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Nutritional Supplements #2: B12
By:  Alicia Berthiaume   (2004/01/12)


Canadian skiers are still buzzing about Beckie Scott’s bittersweet Olympic medal, and as a result, we are gaining hope for a drug-free world of sport. But the debate about the ethics of supplementing (with vitamins, minerals or other) is still a foggy area for athletes. Without a little bit of understanding of the biochemistry behind the supplements, we put ourselves at risk on many levels. We may be taking something that is damaging to our health, we may be taking something in the wrong doses or we may be taking something illegal in competitive sport. It barely sounds worth it right? Don’t be discouraged thought, there are many incredible benefits to supplementing, if you know what to look for. So over the next season XC Ottawa will feature a panel of vitamin, minerals, herbal supplement and others that have been in the limelight recently. Hopefully with a bit of explanation, we’ll be able to understand what all the excitement is about! [Please check with your Doctor before starting use of any new supplement, 'natural' or otherwise]

Hello again! It's time for another nutritional update. This time we're moving away from the herbal nutrients and in to some slightly more serious stuff: vitamins. As you may already know, the word vitamin comes from the combination of the words 'vital' and 'amine'. Around 1900, the isolation of an "accessory food factor" from the hulls of rice led to the discovery of a compound belonging to the amine family (thiamine or vitamin B1) that was vital in maintaining health against a disease called beriberi (a simple B1 deficiency). Since then, research has brought to light 13 vitamins essential to humans. However, not all of these are amines. Today, the term vitamin applies to a compound that is necessary for our health/lives but that we cannot produce in our bodies. Therefore, we must rely on our diets as the sole source of these nutrients. As for the alphabet names, it was a scheme that began as an orderly system (when only 2 vitamins were known A& B!) and it progressed to the mess it is now as many more vitamins were discovered. This feature will focus on vitamin B12, one of the five B vitamins. B1, B2, B3, and B6 make up the rest of this group, and the 4,7,8,9,10,and 11 versions of Bs are not around because they are actually only minor variations of the first five Bs.


As skiers, we are primarily endurance athletes (even our sprint races sometimes feel long!!) so the efficiency of oxygen transport is very important to us aerobic racers. In the hopes of boosting red blood cell (RBC) power and legally improving hemoglobin levels, athletes often supplement with iron, ginseng and vitamin B12. Most don't know why they do so. So, what does B12 really do for our bodies?

The most pertinent function of B12 for athletes is the transfer of oxgyen to muscles. The process is complicated; it helps to transfer methyl groups to several different pathways of the body, one of which is the DNA synthesis pathway. DNA is what our genes are made up of. It is necessary for cell division. A quick review of basic DNA synthesis reminds us that DNA strands are made up of patterns of four nucleotides; A,G,C, and T. Basically, these nucleotides are constructed from amino acids and sugars from our diet, or recycled from the old nucleotides of broken down cells. They are then modified to their specific structures by special enzymes. The vitamin B12 action (methyl transfer) is directly involved in the formation of T. So if you're low in B12 you're also low in T. The significance of this is that if the nucleotide supplies aren't adequate to make DNA, then cell division will slow dramatically.

For rapidly dividing red blood cells (hair follicles and skin cells too!) this is especially significant. When B12 is deficient, DNA synthesis is slowed and, as a result, red blood cells mature too slowly. The end products are oversized red blood cells called megaloblasts. These cells cannot carry oxygen due to the now-too-large distance (compared to normal sized red blood cells) that the oxygen has to diffuse to get to the hemoglobin inside the cells. Not a good thing for the oxygen starved muscles of a hard working skier.

Other pathways that B12 plays a role in are: the synthesis of myelin protein for the central nervous system (B12 deficiency can have a negative neurological effect) and the metabolism of some amino and fatty acids for entrance into the energy production cycle (TCA cycle). Vitamin B12 is also involved in the major route of homocysteine clearance from the body. Inefficient clearance of this amino acid is strongly associated with cardiovascular disease, neurological disorders and other deleterious effects.

So, now that we know all this about B12, there is the question of supplementing. A true deficiency of B12 is rare, as the body stores enough in the liver to last upwards of 6 months and a balanced diet including meat and eggs provides us with the recommended daily intake (6micrograms) of vitamin B12 . However, the absorption of B12 can be hindered at a number of junctions between your mouth and your cells. Digestion and absorption involve highly specific conditions that can be easily disturbed by such things as antibiotics or antacids, intestinal bacterial overgrowth or lack of intrinsic factors. These obstacles are common enough that supplementing with vitamin B12 is now becoming popular as a preventative therapy for deficiency. Evidence shows that daily oral megadoses of the vitamin (up to 1000 micrograms) can provide those with absorption problems enough B12 to prevent deficiency. Other supplement options include a sub-lingual form or an intramuscular injection, both of which bypass the intestine and any potential absorption barrier. Several forms of B12 supplements are available, cyano-, methyl-, and hydroxy-cobalamin, cyanocobalamin being the most common. They are all satisfactory supplements.

It is important to check with your doctor and/or pharmacist before starting any new supplement. However, as vitamin B12 is water-soluble and well tolerated it is very safe to take as a supplement, even when a deficiency is not present. Because of the synergistic action of folate and B12 in some pathways, folic acid (B6) supplementation can enhance recovery when B12 status is poor.

Therefore, in the interest of keeping your red blood cells the right size and full of oxygen, check out this brightly coloured vitamin and discover why it's nature's most beautiful cofactor!

Interesting Reading. . .
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