Tier 4 — mechanistic

Smoking, dietary betaine, methionine, and vitamin D in monozygotic twins with discordant macular degeneration: epigenetic implications

Johanna M Seddon, Robyn Reynolds, Heeral R Shah, Bernard Rosner
Ophthalmology 2011 118(7):1386-1394

Bibliography

PubMed
PMID 21620475
PubMed Central
PMC3711586
DOI
10.1016/j.ophtha.2010.12.020
Funding
Reported funding/support: National Eye Institute : NEIR01 EY011309 || EY
Competing interests
Reported disclosure: Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Study snapshot

DesignDiscordant identical-twin case series
ModelHuman participants
SampleMale twin pairs; 28 discordant for disease stage and larger groups for retinal features
InterventionHabitual dietary choline and/or betaine intake; no randomized TMG treatment
DurationDiet and retinal phenotype comparison
EndpointsMacular degeneration; Dietary differences

What the study showed, in plain terms

Published in 2011, this source examined human observational and biomarker research. Design: Discordant identical-twin case series. Sample/model: Male twin pairs; 28 discordant for disease stage and larger groups for retinal features. The exposure or intervention was Habitual dietary choline and/or betaine intake; no randomized TMG treatment. Follow-up or treatment period: Diet and retinal phenotype comparison.

The twin with less severe macular degeneration tended to have higher dietary betaine intake in the disease-stage comparison.

Observational exposure analysis: residual confounding and reverse causation remain possible. Associations do not establish that betaine supplementation causes the same outcome.

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Key findings

  • The twin with less severe macular degeneration tended to have higher dietary betaine intake in the disease-stage comparison.
  • The recorded outcome domains were Macular degeneration; Dietary differences.

What this study can and cannot tell us

  • Observational exposure analysis: residual confounding and reverse causation remain possible. Associations do not establish that betaine supplementation causes the same outcome.
  • A case report or series cannot estimate how often an event occurs or establish causality without alternative explanations and a suitable comparator.
  • Source basis: Accessible full-text extract plus indexed bibliographic data. Missing method details, funding information or participant denominators are not inferred.

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Elham Sharifi-Zahabi et al. · Journal of diabetes research · 2026
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Association of choline and betaine with the risk of cardiovascular disease and all-cause mortality: Meta-analysis
Qinglin Yang et al. · European journal of clinical investigation · 2023
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Association of choline and betaine levels with cancer incidence and survival: A meta-analysis
Jiyoung Youn et al. · Clinical nutrition (Edinburgh, Scotland) · 2019

Editorial review

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology