Blog Directory - Blogged foodliterate: March 2009

Tuesday, March 24, 2009

The ABC's of Vitamins - Vitamin B6

Ahhh, another day, another B vitamin! Today’s vitamin is vitamin B6, and you may have guessed from the other B vitamins, it too is not a single chemical. Vitamin B6 is the generic term for a group of derivatives which include pyridoxine (PN), pyridoxal (PL) and pyridoxamine (PM). Vitamin B6 was discovered in 1934 and was named “the rat dermatitis factor” due to the finding that a lack of this compound led to dermatitis in rats – how pleasant! (It didn’t take to long for them to figure out there were other B vitamins involved).

Pyridoxine is found primarily in plant tissues, while pyridoxal and pyridoxamine are found primarily in animal tissues. All of these derivatives convert to the main active form pyridoxal 5-phosphate (PLP) in the body. Vitamin B6 is also a coenzyme for over 100 enzymes involved in amino acid metabolism (protein). It is involved in the manufacture of serotonin, melatonin, dopamine and norepinephrine, and is integral to the functioning of our central and peripheral nervous systems. Vitamin B6 also has a role in modulating steroid homone activity in the body and it promotes red blood cell production. Wow! Good thing it is pretty widely available!

Our bodies can’t manufacture this vitamin, so we get it from our diet. Vitamin B6 can be found in potato skins, salmon & trout, bananas, avocados, yeast, whole grains, nuts, pulses, lean meats and liver. Like other water soluble vitamins, it can be lost in processing due to heat or removal of the germ & bran from grains. Because B6 is vital to protein metabolism, as your protein intake increases, so should your B6 intake. The USRDA is 1.3mg per day, or 16 mcg per gram of protein consumed. While this vitamin is not stored in the body, it can become toxic at levels above 50 mg/day causing neurological toxicity. Please come back to learn about vitamin B7 - Biotin.

Sunday, March 15, 2009

The ABC's of Vitamins - Vitamin B5

Vitamin B4 isn’t a vitamin at all (it is actually adenine a DNA metabolite synthesized by the body), and as such has been removed from the list. So that means the next vitamin is vitamin B5. And like so many of its other B-complex cousins, it too has multiple forms: pantethiene, phosphopantethiene, and phosphopantothenic acid. You will find it most commonly referred to as pantothenic acid.

Panto is greek for everywhere, and that pretty well describes this vitamin. It is so pervasive because it is part of coenzyme-A (Co-A) which is found in plants and animals. We cannot manufacture vitamin B5 and must get it from our diet so Co-A is our dietary form of pantothenic acid.

Coenzyme-A (and thus Vitamin B5) is active in many biochemical reactions in the body. It is part of the citric acid cycle (which involves the release of energy from carbohydrates, fats, and protein), necessary for synthesis of red blood cells, synthesis of essential fatty acids, cholesterol and steroid hormones. Milk has the highest amount of unbound vitamin B5 (~90%), but other good dietary sources include mushrooms, avocados, salmon, lobster, soybeans, and yeast. Deficiency is practically unheard of, except in cases of drug-interaction, so there is no recommended daily intake set, although 5mg per day is recommended. There is also been very little toxicity information available, as excess vitamin B5 is water soluble and thus excreted.

Well, we are half way through the B vitamins. I do hope you’re interested in the rest of the family, as B6 is on the sidelines waiting impatiently to be called up. Until next week, eat well & be well.

Tuesday, March 10, 2009

The ABC's of Vitamins - Vitamin B3

Much like vitamin B2, vitamin B3 is not a single substance; the nomenclature covers both niacin and niacinamide. Niacin is the generic name used for nicotinic acid, whereas niacinamide is used for the amide structure (-NH2) nicotinamide.

Nicotinamide is the reactive part of the co-enzymes NAD & NADP. NAD & NADP and their associated co-enzymes are involved in many of the body’s oxidative & reductive reactions (example: lactate to pyruvate to Acetyl-CoA). NAD also plays a role in DNA repair.Vitamin B3 can be made by our bodies from the amino acid tryptophan, but we also get it from chicken, tuna, liver, lean red meats, legumes and peanuts. Like so many of the B vitamins, vitamin B3 is also readily found in many cereal grains. Unfortunately much of it (80-90%) is as bound nicotinic acid, which is not very bioavailable, although treatment with acid or alkali can unbind it and make it more available. And vitamin B3 is completely lost in the milling process, which is why cereal & grain products in the US are fortified; all those wonderful vitamins are stripped away in the processing from whole grain to refined grain.

Normal protein intakes, without any other sources will meet our body’s requirement for this vitamin which means deficiency of vitamin B3 is rare, but among those who are extremely malnourished it can still happen. The symptoms associated with deficiency include dementia, diarrhea, dermatitis and eventually death. Interestingly, pregnancy makes the conversion of tryptophan to niacin twice as efficient and contraceptive pills also increase efficiency too (although not quite as much). Toxicity is rare, but at levels greater than 100mg per day, skin flushing occurs and in even higher doses it can cause gouty arthritis and liver damage.

I’ll be moving on down (or is it up?) the list of the B vitamins, so please come back!