September 11, 2015

B12 Deficiency, A Silent Epidemic – Part 2

What is vitamin B12 and why do you need it? Vitamin B12 works together with folate in the synthesis of DNA and red blood cells. It is also involved in the production of the myelin sheath around the nerves, and the conduction of nerve impulses. You can think of the brain and the nervous system as a big tangle of wires. Myelin is the insulation that protects those wires and helps them to conduct messages.

Severe vitamin B12 deficiency in conditions like pernicious anemia (an autoimmune condition where the body destroys intrinsic factor, a protein necessary for the absorption of vitamin B12) used to be fatal until scientists figured out death could be prevented by feeding patients raw liver (which contains high amounts of vitamin B12). But, anemia is the final stage of B12 deficiency. Long before anemia sets in, vitamin B12 deficiency causes several other problems, including fatigue, lethargy, weakness, memory loss and neurological and psychiatric problems.

Vitamin B12 deficiency occurs in four stages, beginning with declining blood levels of the vitamin (stage 1), progressing to low cellular concentrations of the vitamin (stage 2), an increased blood level of homocysteine and a decreased rate of DNA synthesis (stage 3), and finally, macrocytic anemia (stage 4).

Vegetarians and vegans please read: vitamin B12 is found ONLY in animal products. Vitamin B12 is the only vitamin that contains a trace element (cobalt), which is why it’s called cobalamin. Cobalamin is produced in the gut of animals. It’s the only vitamin we can’t obtain from plants or sunlight. Plants don’t need vitamin B12 so they don’t store it. A common myth amongst vegetarians and vegans is that it’s possible to get vitamin B12 from plant sources like seaweed, fermented soy, spirulina, and brewers yeast. But, plant foods said to contain vitamin B12 actually contain B12 analogs called cobamides that block intake of and increase the need for true vitamin B12. This explains why studies consistently demonstrate that up to 50% of long-term vegetarians and 80% of vegans are deficient in vitamin B12.

The effects of vitamin B12 deficiency on kids are especially alarming. Studies have shown that kids raised until age 6 on a vegan diet are still vitamin B12 deficient even years after they start eating at least some animal products.

Table 2. Some Food Sources of Vitamin B12
Vitamin B12 (mcg)
Clams (steamed)
3 ounces
Mussels (steamed)
3 ounces
Mackerel (Atlantic, cooked, dry-heat)
3 ounces*
Crab (Alaska king, steamed)
3 ounces
Beef (lean, plate steak, cooked, grilled)
3 ounces
Salmon (chinook, cooked, dry-heat)
3 ounces
Rockfish (cooked, dry-heat)
3 ounces
Milk (skim)
8 ounces
Turkey (cooked, roasted)
3 ounces
Brie (cheese)
1 ounce
Egg (poached)
1 large
Chicken (light meat, cooked, roasted)
3 ounces
*A three-ounce serving of meat or fish is about the size of a deck of cards.

Only bacteria can synthesize vitamin B12. Vitamin B12 is present in animal products, such as meat, poultry, fish (including shellfish), and to a lesser extent dairy products and eggs. Fresh pasteurized milk contains 0.9 mcg per cup and is an important source of vitamin B12 for some vegetarians. Those strict vegetarians who eat no animal products (vegans) need supplemental vitamin B12 to meet their requirements. Recent analyses revealed that some plant-source foods, such as certain fermented beans and vegetables and edible algae and mushrooms, contain substantial amounts of bioactive vitamin B12 (this is a point of disagreement among the experts). Together with B-vitamin fortified food and supplements, these foods may contribute, though modestly, to prevent vitamin B12 deficiency in individuals consuming vegetarian diets. Also, individuals over the age of 50 should obtain their vitamin B12 in supplements or fortified foods (e.g., fortified cereals) because of the increased likelihood of food-bound vitamin B12 malabsorption with increasing age.

If you are interested in more reading, please read this from Oregon State U and this from the U of Maryland. These are just two of the many sources I used plus talking with two doctors. I could write more, but much of it would be very technical.

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