Pterostilbene is a natural compound found not only in blueberries and various fruits but also in the heartwood of the Kino tree (Pterocarpus marsupium). Extracts of the Kino tree, rich in pterostilbene, have been used for centuries by humans as the primary ingredient found in Vijaysar, an Ayurvedic medication traditionally used to treat diabetes. However, just because a compound is natural and has been used as traditional medication does not necessarily mean it is safe. Scientific studies are necessary to identify any possible pterostilbene side effect and establish pterostilbene safety.
A number of scientific studies of extracts of Pterocarpus marsupium have been conducted. None have reported any adverse effects or safety issues to date. For example, Hougee et al. had human volunteers consume up to 450 mg/day of Pterocarpus marsupium for 2 weeks (1). None of the volunteers reported a single pterostilbene side effect, and evaluations of blood chemistry did not identify any safety concerns or signs of pterostilbene toxicity.
Purified pterostilbene is in the process of being Generally Recognized as Safe (GRAS). Under FDA regulations, compounds can be demonstrated to be GRAS either through clinical studies or through safe, widespread consumption prior to 1958 (2). The generations of widespread, safe use of pterostilbene in Ayurvedic medicine are being supplemented with clinical studies to establish it as GRAS.
A study in mice established that even at very high doses, pterostilbene seems to be completely safe. The mice were fed up to 3000 mg/kg of pterostilbene per day for 28 days. The equivalent dosage in a human would be 17,670 mg/day of pterostilbene. None of the mice died during the study, and they also did not exhibit any behavioral changes suggestive of pterostilbene toxicity. Complete clinical chemistry, hematological, and histopathological workups of the mice did not reveal any signs of adverse events, any type of pterostilbene side effect, or any pterostilbene toxicity.
Of course, just because a substance is safe for mice doesn’t prove it is safe for human consumption. However, a fairly large clinical study followed humans taking up to 250 mg of pterostilbene per day for up to eight weeks (4). None of the subjects reported any side effects. Analyses of biochemistry did not reveal any signs of liver, kidney, or blood toxicity. The authors of the study concluded that pterostilbene safety has been established in humans.
References:
1. Hougee et al. 2005 Planta Med. 2005 May;71(5):387-92.
2. http://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/
3. Ruiz et al. 2009 J Agric Food Chem. 2009 Apr 22;57(8):3180-6. doi: 10.1021/jf803579e.
4. Riche et al. 2013 Journal of Toxicology Volume 2013 (2013), Article ID 463595, 5 pages
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