Have you ever been in a health food store or drug store and found yourself staring at a multivitamin bottle and wondering what do all these "ABC's" do and how much of each do I really need? Hell, I have.

We're frequently bombarded by commercials and other advertisements letting us know that a particular vitamin is loaded with "X" or covers everything from A to Zinc. Unfortunately, one issue that's often overlooked by many is termed vitamin-vitamin or vitamin-mineral interactions.

It's not news to you that we live a society that sometimes believes that more is better. And when you throw bodybuilders in the equation, you not only get a more-is-better way of thinking, but a how much can I take before it kills me mentality.

What we have to consider is that by combining or overdosing on certain vitamins, we may actually be robbing ourselves of nutrients that aid in growth and health. Ironic, huh?

With that in mind, it's probably time for a quick view into the world of vitamins. Hopefully, after reading this, you will be able to understand how to choose your vitamins and exactly what they do for you.

What does it do?

This section will focus on the function and relationships of each vitamin.

Vitamin A – This vitamin is fat-soluble and has a water-soluble friendly cousin known as the carotenoids (alpha and beta). Thanks to Bugs Bunny, we probably all associate beta-carotene (as found in carrots) as being essential for night vision. Also, vitamin A/carotenoids are essential for normal growth, development and maintenance of skin and the linings of the GI tract. They also help provide for normal bone and tooth development and formation. Keep in mind, though, that the fat-soluble form of Vitamin A is toxic in large amounts.

Interrelationships with other nutrients: Interacts with vitamins E, K, zinc and iron. Pure vitamin A can be teratogenic in females (cause harm to the fetus). The plant source carotenoids need a certain amount of vitamin E to aid in its metabolism, but excess vitamin E can also inhibit beta-carotene absorption. Excess vitamin A interferes with vitamin K absorption, where as a zinc deficiency interferes with vitamin A absorption. Vitamin A deficiency may also result in microcyctic anemia.

What should be in your vitamin supplement: Rather than taking the fat-soluble vitamin A, look for mixed carotenoids (alpha, beta, gamma, and delta).

Vitamin D – The vitamin is really the father of prohormones! It's similar in base structure to Testosterone, and since our bodies convert sunlight on our skin into Vitamin D, it's considered by many to be both a vitamin and a hormone. This vitamin is most famous for its role in bone and teeth development, and it's also involved in the absorption and metabolism of phosphorus and calcium. It too, is a fat-soluble vitamin, and as such is toxic in large amounts.

Interrelationships with other nutrients: Interacts with calcium, phosphorus, vitamin K and iron. Absorption may be decreased during iron deficiency. Promotes calcium absorption while utilizing phosphorus in the intestines; interacts with vitamin K during bone metabolism.

What should be in your vitamin supplement: Vitamin D is best in either the calcitriol or the cholecalciferol form.

Vitamin E – It's perhaps the most well known antioxidant. In fact, in certain scientific circles, only alpha lipoic acid is thought to surpass Vitamin E's antioxidant capability in the body. Vitamin E protects red blood cells from destruction (hemolysis). It also protects, in a complex way, the bad cholesterol (LDL) from doing damage to the lining of arteries and the heart. Probably most overlooked is the protection that E gives to A (in a big brother type of way) throughout the body. From an immune standpoint and athletic recovery view, vitamin E is intimately involved with prostaglandin synthesis.

Interrelationships with other nutrients: Interacts with selenium, specific amino acids (those which contain sulfur-cysteine and methionine), vitamin K, vitamin A, beta-carotene and polyunsaturated fatty acids. Vitamin E protects selenium and glutathione from oxidation. It's also needed for glutathione synthesis. High intakes of vitamin E can negatively interfere with the other fat-soluble vitamins (A, D, and K). Vitamin E is required for beta-carotene production in the body. Excessive intakes of this vitamin can act as a weak blood thinner, thus doses >1000 IU should not be mixed with aspirin or other blood thinning agents.

What should be in your vitamin supplement: The D-alpha-tocopherol form is the best for supplementation. Don't let marketing fool you; this form is better absorbed and recognized by the body.

