The intrinsic factor is vital for B12 absorption

The intrinsic factor is vital for B12 absorption

James Scheer

The Intrinsic Factor Is Vital for B12 Absorption

Putting vitamin B12 to work in the body requires adequate supplies of the protein-based intrinsic factor

Like a temperamental opera prima donna, vitamin B12 (cobalamin) has to have conditions exactly to its liking or it won’t perform.

Because it prevents pernicious anemia, degenerating nerves and mental disorders, cobalamin needs to be present in adequate quantities.

Long before vitamin B12 reaches the stomach, it plays hard-to-get, appearing in appreciable quantities in only eight foods: liver, sardines, clams, mackerel, herring, croaker, snapper and flounder. And one of those sources, clams, is shunned by many people because it is considered a garbage collector of the sea, often full of pollutants.

Even though adults require only 2 micrograms (mcg) of vitamin B12 daily, according to the new Recommended Dietary Allowances, the mineral is present only in tiny quantities, and primarily in meats.

Assuring a good intake of vitamin B12, whatever the source, does not guarantee that it will be properly absorbed. A good supply of what is called the intrinsic factor is necessary for this vitamin to become available to the body.

The intrinsic factor, despite its rather cryptic name, is nothing mysterious. It is innumerable tiny, open ended protein capsules created by the stomach in the exact shape and size required to fit a cobalamin molecule.

These capsules randomly weave and bob around amid digesting food. When they bump into vitamin B12, they quickly trap it inside, snap the open and shut, and transport it to the farthest end of the small intestine, the only place in the gut where cobalamin can be absorbed.

Without intrinsic factor, most B12 could never reach its destination, because bacteria which line the intestine are hungry for this nutrient and would intercept it. So you can be starved for vitamin B12 even when it is richly supplied.

Making protein for the intrinsic factor depends on a good supply of many different amino acids, available mainly from varied animal sources. Plant sources seem to specialize in making one kind of amino acid rather than many, and therefore, a strict vegetarian diet may not offer the required raw materials to synthesize the needed and specialized protein.

What happens if there’s a dearth of intrinsic factor? Intestinal bacteria gobble up much of the vitamin B12, and the rest is excreted.

Ingesting enough vitamin B12, therefore, is not enough. The vitamin has to be delivered to the right spot in the upper intestine for absorption. Otherwise, the consequences can be serious.

One of the serious consequences is dementia, which can mean anything from mild mental impairment to insanity.

A recent study by Ralph Carmel, M.D., a specialist in hematology and a professor of medicine at the University of Southern California, reveals the temperamental character of vitamin B12.

Carmel wrote that “a certain segment of the population, especially the elderly, cannot absorb vitamin B12 from food … Some of them go on to develop low B12 levels with biochemical abnormalities that cannot be detected by standard tests, and some develop dementia.

“In 99 percent of cases, B12 deficiency arises from an inability to absorb the B12 ingested in food. The Schilling test can determine the extent to which a person is able to absorb the B12.

“However, in our study sample, 90 percent of the patients with unexplained low levels of B12 had normal Schilling tests. How could they have developed B12 deficiency if they were adequately absorbing B12?”

An answer to Carmel’s question came from a study done some years ago by Dr. Doscherholmen at the University of Minnesota, showing that certain people, particularly the elderly, can absorb B12 normally when it is given in a pill in the Schilling test, but cannot absorb it in food.

In his observation of cases at the Los Angeles County/USC Medical Center, Carmel found that some people with low blood levels of vitamin B12 may actually be suffering from a deficiency that, if left undetected and untreated, can produce dementia.

Carmel said cobalamin deficiency is a growing problem and cites statistics to make his case. Seven years ago, no more than 30 cases of classical vitamin B12 deficiency were detected at this medical center — cases characterized by anemia or by problems in the spinal cord nerves that supply the arms and legs.

Now each year several hundred cases of low levels of vitamin B12 show up at this medical center without the usual manifestations of deficiency, leading Carmel to believe these patients might actually have a vitamin B12 deficiency that was more subtle or different from the usual form of deficiency.

When Carmel’s group micro-scopically examined bone marrow blood cells from patients with an unexplained low B12 levels, they discovered that even though the cells didn’t show the anemia of B12 deficiency, they behaved biochemically exactly like cells suffering from a vitamin B12 deficiency.

The major functions of vitamin B12 include contributing to the creation of DNA, which contains the genetic code for cell replication, and RNA, which carries the genetic message; helping in cell division and, of special importance in preventing anemia, assisting in the creation and growth of red blood cells that carry oxygen to our trillions of cells.

This last function is important for the prevention of anemia. Without enough oxygen, the burning of fuel in our cells is decreased, causing a lack of energy.

We’ve covered the temperamental quality of vitamin B12, but how can we cope with it? Quite easily today, because health food stores carry two kinds of cobalamin that make supplementation easy: sublingual, a form that you dissolve under your tongue, and another kind that includes the intrinsic factor. The sublingual type is absorbed directly into the bloodstream, avoiding the obstacle course of the stomach and small intestine.

Then, of course, there’s the old-fashioned way of ensuring proper absorption: getting shots from your family doctor. However, for those who dislike getting the needle, the never forms of this vitamin can do the job without being temperamental.

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