On Nutrition by Ed Blonz

Acids Help Dissolve Iron For Absorption

DEAR DR. BLONZ: I am 70 years old, in good health and hope to stay that way. I tend to get at least five or six servings of fruits and vegetables each day, and a lot of grains. I also take a multivitamin that contains between 100 percent and 200 percent of the recommended value of everything. Most of the vegetables I eat (cauliflower, broccoli, carrots, celery and lettuce), and a lot of the fruits, are raw. Is that good, bad or indifferent? I take my vitamins with breakfast; is that OK? I am at the top end of the normal bracket for cholesterol, so I am very careful with fats. I haven't been active recently due to an ankle condition that has finally healed, so I am anxious to get moving. -- J.D., Chicago

DEAR J.D.: This all sounds like you are doing your body a solid. Having your vegetables raw is neither good nor bad; having them is what's most important. The way they are prepared is all a matter of taste. It is best to take a supplement with a meal, but the choice of meal is up to you. What you are doing with your diet sounds good to me, and staying as active as possible will also help your cholesterol. Touch base with your doctor before you start up again.

DEAR DR. BLONZ: I read that acid is important for the absorption of iron. What acid in the body absorbs iron? How exactly does the iron work once it is absorbed? -- J.M. Seattle

DEAR J.M.: It is not an acid that is at play with the absorption of iron. The body produces an iron-binding protein that is released in the digestive tract. Its job is to grab on to dietary iron and help it through the absorption process. The amount of the binding protein present tends to reflect the body's need for iron.

The connection with "acid" that you saw probably relates to the fact that iron needs to be in solution (dissolved) before it can be absorbed, and iron is more soluble in an acid solution. From a food standpoint, acid foods might include tomato-based products, foods that contain vinegar (acetic acid), orange and other citrus juices, or vitamin C supplements (ascorbic acid).

There is one exception to the iron/acid pairing, and that is a form of iron found in meat, fish, eggs and other animal products. This type, called "heme iron," is absorbed at a much more efficient rate and doesn't require acid. Other iron sources include enriched cereals and breads, nuts, seeds, legumes, dried fruits, and dark-green leafy vegetables.

Iron, regardless of where it comes from, is used in a number of enzymes, but its main use is as the focal ingredient in heme, which is an oxygen-carrying substance. Perhaps this is why iron that is already incorporated into heme has an easier time being absorbed.

Heme becomes hemoglobin inside the red blood cells, and there it carries oxygen from the lungs to metabolically active cells in our body. The cells use the oxygen, giving off carbon dioxide as a waste product. The hemoglobin then carries the carbon dioxide back to the lungs, where it can be exhaled in exchange for fresh oxygen that is picked up for a return trip to the cells.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.