I just skimmed the article, too much statistical jargon for me. They used compliance with the DASH diet as the measuring stick for the 4 diets. The metabolites they measured were mostly amino acids but also a pre vitamin B3, glucose, acetate, carnitine (red meat), hippurate from fruit and vegetables, some markers for fish intake, short chain fatty acids and urea.

If big brother or the insurance company ever forces you to give a sample I'm sure you'll be able to buy a "pill" form someone that will fix your urine...