Albert D. Newcomer

Prospective Comparison of Indirect Methods for Detecting Lactase Deficiency

To compare sensitivity, specificity and convenience, four indirect methods of detecting lactase deficiency were tested prospectively in 25 subjects with biopsy-proved lactase deficiency and in 25 with normal lactase activity. After ingestion of 50 g of lactose, containing 1-14Clactose, breath hydrogen was abnormally elevated in all 25 lactase-deficient subjects (greater than 0.30 ml per minute at two hours); breath 14CO2 was below the normal range in 23, and in 19 the plasma glucose increased by less than 20 mg per deciliter. When lactose and ethanol were given together, the rise in plasma galactose remained less than 5 mg per deciliter in 24 of the lactase-deficient subjects. The specificity of the four tests was excellent, with only one false-positive plasma glucose test. Measurement of breath hydrogen is sensitive and specific, and does not require ethanol or isotopes. It is noninvasive, and is not influenced by gastric emptying or metabolic factors. We believe it to be the most suitable test for population screening for lactase deficiency.

Triolein Breath Test: A Sensitive and Specific Test for Fat Malabsorption

In order to develop a simple and accurate screening test for steatorrhea, the authors compared quantitative stool fat excretion with breath excretion of 14CO2 after the ingestion of 14C-labeled trioctanoin, tripalmitin, or triolein. The study group included 24 nonobese subjects without steatorrhea but with diarrhea secondary to irritable bowel syndrome and 40 subjects with steatorrhea. The triolein breath test provided the most reliable discrimination, with 100% sensitivity and 96% specificity. The trioctanoin and tripalmitin breath tests were sensitive, but lacked specificity (69% and 58% false-positive results, respectively). Three of the 12 obese patients with irritable bowel syndrome had false-positive triolein breath results. In detecting steatorrhea, the triolein breath test was moderately superior to the measurement of serum carotene and to qualitative stool fat. Thus, the triolein breath test appears to be a sensitive, specific, noninvasive, and relatively simple screening test for the detection of steatorrhea.

Lactase Deficiency: Prevalence in Osteoporosis

We determined the prevalence of lactase deficiency by analysis of respiratory hydrogen (H2) in 30 women with idiopathic postmenopausal osteoporosis and in 31 female control subjects without evidence of metabolic bone disease. Eight subjects with osteoporosis had breath H2 excretion greater than 0.20 ml/minute at 2 h after receiving 50 g of lactose and were considered lactase deficient; only one control subject was lactase deficient (P less than 0.05). Symptoms developed in seven of the nine lactase-deficient persons after receiving 50 g of lactose; in contrast, only three of the 52 lactase-normal subjects had symptoms. Although none of the lactase-deficient subjects was aware of milk intolerance, their intake of both lactose and calcium was significantly lower than that in the lactase-normal group. Lactase deficiency appears to be one of several factors that predispose to the development of osteoporosis, probably through diminished calcium intake and possibly through an effect on calcium absorption.

Calcium absorption from milk in lactase-deficient and lactase-sufficient adults

To determine whether lactose influences the absorption of calcium, the uptake of calcium from lactose-hydrolyzed milk and from unhydrolyzed milk was measured in 20 adults: 10 were lactase-deficient and 10 were lactase-sufficient as defined by breath hydrogen test, plasma glucose determination after oral lactose dose, and presence or absence of symptoms after lactose ingestion. On different days, each subject received either lactose-hydrolyzed or unhydrolyzed milk. Calcium absorption was measured by a double-isotope technique. In the lactase-deficient group, the mean absorptions were 33.5% from hydrolyzed milk and 36.2% from the same volume of unhydrolyzed milk (P>0.30). In the lactase-sufficient group, mean absorptions were 24.2% from hydrolyzed milk and 25.7% from unhydrolyzed milk. The mean calcium absorption from both lactose-hydrolyzed milk and unhydrolyzed milk was significantly greater (P<0.01) in the lactase-deficient group compared to the lactase-sufficient group, presumably reflecting lower dietary calcium intake in the former. These data indicate that, in lactase-deficient subjects, malabsorption of lactose does not affect calcium absorption.

