Benefits
Exercise recovery and muscle damage markers
In a placebo-controlled crossover trial in 18 healthy middle-aged men and women, Carnipure tartrate supplying 2 g/day of L-carnitine for about 3 weeks lowered blood markers of muscle damage (myoglobin, creatine kinase) after squat and leg press exercise. A 5-week Lonza-funded trial in 80 adults also found lower creatine kinase than placebo.
Perceived muscle soreness after exercise
Both trials that named Carnipure tartrate reported less post-exercise soreness than placebo: lower soreness ratings in 18 middle-aged adults, and better perceived recovery and soreness scores in 80 adults after 5 weeks. The larger trial was funded by Lonza, the maker, and two of its authors were Lonza employees.
Strength and power after a hard workout
In the 5-week Lonza-funded trial, Carnipure tartrate blunted the drop in strength and power after a high-volume exercise challenge versus placebo. In the 3-week crossover trial in middle-aged adults, strength, power and a get-up-and-go test did not change, so performance gains are not established.
Body weight and fat mass (generic L-carnitine)
Generic L-carnitine, not specific to Carnipure: a pooled analysis of 37 randomized trials found about 1.2 kg more weight loss than control and lower fat mass, with no change in waist size or body fat percent. In the 5-week trial of Carnipure tartrate, body composition did not change.
Sperm motility (generic L-carnitine)
Tested as generic L-carnitine, not identified as Carnipure. In a double-blind crossover trial in 100 infertile men with low sperm motility (86 completed), 2 g/day for 2 months improved sperm concentration and motility more than placebo, most in men with the lowest starting values. The authors called for larger trials.
Fatigue scores in very old adults (generic L-carnitine)
Tested as generic L-carnitine, not identified as Carnipure. In 66 fatigued centenarians, 2 g/day improved physical and mental fatigue versus placebo. In 60 adults on thyroid hormone, about 2 g/day for 12 weeks eased mental fatigue only. In 376 adults with cancer, 2 g/day for 4 weeks did not reduce fatigue versus placebo.
Product note: how Carnipure is made and sold
Per Lonza, Carnipure comes as crystalline L-carnitine and as Carnipure tartrate (L-carnitine and tartaric acid in a 2:1 molar ratio, about 68% L-carnitine), made by a proprietary process in an FSSC 22000 certified plant. These are maker statements. No study compares Carnipure with other correctly labeled L-carnitine, and the EU food safety agency did not accept a Lonza claim on lipid metabolism.
Mechanism of action
Fatty acid transport into mitochondria
L-carnitine is a cofactor that carries long-chain fatty acids into mitochondria, where they are oxidized to make ATP. The body makes it from lysine and methionine, and about 95% of body carnitine is stored in heart and skeletal muscle, according to the NIH Office of Dietary Supplements.
Lower markers of exercise stress in working muscle
After squat and leg press exercise, Carnipure tartrate lowered blood markers of purine breakdown (hypoxanthine, xanthine oxidase) and of free radical damage (malondialdehyde). In the 5-week trial, serum superoxide dismutase, an antioxidant enzyme, rose within the supplemented group but did not differ significantly from placebo.
Gut bacteria convert carnitine to TMAO
In a human tracer study, omnivores turned an oral dose of labeled L-carnitine into more than 20 times as much TMAO as vegans or vegetarians, and 2 months or more of L-carnitine supplementation induced the gut bacterial step that produces TMA, the precursor of TMAO.
Clinical trials
Double-blind, placebo-controlled, balanced crossover: Carnipure tartrate (Lonza) supplying 2 g/day of L-carnitine for 3 weeks and 3 days, then a 1-week washout before the other treatment; Lonza describes its University of Connecticut trials of 2001 to 2010 as done in collaboration with the company (Ho et al. 2010, Metabolism)
18 healthy, normally active adults: 9 men (mean age 45) and 9 women (mean age 52)
After a squat and leg press challenge, supplementation lowered markers of purine metabolism (hypoxanthine, xanthine oxidase), free radical formation (malondialdehyde), muscle tissue disruption (myoglobin, creatine kinase) and muscle soreness versus placebo. Strength, power and a get-up-and-go test were not affected.
Randomized, double-blind, placebo-controlled, parallel groups: 3 g/day of Carnipure tartrate (2 g of L-carnitine) for 5 weeks; funded by Lonza, and two authors were Lonza employees (Stefan et al. 2021, Nutrients)
80 men and women aged 21 to 65 (40 per group); 73 completed a maintenance exercise program
Versus placebo: better perceived recovery and soreness (p = 0.021) and lower serum creatine kinase (p = 0.016), plus smaller relative drops in jump power and isometric strength after the exercise challenge, although maximal isometric strength showed no overall group by time effect. Serum superoxide dismutase rose within the Carnipure group but did not differ from placebo. Body composition and salivary IgA did not differ. Mild adverse events occurred at similar rates in both groups and none were serious.
Balanced, placebo-controlled crossover: 3 g/day of L-Carnipure (L-carnitine L-tartrate) for 3 weeks with a 1-week washout; Lonza describes its University of Connecticut trials of 2001 to 2010 as done in collaboration with the company (Rubin et al. 2001, J Strength Cond Res)
10 healthy men who acted as their own controls
No statistically significant differences from placebo in a complete blood count with differential or in a chemistry panel covering liver and kidney function, minerals and electrolytes. Only blood safety markers were measured.