You consume many foods that contain citric acid. Some, such as citrus fruits, are natural sources of citric acid. Other foods contain citric acid as an additive; it helps to increase the tartness of food and is also a preservative. Overall, the citric acid from fruit and other sources has a minimal effect on you.
Citric Acid
Citric acid is a small organic, or carbon-based, molecule with the chemical formula C6H8O7. It's biologically important because you form it when you're in the process of generating energy from nutrient the molecules you consume, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry." Citric acid -- and its biological form, called citrate -- have a sour flavor, and are common food additives for this reason. They also impart a natural sour flavor on citrus and other fruits.
Absorption
One of the major influences on whether a molecule you consume can affect you or not is whether you absorb it into the body via your intestinal lining. You can absorb citric acid, notes Dr. A. Pajor in a 1999 article in the scientific journal "Seminars in Nephrology." Because the molecule has chemical charges on it when it's in your body, it can't pass freely across the intestine; instead, special transporters have to move it into the blood.
Filtration
Citrate, the form in which citric acid exists in the human body, is very soluble in water, and is also therefore very soluble in blood. The vast majority of the citric acid you consume and absorb into the bloodstream ends up being excreted in your urine. Researchers determined this, explains Dr. Pajor, by monitoring concentrations of citric acid in the urine after experimental subjects consumed citric acid in their diet. Most of the citric acid you eat, therefore, passes out of your body with no effect on you.
Uptake
Cells in your liver -- and to a small extent, cells in your brain -- can take up small quantities of citric acid, explains Dr. K. Inoue and colleagues in a 2002 research paper published in the scientific journal "Biochemical and Biophysical Research Communications." Once a cell has taken up citric acid, the cell can convert the acid into fat. Disturbing as this sounds, however, the amount of citric acid your cells take up is so small as to be of little consequence with regard to your overall diet.
References
- "Seminars in Nephrology"; Citrate Transport by the Kidney and Intestine; A. Pajor; 1999
- "Biochemical and Biophysical Research Communications"; Human Na+ - Coupled Citrate Transporter: Primary Structure, Genomic Organization, and Transport Function; K. Inoue, et al; 2002
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