Vitamin K – A vitamin that's essential in the diet but is also produced by bacteria within the intestinal tract. Also, next time you're in the middle of a No Holds Barred brawl and a tad of blood is trickling down your face, call on vitamin K to stop the flow since it's responsible for the clotting of blood. As a fat-soluble vitamin, it too is toxic in large amounts.

Interrelationships with other nutrients: Interacts with vitamins A and E and in a round about way, vitamin D and calcium. Both vitamins A and E are known to antagonize vitamin K. An excessively high intake of vitamin A (over 25,000 IU) will interfere with Vitamin K metabolism. Additionally, high intakes of vitamin E (over 1,000 IU) can also disrupt vitamin K, thus leading to prolonged bleeding times. This means that with high intakes of vitamin A and/or E, your cuts won't clot in an appropriate amount of time. Vitamins D and K are both metabolized in the kidney (among other places) and both play a role in bone metabolism, yet there's no known relationship between the two.

What should be in your vitamin supplement: For supplementation, look for the phylloquinone form of vitamin K.

Thiamin (B1) – B1 is important for all of us who exercise intensely because it's used for the breakdown of carbohydrates for energy. In fact, thiamin is instrumental in the generation of ATP (energy). It's also important for growth, normal appetite, digestion and the maintenance of healthy nerves.

Interrelationships with other nutrients: Interacts with niacin, pantothenic acid (CoA), vitamin C, calcium and magnesium. These interactions are in various cycles of energy production and metabolism. Thiamin does not appear to have any negative effects on other vitamins or minerals. However, excessive intramuscular injections of thiamin can lead to headaches, convulsions, cardiac arrhythmia, shock and other irritable side effects.

What should be in your vitamin supplement: As an oral supplement, look for thiamin pryo (or di) phosphate.

Riboflavin (B2) – Pay attention protein enthusiasts, this vitamin is essential for growth and the production of energy. It's utilized in protein metabolism, the breakdown of fat for energy, and in the regulation of neurotransmitters. This vitamin often acts as a cofactor in oxidation-reduction reactions, the electron transport system, and maintenance of antioxidants within the cell (intracellular glutathione).

Interrelationships with other nutrients: Interacts with phosphorus, magnesium, vitamin B6 and niacin. There are no known negative interactions with other nutrients. However, there is synergism between riboflavin and other nutrients for the production of energy in carbohydrate metabolism and in fat oxidation.

What should be in your vitamin supplement: In a supplement, look for the pure riboflavin or flavin mononucleotide form.

Niacin (B3) – Mainly involved in the metabolism of carbohydrates and protein (amino acids). It plays a role in the breakdown of stored carbohydrate (glycolysis) for energy while simultaneously aiding in fat synthesis. Approximately 200 enzymes require niacin for various metabolic processes. Most importantly to bodybuilders, perhaps, is the role that niacin has in protein synthesis. It was recently discovered that niacin influences post-translational modification of proteins, thus it affects growth. Niacin, along with chromium, also potentiates insulin.

Interrelationships with other nutrients: Interacts with tryptophan, ribose, glutamine, and vitamin B6. The amino acid tryptophan can be converted into niacin in the body in a complicated pathway that requires glutamine. Additionally, niacin is very important for the production of energy on the cellular lever via its use in the production of energy (ATP) along with ribose. Niacin comes in two forms, nicotinic acid and niacinamide. Nicotinic acid is used medically (in doses of 3 grams or more per day) to lower cholesterol and raise HDL (the good cholesterol). However, this form has side effects, namely flushing, and burning sensation in the ears, elbows and other extremities. These side effects can worsen asthma, peptic ulcer disease, liver disease and cause heartburn or vomiting. Sounds great!

What should be in your vitamin supplement: In a supplement, look for the niacinamide form unless your physician tells you otherwise. Niacin does not appear to have any negative vitamin or mineral interactions.

