beet juice , a plain multi vitamin mostly for extra vitamin d , and green tea , have allowed me to make a significant advance in ability , mostly in VO2 max , without extra training , i can feel it , its different from anything i have felt before .
i think if you look at supplements as a food source that has an effect on your body's chemical production you will be better off , ingest the things that support your body's ability to make blood cells , or testosterone , rather than just gulping down stuff in hopes it will just work .