Table 1 Summary and results of the studies reviewed examining the LC supplementation

[11]

Moderately trained male subjects (n = 7)

age 23–25

NRNC

4 g LC/day

for 3 months

Increase of TC plasma concentration after the supplementation;

No change in muscle TC concentration, mitochondrial enzymes activity, physical performance and muscle fiber composition

[12]

Male vegetarians (n = 16)

and omnivores (C) (n = 8)

age 18–40

NRC

2 g LCLT /day

for 12 weeks

Increase of TC plasma concentration after the supplementation and muscle TC concentration only in vegetarians;

No change in physical performance and muscle metabolism either in omnivores or vegetarians.

[13]

Middle aged untrained male subjects

(S n = 12; P n = 12)

age not reported

(both groups involved in endurance training; 3x/week)

RC

2 g LCLT /day

for 12 weeks

Increase of TC plasma concentration after the supplementation;

Plasma triacylglycerols and free fatty acids not affected by training or supplementation;

Training resulted in an increase in the mRNA expression of genes coding proteins involved in long chain fatty acid transport in white blood cells, LC supplementation enhanced the effect on gene expression

[6]

Non-vegetarian, male recreational athletes

(S n = 6; P n = 6)

age 28 ± 2 (S); 25 ± 2 (P)

RC

2 g LCLT + 80 g CHO /day

for 12 weeks

Increase in muscle TC concentration after LC supplementation;

Upregulation of seventy-three genes relating to fuel metabolism in LC vs. control;

Higher exercise energy expenditure after LC supplementation;

No change in carnitine palmitolytransferase 1 activity;

Body mass and whole-body fat mass increased in control, but did not change in LC supplemented

[5]

Non-smoking, non-vegetarian recreational athletes

(S n = 7; P n = 7)

age 26 ± 2

RC

2 g LCLT + 80 g CHO /day

for 24 weeks

Increase in muscle TC concentration after LC supplementation;

Lower muscle glycogen utilization during low intensity exercise, lower lactate production during high intensity exercise, higher work output during a 30 min ‘all-out’ exercise performance test in LC supplemented group;

[7]

Healthy, non-vegetarian, untrained males

(S n = 7; P n = 7)

age 23 ± 2

(both groups involved in HIIT; 3x/week)

RC

2.25 g LCLT + 80 g CHO /day

for 24 weeks

Muscle TC concentration tend to increase after LC supplementation (p = 0.06 vs. pre-supplementation);

Skeletal muscle adaptations to training not augmented by elevated muscle carnitine availability;

[14]

Centenarians

(S n = 27; P n = 27)

age 100–106

RC

2 g LC/day

for 24 weeks

Increase of TC plasma concentration after the supplementation;

Fat mass reduction, muscle mass elevation, physical effort tolerance and cognitive function improvement in LC supplemented group

[15]

Healthy women

(S n = 11; P n = 9)

age 65–70

RC

1.5 g LCLT /day

for 24 weeks

Increase of free carnitine plasma concentration after the supplementation;

No changes in body composition, skeletal muscle strength and IGF-1 after LC supplementation

[16]

Healthy women

(S n = 11; P n = 9)

age 65–70

RC

1.5 g LCLT /day

for 24 weeks

Increase of plasma TMAO concentration after the supplementation;

No changes in serum C-reactive protein, interleukin-6, tumor necrosis factor-α, L-selectin, P-selectin, vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and lipid profile after LC supplementation

[17]

Healthy women

(S n = 11; P n = 9)

age 65–70

RC

1.5 g LCLT /day

for 24 weeks

No changes in plasma GBB or serum ox-LDL, myeloperoxidase, protein carbonyls, homocysteine, and uric acid concentrations

[18]

Healthy aged women

(S n = 12; P n = 13; C n = 12)

age 67 ± 3

(all groups involved in resistance training 3x/week)

RC

1 g LCLT + 3 g L-leucine/day

for 24 weeks

Increase of plasma TMAO concentration after the supplementation;

Increase of D-loop methylation in platelets of LC supplemented