Trace Minerals – Iron and Zinc
Iron is a trace mineral found in many parts of the body that performs many vital functions. It’s a component of two proteins that carry oxygen from the lungs to the rest of the body: hemoglobin, found in the red blood cells, and myoglobin, found in muscle tissue. Iron is also a part of many enzymes, proteins that speed chemical reactions and create energy. Iron also support brain development.
The two types of iron found in foods are heme iron and non-heme iron.
Heme iron is part of the hemoglobin and myoglobin found in animal tissues. Meats, poultry, and fish are the only dietary sources of well-absorbed heme iron.
Non-heme iron is found mainly in plant foods such as beans, leafy green vegetables, legumes, and iron-fortified foods such as grains; small amounts are found in eggs and dairy products. This form of iron is much less absorbed than heme iron. Fortunately, you can absorb more heme iron at meals if you also consume the following:
• A food or beverage rich in vitamin C
• Meat, poultry, or fish
Several substances found in foods reduce iron absorption from foods. These include phytates, which are acids found in legumes (beans and peas), grains, and rice; polyhenols, which are found in coffee, tea, some fruits and vegetables, spices and soy foods such as tofu; oxalates found in spinach, strawberries, chocolate, wheat bran, nuts, beets, and tea; and fiber. Too much calcium, phosphorus, or zinc from foods or vitamins supplements also lowers your non-heme iron absorption.
Deficiencies and Excesses
Getting too little iron is a worldwide problem. In the United States, young children, teenage girls, and women during their childbearing years are most at risk for an iron deficiency. If you have depleted iron stores, you can feel no symptoms. Eventually, you can develop microcytic hypochromic anemia and experience symptoms such as fatigue, weakness, increased sensitivity to cold temperatures, and behavioral changes. Children can become irritable, have a lower attention span, and have difficulty learning.
Too much iron can also have severe consequences, especially in children who accidentally overdose on iron-containing prescription or over-the-counter supplements. Symptoms of iron overload include nausea, vomiting, constipation, or diarrhea; in several cases, a rapid heartbeat, dizziness, confusion, and even death can occur. A common inherited defect can cause iron overload disease in adults. A simple blood test can screen for this. When too much iron builds up in the body over time, it can lead to cirrhosis, diabetes, heart disease, and arthritis. Too much iron also reduces zinc absorption.
Zinc is a trace mineral that’s involved in many important reactions that occur in the body. It plays a key role in growth and sexual development and helps proteins such as enzymes and hormones perform their many functions. It also supports immune function and helps make DNA (genetic material). Zinc also plays a role in maintaining your senses of taste and smell.
Zinc is found in a variety of protein-rich foods including beef, liver, eggs and seafood. It is also found in grains and legumes (beans and peas), but these foods contain phytates – acids that attach to zinc – and fiber that limits zinc absorption by the body. Zinc from animal sources is highly absorbed.
Deficiencies and Excesses
Zinc deficiency is rare, except in populations that live mainly on cereal grains that contain poorly absorbed zinc. However, those with gastrointestinal or digestive disorders or chronic diseases such as liver or kidney disease or with alcoholism can be at risk for a zinc deficiency. People who consume no meat (such as vegetarians or vegans) and pregnant or lactating women (who have higher zinc needs) are also at risk. Older infants (7-12 months) who are exclusively breastfed also need more zinc.
Although excess zinc is not stored in the body for long periods of time, in some people excess amounts from foods and/or supplements can dampen immune function and lead to hair loss, diarrhea, abdominal cramps, and vomiting and other gastrointestinal problems. Too much zinc can also cause a copper deficiency.