Can lysine supplements enhance appetite?

Lysine Supplements and Appetite Enhancement

Lysine supplements are not recommended as appetite stimulants as there is no established evidence supporting their use for appetite enhancement in humans. 1, 2

Evidence on Appetite Stimulants

Established Appetite Stimulants

According to clinical guidelines, the following medications have demonstrated efficacy as appetite stimulants:

• Progestins (strongest evidence):

  • Megestrol acetate: Significant appetite stimulation and weight gain effects (minimum effective dose: 160 mg/day) 1, 2
  • Medroxyprogesterone acetate (MPA): Significant appetite stimulation (minimum effective dose: 200 mg/day) 1

• Corticosteroids: Effective appetite stimulants but with limited duration of use (1-3 weeks) due to side effects 1, 2

• Other agents with some evidence:

  • Cyproheptadine: May stimulate appetite but has reported adverse effects 1
  • Long-chain N-3 fatty acids (fish oil): Some evidence for patients with advanced cancer 2

Agents Without Established Appetite-Stimulating Effects

The following agents have not been shown to have appetite-stimulating effects:

• Dronabinol (except in specific dementia cases)
• Metoclopramide
• Nandrolone
• Pentoxifylline
• Hydrazine sulphate 1

Lysine and Appetite: Current Evidence

Lysine has not been included in any clinical guidelines as an appetite stimulant. The available research on lysine and appetite shows:

1. Animal studies: In broiler chickens, low lysine concentrations were associated with upregulation of ghrelin (an appetite-stimulating hormone) in the hypothalamus and pancreas, but this led to slow growth and high mortality 3.

2. Human studies:

   • A study examining whey proteins (which contain lysine among other amino acids) found that lysine was among eight specific amino acids that correlated with decreased hunger and increased satiety 4.
   • Another study showed that high lysine supplementation in rats with low protein diets actually reduced body weight gain and food intake 5.

3. Metabolic effects: Lysine has been shown to lower glycemic response to mixed-nutrient drinks in humans, but this was not associated with increased appetite 6.

Clinical Implications

1. For appetite stimulation: Use established agents like megestrol acetate (160-800 mg/day) or corticosteroids (short-term) when clinically indicated 1, 2.

2. Monitoring: When using established appetite stimulants, monitor for side effects:

   • Progestins: Risk of thromboembolism, impotence, and vaginal spotting 2
   • Corticosteroids: Risk of muscle wasting, insulin resistance, infections, and immunosuppression 2

3. Avoid unproven supplements: Lysine supplements should not be used specifically for appetite enhancement as there is no clinical evidence supporting this use.

Special Considerations

In patients with dementia, guidelines specifically recommend against the systematic use of appetite stimulants due to limited evidence and potential side effects 1. Instead, focus on:

• Providing feeding assistance
• Ensuring adequate time for meals
• Offering energy-dense meals
• Addressing behavioral issues that may affect eating 1

In conclusion, while lysine is an essential amino acid important for protein synthesis and metabolism 7, there is no evidence supporting its use as an appetite stimulant in humans. Clinicians should rely on established appetite stimulants when medically necessary.