During diet trials, which of the following should be avoided?

• A. Flavored non-hydrolyzed oral preventatives
• B. Plain water additives
• C. Vitamins
• D. Non-hydrolyzed injectable medications

Answer: (A)

The key idea here is that a diet trial must isolate the diet as the only source of nutrition and exposure. Any additive or medication given orally can introduce ingredients outside the trial diet and potentially trigger reactions or muddy the results.

Flavored non-hydrolyzed oral preventatives should be avoided because their flavoring and carrier components often contain intact protein sources. Even small amounts of these proteins can provoke an immune response or alter how the subject reacts to the trial diet, making it hard to tell whether symptoms are due to the diet itself or to the added product. That’s why these palatable oral products are avoided during strict diet trials.

Plain water additives are usually acceptable if they don’t introduce proteins or other restricted ingredients, since they don’t contribute significant dietary antigens. Vitamins are typically allowed to maintain nutritional status, provided they don’t bring hidden proteins or flavorings that could affect the trial. Injectable medications, being delivered outside the gut, don’t alter the oral diet trial directly and are not part of the dietary exposure being tested.