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 anemia,
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 B12
levels, Dr. Helga Refsum, a professor of nutrition at the University of
Oslo, found reduced cerebral atrophy in those treated with high doses of the vitamin.
“A
B12 vitamin deficiency as a cause of cognitive issues is more common
than we think, especially among the elderly.
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 severe.
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
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,
nondairy 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 hematologist now affiliated with New York
University who studied the effects of B12 for decades, cautions against
taking megadoses 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 low-ish B12 levels, I don’t object to taking 500 or 1,000
micrograms a day, but 5,000 is ridiculous.”
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