B12 Deficiency May Be More Widespread Than
Thought By Judy
August 2, 2000
Nearly two-fifths of the U.S. population may be flirting with
marginal vitamin B12 status if the population of Framingham, Mass., is any
A careful look at 3,000 men and women in the ongoing Framingham
Offspring Study found 39 percent with plasma B12 levels in the low
normal range--below 258 picomoles per liter.
While this is well above the currently accepted deficiency level
of 148 pmol/L, some people exhibit neurological symptoms in the higher range,
said study leader Katherine Tucker. She is a nutritional epidemiologist at the
Jean Mayer USDA Human Nutrition Research
Center on Aging at Tufts University in Boston.
Nearly 9 percent of the study population fell below the current
deficiency level. And more than 16 percent fell below 185 pmol/L. Many
people may be deficient at this level, said Tucker. There is a
question as to what the clinical cutoff for deficiency should be.
I think there is a lot of undetected vitamin B12
deficiency out there, she said, noting that the study covered people from
26 to 83 years old. The research was funded by the
Agricultural Research Service (ARS),
USDAs chief scientific agency.
B12 deficiency can cause a type of anemia marked by fewer but
larger red blood cells. It can also cause walking and balance disturbances, a
loss of vibration sensation, confusion, and, in advanced cases, dementia. The
body requires B12 to make the protective coating surrounding the nerves, so
inadequate B12 can expose nerves to damage.
The good news, said ARS administrator Floyd Horn,
is that most people can improve their B12 status by eating more fortified
cereals and dairy products. Dr. Tuckers findings show that these foods
were nearly as effective as supplements containing B12 for getting
peoples blood levels above the danger zone.
Tucker and colleagues looked at B12 levels spanning the adult
population because most previous studies have focused on the elderly, who were
thought to be at higher risk for deficiency. The results were surprising. The
youngest group--the 26- to 49-year-olds--had about the same B12 status as the
oldest group--65 and up. We saw a high prevalence of low B12 even among
the youngest group, Tucker said.
The researchers also expected to find some connection between
dietary intake and plasma levels, even though other studies found no
association. And they did find a connection. Supplement use dropped the
percentage of volunteers in the danger zone--plasma B12 below 185 pmol/L--from
20 percent to 8. Eating fortified cereals five or more times a week or being
among the highest third for dairy intake reduced, by nearly half, the
percentage of volunteers in that zone--from 23 and 24 percent, respectively, to
12 and 13 percent.
Oddly, the researchers found no association between plasma B12
levels and meat, poultry, and fish intake, even though these foods supply the
bulk of B12 in the diet. Its not because people arent eating
enough meat, Tucker said. The vitamin isnt getting
In the elderly, its probably because they dont
secrete enough stomach acid to separate the vitamin from the meat proteins that
tightly bind it. But Tucker can only speculate about the reasons for poor
absorption of the vitamin from meat among younger adults or why B12 appears to
be better absorbed from dairy products than from meats.
Fortified cereals are a different story. Tucker said the vitamin
is sprayed on during processing and is more like what we get in
Scientific contact: Katherine Tucker, Jean Mayer USDA
Human Nutrition Research on Aging at Tufts
University, Boston, Mass., phone (617) 556-3351, fax (617) 556-3344,