Vitamin B6 – Similar to the other B vitamins, it too aids in the synthesis and breakdown of amino acids. B6 also is important for the metabolism of essential fatty acids and the conversion of tryptophan to niacin. Vitamin B6 is also essential for growth, formation of heme iron, the interconversions of amino acids, binding of steroid hormones, and in the breakdown of carbohydrates for energy.

Interrelationships with other nutrients: Interacts with amino acids, cysteine, methionine, niacin, histamine, histadine, carnitine, taurine, dopamine, phosphate and riboflavin. Deficiency of this vitamin affects calcium and magnesium metabolism (for bodybuilders, a deficiency negatively effects strength and muscular contractions). At doses above 2 grams (2,000 mg) per day, vitamin B6 can cause damage to the nervous system. The amino acids histidine, carnitine, taurine along with dopamine and other neuromodulatory agents require B6 for their metabolism. Riboflavin is important for the interconversions of B6 in cells outside that of the liver.

What should be in your vitamin supplement: Vitamin B6 exists in three main forms: Pyridoxine phosphate, Pyridoxal phosphate and Pyridoxamine phosphate. All three forms are well absorbed, but the pyridoxal phosphate form has the highest order of absorption.

Folate – This is a very important vitamin for heart health and for women of child bearing years. Research shows that low levels are correlated with heart disease and in women, increased risks of their children having spina bifida (i.e., cleft palate). It's also used for the synthesis of nucleic acids and maturation of red blood cells.

Interrelationships with other nutrients: Interacts with vitamin C (ascorbic acid), zinc, and vitamin B12. A very important vitamin for amino acid metabolism, cardiac disease risk management, growth, and prevention of certain birth defects. Vitamin C protects folate from destruction by oxidative factors; high folate supplementation may diminish zinc absorption; and folate and B12 have a synergistic relationship (they promote each other's function in the body). However, folate can mask a vitamin B12 deficiency, so never supplement with folate alone, rather make sure to include vitamin B12.

What should be in your vitamin supplement: In a supplement, look for either folate or folacin.

Vitamin B12 – This vitamin is really a generic term for a group of compounds called corrinoids. The corrinoids are intimately involved with the production of nucleic acids and nucleoproteins (DNA synthesis), thus growth. Some bodybuilders who use steroids report that concomitant use of intramuscular B12 aids in the increase in appetite, thus promoting extra muscular growth. This theory has never been tested in a lab setting though. Vitamin B12 also is important for fat burning (beta-oxidation), energy production from carbohydrates and the maintenance of nervous tissue.

Interrelationships with other nutrients Interacts with calcium, vitamin B6, cobalt, methionine, isoleucine, threonine, magnesium, biotin and folate. The family of corrinoids known to most of us as Cobalamins are all well absorbed and utilized in the body. However, new research has shown that ingesting B12 with a high protein meal (high meat, not dairy) may inhibit or disturb its absorption. It may be best to take B12 supplementation at least a half-hour before eating a meal. Vitamin B12 needs calcium for B12 absorption. For amino acids and fats to be catabolized for energy, vitamin B12 is required. There is no indication of any toxicity from "over-dosing" with B12 nor is there any indication that high doses negatively interfere with other nutrients.

What should be in your vitamin supplement: Typically, the cyanocobalamin form is used in dietary supplements. Typically, as we age, we lose the ability to absorb B12 (due to diminished intrinsic factor in the stomach) and thus supplementation is warranted.

Pantothenic acid – The name pantos is Greek in origin and means everywhere. Thus, pantothenic acid is one of the nutrients that we never worry about in terms of deficiency. Perhaps most important is the central role pantothenic acid (CoA) has in energy production. It's involved in carbohydrate metabolism, protein synthesis, and modification of fat. It also aids in the storage of fat. Some data indicates that pantothenic acid accelerates wound healing following surgery.

