So far in our series about vitamins and minerals we have discussed vitamin C, thiamin, calcium, and vitamin D. This month I am going to talk about iron, one of the most important minerals for athletes. Endurance athletes and women are particularly at risk for low iron status or iron deficiency anemia (1-6). Anemia is a condition where your body doesn’t have enough red blood cells. This com-promises the ability to provide oxygen to the tissues thereby reducing sports perfor-mance. It is well documented that anemia reduces athletic performance and that cor-recting the anemia improves performance. Anemia can be caused by a wide variety of things, including deficiency of iron, folate, or B12. Another cause of anemia in athletes is hemolysis (4). This is the destruction of red blood cells by physical stress. “Sports anemia” refers to anemia in athletes undergoing severe training. It occurs in endurance athletes such as marathon runners. It seems to be caused by a combination of iron deficiency and hemolysis .
Iron deficiency is the most common nutritional deficiency in the world. It is estimated that about 500 million people worldwide are iron deficient (4). The main biological function of iron is to bind oxygen. Most of the body’s iron stores (70%) are contained in hemoglo-bin. Hemoglobin is an iron-containing protein in red blood cells. When the blood circulates through the lungs it binds oxy-gen, then the hemoglobin lets go of the oxygen when it circulates through the tissues. If iron intake is inadequate the first thing that happens is iron is released from ferritin, a protein that stores iron. If iron intake remains inadequate eventually body iron stores become depleted. Then the new red blood cells which are matur-ing in the bone marrow can’t make as much hemoglobin as they need, resulting in microcytic (small cells), hypochromic (pale cells) anemia. This impairs oxygen delivery to tissues thus limiting aerobic metabolism and work performance. Good dietary sources of iron include red meat and liver (2).
Vegetables gener-ally are not very good sources of iron. Although spinach contains a fair amount of iron it is not very bioavailable (not very well absorbed by the body). It is useful to consider dietary iron in two ways. It can be classified as “heme iron” or “nonheme iron.” Heme iron is iron that is already incorporated into hemoglobin. This improves its absorption dramatically. Obviously heme iron will only be found in meats or liver. The fact that red meat is a good source of iron is no doubt one of the reasons for its reputation for making you stronger. Non-heme iron is found in plants and most iron supplements . Our Liver-Amino Formula™ contains liver extract and is an outstanding source of heme iron. It should be considered a core supplement for endurance athletes (particularly women), for anyone with a known anemia, and anyone who doesn’t eat red meat. If you seem low on energy it might be worth a try. Iron deficiency is surprisingly common in athletes . Iron has several other important func-tions besides its role in hemoglobin. No-tably it is also found in myoglobin, a protein similar to hemoglobin that is found in muscle. It’s function is to help transport oxygen inside muscle cells.
In addition to decreased work performance, iron deficiency is also associated with impairments in cognitive performance, thermoregulation (maintaining body tem-perature), thyroid hormone regulation, glucose metabolism, nervous system function, immune function, and growth (4). Iron deficiency seems to inhibit normal growth in children. One study demon-strated that 56% of iron deficient children were below the tenth percentile of weight for their age (4). It seems iron status plays some role in modulating growth rates in children. While it is clear iron deficiency negatively impacts sports performance, it is not known if iron deficiency hinders muscle growth in adults, but it seems pos-sible. A group of iron deficient children were treated with either just vitamin C or vitamin C plus iron. The group receiving iron had more of an increase in height and weight than the group receiving only vi-tamin C. Interestingly, this effect seemed not mediated through increased food in-take, suggesting some direct effect of iron in regulating growth (4). In addition to its central role in oxygen transport iron is also important to many basic processes of energy metabolism.
Iron deficient animals are characterized by increased metabolic rate and increased glucose oxidation (4). They rely more heavily on glucose as fuel, meaning they burn less fat. Overall, iron deficiency re-sults in reduced growth, increased meta-bolic rate, lower feed efficiency, and increased reliance on glucose as fuel (4). Iron status also affects thyroid hormone. Iron deficient human beings are func-tionally hypothyroid . When cold stressed these individuals fail to adequately ther-moregulate and core temperature drops . Studies in iron deficient rats show they have half as much active thyroid hormone as control rats. Normal thyroid hormone function is required for growth hormone function. This might be one reason low iron status negatively affects growth. You may be wondering why iron deficiency results in increased metabolic rate. This is mediated by an increase in sympathetic nervous system activity and is thought to represent a compensatory step in response to impaired thermoregulation secondary to low thyroid status. Not only does iron status affect exer-cise performance, but exercise affects iron status too.
There is quite a lot of evidence showing that intense exercise causes iron loss and decreased hemoglo-bin. This seems to affect mainly distance runners. The mechanism behind it is not fully understood. Some people have sug-gested increased iron loss through sweat-ing, increased gastrointestinal blood loss, or red blood cell rupture from footstrike (trauma). For whatever reason, it would appear intense, prolonged exercise has a negative impact on iron status (4,5). Most iron supplements you see at the store are ferrous sulfate – a form of nonheme iron. Parrillo Performance Liv-er-Amino Formula™ contains heme iron which is much more efficiently absorbed. I usually recommend 10 to 15 tablets a day or up to 40 tablets for serious athletes. It doesn’t matter if you take them all at once or in divided portions. This should be a core supplement for any endurance runner. Other people who might benefit from it include any menstruating female and anyone who has anemia. Symptoms of anemia include fatigue and weakness and a decrease in performance. Also, if you have anemia, I would suggest eating red meat or liver once or twice a week. If you have true anemia you should also take a multiple vitamin supplement. Be-sides iron, you also need folate and B12 and protein to make red blood cells.
So I would suggest two servings a day of Hi-Protein Powder™ or Optimized Whey Powder™. Of course, if you’re treating anemia the most important product is the Liver-Amino Fromula .™ That in itself is a good source of heme iron, protein, and B vitamins. Take your Vitamin C at the same time you take your iron, since Vitamin C improves iron absorption (2). If after a month or two you still are fa-tigued you might want to see your doctor to establish if there is another reason for the problem. The recommended daily allowance of iron is 15 mg per day (2). Only about 10% of nonheme iron is absorbed, so this would provide about 1.5 mg of non-heme iron. (In comparison about 20% of heme iron is absorbed.) This is thought to be enough for most of the population ex-cept for women with exceptionally high menstrual blood losses. Also, female en-durance athletes are likely to need more. Daily iron losses average about one mg per day in men and 1 .4 mg per day in women. Pregnant women are generally encouraged to take extra iron, about twice the normal daily amount. The RDA for children is 10 mg . These guidelines are developed for people who normally eat 30 to 90 grams of meat, poultry, or fish Vitamins and Minerals, Part IIIper day. Vegetarians may need a higher intake because of the decreased avail-ability of iron from those sources. Also, adequate vitamin C intake is important.
1 . Macroelements, Water, and Electro-lytes in Sports Nutrition. Judy Driskell and Ira Wolinsky, CRC Press, 1999.
2. Recommended Dietary Allowances, 10th edition. National Research Coun-cil. National Academy Press, 1989.
3. Sports Nutrition: Vitamins and Trace Elements. Ira Wolinsky and Judy Driskell. CRC Press, 1997.
4. Sports Nutrition: Minerals and Elec-trolytes. Constance Kies and Judy Driskell. CRC Press, 1995.
5. Nutrients as Ergogenic Aids in Sports and Exercise. Luke Bucci. CRC Press, 1993 .
6. Nutrition In Exercise and Sport. I. Wolinsky and J.F. Hickson. CRC Press, 1994 .