Journal Club: Ketogenic diet above a certain threshold may be associated with slightly elevated risk of high-frequency hearing loss?

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Today's journal article

Zeng Q, Xiao Y, Sheng M, Liu B. L-Shaped Relationship Between Ketogenic Diet and High-Frequency Hearing Loss. 

Why I picked this article

This research investigates the relationship between the ketogenic diet ratio and hearing loss. The study includes a cross-sectional analysis of NHANES 2005–2012. 

I picked this article because I am very interested in it and am currently on a ketogenic diet myself. A ketogenic diet is one where you remove the majority of carbohydrates from the diet, and get a large proportion of calories from protein and fat. The suggested health benefit comes from reduced blood sugar spikes and insulin resistance, and has been utilised as a weight management strategy. Once you are used to it, it's practically achievable by removing carbohydrate-rich food from the main meals and adding more vegetables and animal/fish products. Potential adverse effects are changes in gut flora; if not carefully managed, the ketogenic diet alters the balance of bacteria in the gut in a bad way. 

As I understand, there are some links to poor diet (ones that have a negative impact on our body system), which is generally bad for the ears and hearing. 

(From Pixabay.com, artist https://galyafanaseva.com)

Some of the research finding

Study design: 
  • Dataset: National Health and Nutrition Examination Survey (NHANES)
    • NHANES assess population health and nutritional data in the United States.
    • cycles 2005–2012 NHANES included 40,790 individuals total.
    • Of those, 4,036 participants were included in the final analysis. This excludes participants who were <20 years old and those without complete hearing tests or missing ketogenic diet data were removed. 
  • Exposure: ketogenic diet ratio (KDR) as a continuous measure of how “ketogenic” the diet is.
  • KDR = (0.9 × grams of fat + 0.46 × grams of protein)/(0.1 × gramsof fat + 0.58 × grams of protein + grams of net carbohydrates)
  • Hearing loss: hearing loss by frequency band, with a focus on high-frequency hearing loss.
  • Statistics: weighted multivariable logistic regression, restricted cubic spline modeling, and trend tests; prespecified subgroup analyses.
Main results
  • Participants: 
    • average 49 year-old, 52% male and 48% female
      • 98% not diabetic, 2% diabetic. 
      • 33% hypertensive 
      • 70% non-Hispanic white, 10% non-Hispanic black, 7.2% other, 7.2 % Mexican American, 5.2% other Hispanic
  • There was a non-linear association between ketogenic diet ratio and high-frequency hearing loss. 
    • Continuous ketogenic diet ratio was positively associated with high-frequency hearing loss. 
    • The association remained significant after multivariable adjustment.
    • No significant association between ketogenic diet ratio and hearing loss at other (lower) frequency ranges.
  • Risk rose when the ketogenic diet ratio exceeded a threshold of greater than 3.41
  • Subgroups: findings were consistent across predefined strata (age, sex, etc.) except for Race, where consistency was not observed.
The non-linear relationship suggests risk is concentrated above a dietary threshold, rather than increasing linearly across the full ketogenic diet ratio range. 

Haruna's takeaway

It was very interesting from the perspective of the person on a ketogenic diet! It seems that there may be a cut-off to when the risk increases. It's impossible to establish cause - effect relationship between dietary factors and the disease from this type of study. I wonder if the increased risk may come from the altered gut microenvironment and inflammation of the gut (and the system) that could happen with a ketogenic diet. The gut-brain axis and gut-cochlear axis have been discussed scientifically. It might be more about the overall health of the body, and the balance between the pros and cons of the ketogenic diet. 

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This is Haruna's 89/100 of the 100-day challenge to post a science blog article every day! I love inner ear biology & cochlear physiology.