Deliberations and evaluations of the approaches, endpoints and paradigms for magnesium dietary recommendations.

The working group on magnesium considered a number of issues relevant to establishing allowances and to providing other pertinent information on this ion for the next edition of the Recommended Dietary Allowances (RDA). An accurate and specific marker for assessing the importance of magnesium nutriture in health and disease remains to be identified. Thus, it is unknown whether marginal magnesium depletion results in a disease. Although it is apparent that abnormal serum concentrations are unusual and obvious signs of acute depletion of magnesium are absent in the U.S. populace, one cannot assume that the associated cellular and intracellular pool sizes are optimal for health. There is a need for systematic studies of these and other parameters in healthy individuals with controlled intakes and during depletion. To address the question of how magnesium allowances should be set, previous editions of the RDA that included magnesium were reviewed; this review indicated the need for the adoption of objective criteria for acceptance of published balance studies and the inclusion in the discussion of an analysis of the balance studies and the specific calculations used in establishing the RDA. Such criteria and evaluations should be placed in a technical addendum to allow readers to evaluate the data. It is recommended that future RDA Committees consider expressing metabolic balance data on a basis other than weight, e.g., energy expenditure, lean body mass or body cell mass. Claims that magnesium nutriture has a role in preventing or ameliorating chronic disease such as heart disease and hypertension need to be critically evaluated if they are to be used to set the next RDA. The pharmacologic effects of magnesium are significant and need to be recognized. Because excess oral magnesium can be toxic to persons with advanced renal disease, more attention should be given to this topic by future RDA Committees.

National Dairy Council Award for Excellence in Medical and Dental Nutrition Education Lecture, 1994: nutrition education in medical schools--the prospect before us.

The criteria usually used for evaluating the state of nutrition education in our medical schools include the numbers of schools with required nutrition courses, attendance at nutrition electives, student satisfaction with their nutrition teaching, and the number of postgraduate clinical nutrition programs. These criteria indicate either no change or actual decreases over the years. More important, barriers persist that exclude essential nutrition education for all students in the clinical years. This pessimistic evaluation is tempered by events that, if properly addressed, may lead to improvement. Changes in the traditional medical curriculum are occurring in an increasing number of schools. More curriculum planning, execution, and oversight by interdepartmental faculty (problem-based and small-group learning); a greater emphasis on health promotion and disease prevention; and expansion of primary care offer the potential for more emphasis on nutrition education. This will not happen automatically but requires a vigorous effort by the Society and its members to become involved in the reform movement.

Liver dysfunction associated with long-term total parenteral nutrition in patients with massive bowel resection.

Sixteen patients with massive bowel resection receiving long-term home total parenteral nutrition (HTPN) for 31 to 145 months were reviewed for evidence of liver disease. Patients were divided into three groups: group 1 with duodenocolostomy (n = 3), group 2 with an estimated 15-43 cm residual small bowel (n = 7), and group 3 with an estimated 55-120 cm residual small bowel (n = 6). Two patients in group 1 developed liver cirrhosis; one was diabetic and died of sepsis and liver failure at the 88th month on HTPN; the other died of lung cancer at the 46th month on HTPN. The third patient, followed for 33 months, had transient severe liver function abnormalities associated with a blood transfusion. In groups 2 and 3, only one patient (with a history of probable liver disease before HTPN) developed biopsy-proven cirrhosis at the 60th month of HTPN. All four patients with clinically apparent liver disease developed persistent elevation of serum aspartate aminotransferase (AST) early in HTPN. Four other patients (all in group 3) with abnormal AST values in the early phase of HTPN normalized them later; they did not develop clinical liver disease over a mean follow-up time of 110 months (range, 39-152). None of the remaining eight patients (seven in group 2 and one in group 3) had significant liver function test abnormalities and none developed clinical liver disease over a mean follow-up period of 72 months (range, 39-120).(ABSTRACT TRUNCATED AT 250 WORDS)

Chromium content of total parenteral nutrition solutions.

Chromium (Cr) present as contaminant was analyzed by flameless atomic absorption spectrometry in a variety of commercially produced solutions and additives commonly used in total parenteral nutrition (TPN) formulas. Total Cr likely to be administered unintentionally per day was estimated both by summing the Cr in appropriate volumes of each solution required for preparation of standard TPN formulas and by analyzing complete TPN solutions. Storage of TPN solutions in plastic bags for 14 days did not affect Cr concentrations. The amounts ranged from 2.4 to 8.1 micrograms/day for a high glucose formula and 2.6 to 10.5 micrograms for a high lipid formula. Amino acid solutions, especially when containing phosphate, or with phosphate salt additives and with lipid emulsions accounted for approximately 85 to 90% of the Cr found.

Nutrition in the curriculum: medical experience.

