3-Methylhistidine (Plasma)

This methylated form of histidine comes from muscle tissue, both dietary and endogenous, where it is part of the muscle proteins actin and myosin. A moderate level of urine 3-methylhistidine is normal.

3-Methylhistidine is a biomarker for meat consumption, especially chicken. It is also a biomarker for the consumption of soy products.

Elevated levels suggest either an inordinately high intake of dietary actin/myosin or accelerated catabolism of muscle tissue. 3-Methylhistidine excretion is increased after strenuous physical exercise and also occurs in muscle wasting conditions - dystrophies, lack of exercise, extended bed rest, terminal stages of severe illness. Convulsions and seizures also feature increased urinary 3-methylhistidine. There is some correlation between elevated 3-methylhistidine and increased need for vitamin B12, folic acid, methionine and perhaps histidine if it is marginal or low.

If these deficiencies show up elsewhere on this test, then even though protein is burning at a rate, the Krebs cycle is operating at a lower rate than normal. This is consistent with fatigue and low body temperature.

If Histidine is also high:

May indicate excessive protein intake. Muscle protein breakdown is indicated.

If Beta-Alanine is also high:

Possible cause for food sensitivity reactions when combined with low taurine and high Beta-Alanine due to impaired renal tubular resorption.

A decreased level of 3-Methylhistidine (3-MH) in plasma typically signifies one or more of the following conditions:

1. Reduced Muscle Breakdown (Proteolysis)

• 3-Methylhistidine is a biomarker of muscle protein turnover, specifically the breakdown of actin and myosin in skeletal muscle.
• Lower levels suggest reduced muscle catabolism, which may be due to:
  • Muscle preservation (e.g., strength training with minimal breakdown)
  • Malnutrition or low protein intake (less substrate for breakdown)
  • Aging-related muscle inactivity or sarcopenia
  • Certain medications (e.g., corticosteroids suppressing muscle breakdown)

2. Protein Malnutrition or Low Dietary Intake

• Since 3-MH is derived from muscle proteins and cannot be reused, a low-protein diet or malnutrition can result in decreased levels.
• Conditions leading to protein deficiency:
  • Chronic illness (e.g., advanced liver or kidney disease)
  • Malabsorption syndromes (e.g., celiac disease, Crohn’s disease)
  • Starvation or prolonged fasting

3. Diminished Muscle Mass

• Individuals with low muscle mass (e.g., due to aging, cachexia, or prolonged immobility) may have lower baseline levels of 3-MH due to reduced protein turnover.

4. Endocrine or Metabolic Disorders

• Hypothyroidism (slower metabolism reduces protein breakdown)
• Insulin resistance or diabetes (altered muscle metabolism)
• Growth hormone deficiency (GH promotes protein turnover)

5. Renal Impairment

• Since 3-Methylhistidine is excreted through the kidneys, its plasma levels can be affected by kidney function. In some cases of severe renal disease, low plasma levels may indicate reduced clearance and altered protein metabolism.

Key Takeaways

• Low 3-MH levels suggest reduced muscle breakdown, which may be beneficial in some cases (e.g., strength training) but could also indicate malnutrition, low muscle mass, or metabolic dysfunction.
• If persistently low, it may warrant nutritional assessment, muscle health evaluation, and endocrine/metabolic screening.

3-Methylhistidine is an amino acid which is excreted in human urine.

The measurement of 3-methylhistidine provides an index of the rate of muscle protein breakdown. 3-Methylhistidine is a biomarker for meat consumption, especially chicken. It is also a biomarker for the consumption of soy products.