Autoimmune Thyroid Disease

An Unfortunate and Lengthy Adventure in Misdiagnosis

Vitamin B6 and pyridoxine glycosides

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β-Glucosides of pyridoxine (a) are prevalent in plant-derived foods, (b) contribute to human nutrition as partially available sources of vitamin B6, (c) undergo partial hydrolysis by a novel mammalian cytosolic β-glucosidase, and (d) exert a weak antagonistic effect on the utilization of free pyridoxine. Nutritional Properties and Significance of Vitamin Glycosides

Science seems to be in agreement over this one. There I was wondering how to get more nuts, bananas and potatoes into my diet without compromising my other nutritional needs, and it turns out I shouldn’t bother.

B6 is a very hard to get hold of vitamin. It’s found in red and white meats, but is partially destroyed by freezing and cooking, and isn’t found in high enough quantities to meet the RDA solely from meats. It’s also found in some very strange plant foods, like bananas, pistachio nuts, some grains, and potatoes. However, current research has found that significant proportions of the B6 found in plant sources is glycosylated. What this means is it is very hard if not impossible for the body to absorb, and that which is absorbed, actually antagonises real B6, making a B6 deficiency worse.

B6 is found in three forms in nature: as pyridoxine, pyridoxal, and pyridoxamine. Pyridoxine is found in plant foods, and pyridoxal and pyridoxamine are found in animal foods. The active form of B6 is pyridoxal-5-phosphate, also known as PLP or P5P. The B6 that you eat is converted into this active pyridoxal form, the form that is found in meat.

This calls all of the information in the USDA database regarding B6 in foodstuffs into question. Querying foods high in B6 brings back a long list of plant foods followed by meats. Have these foods been analysed for their glycoside content? The true B6 content could be much lower. The USDA database also fails to bring up differences between frozen, cooked, and uncooked meats, and B6 levels are reduced by freezing and cooking.

B6 requirements are actually linked to protein requirements. If you eat a lot of protein, you will need more B6, if you eat less protein, you will need less B6. According to the Linus Pauling Institute, “Metabolic studies suggest that young women require 0.02 mg of vitamin B6 per gram of protein consumed daily.” If I eat 50 grams of protein, I will therefore need 1mg of B6 per day, half the RDA, which is based on 100 grams of protein. A lot of RDAs for vitamins are calculated with this somewhat questionable method, and therefore are huge generalisations on the populace.

Another myth about B6 is that white meat is a better source than red meat. Actually, by weight the lean portion of red meat contains almost as much B6 as the lean portion of white meat, except the white meat contains more protein too. By eating red meat, you are actually sparing your B6 supplies, because you are providing your body with proportionately more B6 per weight of protein than by eating white meat.


Written by alienrobotgirl

31 May, 2006 at 9:18 am

Posted in Vitamins

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