Blog Directory - Blogged foodliterate: April 2009

Tuesday, April 28, 2009

The ABC's of Vitamins - Vitamin B12

Alas, B12 is the last of the B vitamin family; that is not to say that it is not as interesting as its kin. Vitamin B12 has the most complex chemical structure of all the vitamins and contains a molecule of cobalt. And has been the case with a number of its cousins, B12 is just an inclusive name for all cobalamins that have anti-pernicious anemic activity [say that three times fast :)]. You see, this vitamin was discovered by research into pernicious anemia and was finally isolated in 1948.

The most stable, and most commonly seen, form of B12 is cyanocobalamin. And the two forms that act as co-enzymes in the body are methylcobalamin and adenosylcobalamin. These co-enzymes work with the inactive form of folate to convert homocysteine into methionine. In the process, the inactive folate is activated and goes to work in DNA synthesis, thus making B9 & B12 very symbiotic.

Vitamin B12 can only be found in animals and microorganisms; no plants can make this vitamin. The best sources are organ meats like liver, heart and kidney, but other muscle tissues, milk, cheese, eggs and shellfish are good sources. Because this vitamin is not found in plants, vegans and very strict vegetarians must pay attention to their intake of B12.

We only need about 1 microgram per day, although the USDRI is set at 2.4 micrograms. This seems such a small amount, that you are probably wondering how big of a deal is it? It is really big! While it is rare to be deficient, it is not unheard of and those who suffer from Crohn’s/celiac disease are at a greater risk (along with those vegans/vegetarians). Some of the manifestations of a deficiency are megablastic anemia (aka pernicious anemia), demyelinization of nerve tissues (which is irreversible) and death.

So, we have finally reached the end of the B vitamins, but that doesn't mean that we have finished our conversation on vitamins just yet. The next post will be on our friend Vitamin C, probably the best known and perhaps most talked about vitamin out there. Hope to "C" you back!

Monday, April 13, 2009

The ABC's of Vitamins - Vitamin B9

Vitamin B9 is the next vitamin in the series, which may lead some to ask, what happened to B8? B8 was used for adenylic acid (a DNA metabolite) until it was discovered that is synthesized by the human body & wasn’t a vitamin. Vitamin B9, like a lot of its B-vitamin brethren, is a generic term for all forms of pteroic acid with vitamin activity. The other common generic name in use is folate; but folic acid is how you are most likely to see this vitamin designated even though it is not the form found commonly in nature.

The folate found in food is bound and must be digested by enzymes in the small intestine before we can utilize it; the same is not true for the form typically found in supplements and fortifications. Luckily, folate is an essential biochemical constituent of living cells, making it pretty easy to find in foods. Orange juice, eggs (cooked), beans, spinach, whole grains, asparagus, and peanuts are all good sources of B9. In addition, folate is added as a fortification to cereals and grain products (required in all commercial grain products per the FDA).

Folate is required for DNA and RNA synthesis, metabolism of some amino acids (proteins), cognitive function, metabolism of fat and reducing homocysteine levels which reduces the risk of cardiovascular disease. The recommended daily intake is 400 micrograms per day, and because we don’t absorb it well (that whole breaking it down problem) and because so many of us don’t eat very well, many people are deficient.

Deficiencies, especially long-term ones, can lead to elevated plasma homocysteine levels which are an early indicator of atherosclerosis and the potential for DNA breaks which may lead to an increased cancer risk. Deficiency during pregnancy is related to the elevated occurrence of neural tube defects (probably the effect with which most people are familiar).

Vitamin B9 works closely with vitamin B12 and that’s great, because that is our next vitamin and the last of the B vitamins to be covered. “B” there for the next post!

Tuesday, April 7, 2009

The ABC's of Vitamins - Vitamin B7

Boy am I behind on my posts - sorry! But I'm back and the next B vitamin on our list is B7, more commonly known as Biotin. Unlike so many of the other B vitamins we've been discussing, vitamin B7 is just biotin, not a generic term for a group of compounds. And the only active form, which coincidentally is the one that occurs in nature, is d-Biotin.

While biotin is present in both animal and plant tissues, even the very best sources are still pretty low in biotin compared to the other B vitamins. Whole eggs, soybeans and peanuts are good sources, as are wheat bran, oatmeal, muscle meats, fish and dairy products. The biotin found in animals, nuts & cereals is usually protein bound, while the biotin found in veggies, fruits and dairy products is "free" biotin. Biotin can also be made by the bacteria in your large intestine, some of which can be absorbed by the body, but it isn't a major contributor.

Biotin acts as a coenzyme for carboylases which is part of the acetyl-CoA formation process; it helps you derive energy from carbohydrates. Biotin also appears to play a role in the removal of glucose in the bloodstream and its storage as glycogen. And it aids in the breakdown of amino acids so they can be used by the body to build necessary proteins.

Because biotin is so widely available, deficiencies are pretty rare, although there are two genetic conditions that exist where biotin cannot be metabolized (known collectively as multiple carboxylase deficiency or MCD). A deficiency manifests itself as anorexia, weakened immune system and skin rashes. The recommended daily requirement for biotin is only 30 micrograms per day.

Wow, we are in the closing stretch of the B vitamins - six down and only two are left. I promise not to wait another two weeks before discussing vitamin B9, so please come back!