Nutrition Science and Everyday Application - beta v 0.1

VITAMINS AND MINERALS INVOLVED IN BLOOD HEALTH 535
Figure 9.19. The structure of hemoglobin and the heme complex. On the left, the structure of
hemoglobin includes four globular peptides (shown in blue and red) and the iron-containing heme
groups (shown in green). On the right is a closer view of the heme complex.
The iron in hemoglobin is what binds to oxygen, allowing for transportation to cells. If iron
levels are low, hemoglobin is not synthesized in sufficient amounts, and the oxygen-carrying
capacity of red blood cells is reduced, resulting in anemia. Iron is also an important part of
myoglobin, a protein similar to hemoglobin but found in muscles.
Dietary Sources of Iron
There are two types of iron found in foods:heme iron and non-heme iron.
• Heme iron is iron that is part of the proteins hemoglobin and myoglobin, so it is
found only in foods of animal origin, such as meat, poultry, and fish. Heme iron is
the most bioavailable form of iron. About 40% of the iron in animal foods is heme
iron and 60% is non-heme iron.
• Non-heme iron is the mineral by itself and is not a part of hemoglobin or
myoglobin. Non-heme iron can be found in foods from both plants (e.g., nuts,
beans, vegetables, and fortified and whole grains) and animals. It is less
bioavailable than heme iron. Consuming vitamin C, meat, poultry, and seafood
with non-heme iron increases its bioavailability. For example, eating an orange ( a
good source of vitamin C) along with your bowl of vegetarian chili will help you to
absorb more of the iron from the beans and vegetables. On the other hand,
chemicals such as phytates (found in beans and grains) and plant polyphenols
(found in fruits, vegetables, some cereals, legumes, tea, coffee, and wine) decrease
bioavailability due to binding with iron. 1