Popeye the Sailor – Man & Spinach

Who hasn’t heard of Popeye the Sailor Man? His strength came from a can of spinach — or did it? Spinach contains nonheme iron, the form of iron that is not readily absorbed unless a person is deficient or it is consumed in combination with heme iron (animal products) or vitamin C. Not only is the form of iron not easily absorbed in spinach, but spinach contains compounds that bind with iron and interfere with its absorption. This article will further explore iron’s absorption and distribution.

Popeye the Sailor, iron, trace minerals, minerals, blood, hemoglobin, anemia, heme iron, nonheme iron, vegetarians, vegetables, absorption, growth, development, animals, meat, RDA, Vitamin C, bone marrow, interference, oxalic acid, tannins, polyphenols, spinach, phytic acid
Tea — Tannins & Absorption of Nonheme Iron

The absorption of nonheme iron is affected by many dietary factors. Oxalic acid in vegetables and phytic acid as well as additional factors found in grain fibers can bind iron and decrease its absorption. In tea, tannins (polyphenols) reduce the absorption of nonheme iron. If someone has an iron deficiency, the intake of tannins should be watched and fiber intake should be kept within current recommendations. Additionally, zinc supplements will interfere with the absorption of nonheme iron since zinc and iron compete for absorption. (1) (2) (3)

Iron Needs & Absorption

The body’s need for iron is the single most important element affecting nonheme iron absorption. Iron needs increase:

  • During growth and pregnancy;
  • During a state of iron deficiency; and
  • At high altitude due to the air’s lower oxygen concentration resulting in the increased concentration of hemoglobin in the blood. (2) (3)

    Popeye the Sailor, iron, trace minerals, minerals, blood, hemoglobin, anemia, heme iron, nonheme iron, vegetarians, vegetables, absorption, growth, development, animals, meat, RDA, Vitamin C, bone marrow, interference, oxalic acid, tannins, polyphenols, spinach, phytic acid
    Colorado Rockies – High Altitude & Iron Absorption

Where there are inadequate iron stores, the main protein that transports iron in the blood easily binds additional iron from intestinal cells, moving this iron into the bloodstream. On the other hand, when there are adequate iron stores and the protein that binds iron in the blood is totally saturated with iron, little is absorbed from the intestinal cells where iron stays bound. (2) (3)

It is through this mechanism that iron, and the nonheme form in particular, is only absorbed as needed under normal circumstances. Intestinal cells have a two to five day life cycle. If iron is not needed, it will be excreted from the iron that is stored in intestinal cells. Even though high doses of iron is toxic, under normal dietary conditions in the majority of people it is carefully regulated. (2) (3)

Popeye the Sailor, iron, trace minerals, minerals, blood, hemoglobin, anemia, heme iron, nonheme iron, vegetarians, vegetables, absorption, growth, development, animals, meat, RDA, Vitamin C, bone marrow, interference, oxalic acid, tannins, polyphenols, spinach, phytic acid
Red Blood Cells & Iron

The hemoglobin molecules of red blood cells contains the majority of iron in the body. The bone marrow stores some, and a small amount is found in other body cells, for example the liver, to store it. The iron found in these body stores can be mobilized if iron is needed. However, these iron stores can be depleted if there is a chronically inadequate intake of dietary iron. (2)

In light of the fact that iron deficiency remains a world wide problem, its absorption is an important factor. Even though a food may be rich in iron does not mean it will be absorbed. The form of iron as well as interference with anti-nutrient compounds and mineral interactions all affect absorption. Taking a specific mineral supplement will interfere with the absorption of other essential minerals. It is for this reason natural supplements are most effective. (2) (3)

(1) https://www.cdc.gov/immpact/micronutrients/index.html
(2) https://www.cdc.gov/nutritionreport/99-02/pdf/nr_ch3.pdf
(3) https://www.cdc.gov/mmwr/preview/mmwrhtml/00051880.htm


Iron Man & Woman – Iron Absorption

“Iron Man & Woman” — For hundreds of years the importance of dietary iron was common knowledge. Despite this understanding, one of the most common worldwide nutrient deficiencies is iron. This is also the only nutrient where the RDA for men is less than the RDA for young women. (3)


Every living cell contains iron, amounting to approximately 5 grams, or one teaspoon for the whole body. Iron absorption is based on a number of factors. This article provides an overview of what factors come into play in its absorption. (2)

Absorption – Controls
Hypertension, Silent Killer, High Blood Pressure, Uncontrollable Risk Factors, Age, Family History, Atherosclerosis, preventable risk factors, obesity, excess weight, inactivity, alcohol.
Hypertension – The Silent Killer — Exercise Makes a Difference

Once iron is absorbed it is not easily eliminated from our bodies, therefore, it is important to control iron absorption. Several mechanisms exist to regulate our body’s ability to absorb iron. Generally, iron absorption depends on:

  • the body’s need for iron,
  • its form in a particular food,
  • and many other factors.

