Sound advice: Nutrition in age-related hearing loss (cont’d)
Last week’s article cited two studies implicating folic acid and vitamin B12 deficiencies with age-related hearing loss. The first study, published in the American Journal of Clinical Nutrition in 1999, found that elderly women with impaired hearing had a significantly lower level of folic acid and B12 than women of the same age with normal hearing. A second study, published in the Jan. 2, 2007, issue of the Annals of Internal Medicine, found that subjects who were given a folic acid supplement of 800 micrograms of folic acid per day for three years had a lower level of age-related hearing loss than subjects not supplemented with folic acid.
How B12 and Folate Deficiencies May Cause Hearing Loss
The cochlea of the inner ear is where much of the hearing loss in the elderly is believed to occur. The cochlea is dependent upon an adequate blood supply. It is highly vascularized and supported by a single artery. Homocysteine, a toxic amino acid, is elevated during deficiencies of vitamin B12, folate or both.
Homocysteine is believed to damage blood vessels, and high levels of homocysteine are a risk factor for cardiovascular disease and strokes. The authors of the study theorized that high homocysteine concentrations, resulting from deficiencies of vitamin B12, folate or both, might also adversely affect blood flow to the cochlea. Homocysteine is toxic to the nervous system, as well, and might damage nerves in the inner ear.
Preventing and Correcting B12 and Folate Deficiencies
The first line of defense is diet. Folate or folic acid is found in green leafy vegetables, including spinach. It is found in tomatoes, eggs, whole grains, citrus fruits, liver, pears, beans, nuts, potatoes, beets, cabbage, asparagus, wheat germ and many other foods in lesser amounts.
Vitamin B12 is found only in foods of animal origin: beef, lamb, poultry, pork, fish, liver, eggs and dairy.
However, vitamins can be destroyed in processing and cooking. Therefore, it is important to eat foods that are fresh, whole and unprocessed and either raw or lightly cooked. Fresh fruit and salads are examples of foods that can be eaten raw. Vegetables should be lightly cooked. Meat, fish and poultry should not be overcooked.
The second line of defense is supplementation. The amount of folic acid in most vitamin supplements, 400 micrograms, works well enough to lower blood homocysteine levels in a week or two.
Most multivitamins contain about 10 micrograms of B12, which is adequate if vitamin B12 is being absorbed. If it is not, then B12 lozenges that dissolve under the tongue might allow adequate B12 to be absorbed through the mucous membranes in the mouth, thus passing the digestive tract. Since only 1 percent or 0.1 percent of vitamin B12 is absorbed in this way, the recommended dosage is 1,000 micrograms per day. It is important to consult a doctor if a B12 deficiency is suspected.
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at (239) 267-6480.