International journal for vitamin and nutrition research. Supplement = Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Supplement最新文献

Oral application of elevated dosages of vitamin B1, B6 and B12 have been found to improve target shooting in marksmen, recruited from a local pentathlon association, in two different studies. Study 1 was performed in an open controlled design, whereas in study 2 the group treated with B-vitamins was compared in a double-blind fashion with a placebo control group including 8 by 8 volunteers and 10 by 9 volunteers, respectively. The volunteers were randomly assigned to the groups. Performance quality was followed in both studies over a period of 8 weeks, while participants were continuously supplied with a combination of vitamins B1, B6 and B12 (Neurobion or Neurobion forte; E. Merck, Darmstadt, and Cascan, Wiesbaden, Germany). In both studies, marksmen in the vitamin-treated groups showed statistically significant, considerably improved firing accuracy as measured by the number of points achieved within a series of 20 shots at each examination. In study 2 the degree of improvement was linearly dependent on the duration of vitamin treatment, whereas the placebo-treated group, similar to the untreated control group in study 1, did not show any prominent change. Performance quality in marksmenship closely correlates with the magnitude of physiological tremor. Tremor can also be involved in the regulation quality of sensory-motor control systems. Thus, an improvement in firing accuracy as found in both studies is by the same token an improvement of fine motor control of slow movements, involving, for example, basal ganglia.(ABSTRACT TRUNCATED AT 250 WORDS)

N-Nitroso compounds are known to form endogenously in the human stomach from the precursors nitrite as well as secondary and tertiary amines. Ascorbic acid has been found to be an effective blocking agent for this process of formation of carcinogenic substances, both in vitro and in vivo. The mechanism by which ascorbic acid reacts is chemical in nature and results in the formation of NO and dehydroascorbic acid. Since NO can be recycled in the presence of O2 to form [NO]x, which is capable of additional nitrosation, greater than stoichrometric amounts of ascorbate are required for effective inhibition in vivo. The efficacy of ascorbic acid for inhibition of nitrosamine formation in humans has been demonstrated both clinically and epidemiologically through the use of "Nitrosoproline Test"--of Ohshima and Bartsch.

Without vitamin D supplementation, the majority of infants seems to be at risk of vitamin D-deficiency rickets. On the other hand, routine vitamin D supplementation of breast-fed infants is not recommended by all authors. In this paper we give an overview of vitamin D metabolism and vitamin D regulation in newborns, which may differ in a certain way from the regulation in adults. Based on this, minimal and optimal requirements for vitamin D in newborns and infants is determined. Furthermore, the paper aims at defining dosages and conditions that are at risk of vitamin D intoxication.

Concepts of vitamin B6 megatherapy are classified in three categories: 1. megatherapy with well-known mechanism of action; 2. megatherapy with hypothetical or unknown, but nevertheless plausible mechanism of action; 3. megatherapy on the basis of pure speculation. Examples of all three categories are shown. The dosages applied extend from 100 mg up to several grams; the duration of treatment varies from weeks to several years. After long-term intake of high doses toxic effects can occur in the form of peripheral sensory neuropathy, in two reported cases combined with a subepidermal vesicular dermatosis. The threshold above which toxic effects can occur appears to be somewhat between 300 and 500 mg/day; however, systematic investigations in this dose range have never been performed. Furthermore, there appears to be an inverse relationship between the dose and the time up to the occurrence of toxic symptoms. The danger consists less in controlled application by a physician as far as he is aware of the clinical picture of sensory neuropathy. Doses in excess of 500 mg are rarely necessary in specific indications. Unlike this situation, self-medication by laymen on the basis of promises in obscure health magazines is much more risky because the dose is frequently raised more and more up to several grams per day when the expected effect does not occur.

Iron requirements remain the same despite the current lower energy requirement. This means that more iron must be absorbed per unit energy. A higher bioavailability of the dietary iron can be achieved by increasing the content of food components enhancing iron absorption (ascorbic acid, meat/fish) or by decreasing the content of inhibitors (e.g., phytates, tannins). The latter is not feasible considering the recent and reasonable trend toward increasing the intake of dietary fibre. The key role of ascorbic acid for the absorption of dietary nonheme iron is generally accepted. The reasons for its action are twofold: (1) the prevention of the formation of insoluble and unabsorbable iron compounds and (2) the reduction of ferric to ferrous iron, which seems to be a requirement for the uptake of iron into the mucosal cells.