Healthy people absorb approximately eighteen percent of the iron present in food, however people who are iron deficient absorb more. (2)

Absorption – Form Counts
Steak – Heme Iron

Iron is found in different forms based on the food. The amount absorbed is influenced by the particular form. Within animal flesh, approximately forty percent of the total iron is:

  1. hemoglobin, the form that is found in red blood cells, and
  2. myoglobin, the pigment that is present in muscle cells.

This kind of iron is referred to as heme iron and is absorbed approximately 2 – 3 times better than nonheme iron (the simple elemental iron). Nonheme iron is the form that is added during the enrichment process to grain products. It is also found in:

  • animal flesh,
  • milk,
  • eggs,
  • grains,
  • vegetables, as well as
  • other plant foods. (2) (3)

    Citrus Fruit – Increases Absorption of Nonheme Iron

Consuming nonheme iron with heme iron together increases the absorption of nonheme iron. Consuming more vitamin C rich foods will increase iron absorption, especially if blood iron is too low or there is inadequate dietary iron. Copper also aids with the body’s iron use.

Iron is the oldest known trace mineral critical for the growth and development of the human body. A number of factors influence its absorption, including its form (whether heme or nonheme) as well as other foods with which it is consumed. The body of knowledge is vast and this article just touches upon its absorption. The next article will further delve into what affects its absorption and its distribution.


Without the Trace – Minerals That Is

Without the trace — minerals that is, you cannot maintain a healthy life. Also referred to as microminerals, this area of nutrition science is growing at a rapid rate. Although the importance of iron has been known for centuries, it is only within the last 50 years that scientists recognized the significance of other trace minerals. Even though only 100 milligrams or less of each of these minerals are required daily, they are as essential as major minerals for good health. (5)

This article provides a general overview of trace minerals. Discover additional key facts and findings including rich sources of specific trace minerals in this next series of articles.

The Mystery Uncovered
trace minerals, microminerals, iron, iodide, zinc, selenium, copper, fluoride, chromium, manganese, and molybdenum, vitamin C, deficiencies
Selenium Deficiency Found in Remote Areas of China

The importance of each micromineral is like following a good mystery, and still, evidence continues to unfold.

  • Scientists found a rare type of heart disease in a remote area of China. This disease was linked to a deficiency in selenium.
  • In 1961 other research scientists linked a zinc deficiency to dwarfism, prevalent among Middle Eastern villagers.
  • In the latter part of the 1960’s and early 1970’s synthetic formulas for intravenous feeding omitted some trace minerals. When recipients of these intravenous feedings showed symptoms of deficiencies, it led to the identification of these trace minerals.  (1) (2)
The Difficulty in Identifying Trace Minerals
minerals, supplements, lab
Mineral Supplements are Manufactured in the Lab

The difficulty lies in the ability to define precisely what our trace mineral needs are since only minuscule amounts are needed. In order to measure these minute amounts in both body tissues and food, highly complex technology is required.

Although the mystery continues to unfold, we are aware of iron, iodide, zinc, selenium, copper, fluoride, chromium, manganese, and molybdenum. In the next article, we will see how foods rich in vitamin C increases the absorption of minerals, and iron in particular, a trace mineral commonly found deficient in a large percent of the world’s population. (1) (2) (3) (4) (5)

1. https://www.cdc.gov/nutritionreport/99-02/pdf/nr_ch4b.pdf
2. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6302a3.htm
3. https://www.cdc.gov/nutritionreport/99-02/pdf/nr_ch4a.pdf
4. https://www.atsdr.cdc.gov/ToxProfiles/tp132-c1-b.pdf
5. https://www.cdc.gov/nutritionreport/pdf/Trace.pdf