Overview
Rejuvelac is a fermented liquid made by soaking and sprouting whole grains (commonly wheat berries or other cereal grains), then fermenting the sprouted grain in water for one to a few days at room temperature — a practice associated with raw-food and living-food dietary movements. Kvass is a traditionally Eastern European fermented beverage, classically made from stale rye bread and water fermented with yeast (bread kvass), though “beet kvass,” fermented with beets and salt, is a related but distinct variant popular in natural-foods circles.
Active compounds and evidence
Both drinks are naturally fermented and contain live bacteria and yeast from their respective fermentation processes, similar in concept to other fermented foods. However, direct human clinical research on rejuvelac and kvass specifically is very limited — much thinner than the evidence base for better-studied fermented foods like yogurt or kimchi. Claims of specific “enzyme” or detox benefits associated with rejuvelac in raw-food literature are not supported by rigorous clinical evidence; what can be said with more confidence is that both are fermented, low-calorie beverages that may contribute some live microbial diversity to the diet, similar to other home-fermented foods.
Safety and contraindications
- Food safety of homemade sprouts and grain ferments: Sprouting grains at room temperature creates conditions that can also support harmful bacteria (such as E. coli and Salmonella) if not done carefully; the FDA has documented foodborne illness outbreaks linked to raw and lightly processed sprouts. Using clean equipment, fresh grain, and proper rinsing reduces but does not eliminate this risk.
- Immunocompromised individuals, pregnant people, young children, and older adults: Given the sprout- and fermentation-related contamination risk, these groups are generally advised to be cautious with homemade raw sprouted-grain ferments like rejuvelac.
- Gluten: Traditional rejuvelac and bread kvass are typically made from wheat or rye and are not appropriate for people with celiac disease or gluten sensitivity unless made with gluten-free grains.
- Trace alcohol: Yeast fermentation in kvass produces a small amount of alcohol, generally low but worth noting for those avoiding alcohol entirely.
How it’s typically prepared
Rejuvelac: grains are soaked, sprouted for one to two days, then left to ferment in fresh water for one to three more days before straining and drinking the liquid. Kvass: stale rye bread is soaked in water with yeast and a little sugar, fermented for one to a few days, then strained.
Sources
- FDA — Foodborne Illness Outbreaks Linked to Sprouts
- Harvard T.H. Chan School of Public Health — Fermented Foods
Clinically reviewed by Dr. Shilpa Thakur. Last reviewed 2026-07-20. Educational information, not medical advice; consult a qualified clinician before regular use if pregnant, immunocompromised, or have celiac disease.