Naringin
Naringin is the bitter compound from grapefruit, chemically a flavonoid. Pre-workouts add it on the assumption that it slows the breakdown of caffeine and so extends its effect. Ballard (2006) gave ten healthy adults 200 mg of caffeine together with 100 or 200 mg of naringin and found no difference at all in blood caffeine levels. Servings of 25 mg sit far below that.
What the research shows
No sound research in humans.
The idea that naringin extends caffeine's effect comes from the test tube: Fuhr (1993) measured in human liver microsomes that naringin inhibits the breakdown of caffeine by CYP1A2, with a Ki of 7 to 29 µM. In humans, 1.2 litres of grapefruit juice a day, good for 600 mg of naringin, produced a 23 percent lower caffeine clearance and a 31 percent longer half-life, after which the authors themselves concluded that this holds no clinical significance. The only study that put naringin on its own alongside caffeine is Ballard (2006), with ten participants and 100 or 200 mg: no difference in caffeine levels, resting energy expenditure or heart rate. Nobody has ever looked at 25 mg.
Who it makes sense for: Nobody who wants caffeine to last longer. As a bitter compound from citrus, 25 mg is harmless, and that is where the story ends.
How we weigh evidenceClinical dosage
Origin
NaturalNaringin occurs in grapefruit, pomelo and bitter orange, mostly in the peel and the white pith. It is what makes grapefruit taste bitter. For supplements it is extracted from citrus peel. In the gut, bacteria cut off the sugar group, leaving naringenin, the form that reaches the bloodstream.
Safety
The grapefruit warning on leaflets for blood pressure medication, statins and immunosuppressants is about furanocoumarins, compounds that shut down the intestinal enzyme CYP3A4. Paine (2006) removed those furanocoumarins from grapefruit juice while leaving the flavonoids such as naringin in place: in 18 participants, felodipine blood levels no longer rose. So naringin does not carry that interaction. What naringin does do happens in the gut. Bailey (2007) gave 300 ml of a 1200 µmol/l naringin solution, roughly 210 mg, and saw fexofenadine uptake drop by a quarter. In Nguyen (2015), 1050 mg of naringin a day in capsules for seven days did nothing to talinolol blood levels in ten participants. The 25 mg in a pre-workout sits below everything that has ever produced a measurable effect in humans and is no reason to take medication differently. Anyone using a drug that carries a grapefruit warning is best off running it past the pharmacy, because that warning is about the fruit and the juice themselves.
For comparison
A 300 ml glass of grapefruit juice contains roughly 150 to 210 mg of naringin: Fuhr (1993) worked with 0.5 grams per litre, Bailey (2007) with 1200 µmol/l. The 25 mg in a scoop of pre-workout therefore matches 35 to 50 ml of juice, a couple of sips. Reaching the 600 mg a day at which Fuhr saw caffeine clearance fall by 23 percent takes 1.2 litres of juice, or 24 scoops.
Dosage by weight and gender
Naringin is not dosed by body weight, and no dose is known to do what the label promises. The amounts used in research: Ballard (2006) tested 100 and 200 mg alongside caffeine with no effect, Bailey (2007) saw an effect on an intestinal transport protein at roughly 210 mg in solution, and Fuhr (1993) measured a 23 percent lower caffeine clearance at 600 mg a day from grapefruit juice. That 600 mg is the figure listed above, because it is the only amount at which anything involving caffeine has been measured in humans. Differences between men and women have never been studied.
Scientific sources
The clinical dosages on this page are based on peer-reviewed research.
- Naringin does not alter caffeine pharmacokinetics, energy expenditure, or cardiovascular haemodynamics in humans following caffeine consumptionBallard TL et al. (2006)
- Inhibitory effect of grapefruit juice and its bitter principal, naringenin, on CYP1A2 dependent metabolism of caffeine in manFuhr U et al. (1993)
- A furanocoumarin-free grapefruit juice establishes furanocoumarins as the mediators of the grapefruit juice-felodipine interactionPaine MF et al. (2006)
- Naringin is a major and selective clinical inhibitor of organic anion-transporting polypeptide 1A2 (OATP1A2) in grapefruit juiceBailey DG et al. (2007)
- High-dose short-term administration of naringin did not alter talinolol pharmacokinetics in humansNguyen MA et al. (2015)
Pre-workouts with Naringin
No products found with this ingredient
We keep the dosages and values on this page as accurate as possible based on selected studies. New research may change these values. Nothing on this page is medical advice. If you have any doubts, always consult a doctor.