Bad Vitamins?
The American Medical Association recommends supplementing the diet with vitamins due to nutrient deficiencies in food (JAMA. 2002;287:3116-3126). However, not all vitamins are made equal. 
The biggest difference between big box-store brands and higher quality supplements like those you may get from a holistic health professional are in how the nutrients are derived and how the pills are constructed.  Drug-store vitamins are chemically derived sometimes even made from coal tar or other industrial byproducts, while natural vitamins are derived from plants or other organic sources.  Believe it or not, your body can tell the difference.  Drug store vitamins must be processed by the liver, are absorbed less and take longer to enter the blood stream.  Organically derived vitamins are digested and absorbed in the intestinal track with ease just like food and are far superior for a number of reasons.   
Vitamins derived from plant sources are concentrated raw ingredients that often contain co-factors such as bioflavonoids.  These co-factors work synergistically with vitamins.  Many studies have been done on isolated nutrients like vitamin D, E and A and have found that they do not have a positive effect on health, however, when studies are done using plant sources that include naturally occurring co-factors, results show a completely different picture.  Naturally sourced vitamins typically are made without sugar, chemicals, preservatives or fillers.  This ensures maximum absorption and purity. 
Below is a list of additives and preservatives that are commonly added to leading drug store brand supplements. These additives can cause anything from inflammation to neurological damage:

 
Color Additives – these are neurotoxins and should be avoided in any product.

FD&C Red 40 Aluminum Lake, FD&C Yellow #6 Lake,– has been shown to damage DNA in mice – Toxicol Sci. 2001 May;61(1):92-9.
 
FD&C Yellow #5 (tartrazine) Lake – shown to adversely affect biochemical markers in the vital organs of rats. Food Chem Toxicol. 2010 Oct;48(10):2994-9. Epub 2010 Aug 3.

Preservatives:
  Hydrogenated Palm Oil – This is a trans-fat that causes inflammation and is being banned in cities across the U.S.
  Butylated hydroxytoluene (BHT) – being investigated for its ability to damage genetic materials


 
Centrum Silver (Drug Store Vitamin)