Interrelationships with other nutrients: Interacts with cysteine, phosphate, vitamins B1, 2, 3, and 6, and magnesium. As a nutrient that occurs in almost every type of food, overdosing is almost a non-issue. If you take 100 mg or more of the pantothenate form (a very expensive form), it may increase niacin excretion. However, it may also aid in cholesterol reduction. The B vitamins (1,2,3, and 6), along with pantothenic acid, are needed for the molecule pyruvate to be converted into acetyl CoA for the burning of carbohydrates in the Krebs cycle. Pantothenic acid along with magnesium and cysteine also is used for the production of acetyl CoA. Research studies examining 20 grams a day of calcium pantothenate demonstrated very little side effects.

What should be in your vitamin supplement: The best form is plain old pantothenic acid.

Biotin – Is primarily involved with the synthesis and breakdown of fatty acids and amino acids. Aids in the removal of amine groups from amino acids, thus allowing the blood to maintain a proper pH. Many enzymes in the body are dependent upon biotin.

Interrelationships with other nutrients: Interacts with magnesium, phosphate, and indirectly also vitamin B12. Once referred to as vitamin H and was later given it's current moniker. Biotin needs magnesium along with ATP (energy) to release specific types of energy and inorganic phosphates from within a cell. In fat metabolism, biotin interacts with magnesium and amino acids.

What should be in your vitamin supplement: Supplements often contain free biotin or biotinyllysine. It's best absorbed from cooked foods. There are no reports of toxicity with biotin and doses of up to 60 mg/d have been shown to be safe.

Vitamin C – Thanks to Linus Pauling, this is perhaps the most famous of all vitamins. Vitamin C maintains the integrity of capillary walls; is used in wound healing; allergic responses; has anti-inflammatory action; decreases the duration and intensity of the common cold; enhances the absorption of non-heme iron; is involved in cholesterol metabolism; protects vitamin A; and of course, serves as an antioxidant.

Interrelationships with other nutrients: Interacts with iron, copper, folate, carnitine, tyrosine and in neurotransmitter synthesis. Vitamin C enhances the absorption of non-heme iron (iron from vegetable or fruit sources). Excessive iron in the presence of vitamin C can actually cause the accelerated destruction of vitamin C (counterproductive). Therefore, a balance is always recommended. And, high doses of vitamin C taken at the same time that iron is ingested in the wrong or susceptible person may increase the chances of developing a disease known as hemochromatosis (iron overload), which essentially can destroy the liver

There is scant evidence that high intakes of zinc may impair vitamin C absorption, the same holds true with iron. Vitamin C is also needed for carnitine production. Carnitine is important because it transports fats into the mitochondria (powerhouse) of the cell for oxidation. The amino acid and neurotransmitter precursor tyrosine, also requires vitamin C for its production. The relationship to folate isn't so obvious, but simply it helps to maintain folate in its active form. One negative or possible interaction of vitamin C is with copper. High vitamin C intakes have been shown to diminish copper stores and blood status. Reduced serum copper levels are associated with decreased Testosterone levels, therefore, vitamin C may indirectly influence your Testosterone levels.

What should be in your vitamin supplement: Doses over 2 grams have been shown to induce GI distress (diarrhea) in certain individuals and may increase chances of kidney stones in susceptible people. Vitamin C is absorbed in a saturable and dose dependent fashion, thus many small doses throughout the day will produce greater retention than one or two large doses. Look for the ascorbate form in your vitamin.

A Quick Recap

The "Cliff Notes" way of understanding what vitamins do is to list them by their innate properties. In other words, to either classify them as energy-releasing, involved in blood maintenance or production, or other (and many of these other properties were, of course, alluded to above).

Energy Releasing Hematopoietic (blood maintenance) Other
Thiamin Folic acid Vitamin B6
Riboflavin Vitamin B12 Thiamin
Niacin Vitamin B6 Folic acid
Pantothenic acid Pantothenic acid Vitamin B12
Biotin Vitamin E Niacin
Vitamin B6 Vitamin K Vitamin A
  Vitamin C Vitamin D
    Vitamin C

Well, how much do I take?

