"Greens blend" proprietary mixtures typically include powdered forms of various green vegetables, grasses, algae, and sometimes herbal extracts (such as wheatgrass, barley grass, spirulina, chlorella, spinach, kale, etc.). The rationale for their use against free radical damage is grounded in their high concentrations of antioxidant compounds, including vitamins C and E, carotenoids, flavonoids, and chlorophyll. Free radicals are unstable molecules that can cause oxidative stress, contributing to cellular damage and aging, as well as a variety of chronic diseases.

Scientific studies have demonstrated that many individual components of greens blends possess antioxidant properties. For example, spirulina and chlorella have been shown in laboratory and small-scale human studies to increase antioxidant enzymes and reduce markers of oxidative stress. Similarly, green vegetables are rich in polyphenols and other phytochemicals known to scavenge free radicals. However, while these ingredients are individually well-studied, evidence specifically for commercial "greens blends" as a whole is less robust, with only a handful of small clinical trials suggesting modest improvements in antioxidant status or reduction in oxidative damage markers when consumed regularly.

In summary, there is moderate scientific justification for the use of greens blends to support the body's defense against free radical damage, primarily based on the known antioxidant content of their ingredients. However, larger and better-controlled human studies are needed to confirm the efficacy of these proprietary blends for this purpose.