The NO generating nitrates that enhance endothelial function, not the carcinogenic nitrites in processed meat.
Personally, I'm not a fan of high beet consumption, whether whole or freeze dried juice. Stick to rocket/arugula if you want a very high nitrate vegetable.
Rubenstein et al, 2006. Azetidine-2-carboxylic acid in garden beets (Beta vulgaris). Phytochemistry, 67(9), pp.898-903.
Rubenstein, 2008. Misincorporation of the proline analog azetidine-2-carboxylic acid in the pathogenesis of multiple sclerosis: a hypothesis. J Neuropathology & Exp Neuro, 67(11), pp.1035-1040.
Rubenstein et al, 2009. Azetidine-2-carboxylic acid in the food chain. Phytochemistry, 70(1), pp.100-104.
Bessonov et al, 2010. Misincorporation of the proline homologue Aze (azetidine-2-carboxylic acid) into recombinant myelin basic protein. Phytochemistry, 71(5), pp.502-507.