Open trial of vitamin B12 nasal drops in adults with myalgic Encephalomyelitis/Chronic fatigue syndrome: comparison of responders and Non-Responders
(2014, Nature Medicine) established NNMT as a major regulator of metabolic rate in white adipose tissue, showing that NNMT knockdown in mice produced a lean phenotype with elevated energy expenditure providing the foundational rationale for NNMT inhibition as a metabolic research target
doi:10.3389/fnsys.2013.00102
The only minor side effects have been cramping, bloating, and lower zinc levels in people who used glutathione over long periods
Quick answer: Skip L-carnitine if you expect it to replace a calorie deficit, if you are pregnant or breastfeeding without medical guidance, if you have seizure history, kidney disease, cardiovascular risk concerns, hypothyroidism concerns, or if you are on medications that make supplement use a clinician-level decision