Millimolar obscurity: implementing SI units.
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Humans↗
Biomedical subjects
N W Flodin
Publications and source records attributed to N W Flodin.
Micronutrient supplements: toxicity and drug interactions.
Self-prescribed use of single micronutrients in excessive or pharmacologic dosage, without professional medical supervision, is on the increase. This raises potential problems of chronic toxicity and adverse interactions with prescribed and over-the-counter drugs. These questions are of special concern in the elderly, who utilize micronutrient supplements the most and at the same time have the greatest incidence of chronic illness and take the largest amount and variety of drugs. This review examines the toxicity and drug interactions of the thirteen vitamins and the trace elements chromium, selenium, and zinc.
Animals↗
Atherosclerosis: an insulin-dependent disease?
Evidence is reviewed that dietary habits in industrially developed countries, especially an increased frequency of ingestion of foods of high energy density, may contribute to excessive hepatic cholesterol synthesis and to a preponderance of lipogenic versus lipolytic effects on the arterial intima, thereby favoring the formation and progression of atheroma. These effects are mediated by the rise and fall of circulating insulin levels. The evidence is suggestive of the possibility that frequent and prolonged exposure of the arterial wall to high circulating levels of insulin may favor the development of atherosclerotic lesions. Research on diet-atherosclerosis relationships should take into account not only overall diet composition but individual meal composition and size and their effects on serum insulin levels, as well as meal spacing and the relative durations of absorptive and postabsorptive periods during the 24-hour daily cycle.
Arteries↗
New methods for comparing the biological efficiency of alternate nutrient sources.
The objective of this study is to propose new methods for the determination of biological efficiency (the ability of a nutrient to produce a response) and for comparison of the efficiencies of alternate nutrient sources. The proposed methods are based on a four-parameter kinetic model which describes response as a function of intake. The comparison of the abilities of two proteins (casein and soybean protein concentrate) to promote weight gain in weanling rats is presented as an example; however, the model is also useful for other nutrients (proteins, amino acids, vitamins, minerals, etc.) and other responses (blood enzyme or protein levels, tissue enzyme levels, etc.). Application of the method leads to useful comparisons of nutrient sources as well as information concerning the maximum efficiencies and rates of nutrient utilization from different sources.
Animals↗
General model for nutritional responses of higher organisms.
A general saturation equation is derived which is shown to describe a wide variety of nutrient-response relationships in higher organisms. Iterative multiple linear regression analysis is used to obtain least squares estimates of the constants defining theoretical nutrient-response curves. Curves thus generated accurately predict experimentally observed responses. From this treatment, response parameters are developed which are analogous to Vmax and Km of enzyme kinetics. It is proposed that this model be applied in evaluating nutritional requirements and in assessing the relative biological efficiency of nutrient sources.
Animals↗
Nitrogen balance responses of young men to lysine supplementation of bread.
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Bread↗
The problem of human protein requirements: some kinetic and metabolic considerations.
Estimated human protein requirements have been substantially lowered by FAO/WHO expert committees over the past two decades. The estimates and methods of calculation are considered in the light of the kinetics of response to protein intake, body protein turnover, amino acid flows in the body, and the concept of nitrogen (N) steady state. Whereas traditional methods of estimation have assumed an essentially linear (first order) response of N retention to absorbed N, animal studies show that response to graded protein intakes obeys saturation kinetics. Corrections for protein quality have also assumed a linear relation between response and supply of limiting amino acid, while animal experiments indicate that this response likewise follows saturation kinetics. Evidence is lacking that the present minimum protein standards for humans can support acceptable internal nitrogen steady states at any age above infancy or foster normal growth in the child. New research approaches to determination of protein requirements are suggested , including study of the kinetics of human response to graded protein intakes and graded variations of quality; development of indicators of nitrogen steady state and correlation with clinical status; and determination of optimum protein-energy ratios by age and sex.
Amino Acids↗