Nutrition in the Curriculum--Medical experience, current practices, and educational status in U.S. medical schools are briefly reviewed. There continues to be a need for more adequate instruction of clinical nutrition to physicians in training and in practice. A major problem is the failure to provide patient oriented, case-related, nutrition teaching in the clinical years to all clinical clerks. Desirable changes are listed to help achieve better training in this field.

Serum lipoproteins in home total parenteral nutrition patients.

Patients maintained in our home total parenteral nutrition (HTPN) program receive very small amounts of cholesterol in their solutions. Because of the severe intestinal insufficiency which is characteristic of this group, they do not absorb significant amounts of cholesterol or bile salts from their intestines. We investigated the serum lipoproteins in nine patients maintained on HTPN for 36 +/- 4 (mean +/- SEM) months. Fat emulsions were given twice a week as a source of essential fatty acids. Mean serum cholesterol 110 +/- 6.5 mg/dl, LDL-cholesterol 75 +/- 6 mg/dl, and HDL-cholesterol 29 +/- 1 mg/dl, were at or below the 5th percentile compared with age- and sex-matched Lipid Research Clinic controls. HDL-cholesterol to serum cholesterol ratio was in the normal range (0.25 +/- 0.30). The mean serum cholesterol did not rise, but the mean serum triglyceride rose significantly from 72 +/- 4 to 104 +/- 16 mg/dl (p less than 0.05) immediately after completion of TPN infusions with fat emulsions. There was a negative correlation between the length of HTPN therapy and the total serum cholesterol (r = 0.43, p less than 0.05). Thus, HTPN patients have markedly depressed concentrations of total serum cholesterol, LDL-cholesterol, and HDL-cholesterol, but the ratio of HDL cholesterol to total serum cholesterol is in the normal range.

Bone disease in prolonged parenteral nutrition: osteopenia without mineralization defect.

A metabolic bone disease characterized by a mineralization defect, low plasma 1,25(OH)2D, and hypercalciuria has been described in patients receiving prolonged total parenteral nutrition (TPN). Because the practice of TPN differs from center to center, we investigated 13 home TPN patients to determine whether they had similar or different bone abnormalities. They had received TPN for a mean period of 51 +/- 38 mo. Bone pain occurred in six patients and two had multiple vertebral and rib fractures (with trauma in one patient). Bone pain was mild to moderate and not incapacitating. Bone histomorphometry showed reduced bone volume, reduced osteoid with normal resorption and calcification rates. These abnormalities were associated with hypercalciuria, but the plasma levels of 1,25(OH)2D were normal. Abnormalities in bone metabolism in this group of patients suggest a fundamental decrease in bone matrix-formation rather than a mineralization defect as the underlying mechanism.

Blood vitamin levels of long-term adult home total parenteral nutrition patients: the efficacy of the AMA-FDA parenteral multivitamin formulation.

Although the AMA-FDA parenteral adult multivitamin formula is now widely used, there are no published data on the efficacy of this formulation in maintaining adequate vitamin nutriture in patients on long-term parenteral nutrition. Blood levels of its constituent nutrients were determined in 16 clinically stable home total parenteral nutrition patients with severe gastrointestinal dysfunction, the majority of whom had been on home total parenteral nutrition for 1 to 9 yr and most of whom were ingesting some food orally. The daily formula (MVI-12) was added to the basic total parenteral nutrition formula in 2-day batches; the vitamins were thus infused approximately 3 hr after preparation on day 1 and after 27 hr on day 2. The duration of infusions was from 8 to 16 hr. Blood was drawn approximately 36 hr after completion of the last vitamin infusion. Plasma, trichloroacetic acid-treated plasma, and whole blood were frozen until analyzed for the vitamins by microbiologic or chemical methods. All vitamin levels, except for vitamin D metabolites, were measured four times in each patient between the 4th and 36th wk while receiving daily MVI-12. Single determinations of 25-OH and 1:25 (OH)2 vitamin D were made in eight of the 16 patients between the 61st and 84th wk while on MVI-12. Repeat values during this extended period were also made on five of the patients for vitamins A and E. These values were compared with serum vitamin levels obtained on an earlier formulation (MVI concentrate, Berocca C, and folate each given twice weekly and B12 given once weekly). The AMA-FDA formula given daily maintained blood levels above the lower normal limits for most of its constituent vitamins and vitamin D metabolites for the great majority of stable home total parenteral nutrition adults with unexplained occasional exceptions. However, almost half of the vitamin A levels and some of the pantothenate and biotin values were above the normal range; these tended to be associated with the presence of renal disease. Ascorbic acid and thiamin levels tended to be clustered in the lower normal range. Because of evidence for loss of ascorbic acid standing in total parenteral nutrition solutions for 24 hr prior to infusion, it is recommended that the vitamin formulation be added to the total parenteral nutrition solution just prior to infusion.