Public health nutrition — An endemic cardiomyopathy seen in children (e.g., Keshan disease) is primarily attributed to which environmental or dietary factor?

Introduction / Context:
Endemic cardiomyopathy in children, classically exemplified by Keshan disease, has been linked to selenium deficiency in regions with selenium-poor soil and food chains. Understanding the micronutrient basis of such cardiomyopathies helps clinicians and public health professionals target prevention through diet diversification and fortification.

Given Data / Assumptions:

• The disease is endemic (geographically clustered).
• Children are the most affected demographic in classic descriptions.
• Local soil and food selenium content are low, reducing dietary Se intake.
• Other nutrients (iron, vitamin B12) may influence health but are not the primary etiologic factor here.

Concept / Approach:
Selenium is required for antioxidant selenoproteins (e.g., glutathione peroxidases, thioredoxin reductases) that protect cardiomyocytes from oxidative damage. In selenium-deficient settings, viral co-factors may worsen myocardial injury. Therefore, the best single-cause descriptor among the options is low environmental selenium leading to inadequate intake.

Step-by-Step Solution:

Verification / Alternative check:
Interventions with selenium supplementation and dietary diversification reduce incidence in affected regions, supporting causality.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing general anemia-related cardiac stress with the specific oxidative-injury pattern from selenium deficiency.

Final Answer:
Low selenium in the environment leading to inadequate intake.