Test meals

Gastric tube meal ingestion — gastric sampling x 

Post-pyloric lumen Occluding balloon Re-injection lumen 

Different complete test meals containing proteins, carbohydrates and lipids have been tested for measuring digestive hpase secretions and hpolysis levels in the CI tract. Shak Iso (initially from Sopharga Laboratories, later from Nestle Chnical Nutrition, France) was used as a complete hquid test meal. A standard 375 mL 

In addition, a non-absorbable marker, polyethylene glycol (PEG 4000, 10 g/L) was added to each meal in order to estimate the percent recovery of the meal and to adjust the volumes at the end of the test meal digestion (Borgstrom et al., 1957). This marker also allowed to estimate the rate of gastric emptying, the volume of gastric contents and the pyloric outputs of HGL and hpolysis products (Carriere et al., 1993 a). 

The importance of the physical state of the lipids in the meal was demonstrated by measuring in vitro the specific activities of HGL and HPL on the triglycerides of the liquid and the mixed liquid-solid test meals. HPL was found to display a higher activity on the pre-emulsified TG of Shak Iso (43-47 U/mg) than on the TG found in the mixed hquid-solid meal (12-15 U/mg) (Carriere et al., 2000). As will be shown below (section 10.7), these observations were essential to understand the mechanism of hpolysis inhibition by the hpase inhibitor orhstat . 

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J. Pollack, J. M. Campbell, S. M. Potter, and J. W. Erdman, Mongolian gerbils (Meriones unguiculatus) absorb beta-carotene intact from a test meal, J. Nutr. 124 (1994) 869-873. 

In studies on test meals, Walker et al. (32) discovered that the calcium of Swiss chard, which has a high oxalic acid content, was poorly absorbed. Children excreted more calcium during the 6 hours after a test meal of milk, Pumpkin leaves, cassava leaves, or pigweed leaves than after Swiss chard. All supplements contained 200 mg calcium. 

In the studies on humans there appeared to be decreased calcium balances when 200 g or more of spinach per day was included in the diet. In two of the studies in which women were fed spinach, calcium intakes were below the Recommended Dietary Allowance of 800 mg/day (37). Some studies were conducted for short period of a week or less, which may not be sufficient time to adjust to a change in diet. From measurement of calcium excretion in urine after a test meal, it was shown that the calcium in oxalate-containing vegetables was less well-absorbed than that of milk or of vegetables not containing oxalic acid. However, this would not necessarily affect calcium balance, since the total amount of calcium in the diet would have to be considered. The effect of a combination of oxalic acid and fiber on calcium bioavailability should be further investigated. 

Results from some recent studies (19-36) on the effects of fiber are summarized in Table I. For the most part, the results are from multi-day balance studies. However, Turnland et al. (36) used the stable isotope fecal monitoring method to assess zinc utilization and Simpson et al. (24) measured iron absorption from a single test meal. 

Utilization of iron was not affected at levels of 9 to 26g bran/day from corn or wheat (19, 2J0 2 ) or bY 16 g of bran/day (25). Negative balances were observed by Morris and Ellis (21) during the first balance period with daily intakes of 36g bran but not during the second 5-day balance period. However, Simpson et al. (24) found a marked inhibition of non-heme iron absorption from a single test meal which included 6 g of wheat bran. With a diet which provided 35g/day of NDF (neutral detergent fiber from bran bread), iron balances were decreased (26) compared to the 9 or 22g/day intake levels. 

Simpson et al. (24) did not observe increased non-heme iron absorption when dephytinzed bran was included in a test meal compared to the non-dephytinized bran. Removal of phytic acid from soy protein likewise did not improve non-heme absorption (38). Decreased iron balances, observed by Bodwell et al. (40) with soy isolate diets, did not appear to be associated with the level of phytic acid a tendency for zinc balances to decrease with increased phytic acid was observed. 

Gillooly et al. (42J observed that iron absorptions were markedly decreased by the additon of sodium phytate to test meals while similarly marked decreases in zinc absorption have been observed (36,43 Table II). Contradictory results were recently reported (23.44). Addition of high levels (1.5 to 2.9g/day) of sodium phytate did not significantly affect the apparent absorption of iron, manganese, copper or zinc. 

In a series of studies, Cook and co-workers (48,49,50) observed a marked decrease in non-heme iron absorption when soy protein was added to beef or protein mixtures or when soy protein was consumed as the primary protein source in test meals and compared to the effects of including egg albumen or beef alone in the test meal (Table III) Hallberg and Rossander (38J, however, found less of an effect when total iron absorption (heme plus non-heme iron) was considered. Likewise, in a study in which reconstituted textured soy was used to replace 30% of the beef, the absorptions of total iron were not greatly altered (51). In a study by Stekel et al. (52), replacing part of the beef with soy isolate or adding hydrated isolate to beef decreased non-heme iron absorption from 12.4% to 9.2 and 9.3%, respectively. In a related study, non-heme and total iron absorptions were low when soy isolate was the major protein source. 

Hallberg and Rossander (38) fed 9 or 10 subjects a basal test meal containing maize, rice and black beans or the same meal with beef or soy flour added. 

Infant food supplements (corn, soy, whey and/or wheat protein blends) given in test meals to 3 or 14 adult men... 

Added 100 mg ascorbic acid to soy isolate or egg albumen semipurified test meals 9 adult men... 

Semi-purified test meals, fed to 7 men contained (a) soy isolate, (b) soy isolate,... 

Series of studies with test-meals in which the major protein sources were (g protein and source) (a) 14g, beef, (b) 7g, beef,... 

Lynch et al. (5 7) found non-heme iron absorptions, as measured by single test meals, for black beans, lentils, mung beans split peas, and whole soybeans to be low (0.84 to 1.91%). This suggests that many commonly consumed legumes are poor sources of iron whether legumes other than soy may have an "offsetting" enhancing effect on heme-iron absorption cannot be predicted. 

Sandstrom and Cederblad (39) fed single test meals of chicken, beef, chicken or beef plus soy flour or soybeans. The amount of zinc in the test meal affected absorption (Table IV) but not soy flour per se. Higher levels of zinc resulted in lowered absorptions. 

As noted above, disagreement has often been observed among different studies on the effects of fiber, phytic acid and protein source on mineral utilization. Some possible reasons include (a) estimates of absorption from single meals (with or without previous consumption of the same foods used in the test meal which may also affect results) may not always be equivalent to results from multi-day balance studies, (b) in balance studies, the failure to allow sufficient time (e.g., 1-2 weeks or more) for adaptation may alter the findings, (c) variations in the compositions of meals or diets, including mineral levels, between studies may influence the results obtained, and (d) the persons used as subjects vary and this may have an affect. In addition, in the fiber studies, the levels, types, and particle size of fiber fed have varied widely and levels of other possibly confounding components (e.g., caffeine, tanins, oxalates) may have differed. 

Bennink R, Peeters M, Van den Maegdenbergh V, Geypens B, Rutgeerts P, De Roo M, Mortelmans L. Evaluation of small-bowel transit for solid and liquid test meal in healthy men and women. Eur J Nucl Med 1999 26 1560—1566. 

In another study in which the test meal procedure was used,59 "true achlorhydria" was found in about 3 per cent of the younger men, but the incidence increased up to 23 per cent for men between 60 and 69 years old. Corresponding values for women were about the same for the younger group, but the incidence was 26 to 28 per cent in women between 60 and 70. Presumably the lack of hydrochloric acid would show a much higher incidence in older people if the fasting juice or the first collection of histamine juice were analyzed. 

The test Ca source was always consumed at the midpoint of a neutral test meal with no food post-load (4 h). 

Bioavailability of starch. Cooked rice was administered to colectomized rats by gastric intubation and the recovery of starch in the ileal digesta measured after 10 hours of ingestion. Significant starch (11-15%) was recovered from animals fed peas, lima beans, or kidney beans 0.2-0.4% of starch from rice. Oligosaccharide extraction, the size of the test meal, and the amount of starch did not affect starch biovailability . cAMP accumulation. Methanol extract of the grain, in cell culture at a concentration of 1 mg/mL, was active on mast cells " . 

Some (Geracioti and Liddle, 1988 Pirke et ah, 1994), but not all (Philipp et ah, 1991) studies have shown that bulimics have reduced plasma CCK after a test meal. Lower-than-average basal levels of CSF CCK have also been found in women with BN (Lydiard et... 

FIGURE 5.2 Compound A total exposure (AUC) increase under fed condition is fat content dependent in test meals. 

Radioisotopes 55Zn-labeled corn products were served once in the form of corn flakes and once in the form of corn grit cereal to each volunteer. At the time of feeding the radioactively labeled cereal, a portion was measured to obtain the desired level of radioactivity and then the corresponding unlabeled product was added to obtain the total desired weight of cereal. Each test meal contained 0.1-0.5 pCi 65Zn. 

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