Klean Endurance 1.67 g by Klean Athlete

D-ribose for energy makes the most sense for endurance athletes stacking hard sessions, people who feel wiped after repeat sprints, and those with persistent fatigue after illness or overtraining. It’s not a stimulant; it helps you rebuild what you spent. If your Fasting Glucose or Hemoglobin A1c is high and you’re improving diet and training, this can be a useful add-on. For well-rested, lightly training adults, effects are usually subtle.

ATP (the cellular energy currency) needs a ribose backbone. During very hard efforts, ATP breaks down faster than your cells can rebuild it. Supplemental D-ribose feeds the pathway that makes ribose-5-phosphate (the building block for ATP and RNA), so tissues can restore ATP levels more quickly. That can translate into better repeat efforts and less next-day heaviness. Evidence in trained athletes is mixed; recovery benefits show up more in those who deplete deeply.

Each chew provides 1.67 g. Most athletes do best with 3–5 g per day split before and after key workouts, which here means 2–3 chews across the day. Take with food to limit stomach upset. If you’re training twice daily, use one chew pre-session and one post. Expect any performance or recovery change within 1–2 weeks; if nothing changes by 3 weeks, reconsider the fit.

D-ribose can lower blood sugar for a few hours, so people on insulin or diabetes medications should monitor closely and involve a clinician. It can raise Uric Acid in susceptible individuals; if you have gout, avoid or test your level after starting. Common side effects are loose stools and bloating, especially above 5 g per day. Pregnancy and nursing: safety data are limited, so avoid.