By Dr. Mercola
You're probably aware that certain nutrients can support optimal vision, but did you know your hearing may benefit from certain foods as well? If you have trouble hearing, or notice that your hearing is not as good as it used to be, your diet (and/or additional supplementation) may hold the answer.
In fact, nutritional imbalances are increasingly thought to be a causative factor in hearing loss.1 Age-related hearing loss is actually not due to any kind of mechanical dysfunction in your ear. Rather it's how your brain processes information that results in reduced hearing.
Furthermore, it's your brain's ability to provide proper feedback to your ear, by filtering out unwanted information, that declines when you reach your 40s and 50s. Without this filtering system, you're more likely to be overcome by a mass of information that is difficult to sort out.
The good news is age-related hearing loss may be reversible. Tinnitus, which is typically caused by noise-induced damage, may also be greatly improved, as can sudden loss of hearing.
Nutrients That Protect and Improve Hearing
These nutrients support hearing in a number of ways, including:
- Protecting against oxidative stress in the cochlea
- Preventing free radical damage
- Improving blood flow, thereby reducing cochlear damage related to a compromised vascular system
- Improving homocysteine metabolism
The support for vitamin A is mixed. In one large study that included data from more than 65,500 women, no correlation was found between vitamin A intake and risk for hearing loss.9 However, a number of other studies have indeed found a positive correlation. As reported by Weston A. Price:10
"A 1984 European study reported a 5 to 15 decibel improvement in patients with age-related hearing loss when given vitamins A and E. Other researchers reported that vitamin A deficiency results in a decline in the number of sensory cells in the nose, tongue and inner ear.
A 1993 study reported in Science found that vitamin A can stimulate the regeneration of mammalian auditory hair cells. In 2009, Japanese researchers found that adults with the highest blood serum levels of vitamin A and carotenoids have the lowest risk for hearing loss.
And, in 2014, researchers determined that vitamin A deficiency during pregnancy, especially during the early stages of fetal development 'may predispose offspring to inner ear malformations and sensorial hearing loss.'"
Folate May Improve Tinnitus
For noise-induced tinnitus, which is characterized by a chronic or near-chronic ringing in the ears, folate (vitamin B9), has been shown to be beneficial. Folate also lowers your homocysteine, and having a high blood level of homocysteine has been linked to age-related hearing loss.11,12
As a general rule, the ideal way to raise your folate levels is to eat plenty of fresh, raw and organic leafy green vegetables. Folic acid is the synthetic form typically found in supplements.
There is good reason to consider getting your folate from food rather than folic acid supplements. In order for folic acid to be of use to your body, it must first be activated into its biologically active form — L-5-MTHF. This is the form that is able to cross the blood-brain barrier.
It's been estimated that early half of all adults have difficulty converting folic acid into the bioactive form because of a genetic reduction in enzyme activity. For this reason, if you take a B-vitamin supplement, make sure it contains natural folate rather than synthetic folic acid. Children seem to convert folic acid more easily.
Asparagus, spinach, turnip greens and broccoli are all good sources of folate, as are beans, including lentils and garbanzo beans.
Zinc for Sudden Hearing Loss
Research has shown zinc may be useful for idiopathic sudden sensorineural hearing loss (SSNHL). SSNHL — a sudden, unexplained loss of hearing — is typically treated with high-dose steroids, even though steroid treatment is controversial and evidence to support their efficacy is limited.
The good news is that 47 to 63 percent of those affected end up recovering most or all of their hearing.13 While the cause for SSNHL is unknown, one theory is that a viral infection or immunologic disease is involved. This may help explain the high rate of recovery, and why zinc appears to be so beneficial for this condition.
Zinc has anti-viral properties, and studies have shown it can prevent common cold viruses from replicating or attaching to your nasal membranes. Zinc also has immune-boosting properties, allowing your body to mount a stronger first response at the onset of a viral infection.
