The juice appears to inhibit a protein in the membrane of cells called P-glycoprotein (P-gp), which thereby leads to an increased absorption of CoQ10, according to results of a laboratory study published in Food Chemistry.
“We have demonstrated that a higher cellular uptake of CoQ10 was achieved in the presence of grapefruit juice,” wrote the Japanese researchers, led by Ken Iseki from Hokkaido University.
The formulation of the CoQ10 is known to play a key role in its bioavailability. Since the coenzyme is lipophilic (fat-loving) its absorption is enhanced in the presence of lipids. Therefore, when taken as a supplement apart from meals, the absorption of some formulations is lower.
“It is possible that co-administration of CoQ10 with grapefruit juice constitutes an easily accessible way to improve the intestinal absorption of CoQ10,” added Iseki and his co-workers.
Grapefruit juice is well-known to interact with other compounds in the digestive system. Chemicals in juice and pulp of the fruit are reported to interfere with the enzymes that metabolise certain drugs in the digestive system, including statins to lower cholesterol. This results in potentially toxic quantities of drugs circulating in the blood.
The new study, however, suggests that grapefruit juice’s inhibiting effects may actually benefit CoQ10 absorption.
CoQ10 has properties similar to vitamins, but since it is naturally synthesized in the body it is not classed as such. Our ability to synthesise the compound peaks at the age of 20 and amounts in our body decrease rapidly after we pass the age of 40.
With chemical structure 2,3-dimethoxy-5-methyl-6-decaprenyl-1,4-benzoquinone, it is also known as ubiquinone because of its 'ubiquitous' distribution throughout the human body.
The coenzyme is concentrated in the mitochondria - the 'power plants' of the cell - and plays a vital role in the production of chemical energy by participating in the production of adenosince triphosphate (ATP), the body's co-called 'energy currency'.
There is an ever-growing body of scientific data that shows substantial health benefits of CoQ10 supplementation for people suffering from angina, heart attack and hypertension. The nutrient is also recommended to people on statins to off-set the CoQ-depleting effects of the medication. Other studies have reported that CoQ10 may play a role in the prevention or benefit people already suffering from neurodegenerative diseases.
The Japanese researchers used Caco-2 cells, a cell line used to model the lining of the human intestine. Cells were cultured in the presence of CoQ10 powder (10 micromoles, supplied by Kougen Co. Ltd.) and grapefruit juice (diluted to a concentration of 1 per cent, purchased from the Dole Food Company Inc., USA).
Results showed that CoQ10 uptake in the presence of grapefruit juice was increased by almost 50 per cent. “These results indicate that the combined administration of CoQ10 and grapefruit juice could enhance CoQ10 absorption,” said the researchers.
“Taking these findings into consideration, it is possible that co-administration of CoQ10 with grapefruit juice will be an easily accessible way to improve the pharmacological effects of CoQ10,” they added.
The researchers concluded that additional studies are required in order to investigate the pharmacological effects of CoQ10 when administration with grapefruit juice. “Such investigations will provide important information for improving the pharmacological effects of CoQ10,” concluded Iseki and his co-workers.
Source: Food Chemistry
2010, Volume 120 (2010) 552–555
“Grapefruit juice enhances the uptake of coenzyme Q10 in the human intestinal cell-line Caco-2”
Authors: S. Itagaki, A. Ochiai, M. Kobayashi, M. Sugawara, T. Hirano, K. Iseki