Nutrient Sinks: Scenarios Leading to Reduced Nutrient Absorption

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10/22/2005| 0 comments
by Kathy Zawadzki

Nutrient Sinks: Scenarios Leading to Reduced Nutrient Absorption

Calcium and iron are two minerals that are very important to the active individual.

body's calcium/phosphorus ratio. Under these circumstances, the body attempts to maintain balance by drawing calcium from bone.


To help improve calcium availability, be sure to wait until after your morning coffee to consume your calcium-rich foods (low-fat dairy products) such as skim milk and low fat yogurts.   There is some evidence that suggests caffeine may also decrease availability of calcium when the two are consumed together.   Other good calcium sources include green leafy vegetables such as kale and collard greens, broccoli, and calcium-fortified items such as fortified orange juices and soy milks.



Iron is another very important mineral for active individuals.   When iron combines with protein to form hemoglobin, they act together as an oxygen carrier in our bodies. Hemoglobin is a major component of red blood cells and a deficiency in iron can cause anemia. The body has to absorb enough iron each day to compensate for the loss of old blood cells and meet the body?s needs to remain healthy.



The body absorbs various forms of iron at different rates. Heme iron comes primarily from animal products, such as meat, fish, poultry and seafood. It is more readily absorbed than the non-heme form of iron, which is mostly found in plant sources such as green leafy vegetables, nuts, whole grain breads, and iron-fortified cereals. Generally, non-heme iron is more difficult for the body to absorb.   This is because the absorption of non-heme iron can be inhibited by other foods, even though it usually takes large amounts of the offending foods to interfere.   Some of the basic foods that will do this are: oxalic acid found in spinach and phosphates found primarily in milk, dairy products and egg whites. Also many sodas and tannins in tea and coffee can interfere with iron absorption.


Caffeine blocks iron absorption when the two are consumed at the same time. When caffeine is consumed one hour before eating, iron absorption is not affected.   So, if you must have tea or coffee, avoid having them with or just after your meals containing non-heme iron sources, such as iron-fortified cereals.   This means waiting about 30 minutes after you finish your bowl of raisin bran before the morning coffee.   However, combining plant sources of iron with foods high in vitamin C will help to increase your absorption of plant iron, so replace that coffee with orange juice or other citrus food and you are ready to roll.


Clearly, the interactions and interrelationships between nutrients are complex and varied. It is nearly impossible to know everything a food item may interfere with for optimal metabolism and absorption of other nutrients.   Just keep in mind that by eating a variety of foods and not overloading on one nutrient, you should be able to keep things in balance.


Kathy Zawadzki is a licensed Sports Nutritionist and cycling coach for
Carmichael Training Systems.   She lives and trains in
Littleton, CO.



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