A natural, noninvasive remedy that prevents hearing loss would be a big health boon. After all, 38 million Americans have hearing loss, including 14% of people between ages 45 and 65 and 30% to 40% of those over age 65. Hearing aids are a great help, but even the best are a poor substitute for the miraculous miniature machinery of the inner ear.
Now researchers seem to have a strong candidate—a building block of niacin (vitamin B-3) that’s already found in tiny amounts in milk and that has protected hearing in studies. It’s called nicotinamide riboside, or NR for short. Even better, NR may have cardiovascular and brain benefits and for that reason is being added to antiaging supplements.
So, for people who want to protect or improve their hearing, is this vitamin-related supplement safe and ready for prime time?
THE BIG BANG HYPOTHESIS
The most common type of hearing loss is called “noise-induced” and results from exposure to loud and/or high pitched sounds. This damages the sensitive hair cells of the cochlea, the part of the ear that transmits sound to the spinal ganglion, which sends the information on to the brain. Significant noise exposure also damages the synapses connecting the nerves of the inner ear and the hair cells.
At Weill Cornell Medical College, researchers gave mice NR and then exposed them to noises loud enough to damage the cochlea. Results: Mice that were given NR five days before the noise exposure and for 14 days afterward had less damage to the synapses of the inner ear than mice that weren’t given NR. In separate experiments, similar benefits were found with NR given only before the noise (for five days) or only after the noise (for 14 days).
This evidence of NR’s ability to protect the inner ear from noise damage is promising because it follows previous studies showing that a coenzyme that is in all body cells, nicotinamide adenine dinucleotide (NAD+), is a key factor in age-related hearing loss. NR helps the body make NAD+. Digging deeper, the researchers demonstrated that NR and NAD+ both protect cells from hearing damage because they increase the activity of a protein known as sirtuin3 (SIRT3).
SIRT3, it turns out, is a famous molecule. It’s been known for decades that feeding animals a nutritious yet very low-calorie diet lengthens life. So does exercise. Both boost SIRT3, which helps keep mitochondria, the cells’ energy engines, healthy. SIRT3 protects neurons. Because levels of SIRT3 naturally decline with age, researchers think that lowered levels of the protein might be at the heart of age-related hearing loss…and other age-related diseases including Alzheimer’s disease.
So it should come as no surprise that NR, which boosts SIRT3, is hot right now on the supplement market. One company, Niagen, markets 250-mg capsules of NR. Another, called Elysium Health, guided by Nobel Prize winners in molecular biology and related fields, sells Basis, an antiaging supplement that includes 250 mg of NR and 50 mg of pterostilbene, a neuroprotective compound found in blueberries.
SHOULD YOU TAKE NR TO PROTECT YOUR HEARING?
The promise of this new research realm is truly exciting, but let’s walk back this particular study. Remember, this is early research. The mice got about 455 mg of NR for each pound of body weight by injection. The human equivalent would be about 50,000 mg of NR for a 110-pound person. How taking 250 mg in an oral supplement (the amount in the products mentioned above) relates to receiving 50,000 mg by injection (the equivalent used in the study) is, well, unclear. On the plus side, NR is found naturally in food—there are tiny amounts in milk and, possibly, in beer—and it appears to have a good safety profile. It’s not likely to cause flushing, like large doses of niacin (vitamin B-3) do.
To put all this in perspective, we checked in with naturopathic physician Andrew L. Rubman, ND, contributing medical editor for Bottom Line and founder and medical director of the Southbury Clinic for Traditional Medicines in Southbury, Connecticut. He’s not quite ready to jump on the NR bandwagon for everyone: “I don’t believe that supplementation will be either advisable or productive as a generalized intervention to slow aging or produce other supported claims generated by mouse studies,” Dr. Rubman said.
However, if you have hearing loss, Dr. Rubman said, it’s a different story—you may want to check with your doctor about your body’s level of NAD+. (Yes, some labs can test for this, as part of testing for a B-3 deficiency.) Reason: “For a limited segment of the population that have pathologies related to NAD+ biosynthesis, some supplementation with NR (which helps the body make NAD+) may be helpful.” (In case you’re wondering, NAD+ itself is not a stable compound and can’t be taken as a supplement.)
Dr. Rubman is comfortable with doses as high as 2,200 mg a day, preferably as a part of a plan that you and your doctor work out. Because of possible interactions with other B vitamins such as thiamin and riboflavin, Dr. Rubman recommends that NR supplements be taken along with a multi-B vitamin supplement. He often prescribes two doses a day to his patients for better absorption.
To learn more ways to protect your hearing, see Listen Up! These Vitamins Can Prevent Hearing Loss and Surprising Ways to Improve Your Hearing.