Grapefruit Juice..general

Continuing the discussion from Grapefruit interaction with longevity meds?:

From perusing lots of published work on gfj and rapa (and other drugs) I see that there is individual varialbility in the activity of gfj on the enzyme…for some 6 oz. knocks it back to a level that gives 3.5x, and some may need more gfj to get the same effect. It’s a function of what happens in your gut where this enzymatic reaction takes place. Not surprising as most everything that happens in the gut varies by person.

In practical terms, this means that those wanting to ensure the maximum effect (3.5X) should go to the high side…10-12 oz of gfj.

It appears that 3.5x is the max enhancement at any gfj dose and for those taking less than their optimal gfj dose that enhancement is relative to some point below the max…not all or none.

Timing is said to be optimal if the rapa is taken within 4 hours of the GFJ…some notations being that 1 hour is best.

I take mine split: 4oz. 3 hours prior and 6oz. 1 hour prior…the 3 hour prior just in case the stuff needs more time to get to work on the enzymes.

Also, I see people eating whole grapefruit rather than just juicing. Great but be sure you get enough volume from the whole grapefruit…I measured 5 GF and typical juice squeeze is 7 oz with the collected pulp…so 1 does not give you quite enough.

Finally, bottle (or canned) gfj is pasteurized. Likely knocks out the enzyme that make all this happen. Not sure about frozen concentrate…some may also be pasteurized, but I think some not. Best bet is to squeeze fresh.


Agreed, lots of variability in type, dose, timing. We may have different polymorphisms for the enzyme, and different mTOR gene expression! Pheww, very complicated. Even in the Sirolimus only trials with pharma grade control drug, there was great inter person variability.

Most important is to try and bring some science to it all as n=1. Set a protocol and monitor with blood tests (as many as you possibly can, way beyond Sirolimus, but all your key markers), along with side effects. Iterate.

Otherwise, flying blind.

1 Like

The black cat in the darken room.

Is people’s primary motivation for using GF cost? By that I mean, if you had an unlimited supply of Rapamune would you still take GF or simply increase the dose?

Perhaps I’m a stuck record but I feel we already have enough unknowns with rapamycin directly without throwing in another (difficult to measure) variable. Also note worthy that both AG and MK advise against it…

1 Like

I don’t mind that GF gives possibly variable results: the variances won’t be extreme and perhaps variable doses are better than constant doses–who knows?

Re “typical juice squeeze is 7 oz with the collected pulp…so 1 does not give you quite enough”: cronometer has them as fairly in equal calories by weight, so the reduced juice yield is probably just inefficient juicing.