@ kiara: dazu müsste ich rekonstruieren, wo genau ich das freitag gelesen hab usw. und das ist mir zu kompliziert. die studie zu jordanien war einfach:
This study aimed to estimate the status of serum vitamin B12 level in patients attending Jordan University Hospital in Amman, and to examine the relationship with demographic data, chronic illness, dietary habits, haematological parameters and symptoms related to vitamin B12 levels. A total of 838 patients completed a questionnaire and gave blood samples; 44.6% were vitamin B12 deficient (< 180 pg/mL) and 34.2% had hypovitaminosis (180-300 pg/mL). Vitamin B12 deficiency was associated with memory impairment, low meat intake and strict vegetarian (vegan) diets. The high frequency of low vitamin B12 warrants the development of a strategy to correct this problem in Jordan.
http://www.ncbi.nlm.nih.gov/pubmed/20187536
ich bring dafür ein paar neue abstracts:
Pernicious anemia is a common cause of megaloblastic anemia throughout the world and especially in persons of European or African descent. Dietary deficiency of vitamin B12 due to vegetarianism is increasing and causes hyperhomocysteinemia. The breast-fed infant of a vitamin B12–deficient mother is at risk for severe developmental abnormalities, growth failure, and anemia. Elevated methylmalonic acid and/or total homocysteine are sensitive indicators of vitamin B12–deficient diets and correlate with clinical abnormalities. Dietary vitamin B12 deficiency is a severe problem in the Indian subcontinent, Mexico, Central and South America, and selected areas in Africa. Dietary vitamin B12 deficiency is not prevalent in Asia, except in vegetarians. Areas for research include intermittent vitamin B12 supplement dosing and better measurements of the bioavailability of B12 in fermented vegetarian foods and algae.
http://www.annualreviews.org/doi/abs/10 ... lCode=nutr
In considering the vitamin B-12 fortification of flour, it is important to know who is at risk of vitamin B-12 deficiency and whether those individuals would benefit from flour fortification. This article reviews current knowledge of the prevalence and causes of vitamin B-12 deficiency and considers whether fortification would improve the status of deficient subgroups of the population. In large surveys in the United States and the United Kingdom, approximately 6% of those aged > or =60 y are vitamin B-12 deficient (plasma vitamin B-12 < 148 pmol/L), with the prevalence of deficiency increasing with age. Closer to 20% have marginal status (plasma vitamin B-12: 148-221 pmol/L) in later life. In developing countries, deficiency is much more common, starting in early life and persisting across the life span. Inadequate intake, due to low consumption of animal-source foods, is the main cause of low serum vitamin B-12 in younger adults and likely the main cause in poor populations worldwide; in most studies, serum vitamin B-12 concentration is correlated with intake of this vitamin. In older persons, food-bound cobalamin malabsorption becomes the predominant cause of deficiency, at least in part due to gastric atrophy, but it is likely that most elderly can absorb the vitamin from fortified food. Fortification of flour with vitamin B-12 is likely to improve the status of most persons with low stores of this vitamin. However, intervention studies are still needed to assess efficacy and functional benefits of increasing intake of the amounts likely to be consumed in flour, including in elderly persons with varying degrees of gastric atrophy.
http://www.ncbi.nlm.nih.gov/pubmed/19116323
Reasons to fortify flour with vitamin B12 are considered, including the high prevalence of depletion and deficiency of this vitamin that occurs in persons of all ages in resource-poor countries and in the elderly in wealthier countries, and the adverse functional consequences of poor vitamin B12 status. From a global perspective, the main cause of inadequate intake and status is a low intake of animal-source foods; even lacto-ovo vegetarians have lower serum vitamin B12 concentrations than omnivores, and for various reasons many populations have limited consumption of animal-source foods. Infants are vitamin B12-depleted from early infancy if their mothers' vitamin B12 status and intake are poor during pregnancy and lactation. Even in the United States, more than 20% of the elderly have serum vitamin B12 concentrations that indicate depletion, and an additional 6% have deficiency, primarily due to gastric atrophy, which impairs the absorption of the vitamin from food but usually not from supplements or fortified foods. Although the evidence is limited, it shows that fortified flour, consumed as bread, can improve vitamin B12 status. Where vitamin B12 fortification is implemented, the recommendation is to add 20 microg/kg flour, assuming consumption of 75 to 100 g flour per day, to provide 75% to 100% of the Estimated Average Requirement; the amount of the vitamin that can be added is limited by its cost. The effectiveness of this level of addition for improving vitamin B12 status in programs needs to be determined and monitored. In addition, further research should evaluate the bioavailability of the vitamin from fortified flour by elderly people with food cobalamin malabsorption and gastric atrophy.
http://www.ncbi.nlm.nih.gov/pubmed/20629351
allerdings ist laut dieser metastudie die datenlage einfach zu dünn, um zuverlässige aussagen treffen zu können:
Review of the magnitude of folate and vitamin B12 deficiencies worldwide.
