Does L-carnitine raise testosterone?
The administration of a dietary supplement containing acetyl-L-carnitine has been shown to cause an increase in testosterone levels by increasing nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) levels via enhanced acetylcholine levels.
May Support Brain Health
Research has found that L-carnitine may support various aspects of brain health. For example, studies have found it may help slow cognitive decline associated with dementia and Alzheimer’s disease.
Alzheimer’s disease can be treated by increasing acetylcholine levels. Evidence suggests carnitine may be conditionally essential for people with Alzheimer’s since it might support acetylcholine synthesis and removal of toxins from cells.1
A research review found some promising results regarding the effects of L-carnitine supplementation on dementia, but the results were still mixed and warrant further research.2
Some studies have also found that L-carnitine was more effective than a placebo for treating depression. Other research found that L-carnitine was as effective as two depression medications—Prozac (fluoxetine) and Deniban (amisulpride)—in participants with persistent depressive disorder.3 However, more studies with bigger sample sizes are needed to further evaluate these mood-related benefits.
May Prevent Cardiovascular Disease
Carnitine plays an important role in supporting cardiovascular health. However, research is still evaluating the effects of L-carnitine supplementation on cardiovascular health.
A meta-analysis that included over 3,500 adults who had heart attacks evaluated the effects of five days to 12 months of L-carnitine supplementation compared to a placebo. The researchers found that L-carnitine significantly reduced the rate of mortality, ventricular arrhythmias, and new-onset angina, regardless of the dose or duration of L-carnitine supplementation.1
However, some studies have found that L-carnitine supplementation may worsen heart health. It’s metabolized by the microorganisms in your intestines to form trimethylamine-N-oxide (TMAO), which is associated with higher cardiovascular disease risk.1
Since the results are mixed on the effects of L-carnitine supplementation on heart health, more research is needed to further explore this area.
May Aid With Type 2 Diabetes Management
Some studies have found promising benefits of L-carnitine supplementation on markers of type 2 diabetes. For example, a large meta-analysis found that L-carnitine supplementation significantly improved fasting blood glucose, hemoglobin A1C, and HOMA-IR—a marker of insulin resistance. This was particularly true for doses at or above 2 grams (g) per day for at least 12 weeks.4
The study authors note this may be due to L-carnitine’s role in maintaining insulin sensitivity and metabolizing fat and glucose.
May Support Reproductive Health
L-carnitine supplementation may improve fertility, particularly for males and people with polycystic ovary syndrome (PCOS). PCOS is a hormonal condition that occurs when the ovaries make more androgens (the male sex hormone) than needed.
A meta-analysis of studies involving about 200 men struggling with infertility found that 1–3 g/day of L-carnitine supplementation for two to six months improved sperm motility and morphology (the size and shape of sperm).5
Another review found that L-carnitine supplementation improved sperm motility and concentration. However, this didn’t translate to more pregnancies.6
One study of 280 women with PCOS found that participants who took 3 g of L-carnitine in addition to metformin and the fertility drug clomiphene-citrate had higher ovulation and pregnancy rates than the women who took the two medications without L-carnitine.7 Notably, these were women who were clomiphene-resistant, so the fertility medication alone hadn’t worked for them before.
