HRV & Nutrition

Methods

Randomized controlled trial, 100 participants, 90-day intervention

Key Findings

• pNN50 (parasympathetic indicator) significantly increased
• Stress index decreased with supplementation
• 400mg daily magnesium showed benefits in stressed individuals
• Effects emerged over weeks of consistent supplementation

Limitations

Single study, specific population already experiencing stress, needs replication in broader populations

Methods

Review of cross-sectional and intervention studies

Key Findings

• SDNN, SDANN, and triangular index lower with vitamin D deficiency
• Relationship strongest in hypertensive patients
• Some studies show no association in low-risk populations
• Supplementation may stabilize cardiac autonomic tone

Limitations

Mostly cross-sectional data, causation not established

Methods

Population studies and randomized controlled trials

Key Findings

• Higher gut microbial diversity associated with higher SDNN
• Probiotics improved vagal function in depression patients after 3 months
• Low HRV linked to gut dysbiosis and altered microbiota composition
• SCFAs from fiber fermentation may influence vagus nerve

Limitations

Emerging field, heterogeneous study designs, causation unclear

Methods

Twin study, 276 middle-aged male twins, 24-hour ECG monitoring

Key Findings

• 1-unit higher Mediterranean diet score = 4-13% higher HRV
• Higher SDNN, RMSSD, and frequency domain parameters
• Effects independent of genetics and shared environment
• Omega-3 intake likely a key mediating factor

Limitations

Male-only sample, observational design

Methods

Studies of time-restricted eating and alternate-day fasting

Key Findings

• First 1-2 weeks often show HRV suppression
• After adaptation, some studies show HRV improvement
• Effects vary by fasting protocol and individual
• Weight loss component may drive HRV benefits

Limitations

Small studies, varying protocols, short durations

Methods

Analysis of wearable HRV data correlated with self-reported alcohol intake

Key Findings

• 1-2 drinks suppress HRV for approximately 2 days
• 3+ drinks can affect HRV for 4-5 days
• Effect is dose-dependent and cumulative
• Sleep quality also impaired during recovery period

Limitations

Self-reported alcohol intake may be underestimated

Methods

Meta-analysis of 15 RCTs with HRV outcomes

Key Findings

• 1-2g daily EPA/DHA showed most consistent benefits
• RMSSD improved by 5-15% on average
• Benefits more pronounced in those with lower baseline omega-3 status
• Effects take 8-12 weeks to fully manifest

Limitations

Heterogeneous study designs, varying doses and formulations

Methods

Systematic review of caffeine and HRV studies

Key Findings

• Acute caffeine may decrease HRV in non-habitual users
• Habitual consumers show blunted or no HRV response
• Individual variation is substantial
• Effects may depend on dose, timing, and baseline state

Limitations

Heterogeneous study designs and caffeine doses