. 2018 Dec 24;11(1):35. doi: 10.3390/nu11010035

Table 4.

Main results of the epidemiological studies that evaluate micronutrients effects on hearing loss.

Micronutrient	Study Subjects	Effect	Author and Year
Carotenoid, retinol, thiamine, riboflavin, niacin and vitamin C	Adults	High dietary intake of vitamin C was associated with a better auditory function	Kang et al., 2014 [98]
		Retinol, niacin and riboflavin consumption showed minor association with HL
		Vitamin D serum concentration associated with worse auditory function
Retinol, vitamin B₁₂, β-carotene, folate, vitamins B6, C and E	Adults	High retinol and vitamin B₁₂ intake associated with better auditory function in women	Hercberg et al., 2004 [102]
	Adults	No associations found for β-carotene, folate and vitamins B6, C and E	Hercberg et al., 2004 [102]
Carotenoids, FA, vitamins C, A and E	Women	Inverse correlations between carotenoids (β-carotene and β-cryptoxanthin) and folate intakes and risk of acquired HL	Curhan et al., 2015 [103]
		Direct correlation between high vitamin C intake (from supplements) and risk of HL
		No significant associations for vitamin A, E, and other carotenoids
Dietary antioxidants	Adults	High vitamin A and E consumption showed inverse associations with HL prevalence	Gopinath et al., 2011 [93]
Dietary antioxidants	Adults	Dietary antioxidants consumed alone or in combination were unable to predict 5-year incidence of ARHL	Gopinath et al., 2011 [93]
Vitamins and minerals	Adults	Dose-dependent trend between all individual nutrients (except vitamin E) and better speech pure tone average	Choi et al.,2014 [94]
Vitamins and minerals	Adults	Synergistic effect of high intakes of β-carotene and vitamin C with magnesium and better pure tone average at high frequencies	Choi et al.,2014 [94]
Folic acid and vitamin B₁₂	Women	Consistent associations between low vitamin B₁₂ and folate levels and ARHL	Houston et al., 1999 [112]
Folic acid and vitamin B₁₂	Women	Stronger association with folate intake rather than with vitamin B₁₂ ingestion, according to dietary intake	Houston et al., 1999 [112]
Folic acid and vitamin B₁₂	Elderly	Low serum vitamin levels were significantly associated with HL in the high frequencies	Lasisi et al., 2016 [16]
Folic acid and vitamin B₁₂	Elderly	Significant correlations, after adjusting for age, in folate but not in B12	Lasisi et al., 2016 [16]
Folic acid and vitamin B₁₂	Adults	Non-significant associations between serum folate, vitamin B₁₂, Hcy and HL	Berner et al., 2000 [113]
Folic acid and vitamin B₁₂	Adults	Low serum folate status increased risk of developing HL	Gopinath et al., 2010 [114]
		Serum vitamin B₁₂ levels had no association with ARHL
		Neither folate nor vitamin B₁₂ showed predictive potential for 5-year incidence of HL
Folic acid, carotene, vitamins C and E	Men	No prospective associations between vitamin C, E, β-carotene or folate consumption and HL	Shargorodsky et al., 2010 [119]
Folic acid, carotene, vitamins C and E	Men	High folate intakes were associated with reduced risk of HL	Shargorodsky et al., 2010 [119]
Folic acid	Adults	Adequate folate intake is beneficial for hearing	Kabagambe et al., 2018 [116]
Folic acid	Adults	High folate intake showed non-significant association with an increased risk of HL	Kabagambe et al., 2018 [116]
Iron	Children and adolescents	Increased odds of SNHL in volunteers with iron deficiency anaemia	Schieefer et al., 2017 [119]
Iron	Children	Negative correlation between hemoglobin levels and auditory function	Kamel et al., 2016 [121]
Iodine	Children	More severe HL in children with mild-to-moderate iodine deficiency compared to those with normal iodine levels	Valeix et al., 1994 [123]
Iodine	Children	HL prevalences of 44 to 15% in children with iodine deficiency compared to 2% in children with adequate levels	Azizi et al., 1993 [124]