Can the absorption of vitamins be enhanced?
There are two types of vitamins:


Fat soluble vitamins - Vitamins A, D, E, K
Water soluble vitamins - B complex Vitamins and Vitamin C


Fat soluble vitamins get better abosorbed when fat content of food is good. The bile secretion is also very important. These vitamins form miscelles with the fat molecules and get absorbed as such. The absorption of these vitamins can be enhanced by taking fatty diet.

The water soluble vitamins are absorbed freely and they are also excreted freely - Excess are expelled through urine.

There are inter-vitamin competition and some food biomolecules can inhibit vitamin absorption. For example avidin in the egg would bind to biotin and prevent its absorption. The articles below deal a little with such inhibitions.

For more see:


http://healthyeating.sfgate.com/improve-bodys-absorption-vitamins-2898.html
http://www.ncbi.nlm.nih.gov/pubmed/17023940
http://health.howstuffworks.com/wellness/food-nutrition/vitamin-supplements/body-absorb-vitamins.htm