The honest takeGuanidinoacetic acid is an interesting molecule and a strange thing to find in a pre-workout that already contains 1,500 mg of dicreatine malate. You are being sold the precursor next to the product. At the doses studied — 1.2 to 4.8 g a day — it does raise tissue creatine, and it also reliably raises homocysteine: in one eight-week trial, more than half the people taking 2.4 g a day on its own crossed into hyperhomocysteinaemia. Our share averages about 78 mg, which is one fifteenth to one sixtieth of the trial doses. At that amount it is below the effect and below the risk. That is a fair description and not a compliment: it means the ingredient is doing nothing in either direction. It should also be said that the human evidence here is thin and concentrated — one research group, and the strength trial and the dose-response trial share the same 48-person cohort, so they are not independent replication. If you want muscle creatine, take creatine monohydrate. It is cheaper, better studied by an order of magnitude, and it does not push your homocysteine anywhere.
What it isThe immediate precursor to creatine. Your kidneys build it from arginine and glycine, and your liver adds one methyl group to turn it into creatine.
How it worksTwo enzymes make creatine. AGAT joins arginine and glycine into guanidinoacetic acid, mostly in the kidney, and GAMT then transfers a methyl group from S-adenosylmethionine to finish the molecule, mostly in the liver. Supplying guanidinoacetic acid bypasses the first step and leans hard on the second. That is the appeal and the problem in one sentence: each methylation spends an SAM and yields a homocysteine, so pushing this pathway raises homocysteine unless the methyl supply keeps up. It is a real biochemical route with a real cost attached, and the cost scales with the dose.
What it doesSupplies the body's own creatine synthesis pathway. At gram doses it raises tissue creatine — the same job the creatine already in this formula does directly.
Who it's forRealistically nobody, at this dose. At research doses it is of interest only under supervision and with methyl donors alongside. It must be avoided by anyone with raised homocysteine, an MTHFR variant, low B12 or folate, kidney disease or existing cardiovascular disease, and by anyone pregnant or breastfeeding.
How to use itThe trials dosed it daily rather than around training, because like creatine it works by saturating tissue over weeks. Anyone using it at gram doses should take methyl donors with it — betaine, folate, B6 and B12 — which was shown to remove the homocysteine rise entirely in an eight-week trial. In IGNITE there is nothing to manage, because there is nothing there.
What to expectNothing you will notice. Creatine loading of any kind is invisible day to day; it shows up as a slightly better last set after several weeks, if it shows up at all. At roughly 78 mg alongside a separate creatine dose, expect no independent contribution.
The researchOstojic and colleagues carried out most of the human work, and much of it draws on one cohort. A randomised, double-blind, placebo-controlled trial in 48 healthy volunteers (2014, European Journal of Nutrition) tested 1.2, 2.4 and 4.8 g a day for six weeks and found significant rises in serum and urinary guanidinoacetic acid, creatine and creatinine, alongside raised homocysteine most marked at the top dose, without depleting the B vitamins needed for remethylation. The same 48-participant design reported as a pilot in the Journal of Investigative Medicine (2015) found improved handgrip strength at 1.2 and 2.4 g a day and more bench-press repetitions at 1.2 and 4.8 g a day, with no dose-response relationship. A four-week randomised crossover superiority pilot in five healthy men (2016, Applied Physiology, Nutrition, and Metabolism 41:1005–1007) reported that 3 g a day raised creatine in vastus medialis and two brain regions by up to 16.2% more than creatine itself — five participants, which is a signal and not a result. A separate randomised trial in 20 volunteers (2013, British Journal of Nutrition) gave 2.4 g a day for eight weeks with or without methyl donors: hyperhomocysteinaemia occurred in 55.6% on guanidinoacetic acid alone and 0% with methyl donors (p = 0.01), and minor adverse events in 33.3% versus 10.0%. A 2021 safety review in Nutrients summarises animal reports of neurotoxic and pro-oxidant effects from guanidinoacetic acid accumulation. EFSA's FEEDAP panel has assessed it repeatedly as a feed additive for poultry and pigs. What is not supported: any benefit at sub-gram doses, any established advantage over creatine monohydrate for general use, and any claim that it is free of the homocysteine effect.
Read the labelThis is the one in the blend with a genuine safety signal. Oral guanidinoacetic acid raises homocysteine, because every molecule converted to creatine spends a methyl group and releases homocysteine. In an eight-week trial at 2.4 g a day, hyperhomocysteinaemia was found in 55.6% of participants taking it alone, and in none of those taking it with methyl donors — betaine, folic acid, B6 and B12 — alongside. In the six-week dose-response study, the homocysteine rise was dose-dependent and most marked at 4.8 g a day. Animal work reports neurotoxic and pro-oxidant effects where guanidinoacetic acid accumulates. Anyone with raised homocysteine, an MTHFR variant, B12 or folate deficiency, kidney impairment, or cardiovascular disease should not take it at gram doses. No pregnancy or breastfeeding data. On regulatory position: it is authorised in the EU as an animal feed additive and is regulated in the US as a food additive for animal feed; we could not confirm a novel-food authorisation covering it as a human food ingredient in the EU or UK, so treat its status as unsettled rather than settled. Not a treatment for anything.
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