Vitamins and Minerals
Vitamins and minerals are essential to life. They act as cofactors or prosthetic groups for most enzymes, thus making biochemical reactions possible. Some cofactors are transiently associated with a given enzyme and in this capacity they function as cosubstrates. They are also called coenzymes.
Besides being cofactors for enzymes some vitamins such as the fat-soluble vitamins A and D have been shown to exhibit hormone-like functions. Thus, vitamin A and its metabolites retinaldehyde and retinoic acids are involved in the growth, differentiation and maintenance of epithelial tissues as well as for reproduction. Retinoic acids can substitute for vitamin A--deficient animals in growth promotion and epithelial differentiation. As for vitamin D is interesting to note that the skin is both the site of vitamin D3 and 1,25-dihydroxy vitamin D3 synthesis and a target organ for the latter. 1,25 (OH)2 vitamin D3 is essential for mineral homeostasis and bone integrity as well as the regulation of growth and differentiation in normal and malignant tissues.
Minerals are generally tightly bound to the protein moiety and are either directly involved
in the catalytic process or help the protein perform its specific biological function.
Among the former are metal ions such as Cu2+, Zn2+, Mn2+,
Se2+, Fe3+, which are part of the active site of enzymes involved in redox reactions
while the latter group comprises cations that do not take part in catalytic reactions.
A typical example is Zn2+, which can function as a non-catalytic agent in the
zinc-finger motifs found in the transcriptional factors that are proteins involved in DNA replication.
These are specific repetitive amino acid sequences (some 30 residues long) that have Zn2+
covalently linked to Cys and His residues.
Most of the higher organisms, including humans are not able to synthesize their own essential factors, which they must, therefore, acquire through diet. The high turnover of vitamins, especially the water-soluble ones, requires that they be replenished through food on a daily basis. It is well known that food processing causes the foodstuff we buy at the supermarket to be depleted of most vitamins and minerals. A diet rich in fresh fruits and vegetables restores the balance of essential nutrients in the body.
It is important to bear in mind that vitamins and in particular those in the B group are working and get absorbed synergistically that is they need each other and the presence of other factors, which could be other vitamins or minerals.
In vitamin deficiency, enzyme-catalyzed reactions may slow down or not occur at all. This leads to profound changes in the cellular metabolism and if vitamin/mineral deficiency is allowed to continue for a longer period of time degenerative diseases such as cardiovascular disease, rheumatoid arthritis, cancer and others may develop.
It is important to distinguish between severe vitamin deficiency -- which is very rare nowadays in the Western world -- and that which affects over half of the population in the Western hemisphere and is called subclinical deficiency by many nutritional experts. This means people may get most of their daily vitamin requirements from food but not in the optimal amounts. Over time this will lead to a partial breakdown of the finely-tuned cellular metabolism with unfavorable consequences for the body as a whole. Because these subtle changes occur over an extended period people are not aware that anything is going wrong.
Although most people believe that they might have an adequate supply of vitamins and minerals
from various foods it has become apparent that even with a "normal" well-balanced diet it is difficult to get
all the necessary micronutrients required for optimal body functions because:
- Extensive farming and the use of pest-control chemicals lead to mineral depletion in soil
- Processed foods lack most vitamins and minerals
- Absorption of nutrients decreases with age
- Un-ripened fruits and vegetables (such as they are usually transported to supermarkets) as well as hybrid crops lack certain nutrients and natural flavours.
So, even if the fruits and vegetables are looking very appealing in the farmers' market (see pictures below) or in leading
food supermarkets for that matter, we should bear in mind that their vitamins and minerals contents are likely to be lower than
normal because they were grown mostly on farms that practice industrial agriculture. Organic foods are beginning to make some
headways in the marketplace but they are generally more expensive and far less available than their non-organic counterparts.
Some sobering facts
Therefore, it would appear that it is quite improbable to get
all the necessary nutrients
from the diet alone, no matter how well balanced it is.
