously infusing single amino acids, glycine, valine and histidine into the stomach and ileum was compared with saline and an amino acid mixture (AA) in rats fed to parenteral nutrition. After gastric infusion, glycine did not differ from saline, valine increased mucosa in the proximal segments and histidine alone increased mucosa in the proximal bowel equal to AA. After ileal infusion, all amino acids increased mucosa in the ileum. Valine and histidine, but not glycine, increased mucosa in the remote proximal small bowel. Therefore, regional differences occur in mucosal growth response to single amino acids.

Comparative study of nutritional adaptation to defined formula diets in rats.

Little is known about the specific effects of defined formula diets (DFD) on mucosal growth of the small intestine, pancreas, or liver. In the present study male Sprague Dawley rats weighing 220 to 250 g were fed isocaloric amounts of DFD (61 kcal/day) by continuous intragastric infusion. The diets fed were Vivonex, Vivonex-HN, Flexical, and Ensure. Oral chow-fed rats with intragastric water infusions served as reference. All groups gained weight: chow 50.50 g, Vivonex 21.17 g (P < 0.005), Vivonex-HN 25.40 g (P < 0.005), Flexical 30.5 g (P < 0.01), Ensure 39.29 g (NS). After 2 weeks rats were killed, the small bowel excised, rinsed, and divided into eight equal segments. Mucosal weight, DNA, and protein concentration per centimeter segment were measured. The pancreas was also removed, homogenized, and amylase activity assayed (units/g). Livers were excised, weighed, lipid content measured, and liver histology was examined by light microscopy. Mucosal weight, DNA, and protein concentrations per segment were decreased significantly in most bowel segments of DFD fed rats. Amylase activity per gram pancreas was significantly reduced in rats fed Vivonex, Flexical, and Ensure, Serum amylase activity was also lowered in animals on DFD. There was significant accumulation of lipid in the liver of Vivonex and Flexical animals (P < 0.01). Liver histology confirmed the striking increase in fat in the Vivonex and Flexical groups. These effects may result from differences in DFD absorption, mucosal metabolism, stimulation of enteric hormone release, and/or bile and pancreatic secretions.