NO, THIS IS NOT GENERALLY TRUE FOR ALL VITAMINS. It is quite amazing to hear a health professional say synthetic vitamins are the same as natural. THAT statement exhibits such a profound ignorance on the molecular level that it defies logic and reason. The professionals are leaving out a very important part that needs to be included with such a statement. And that is "scientists have always known that some synthetic vitamins exhibit different molecular structures than natural and that the activity levels in the body were adjusted using different amounts of each vitamin type to generate identical, or nearly so, activity. Not mentioned here is that it takes almost 40% more synthetic vitamin E material to equal the same activity that was measured for natural vitamin E. New research now puts natural E at twice the absorption value of synthetic E, with even greater biological activity.
You will hear and read that vitamin C as ascorbic acid is not a complete vitamin since it does not have all the synergistic or "cofactor" elements often found with it in foods. But, in the case of vitamin C, this is simply not the reality of physiological facts. Most mammals, except humans and a few other animals and birds, can make vitamin C inside their bodies from the sugar glucose in their blood. An enzyme needed for this glucose conversion is missing in humans. Yes, the form this vitamin C takes in the body is as an ascorbate, or a mineral combined with ascorbic acid. In the Lab, Scientists use this same enzyme to turn usually corn sugar into vitamin C as ascorbic acid.
There are ascorbate supplements. And ascorbic acid does turn into the ascorbate form in the body. But what is important here is that the animals that make their own vitamin C do not also make any of the other synergistic parts of vitamin C or the cofactors often mentioned as being needed for complete vitamin C activity. The reason being of course is that vitamin C as a mineral ascorbate is all that is needed for most vitamin C functions. Yes, these "cofactors" do offer some protection to preserve vitamin C and also have similar and related functions to perform as well. That is how they relate to vitamin C, not that they are needed for ascorbic acid as vitamin C to function. Vitamin C also combines with proteins and minerals to form enzymes. Some of the functions of these enzymes are sometimes referred as vitamin C functions, but really is the enzyme function of which vitamin C is just one part. ref
Yes, it is true that these enzymes would not be able to function without vitamin C, but then they would not be able to funciton without the proteins or minerals either, even though there was plenty of vitamin C. So, in some way these minerals and proteins are cofactors for a vitamin C function, but just not the cofactors mentioned by the "whole food" vitamin people attempting to make their case.
SIDEBAR: Here is copy from a website blog talking about synthetic vitamins. This needs a dose of reality.
"Much of the synthetic vitamin passes through the urine unabsorbed." Stop and think about this for a moment. In order for some element to pass out of the urine, it must first GET ABSORBED into the body. If it was unabsorbed it would pass out of the colon. Yes, it is true that some synthetic forms of vitamin metabolites are eliminated quicker than natural vitamin metabolites from the body. Metabolites are the elements that dietary vitamins whether natural or synthetic breakdown into during body processing. So what that author meant to say is that synthetic vitamins do not as readily participate in these body processes and the body might even recognize some of them as foreigners and attempt to quickly expel them. Some parts of Synthetic vitamins are used by the body.
Wrap UP Factors
There is one factor that is prehaps the telling end all for the many discussions about the differences between natural and synthetic vitamins. At the end of the day, it is a measure of the level of increase for each vitamin in the body or blood that determines the real benefit of natural or synthetic vitamins.
A vitamin level in the body is first measured, than the same amount of either a natural vitamin or a synthetic version of that vitamin is consumed. Blood is later drawn and levels of each vitamin are measurmented and compared. Sometimes both are pretty close, but other times, they are widely different. But only a few times does the synthetic version come out on top. Folic Acid is one example. These are largely due to absorption factors since some synthetic vitamins are produced in a more stable form that the natural form.
Also remember that some synthetic vitamins are excreted out of the body faster that their natural counterpart. So, while the synthetic might measute nearly the same at the beginning, the natural could win the longevity factor. Vitamin D3 is the longer lasting form while D2 is shorter.
Another factor would be the biological participation aspect. Natural vitamin E represents the vitamin with the greastest difference of the natural over synthetic. To see these differences, read this article.