In one study,14 66 SSNHL patients were randomly divided into two groups; half received corticosteroid treatment while the other half received oral zinc gluconate plus corticosteroid treatment. Serum zinc levels were ascertained at the outset and end of the study.
Those receiving zinc experienced significantly larger gains in hearing gain and a greater percentage of recovery. According to the authors:
"There was a significant correlation between serum zinc level changes and posttreatment hearing thresholds by correlation analysis, as well as between changes of serum zinc levels and percentage of recovery in the zinc group.
Zinc supplementation may enhance the hearing recovery of SSNHL patients. Its antioxidant and anti-inflammatory effects may help reduce the oxidative stress of the cochlea in SSNHL, implying a new direction in the treatment of this disease."
A Well-Balanced Diet Is the Best Source of Zinc
Any time you isolate one mineral and ingest it independently of others, you run the risk of creating an imbalance. This is certainly true of zinc, and taking zinc indiscriminately can be quite problematic. Excess zinc has been shown to:
- Interfere with your body's ability to absorb other minerals, especially copper, which may lead to anemia
- Raise the risk of prostate cancer in men15
- Induce nausea, stomach pain, vomiting and diarrhea
The recommended daily allowance (RDA) for zinc is:
- 11 milligrams (mg) per day for adult men
- 8 mg for women (If you are lactating or pregnant, you need about 3 mg more)
- 5 mg for 4- to 8-year-olds
- 8 mg for 9- to 13-year-olds
- 3 mg for infants
Anything over 50 mg is thought to be excessive. To be on the safe side, focus on getting your zinc from food. Besides protein-rich foods like grass-fed beef and seafood, other dietary sources of zinc include pumpkin seeds, tahini (ground sesame seeds), cashews, almonds, crimini mushrooms, spinach, sea vegetables and cheddar cheese.
Oysters top the list of zinc-rich foods, with anywhere from 16 to 182 mg of zinc per 100-gram serving, followed by liver, which has 12 mg of zinc per 100 grams. It appears zinc is better absorbed from animal sources than plant sources, so if you are serious about increasing your zinc intake, consider adding more organic grass-fed beef or liver to your diet.
Intravenous Magnesium May Also Improve Sudden Hearing Loss
Intravenous magnesium has also been shown to improve SSNHL. In one study,16 48 percent of SSNHL patients achieved recovery after receiving intravenous magnesium in combination with carbogen inhalation17 (a mixture of carbon dioxide and oxygen gas). Another 27 percent experienced significant improvement.
Factors that reduced the effectiveness of the treatment included vestibular symptoms (patients who had vertigo) and delaying treatment for more than eight days after onset.
Increasing NT3 Production Restored Hearing in Mice
Two years ago, researchers looking at ways to restore hearing lost due to noise came upon an interesting finding. By increasing the production of a protein called neurotrophin-3 (NT3), they were able to reverse hearing loss in mice that had been partially deafened by loud noise.
As it turns out, NT3 plays a key role in the communication occurring between your ears and your brain. NT3 helps establish so-called ribbon synapses that link the hair cells in your inner ear to nerve cells in your brain. When exposed to extremely loud noise, these ribbon synapses are damaged, resulting in the loss of hearing.
Normal aging can also damage your ribbon synapses, so NT3 may counteract normal age-related hearing loss as well. To boost production of NT3, the researchers used conditional gene recombination. As explained by Medical News Today:18
"This allows researchers to activate genes in particular cells by administering a drug that prompts the cells to 'read' additional copies of a gene that have been inserted into them. For this study, the team used the technique to activate additional NT3 genes that had been introduced to the supporting cells of the inner ear in mice that had been partially deafened by loud noise.
The drug tamoxifen was introduced to the supporting cells in the inner ear, which prompted them to produce extra NT3 protein … The researchers found the mice that had experienced boosted NT3 production regained their hearing over a 2-week period, compared with mice that had not had additional NT3 production …
[T]hey now plan to … identify drugs that produce the same effect as the protein, offering the potential to restore hearing loss in humans. The researchers note that the gene therapy technique used in this study has the potential to work in humans, but that a drug-based method would be 'simpler' and a drug could be repeatedly administered for as long as it takes for hearing to be restored."
