Vitamins have always been an essential component in human nutrition. It was not until the late nineteenth century, however, that they began to be isolated and so named. Identification of the specific role of individual vitamins was then, and continues now to be an important area of inquiry. Extensive scientific research focusing specifically on vitamins has been conducted in recent decades, the results of which are both enlightening as well as confusing... or perhaps, more to the point, quite contentious.
      There are certain fundamentals, however, that everyone with an eye to preventive health should be aware of. These include the essential role of vitamins in human nutrition, when how much of a good thing begins to be dangerous, with regard to supplements in particular, and how to recognize health dangers, from the standpoint of vitamin deficiency as well as toxicity.

      There has been an enormous amount of misleading and downright ridiculous claims made about the beneficial effects of many vitamins. If mega doses of vitamin X really made people live to be 150 years old, we would see many 150 year-olds out there. Absent that, the claims that are made, and who they are made by, must be looked upon carefully and objectively, if it is your intent to come away with some useful and beneficial information for preventive health.
      If you are looking for simple answers, however, you will likely come away very disappointed. Nutrition is a very complicated, and technical subject. If meaningful answers to our varied questions were simple, we would have had those answers by now. If you are willing to avail yourself to what is known about vitamins, you will have gone a long way to improving your nutrition and your general health.

      There are thirteen known vitamins that fall into two groups, those that are water-soluble and those that are fat-soluble. The water-soluble vitamins, B complex vitamins (eight in all) and vitamin C, are easily dissolved in body tissues and excreted in the urine. As a result, these vitamins do not tend to build up in the body and need to be replenished often (there are some exceptions).
      In contrast, the fat-soluble vitamins (vitamins A, D, E and K) are stored in the body's fatty tissue until they are broken down and, for the most part, are not excreted in the urine. It is for this reason these vitamins do not need as frequent replenishment, and their potential for toxicity is much higher than for the water-soluble vitamins.

      The manner in which food is stored and prepared, fresh fruits and vegetables in particular, will significantly affect their nutrient value. Certain vegetables exposed to sunlight lose their vitamin content and should be stored in the dark. Fresh vegetables, compared to those that are steamed, and again to those that are boiled, for example, will have different concentrations of vitamins. After you have absorbed a working knowledge of the vitamin (and other nutrient) content of foods, a competent lesson in food storage and preparation is definitely in order.

      Another matter of no small importance, are the individual compounds that make up the substances we commonly refer to as "vitamins." If you have ever wondered how dietary supplements differ, vitamins in particular, and why some are so much more (or less) expensive than others, the answer is here: Not all vitamin A or vitamin E, or some others, are equal. In other words, vitamin A is vitamin A is vitamin A is a misconception that supplement manufacturers would have you believe. If you read the labels carefully, you will see that some have considerably different amounts of the individual components than others.
      To wit: The following examples were copied directly from the labels of a random sampling of vitamin A supplements. These products are very different.
      Vitamin A - 5000 IU [no qualifying comments]
      Vitamin A - 5000 IU (as acetate and beta-carotene)
      Vitamin A - 5000 IU (5% as beta-carotene)
      Vitamin A - 5000 IU (100% as beta-carotene)
      What does your vitamin supplement label say? Do you know what you are putting in your mouth? Is it doing you any good? Do you care? If you are purchasing and consuming vitamin supplements of any kind and do not understand these distinctions, you owe it to yourself (and your families) to find out more.

      One of the most annoying issues in attempting to quantify vitamins are the various (and confusing) terms in common use, not to mention the inconsistency in the units of measurement. Understand this, and you will know how much of a particular vitamin you need, and are consuming. If you cannot convert from one system of measurement to another, "you won't have a clue." For starters, please refer to our handy reference on Abbreviations, Units and Measurements.
      If you rely entirely on the percentages on the current food label (the so-called %DV), you will be "in the ball park," as they say, but remember that these figures are the FDA's Reference Daily Intake (RDI) [the same as the old U.S. Recommended Daily Allowance (U.S. RDA)], and are based upon science that dates back to the 1960s! (For more information on reading the food label, please see Today's Food Label.)
      The most recent set (that is, "complete set") of dietary standards, published by the National Academy of Sciences (NAS), and confusingly referred to as Recommended Dietary Allowances (RDA), provides access to much more recent science... but alas, the NAS uses different, though more modern units of measurement for some of the vitamins (it's not confusing enough without this!).
      And finally, a major study currently in progress by the NAS promises to at least update current dietary information, if not bring it into the current century. This work is important because it is fair to assume that these studies, when completed, will be adopted by the FDA and will be the basis of the reference values used on our food labels (and dietary supplement labels) in the years to come.
      This study is also important because it introduces a new parameter for each vitamin (for which it has been established), the Tolerable Upper Intake Level, abbreviated UL. The NAS defines this measurement as "the maximum level of daily nutrient intake that is likely to pose no risk of adverse effects to members of the healthy general population."
      The information we provide in our Reference Values tables for the vitamins includes all of the above. In this way it is possible to see if, and how much the recommendations for each vitamin have changed over time.
      In conclusion, we can only say this: the story does not end here. Scientific research continues apace, and the "newest" reference values that will presumably be the basis of food labels within the next several years, will be woefully out of date long before those freshly labeled products appear on the shelves. We will do our very best to keep our site (and you!) up to date on this new science as it emerges.

      In the years to come, likely sooner than later, the mountain of data that has been accumulated on vitamins will begin to come into focus. What is certain is that we will be painfully reminded about how naïve we have been on some matters relating to nutrition, and delightfully informed about new science that will enhance preventive health measures and help us to live longer, healthier lives.
      In the mean time, we invite you to peruse the information we have collected here on the vitamins. And please don't be afraid to make inquiries about details that are important to you.