Final answer:
Vitamins are absorbed in the gut via different mechanisms; fat-soluble vitamins with dietary lipids, and most water-soluble vitamins by simple diffusion, except B12 which requires an intrinsic factor and is absorbed by endocytosis.
Step-by-step explanation:
No, not all vitamins are absorbed in the gut by the same mechanism. Fat-soluble vitamins (A, D, E, and K) are absorbed through the intestinal tract with lipids in chylomicrons, a process that is facilitated by the presence of dietary fats. Eating fatty foods can therefore aid in the absorption of these vitamins. Most water-soluble vitamins (including most B vitamins and vitamin C) are absorbed by simple diffusion. However, vitamin B12 is a notable exception because of its large molecular size. B12 requires the intrinsic factor from the stomach to form a complex that is eventually absorbed in the terminal ileum via endocytosis.
The process of absorption for different types of nutrients varies. For instance, lipids and fat-soluble vitamins are emulsified into micelles with bile salts and lecithin before being taken up by enterocytes, whereas other nutrients might be absorbed using different transport mechanisms. It's also worth noting that some vitamins, like B12, are absorbed in specific parts of the small intestine, such as the ileum, whereas others might be absorbed in different segments like the jejunum.