Reziva® contains resveratrol from concentrated extract of French red wine grapes rather than the common Japanese Knotweed (polygonum cuspidatum).
Reziva's active ingredients include not only trans-resveratrol, but also Proanthocyanidins and total polyphenols. Although no published negative effects are noted with Japanese Knotweed, the extraction process creates not only trans-resveratrol, but also emodin. While emodin has been used to reduce inflammation, it can cause gastrointestinal problems including diarrhea, stomach cramps and bloating. Prolonged use of emodin has been associated with an increased risk of liver and kidney damage.