This study was done to see whether citric acid or l-carnitine (an amino acid) has an effect on physical fatigue. Eighteen subjects were divided into three groups and each group received either citric acid (2,700 mg/day), l-carnitine (1,000 mg/day) or a placebo for eight days. (The study was double-blind and crossover.)

Citric acid is an important component of the tricarboxylic acid (TCA) cycle by which carbohydrates, fats and proteins are converted into energy. This cycle takes place in the cells’ mitochondria.

Fatigue can be mental or physical and is generally defined by the authors as “difficulty in initiating or sustaining voluntary activities”. Another chemical, hydroxycitric acid (HCA) from the plant Garcinia cambogia, can relieve fatigue, but, can cause some “reproductive toxicity”.

The subjects were given workloads designed to induce fatigue, with a fixed load for two hours each at two different times.

Salivary chromogranin A was measured as a marker of physiological stress. Fatigue was evaluated with the use of a “Visual Analogue Scale”. The results of the study demonstrated that citric acid can reduce signs and symptoms of stress, and physical fatigue. Carnitine and placebo did not relieve or prevent fatigue.

CONCLUSION: Citric acid was able to reduce physiological stress and physical fatigue in this study. Carnitine (an amino acid)did not reduce physiological stress or physical fatigue.

NOTE: Citric acid is formed by sugar fermentation. Foods high in citric acid include lemons, limes, pineapples and gooseberries, and most citrus. Low urinary citrate levels (hypocitraturia) are seen in 20% of people who form urinary stones. Alkaline citrate is often an effective treatment for kidney stones. See summary 196.

Read about the effect of beta-alanine on fatigue in the elderly.

ASK YOUR DOCTOR FOR: Testing of urinary citric acid levels.

PMID: 18299720.

Summary #251.