Minerals Versus Cancer, Part II

Be Careful with Supplements

Encouraged by reports linking the mineral to cancer protection, people are buying – and taking – selenium supplements. In some Asia countries, they call selenium as the king of anti-cancer substances.  But, a few words of caution are in order.

At high doses, selenium can cause health problems. Fatigue and irritability, as well as brittleness or loss of hair, have been seen in patients suffering from toxic amounts of selenium. A research scientist exposed to too much selenium developed bronchitis and skin problems.

How Much is Too Much?

According to the Food and Nutrition Board of the National Research Council, a long term intake of 2400 to 3000 micrograms of selenium per day would be expected to cause a toxic reaction.

It is very unlikely that the diet could provide such a high level of selenium. In fact, there is only recorded instance of selenium toxicity caused by food. It dates back about seventy five years and occurred among people living in an area of the country where the soil was unusually rich in this mineral.

To overdose on selenium, you would probably have to work with it or take supplements. In 1977, the Food and Nutrition Board (U.S.) advised:

There is no justification at this time for the use of selenium supplements by the general population. Should selenium supplements eventually be condidered desirable for those persons living in low-selenium areas, or for those consuming vegetarian diets, a daily supplement of 50 to 100 micrograms could probably be taken safely. (Emphasis added.)

Five years later, in 1982, the Committee on diet, Nutrition, and Cancer (U..S.) seemed to agree with the Food and Nutrition Board’s opinion. “Increasing the selenium intake to more than 200 micograms a day…….. by the use of supplements has not been shown to confer health benefits exceeding those derived from consumption of  a balanced diet,” said tyhe panel.

Selenium in Our Diet

It is not easy to list the selenium content of common foods. The amount of selenium in meat, for instance, can vary. It depends partly on the amount of the mineral in the animals’ diets.

The selenium content of the soil also varies throughout the regions of each country. The soil content, inturn, greatly affects the amount of selenium in grains. But most of us  now eat foods grown from many parts of our country; no longer do we eat only foods grown nearby. Furthermore, recently so many foods were imported from Asia and other countries.

As a result, nutritionosts rarely see signs of selenium deficiency among Americans. The average selenium intake in the United States, for instance, is 150 micrograms per day, which is considered more than enough  for most people.

Good sources of selenium are:

  • Meat and seafood
  • Grains, unless, grown in soil low in selenium
  • Asparagus and mushrooms
  • Garlic
  • Meats and seafood are the richest source of this mineral.

Fruits and most vegetables contain little selenium. The selenium content of dairy products and eggs varies.

Can Iron Help, Too?

Adequate iron in the diet prevents a condition called Plummer-Vinson syndrome. This condition has been linked to increased risk of developing stomach cancer and cancer of the esophagus.

Probing these findings, scientists have found that iron deficiency allows bacteria to grow in the stomach. It is possible that these bacteria turn nitrites into the cancer causing substances called nitrosamines.

But, as is the case with selenium, there is still not much evidence to go on. It certainly makes sense, though, to eat iron-rich foods (unless your doctor has advised against it. Some people, though not many, have a disorder that causes them to retain too much iron).

Iron deficiency is not truly widespread in some countries. But many people, such in case of Americans, don’t get the RDA for iron. This hardly means that all of these people have iron deficiency. The RDA is set higher than about 96 % of us need. It is not a requirement, but rather a “better-safe-than-sorry” approach.

The Best Sources of Iron

If you are concerned about your iron intake, consider some of these sources:

  • Lean meats and shellfish
  • Whole grain or enriched cereals
  • Dried apricots, prunes, or raisins
  • Nuts and wheat germ
  • Dried beans and peas
  • Leafy green vegetables

Next Story, the Part III )