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. 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 who live
alone and don’t eat properly,” Rajarethinam said.
The academy
estimates that between 10% and 30% 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 micro grams 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 re flux; 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, California,
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 micro grams 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
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 micro grams a day.
We don’t know what such doses can do in the long run. If an older person
has low-sh B12 levels, I don’t object to taking 500 or 1,000 micro grams a day, but 5,000 is ridiculous.”
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