According to the National Academy of Sciences (NAS), the amount of each vitamin or mineral that you need daily is dependent upon your age. Thankfully, due to the diligence of people like Shari Lieberman, PhD, Adriene Bendich, PhD and Jeff Blumberg, PhD, the NAS has realized that one dose level does not fit all. Therefore, before we criticize these recommended levels of intake, let's take a look at what the NAS has typically recommended:

*All levels of recommended intake presented here are based upon males between the ages of 31 and 50. The list is broken into two parts, estimated average requirements and tolerable upper limits (levels above this may cause harm or negative vitamin-vitamin, vitamin-mineral interactions.

Vitamin Estimated Adequate Intake Tolerable Upper Limits
A 1000RE (retinol equivalents) 25,000 IU (5,000IU pure A)
D 5 mcg/d 50 mcg/d
E 12 mg/d 1,000 mg/d
K 80 mcg 160 mcg
Thiamin 0.9 mg/d *unknown
Rioflavin 0.9 mg/d unknown
Niacin 11 mg/d 35 mg/d
B6 1.3 mg/d 100 mg/d
Folate 320 mcg/d 1,000 mcg/d
B12 2.0 mcg/d unknown
Pantothenic acid 5 mg/d unknown
Biotin 30 mcg/d unknown
C 60 mg/d 2,000 mg/d

* unknown indicates that a "toxic" dose level has either not been determined, does not occur or is controversial.

So what's a T-man or Vixen to do?

In reviewing the basics of vitamins and getting a quick peek into what they do and just how important they are, I hope that more and more of you realize that in order to maintain or obtain good health, an eating program that emphasizes a variety of high quality foods (vegetables, fruits, unprocessed foods, etc.) is in order.

A supplement, by definition, means "in addition to". In principle, I agree with this premise, but since we know almost 88% of the good ol' USA doesn't eat 5-9 fruits and vegetables per day and that 67% of the population are now classified as overweight, a sure bet is that good, high quality nutrition is a rarity. Besides, nutrient density of a particular fruit or vegetable varies enormously from crop to crop.

Multivitamin and mineral formulas do play a role, even for the best eaters. Even the most nutritionally minded among us aren't getting all their vitamins and minerals through foods. Add intense exercise to the equation and it's easy to see why we need to supplement daily with a high quality multi-vitamin/mineral product.

Now, when it comes to "vitaminology," our bodies don't operate on the same kind of circadian rhythm as does our general metabolism or even our Testosterone levels. In essence, the time of day that we take a single vitamin, a combination of vitamins, or even a multiple vitamin isn't necessarily the most important thing when health is concerned. However, it is important to be aware of possible vitamin interactions (especially the negative ones).

Along the same lines, some people are concerned that taking vitamin E at the same time that they take iron will have negative effects; the truth is it won't. However, as mentioned, high doses of vitamin C taken at the same time that iron is ingested in the wrong or susceptible person may increase the chances of developing a disease known as hemochromatosis (iron overload). And high levels of iron intake may be correlated with increased chance of developing heart disease, though the research is still somewhat inconclusive.

For those of you who do not have a specific condition that you are looking to avoid or prevent, the best defense (shown by clinical research) is to take a moderate level multivitamin/mineral formula a few times a day (better absorption and retention, as studies have demonstrated a superiority of multiple dosing versus a "one-a-day" dosing used a dosing regimen of three times per day). Even though many of the manufacturers really haven't paid all that much attention to possible interactions, the small doses of multi-vitamins, combined with a solid diet, is probably your best bet in achieving a healthful vitamin status.

And remember that while there are both water-soluble vitamins (the B's, C, biotin, pantothenic acid, folate) and fat-soluble (A, D, E, and K) vitamins, both are better absorbed when taken with food rather than on an empty stomach.

Obviously, in the case of vitamins, more does not always mean better and that vitamins and minerals at high doses (2-5x RDI) often can cause negative reactions between the nutrients in the body, thus leading to a poorer – not better – nutrition or health status.

References

1. Mahan LK, Escott-Stump S. Krause's Food, Nutrition and Diet Therapy. 10th edition. Saunders Publishers.

2. The National Academy of Sciences. Dietary Reference Intakes: Applications in Dietary Assessment 2000. NAP.edu.