[Poster's comment:- The precise details given in this article regarding the physiological mechanisms involved in the transport and absorption of B12 are over-simplified; as far as IL patients are concerned. In particular there is a counter argument suggesting that the surgical reduction in the number of hydrochloric acid secretion sites (which co-exist with Intrinsic Factor (IF) secretory cells) thereby reduces the need for a compensatory titre of IF. GW ]
As a woman of a certain age who consumes a well-balanced diet of all the usual food groups, including reasonable amounts of animal protein, I tend to dismiss advice to take a multivitamin supplement. I’ve been told repeatedly by nutrition experts that the overuse of dietary supplements for “nutritional insurance” has given Americans the most expensive urine in the world.
I do take a daily supplement of vitamin D, based on considerable evidence of its multiple health benefits, especially for older people. However, based on advice from the National Academy of Medicine and an examination of accumulating research, I’m prompted to consider also taking a vitamin B12 supplement in hopes of protecting my aging brain.
Animal protein foods —meat, fish, milk, cheese and eggs —are the only reliable natural dietary sources of B12, and I do get ample amounts of several in my regular diet. But now at age 75, I wonder whether I’m still able to reap the full benefit of what I ingest.
You see, the ability to absorb B12 naturally present in foods depends on the presence of adequate stomach acid, the enzyme pepsin and a gastric protein called intrinsic factor to release the vitamin from the food protein it is attached to. Only then can the vitamin be absorbed by the small intestine. As people age, acid-producing cells in the stomach may gradually cease to function, a condition called atrophic gastritis.
A century ago, researchers discovered that some people —most likely including Mary Todd Lincoln —had a condition called pernicious anaemia, a deficiency of red blood cells ultimately identified as an autoimmune disease that causes a loss of stomach cells needed for B12 absorption. Mrs. Lincoln was known to behave erratically and was ultimately committed to a mental hospital.
“Depression, dementia and mental impairment are often associated with” a deficiency of B12 and its companion B vitamin folate, “especially in the elderly,” Dr. Rajaprabhakaran Rajarethinam, a psychiatrist at Wayne State University School of Medicine, has written.
He described a 66-year-old woman hospitalized with severe depression, psychosis and a loss of energy and interest in life who had extremely low blood levels of B12 and whose symptoms were almost entirely reversed by injections of the vitamin.
European researchers have also shown that giving B12 to people deficient in the vitamin helped protect many of the areas of the brain damaged by Alzheimer’s disease. In a two-year study at the University of Oxford of 270 people older than 70 with mild cognitive impairment and low B12levels, Dr. Helga Refsum, a professor of nutrition at the University of
Oslo, found reduced cerebral atrophy in those treated with high doses of
“A B12 vitamin deficiency as a cause of cognitive issues is more common
than we think, especially among the elderly who live alone and don’t eat
properly,” Dr. Rajarethinam said.
The academy estimates that between 10 percent and 30 percent of
people older than 50 produce too little stomach acid to release B12 from
its carrier protein in foods, and as the years advance, the percentage of
low-acid producers rises.
But many people do not know they produce inadequate amounts of
stomach acid. In fact, evidence from a study of young adults called the
Framingham Offspring Study suggests that insufficient absorption of B12
from foods may even be common among adults aged 26 to 49, so the
following advice may pertain to them as well.
The academy recommends that adults older than 50 get most of their
daily requirement of B12 — 2.4 micrograms for people 14 and older,
slightly more for women who are pregnant or nursing — from a synthetic
form of the vitamin found in foods fortified with B12 or in a multivitamin
supplement. Synthetic B12 is not attached to protein and thus bypasses
the need for stomach acid. Given that I eat very few fortified foods, a
supplement with B12 is likely to be my best option.
Certain groups besides older people are also at risk of a B12 deficiency.
They include vegetarians and vegans who consume little or no animal
foods; people with disorders of the stomach and small intestine like celiac
disease and Crohn’s disease; chronic users of proton-pump inhibitors to
control acid reflux; and people whose digestive systems were surgically
reduced for weight-loss or treatment for cancer or ulcerative colitis.
Among those most likely to be B12 deficient are the older patients in
nursing homes whose diets are limited, and this deficiency may account in
part for the symptoms of cognitive dysfunction so common among
nursing home residents.
While a B12 deficiency can take years to develop, encroaching symptoms
can be distressing and eventually devastating. It can also be challenging
to link such symptoms to a nutrient deficiency.
In an online posting in July, David G. Schardt, the senior nutritionist for
the Center for Science in the Public Interest, noted that symptoms of B12
deficiency include fatigue, tingling and numbness in the hands and feet,
muscle weakness and loss of reflexes, which may progress to confusion,
depression, memory loss and dementia as the deficiency grows more
Early symptoms can be reversed by treatment with high doses of B12,
usually given by injection. But symptoms related to nerve damage and
dementia are more likely to be permanent. Thus, it is especially important
for people at risk of a B12 deficiency to have their blood tested for it
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for people at risk of a B12 deficiency to have their blood tested for it
periodically. For example, experts at Kaiser Permanente in Oakland,
Calif., suggest that chronic users of proton-pump inhibitors should have
their B12 level tested every two years.
Vegetarians and vegans need not despair. In addition to B12
supplements, various commercially prepared plant-based foods, like some
breakfast cereals, non-dairy milks and soy products and one type of
nutritional yeast, are fortified with synthetic B12. The Vegan Society
recommends eating two to three servings a day of fortified foods to get at
least three micrograms of B12.
However, Dr. Ralph Carmel, a retired haematologist now affiliated with
New York University who studied the effects of B12 for decades, cautions
against taking mega doses of the vitamin. He said in an interview that too
often, “People who really need B12 don’t get it, and those who don’t need
it, like athletes, often take huge doses — 2,000 or 5,000 micrograms a
day. We don’t know what such doses can do in the long run. If an older
person has relatively low B12 levels, I don’t object to taking 500 or 1,000
micrograms a day, but 5,000 is ridiculous.”
By JANE E. BRODY
A version of this article appears in print on September 6, 2016, on page
D5 of the New York edition with the headline: A Vitamin to Protect the
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