Astaxanthin Raises NT3 Expression
While researchers are looking for a drug solution to raise NT3, a Chinese study suggests astaxanthin could be used for this purpose.19 Astaxanthin, which is part of the carotenoid family, is believed to be one of the most potent antioxidants nature has to offer.
It's FAR more potent than beta-carotene, alpha-tocopherol, lycopene and lutein, for example, and exhibits very strong free radical scavenging activity that protects your cells, organs and body tissues from oxidative damage. It's also a powerful anti-inflammatory and is able to cross both the blood-brain barrier and the blood-retinal barrier.
Indeed, astaxanthin has been shown to have potent benefits for brain and eye health, and may be beneficial for your hearing as well, thanks to this NT3-boosting ability. The study in question looked at astaxanthin's effect on NT3 expression in rats with compressive spinal cord injury, as NT3 has been shown to increase the growth of spinal cord neurons as well. According to the authors, astaxanthin was able to "significantly promote the expression of NT3."
There are only two main sources of natural astaxanthin — the microalgae that produce it (Haematococcus pluvialis), and the sea creatures that consume the algae, such as salmon, shellfish and krill. If you decide to give astaxanthin a try, I recommend starting with 2 mg per day.
If you are on a krill oil supplement, take that into consideration; different krill products have different concentrations of astaxanthin, so check your label. While it's unclear how much you'd need to improve your hearing, doses of 8 to 10 mg a day are typically recommended if you're trying to improve your eye health.
Boosting BDNF May Also Improve Your Hearing
Earlier research has also shown that, in addition to NT3, brain-derived neurotrophic factor (BDNF) also plays an important role in the development and survival of auditory neurons in your brain. One 1996 study20 found that loss of auditory hair cells and auditory neurons can be prevented by therapies that boost either NT3 or BDNF.
Interestingly, one lifestyle factor that naturally boosts BDNF is exercise. Part of what makes exercise so effective for preventing cognitive decline is related to a boost in BDNF. It's intriguing to speculate whether exercise may also help prevent hearing loss through this mechanism.
What's the Best Way to Protect Your Hearing?
Worldwide, 360 million people have moderate to severe hearing loss due to various causes, from noise or infectious disease to the use of certain drugs and aging. It's estimated that halfof these cases of hearing loss are avoidable.21 This includes cases of hidden hearing loss or noise-induced hearing loss. Of course, protecting yourself from loud noises in the first place is prevention 101. The following recommendations can help protect your hearing and avoid hearing loss:
✓ Turn down the volume on personal audio devices
✓ Try a decibel meter app for your smartphone, which will flash a warning if the volume is turned up to a potentially damaging level
✓ Wear earplugs when you visit noisy venues, and if you work in a noisy environment, be sure to wear ear protection at all times
✓ Use carefully fitted noise-canceling earphones/headphones, which may allow you to listen comfortably at a lower volume
✓ Limit the amount of time you spend engaged in noisy activities
✓ Take regular listening breaks when using personal audio devices
✓ Restrict the daily use of personal audio devices to less than one hour
✓ If you live in a very noisy area, you may want to consider moving.
If that's not an option, consider adding acoustical tile to your ceiling and walls to buffer the noise.
Double-paneled windows, insulation, heavy curtains and rugs can also help
✓ Use sound-blocking headphones to eliminate occasional sound disturbances such as that from traffic or lawnmowers.
Also wear ear protection when using your lawnmower or leaf blower
Aside from that, eating a healthy, varied diet of real food can go a long way toward protecting against age-related hearing. And, even if you've already lost some degree of hearing, you may be able to recover some of it by optimizing your intake of carotenoids, especially astaxanthin, vitamin A, folate, zinc and magnesium.