With a method that converted 4-hydroxy-3-methoxymandelic acid (vanillylmandelic acid [VMA]) to vanillin, six healthy volunteers had a normal mean 24-hour urinary VMA excretion when given each of three different diets of varying amounts of bananas, coffee, and other foods known to interfere with older chromatographic procedures. The data suggest that dietary restrictions during VMA collections using the present method can be omitted in the screening of hypertensive patients for pheochromocytoma.
Rayfield EJ, Cain JP, Casey MP, Williams GH, Sullivan JM. Influence of Diet on Urinary VMA Excretion. JAMA. 1972;221(7):704-705. doi:10.1001/jama.1972.03200200050012