Dietary Vitamin C Supplementation Reduces Noise-Induced Hearing Loss in Guinea Pigs

Dietary vitamin C supplementation reduces noise-induced hearing loss in guinea pigs.
McFadden SL1, Woo JM, Michalak N, Ding D.
Author information

Abstract
Vitamin C (ascorbate) is a water-soluble, low molecular weight antioxidant that works in conjunction with glutathione and other cellular antioxidants, and is effective against a variety of reactive oxygen species, including superoxide and hydroxyl radicals that have been implicated in the etiology of noise-induced hearing loss (NIHL). Whereas most animals can manufacture their own vitamin C, humans and a few other mammals such as guinea pigs lack the terminal enzyme for vitamin C synthesis and must obtain it from dietary sources. To determine if susceptibility to NIHL could be influenced by manipulating dietary levels of vitamin C, albino guinea pigs were raised for 35 days on a diet with normal, supplemented or deficient levels of ascorbate, then exposed to 4 kHz octave band noise at 114 dB SPL for 6 h to induce permanent threshold shifts (PTS) of the scalp-recorded auditory brainstem response. Animals that received the highest levels of dietary ascorbate developed significantly less PTS for click stimuli and 4, 8, 12, and 16 kHz tones than animals on normal and deficient diets. Outer hair cell loss was minimal in all groups after noise exposure, but permanent damage to stereocilia were observed in noise-exposed ears. The results support the hypothesis that dietary factors influence individual susceptibility to hearing loss, and suggest that high levels of vitamin C may be beneficial in reducing susceptibility to NIHL.

http://www.ncbi.nlm.nih.gov/pubmed/15811712

 

I find interesting the fact tha vitamin C can work to prevent hearing loss, although if I'm not mistaken cannot reverse the damage done, right?

 

Vitamin C is a potent anti-oxidant and thus can take care of free radicals that can cause damage to cells. If I'm not mistaken a cascade reaction that involves free radicals is set off in the cochlea in response to loud noise. I know that there is a cascade reaction that kills hair cells as this is what AM-101 is supposed to treat but I'm unsure about the involvement of free radicals. But I think I have read it somewhere.

 

I ran across a testimonial a few days ago by a person who claimed that taking high doses of Vitamin C within 24 hours of an acoustic trauma can dramatically improve the prospects for avoiding NIHL and long-term tinnitus. I just tried to find that testimonial, but couldn't (I could kick myself for not bookmarking it). But I just did an online search, and discovered the study that's the title of this thread--and thought it would be good to revive this old thread.

The study seems to support the testimonial I ran across and the hypothesis that Vitamin C can possibly make a big difference for somebody experiencing an acoustic trauma. Running across this study reminded me of so many on this forum who have tried prednisolone to try to achieve the same positive results. Some have gotten improvement, others haven't, and some have not been able to get their doctors to even provide a prescription for it.

In my search this morning, I also came across another somewhat similar study. I think the two studies combined make a strong case for taking high doses of Vitamin C as soon as possible after an acoustic trauma. Seems like nothing to lose, perhaps a whole lot to gain. The following study and abstract give some clues on some other things that might also be helpful...

Vitamin E and vitamin C in the treatment of idiopathic sudden sensorineural hearing loss

Abstract

The results of this study suggest that the administration of vitamin E and vitamin C to patients with idiopathic sudden sensorineural hearing loss (ISSHL) has beneficial effects by reducing the level of reactive oxygen metabolites produced by inner ear ischaemia and reperfusion injury after treatment. The purpose of this study was to investigate the efficacy of antioxidant vitamin E and vitamin C in the treatment of ISSHL.

In a retrospective chart review, a total of 87 patients were enrolled who fulfilled the following inclusion criteria: 1) sudden onset of sensorineural hearing loss, 2) cause of hearing loss unknown, 3) hearing loss did not fluctuate, 4) arithmetic mean of hearing levels at 250, 500, 1000, 2000 and 4000 Hz exceeded 40 dB and 5) treatment was started within 14 days from the onset of hearing loss.

All the patients were treated with steroids and/or alprostadil. In the study group, patients additionally received vitamin E (tocopherol nicotinate, 600 mg/day) and vitamin C (1200 mg/day) orally. The hearing gain after therapy was 29.4 dB and the improvement rate was 63.3% in the study group, compared with 18.5 dB and 44.0% in the control group. Significant improvement was seen in the hearing gain and recovery rate in the study group.​

 

Your study is for idiopathic loss, not acoustic trauma. Which may point to it being better for viral causes since that's suspected to be a common cause of idiopathic loss.

 

@Lane
Check out

https://www.sciencedaily.com/releases/2020/05/200512151941.htm

 

Positive modulation of the α9α10 nicotinic cholinergic receptor by ascorbic acid [vitamin C]

The activity of efferent inhibitory cholinergic fibres projecting from the brainstem and synapsing onto cochlear hair cells can ameliorate acoustic trauma in rodents (Maison et al., 2002; Taranda et al., 2009). This inhibitory control of auditory function is mediated by α9α10 nicotinic cholinergic receptors (nAChRs) coupled to SK2 Ca2+-activated K+ channels, both present at the postsynaptic membrane of cochlear hair cells (Elgoyhen and Katz, 2012). Consequently, enhancing α9α10 receptor-mediated responses by means of a pharmacological positive modulator could have a potential therapeutic use in the prevention or treatment of noise induced hearing loss (Elgoyhen et al., 2009).

Ascorbic acid potentiated ACh responses in X. laevis oocytes expressing α9α10 (but not α4β2 or α7) nAChRs, in a concentration-dependent manner, with an effective concentration range of 1–30 mM.

ASC (Vitamin C) is an endogenous antioxidant which is present in ∼0.05 mM concentrations in plasma, ∼0.2 mM in CSF and ∼1 mM in whole brain. In certain tissues like the retina, concentrations of ASC are 100 times more concentrated than in plasma. Particularly, in blood cells it reaches ∼3 mM concentrations and in neurons 10 mM concentrations. Extracellular ASC levels can transiently rise substantially during neuronal activity. It has been shown that ASC modulates the activity of several ion channels like NMDA glutamate receptors and [inhibits] T-type Ca2+ channels. Interestingly, in contrast to the effect of ASC on the above-mentioned channels where it decreases responses, it has been demonstrated recently that ASC potentiates responses through GABAA and GABAC receptors.

The effective potentiating concentration of ASC on the α9α10 nAChRs is similar to that described for GABAA and GABAC receptors and within the concentration that can be attained [how?] in neuronal tissues.

Does the potentiating effect of ASC on α9α10 nAChRs have a potential physiological or pathophysiological role? Antioxidants prevent cochlear damage from toxic reactive oxygen species that are produced at high levels during and after noise exposure (Lynch and Kil, 2005; Le Prell et al., 2007). In particular, it has been described in rodents that ASC is beneficial in reducing the sensitivity to noise-induced hearing loss (McFadden et al., 2005). Thus, in addition to its antioxidant effects and based on the described protective effect of the medial olivocochlear system (Maison et al., 2002; Taranda et al., 2009), potentiation of responses mediated by α9α10 nAChRs at the efferent-hair cell synapse might also play a role.