Lactose tolerance tests in adults with normal lactase activity

Summary Thirty-six oral lactose tolerance tests were done in 18 healthy persons who had normal jejunal lactase activity at the ligament of Treitz. Each subject received both a 50- and a 100-g dose of lactose in solutions of different tonicity. An absorptive defect was ruled out in each subject. A rise in blood sugar of less than 20 mg per 100 ml (flat curve) above the fasting level was observed in 28% of the tests. Failure to obtain a blood sugar at 15 min would have resulted in flat curves in an additional 14%. Flat curves were obtained with the oral administration of both doses of lactose. Two subjects had flat curves after the oral administration of both doses and also after ingesting the component monosaccharides. Duodenal instillation of lactose in these two subjects produced a normal curve. This suggested that delayed gastric emptying contributed to a low rise in blood sugar after oral intake of lactose. The limitations in the use of the oral lactose tolerance test to diagnose lactase deficiency are apparent.

Absorption of nutrients in lactase deficiency.

The influence of malabsorption of lactose, as a result of primary lactase deficiency, on the absorption of the nutrients in milk was tested in four healthy controls and four subjects with lactase deficiency. An ileal perfusion technique was used to quantify arrival in the ileum of nutrients and a nonabsorbable marker (polyethylene glycol, PEG 4000) ingested as a test meal of milk. The meal was 250 ml of whole milk or milk in which the lactose had been hydrolyzed to glucose and galactose. In the fasting state, ileal flow of volume, protein, carbohydrate, and electrolytes was small and not different in controls and lactase-deficient subjects. Ileal flow increased in all subjects after the test meal of milk; more fluid and nutrient was recovered from the ileum in lactase-deficient subjects after whole milk than in control subjects or in lactase deficiency after hydrolyzed milk. Two deficient subjects showed marked malabsorption of lactose (35 and 50%); two did not. Protein, calcium, magnesium, and phosphorus were also recovered from the ileum in greater quantities in lactase deficients after whole milk. However, apart from decreased absorption of lactose, the nutritional consequences of malabsorption in association with primary lactase deficiency in adults are probably minimal.

Extrahepatic Portal Hypertension Caused by Chronic Pancreatitis

Abstract Of 164 patients with extrahepatic portal hypertension, only 5 had chronic pancreatitis as the only predisposing disease. Four of the five had bleeding from esophagogastric varices, and all...

Lactase deficiency: a common genetic trait of the American Indian.

Intestinal lactase activity was assessed indirectly in 156 American Indians by measuring breath hydrogen after an oral lactose load. Lactase deficiency was present in 66% of subjects and correlated highly with the percentage of Indian blood. Lactase deficiency was present by the age of 5 years and was unrelated to sex. Most lactase-deficient subjects (81%), but only a minority (23%) of lactase-sufficient subjects, developed symptoms after the oral lactose load, and among lactase-deficient subjects, symptoms occurred more frequently in adults than in children (P = 0.05). Indeed, by history, 53% of lactase-deficient adults, but only 10% of lactase-deficient children under 18 years of age, were aware of milk intolerance. Despite these differences, milk consumption was only slightly less (19 g) in the lactase-deficient subjects than in those with normal lactase activity (25 g) (P less than 0.05). The results indicate that lactase deficiency is a common autosomal genetic trait in the American Indian that becomes manifest in early childhood. Tolerance to dietary lactose appears to decline in the American Indian as he reaches adulthood, but in this population the decline in tolerance had only minor influence on lactose intake.

Abdominal Pain Caused by Diabetic Radiculopathy

In diabetes mellitus, pain and weakness in a lower extremity can result from lumbosacral radiculopathy. However, abdominal pain caused by a similar type of thoracic nerve root disease is not generally recognized. Four diabetic patients with abdominal pain were studied. In none of the patients was the actual cause--radiculopathy--suspected until after extensive negative diagnostic investigation, which frequently included invasive procedures. Their clinical features were suggestive of malignant disease. Electromyographic examination revealed the correct diagnosis, and all four of the patients had a spontaneous and complete recovery.

Diastolic bruit in chronic intestinal ischemia

Application of abdominal phonoangiography in patients with suspected chronic intestinal ischemia may be diagnostic or highly suggestive of vascular compromise. The importance of a diastolic abdominal bruit is illustrated in two patients with intestinal ischemia.