And what about the remaining 32% of the population, are they really receiving adequate nutrients from diet alone? Research indicates the answer to this question is a resounding no. Eating plenty of fruits and vegetables, while necessary for good health, may offer a false sense of security. Furthermore, in some cases, the food we consume and the water we drink are more a cause for concern than a source of nutrition, endangering rather than benefiting our health.

These facts suggest we need to look beyond our diet to obtain sufficient supplies of vitamins, minerals and amino acids.

So how is it we have to take vitamins when our ancestors lived quite fine without them? The fact is that the soil in which our food is grown isn't quite the same as it used to be. For instance, selenium, washed out from the upper layers of the soil during the ice ages, is deficient in most soils worldwide. Zinc, too, may be depleted in many soils. Dwarfism in males is frequent around the Mediterranean, where wheat, grown for 4,000 years on the same soil, has exhausted the zinc content.

Many epidemiological studies have focused on the role mineral-deficient soil plays in disease. The incidence of death from ischaemic heart disease and acute cardiac arrhythmias is increased in many regions where magnesium and/or selenium levels are reduced in soil and water. In Serbias Zlatibor district, a region with higher selenium soil content, residents have lower mortality rates from cancer and cardiovascular diseases and higher serum selenium and magnesium values compared with other Serbian regions. In Poland, the number of deaths from digestive tract and respiratory system malignancies was nearly threefold higher (27.67%) in one community with low magnesium soil content compared to a community with high magnesium soil content, where only 9.87% of deaths resulted from malignancies.

In the United States, Texas has one of the highest selenium concentrations, Florida one of the lowest. Massachusetts, Pennsylvania, New Jersey, New York, Ohio, Connecticut and Maryland also have low selenium soil content, while California is in the mid-range. Levels of selenium in test subjects from 11 states corresponded with levels in the soil.

Researchers have determined that the cancer mortality rate rises in US counties with low levels of forage selenium. The lower the level of selenium in a county, the higher the rates of death from cancers of the lung, rectum, bladder, esophagus, cervix and breast. According to the researchers, this remarkable degree of consistency strengthens the likelihood of a causal relationship between low selenium status and an increased risk of cancer mortality.

Another consideration in deciding whether we are getting enough vitamins and nutrients from our foods is to recognize whether the diet truly provides adequate amounts of each form of a particular vitamin. For instance, all of the different forms of vitamin E (tocopherols, tocotrienols) play important roles in the body, but are not found in every food that contains vitamin E. Depending on variety, the gamma-tocopherol content of pumpkin seeds is about 5-10 times as much as that of alpha-tocopherol.

Often, in order to obtain an effective dose of a certain nutrient, the required quantity is far more than even the healthiest eater probably wants to consume. A good example is indole-3-carbinol (I3C) and its metabolite diindolylmethane (DIM). I3C is a phytonutrient derived from cruciferous vegetables (cabbage, broccoli, cauliflower and brussels sprouts). I3C and DIM have been shown to inhibit breast, cervical-vaginal, and skin cancer. In order to eat enough cruciferous vegetables to achieve beneficial effects, a pound or more of cabbage or cauliflower daily would have to be consumed. Furthermore, the concentration of I3C varies greatly depending on the seed strain, climate and soil. Cabbage grown in Israel, for instance, has been found to contain virtually no I3C.

There are other considerations that factor into why we don't get enough nutrients in our diet such as over cooking foods and irradiation. The fact is, things aren't the same as when our ancestors farmed the land and our food isn't as pure. So do eat your brussel sprouts but also remember to take your vitamins.