Yes, for the right claims.
A number of peer-reviewed scientific studies have found matcha to be a highly nutritious food with multiple health benefits. It has all the health benefits of regular green tea, and more antioxidants, because we consume the high-grade leaves.
A 1997 study suggests that consuming matcha assists the body to purge potential carcinogens, such as PCB's (polychlorinated biphenyls), PCDF's (polychlorinated dibenzofurans) and PCDD's (polychlorinated dibenzodioxins).
A 2003 study indicates that there are 137 times the antioxidants in matcha than there are in the popular brand of green tea that was tested in the study. These antioxidants are known as catechins, which other studies have found to help promote weight loss.
A 2009 study confirms that matcha is indeed richer in antioxidants than other green teas. It also suggests that: a) these antioxidants can protect against kidney damage; and b) they can help reduce levels of glucose (sugar), triglycerides (fat) and cholesterol in the liver.
A 2011 study indicates that l-theanine, an amino acid found in matcha and other green teas, assisted in reducing mental and physical stress. It also suggests that the effects of this compound could be described as "antidepressant-like".
Of course, our knowledge about these benefits must be considered in the context of a healthy diet involving the consumption of a variety of foods.