The correct answer is E: influence many important chemical processes in the body.

Vitamins are essential micronutrients that play a key role in various biochemical processes in the body, including metabolism, immune function, and maintaining healthy skin, eyes, and bones. They help enzymes in the body function properly, thereby influencing numerous important chemical reactions.

Here’s why the other options are incorrect:
- A: Vitamins do not contain carbohydrates and fats; they are organic compounds that are required in small amounts for various bodily functions.
- B: Kwashiorkor is a form of protein malnutrition, and while vitamins are important for health, they do not directly prevent kwashiorkor. Protein intake is what prevents kwashiorkor.
- C: Vitamins do not directly stimulate the alimentary canal, though some (like vitamin B12) are involved in digestive processes.
- D: Vitamins do not digest proteins; they are involved in the metabolism of nutrients, but not in digestion directly.

Therefore, E: influence many important chemical processes in the body is the correct answer.