A recent U.S. Department of Health, Education and Welfare report showed that:
- over 90% of adults are chromium deficient
- over 60% of adults have an inadequate calcium intake
- over 30% have diets low in vitamins C and A
- over 50% have a low intake of vitamin B6 and folic acid
- over 50% have a low manganese intake
- over 40% have a low zinc intake
How much we should get daily
We may ask then, what is the necessary daily intake of biocatalysts in order to maintain optimum health? According to many medical and government health organizations, optimum intake of vitamins and minerals
should come mainly from food sources. This may be true when people eat a well balanced diet with lots of
fresh fruits and vegetables. However, a large segment of the population does not appear to follow this good
advice particularly the young generation, always busy, always on the run. Today's lifestyles and the stress
of the workplace together with the environmental conditions and the quality of food available in the grocery stores
are forcing us to rely, at least in part on nutritional supplementation.
Although further research into the usefulness of nutritional supplementation in pill form is needed before making definite recommendations for additional vitamin and mineral supplements a large percentage of North Americans are already taking nutritional supplements on a daily basis. This is reflected by the sales of nutritional supplements in all forms that have reached some $25 billion worldwide in 2006.
So, how much vitamins and minerals should we have on a daily basis?
Although there is not as yet a wide consensus on a set of values
for the daily intake of the most important biocatalysts most experts in nutrition suggested
that the RDA issued almost 60 years ago must be ammended. And so it was. In 1989 the National Research Council of U.S.A. issued a new RDA (1) that took into account the developments in the nutritional sciences since late 1940s. However, as R.A. Sunde argued in a recent article (2) most of the nutrient requirements were still based on old methods
of calculating the RDA, i.e. based on balance or factorial analysis rather than on biomarkers. Since many enzymes that
require vitamins and minerals as cofactors are regulated by gene expression it is obvious that the analysis
of that expression could form a better foundation on which to build a sound dietary allowances program for human nutrition. Since 1989 the new Dietary Reference Intakes guideline, which replaced the old RDA has been further amended(1998-2001) (3,4) but there is still a long way to go until all nutrient requirements could be set based solely on good biochemical markers. Meanwhile, based on several major scientific studies leading nutritionists recommend that a well balanced diet should still be supplemented with vitamins and minerals in the range shown in the table below. This is to ensure optimal health and to reduce the risk of degenerative diseases and premature aging.
Recommended Daily Vitamins & Minerals Intake
||Range for Adults
||Range for Adults
||1,000 - 5,000 I.U.
||1 - 3 mg
||500 - 1000 I.U.
||250 - 1,000 mg
||200 - 400 I.U.
||100 - 300 mcg
||200 - 1000 mg
||1 - 2 mg
||10 - 100 mg
||10 - 25 mg
||10 - 50 mg
||200 - 400 mg
||10 - 50 mg
||5 - 10 mg
||25 - 50 mg
||10 - 25 mcg
||25 - 100 mg
||2000 - 3000 mg
||25 - 50 mcg
||25 - 100 mcg
||200 - 400 mcg
||5 - 10 mg
||100 -300 mcg
||20 - 50 mg
Adapted from "Encyclopedia of Nutritional Supplements" by Michael T. Murray, N.D., Prima Publishing, Rocklin, CA, 1996.
Note: The recommended intakes of vitamins and minerals apply to healthy individuals eating a balanced diet and wishing to maintain good health. For certain medical conditions the daily doses of vitamins and minerals may need adjustment and the advice of a nutritionally oriented health care provider should be sought.
1. National Research Council(1989) Recommended Dietary Allowances. National Academy Press, Washington, D.C.
2. Sunde, R.A.(2001) Research Needs for Human Nutrition in the Post-Genome-Sequencing Era. J.Nutr. 131, 3319-3323.
3. Food and Nutrition Board(2000) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium and Carotenoids. National Academy Press, Washington, D.C.
4. Food and Nutrition Board(2001) Dietary Reference Intakes for Arsenic, Boron, Chromium, Copper, Iodine, Iron,
Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. National Academy Press, Washington, D.C.
Those interested in more in depth information about the role of vitamins and minerals in the body as well as something about accessory nutrients should turn to