4. Low intake of B vitamins can cause mental decline?
True. Researchers have long known that a gross deficiency of vitamin B12 can cause a certain type of dementia, and that correcting the deficiency can sometimes restore clear thinking. However, recent research suggests that even moderate deficiencies of B12 or folic acid (another B vitamin) may contribute to cognitive decline and possibly the onset of Alzheimer's disease, probably by elevating levels of the amino acid homocysteine. Other evidence links low levels of B vitamins or high homocysteine levels with an increased risk of depression. To help explain those findings, laboratory studies show that homocysteine inhibits the growth of new brain cells and may interfere with the metabolism of certain brain chemicals that help regulate mood and memory. In addition, folic acid and vitamins B6 and B12 help preserve the brain by preserving the cerebral arteries.
While a diet high in grains, produce, and low-fat dairy products generally provides plenty of the three Bs, many older people don't secrete enough stomach acid to extract and absorb vitamin B12 from unfortified food. So everyone over age 50 should take a modest daily B12 supplement or consume B12-fortified foods, notably breakfast cereals.
Note that folic acid may further protect against mental decline by maintaining adequate supplies of choline, a nutrient that helps control homocysteine and is a precursor to acetylcholine and other brain chemicals.
While most people obtain enough choline from their diet, the body uses folic acid to create choline when the level dips too low. Choline's essential role in brain function is one reason why the Food and Drug Administration has started allowing manufacturers to label certain foods as high in choline.
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