Chemistry Reference
In-Depth Information
13.10.
Selected Actual Publications of Meta-analyses
Concerning More Than One of the B-Vitamins
To evaluate the disappearance of supplementary B-vitamins before and from
the small intestine, four lactating Holstein cows were equipped with ruminal,
duodenal and ileal cannulas and supplemented with a number of B-vitamins
either with the food 5 days before and during a 4-day collection period or by
post-ruminal infusion 1 day before and during a 4-day collecting period; the
concentrations of the vitamins were (in mg day
-1
) thiamine: 300 and 10;
riboflavin: 1600 and 2; niacin: 12,000 and 600; vitamin B6: 800 and 34; biotin:
20 and 0.02; folic acid: 2600 and 111; vitamin B12: 500 and 0.4. Apparent
intestinal absorption values differed greatly among vitamins, but the propor-
tion of vitamins disappearing from the small intestine was not negatively
influenced by supplementation. Except for riboflavin and niacin, absolute
amounts disappearing from the small intestine were greater during the treat-
ment than the control periods, suggesting that B-vitamin supply in dairy cows
is increased by supplementation, although losses in the rumen are extensive
(Santschi et al., 2005).
Meta-analyses on the influence of the vitamins B6, B12 and folic acid on
cognitive functions gave no clear or even contradictory results for an evidence
of an impact of these vitamins. One analysis postulated no impact, independent
from a single or a combined application or if normal or cognitively impaired
persons were investigated, while another meta-analysis postulated an associa-
tion between these vitamins (low vitamin level and high homocysteine levels)
and cognitive dysfunction as well as dementia; however, the biological path-
ways and possible therapeutic interventions remain unclear, i.e. large-scale
randomized trials are demanded by the authors (Balk et al.,2007).Anyhow,
an important role of these vitamins in the nervous system seems to be generally
accepted, but the details and separated functions of the respective vitamins
need to be further elucidated (Bourre, 2006; Reynolds, 2006).
References
Achanta, K., Boeneke, C.A., Aryana, K.J. 2007. Characteristics of reduced fat milks as influ-
enced by the incorporation of folic acid. J. Dairy Sci. 90, 90-98.
Ahmad, I., Fasihullah, Q., Vaid, F.H. 2006. Effect of light intensity and wavelengths on photo-
degradation reactions of riboflavin in aqueous solution. J. Photochem. Photobiol. B 82,21-27.
Alonso, A., Almendral, M.J., Porras, M.J., Curto, Y. 2006. Flow-injection solvent extraction
without phase separation. Fluorimetric determination of thiamine by the thiochrome
method. J. Pharm. Biomed. Anal. 42, 171-177.
Arkaravichien, T., Sattayasai, N., Daduang, S., Sattayasai, J. 2003. Dose-dependent effects of
glutamate in pyridoxine-induced neuropathy. Food Chem. Toxicol. 41, 1375-1380.
