Study suggests that folic acid can slow or speed cognitive decline in old age, depending on B-12 levels; folate may also reduces hearing loss
by Craig Weatherby
Recent headlines from Holland trumpeted the apparent ability of folic acid (folate)—one of the B vitamins—to slow progress toward senility. Folate is concentrated in green leafy vegetables, beans, lentils, hazelnuts, and liver.
But most media reports overlooked a simultaneous announcement by researchers from Boston’s Tufts University, which suggest that taking folate alone could increase one's age-related slide toward senility.
Dietary folate can also accelerate progress toward senility and dementia unless people also consume adequate amounts of vitamin B-12, which, supplements aside, is abundant only in animal foods and fermented soy beans (tempeh).
The Tufts researchers suggest that public health officials consider requiring food makers to fortify flour with B-12, because folic acid is already added to flour to help mothers prevent neural tube defects in their developing fetuses (Morris MS et al 2007), this creating the possibility of a senility-promoting imbalance between these B vitamins.
Therefore, as the Dutch group noted, the effect of taking supplemental folic acid might be less in the US, where fortification of flour with folic acid is mandatory, and people have lower blood homocysteine levels.
They also note that—unlike many nursing home residents—all of the participants had sufficient levels of vitamin B12, deficiency of which can cause anemia and dementia in elderly people.
They noted that the study involved people with slightly raised levels of the amino acid homocysteine, so the results might not be as clearly beneficial in people with lower homocysteine levels.
Folate benefits brains only when B-12 is present
The well-designed Dutch trial (randomized, double-blind, placebo-controlled) was intended to see whether supplemental folic acid would enhance mental performance in people with adequate levels of vitamin B-12 but slightly elevated blood levels of homocysteine (Durga J, van Boxtel MP, et al 2007).
Elevated homocysteine may promote cardiovascular disease, and people with slightly raised levels run an increased risk of or age-related cognitive decline (ARCD): the medical term for geriatric senility.
Homocysteine in the blood is either metabolized (broken down) through a mechanism that uses vitamin B6, or can be converted into harmless methionine through one of two separate routes that require either folic acid or vitamin B12.
The Dutch researchers recruited 818 men and women between the ages of 50 and 70, with slightly elevated blood homocysteine levels (13 micromoles per liter or more) and healthy vitamin B12 levels (at least 200 picomoles per liter).
The participants were randomly assigned to take either 800 micrograms of supplemental folic acid—which is double the US RDA—or a placebo for three years.
Their cognitive function was assessed at the beginning and end using a battery of tests.
The researchers found that folic acid supplementation gave subjects the memory performance of someone 4.7 years younger, the reaction time of someone 1.7 years younger, the information processing speed of someone 2.1 years younger, and the “global cognitive function” of someone 1.5 years younger.
They also reported that the “delayed recall” performance of the folic acid group compared favorably to the performance of someone 6.9 years younger (Delayed recall means remembering information after a delay; usually about ten minutes).
As the authors wrote, “We have shown that 3-year folic acid supplementation improves performance on tests that measure information processing speed and memory, domains that are known to decline with age.”
Folate may reduce hearing loss
The same Dutch team also looked at hearing loss among study participants.
At the outset of the three-year study, they measured the participants' average threshold for hearing in the low and high frequency ranges.
By the end of the study the hearing thresholds had increased among members of the folic acid and placebo groups. In other words, noises had to be louder before the participants heard it.
However, the undesirable increase in hearing thresholds in the low frequency range was substantially smaller in the folate group than in the placebo group (1.0 decibels versus a 1.7 decibels increase).
As far as the higher frequency regions, there was no significant difference between the folate and placebo groups.
The researchers believe that inadequate intake of folic acid may contribute to hearing loss.
As with the senility study, these results occurred in people from a country that does not require folic acid fortification of food. Accordingly, as the researchers said, “The effect requires confirmation, especially in populations from countries with folic acid fortification programs” (Durga J, Verhoef P, et al 2007).
In an accompanying editorial, Dr. Robert Dobie of the University of California, Davis calculated that if this benefit were applied to people in general over a 20-year period, it could mean that folate intake could reduce age-related hearing loss by five-decibels: an outcome that would reduce the need for hearing aids significantly (Dobie RA 2007).
- Durga J, van Boxtel MP, Schouten EG, Kok FJ, Jolles J, Katan MB, Verhoef P. Effect of 3-year folic acid supplementation on cognitive function in older adults in the FACIT trial: a randomised, double blind, controlled trial. Lancet. 2007 Jan 20;369(9557):208-16.
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