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Female athletes: avoiding iron deficiency (anaemia)
As we’ve already indicated before at Sports Performance Bulletin, iron problems and female athletes are as closely linked as Westminster Abbey and Big Ben. In Great Britain and the United States, about 30 per cent of adult women and 40 per cent of adolescent women are iron deficient, while around 6 per cent of both groups suffer from true iron-deficiency anaemia. However, studies of athletes report higher frequencies of iron problems; research indicates that up to 19 per cent of swimmers and runners may be troubled by iron-deficiency anaemia, which can have a strongly negative impact on performance.
Basically, iron difficulties can take two forms, either iron deficiency or true anaemia. Iron deficiency itself has two distinct stages. Stage 1, the iron- depletion stage, is characterized by blood-ferritin levels of less than 12 ng/ml, which indicates that iron levels have been significantly reduced. Ferritin, a key protein which latches onto iron, serves as an important mechanism for iron storage within the body. Stage ll of iron deficiency involves iron- deficient erythropoiesis, which basically means that newly created red blood cells contain lower than normal amounts of iron.Stage ll iron deficiency can eventually lead into true iron-deficiency anaemia, with abnormally low levels of blood haemoglobin (haemoglobin is the iron-containing compound found in red blood cells which actually carries oxygen to the tissues) and truncated haematocrit readings (haematocrit is simply the percentage of blood which is made up of red blood cells).
In women, the act of training for a specific sport can increase the risk of iron deficiency. Studies with female hockey players uncovered a steady drop in ferritin levels during each of three consecutive seasons, with a return to normal between seasons, and other research with female high school and college athletes detected unusually high frequencies of iron deficiency. Causes of the iron problems were not exactly clear but were thought to be related to iron-poor diets, losses of iron through menstruation, bleeding in the digestive system, poor iron absorption, and losses in sweat and urine.
Experts contend that a paltry intake of iron is the most significant cause of iron deficiency in female athletes. The basic problem seems to be that many females consume only 2000 daily calories (or less) in hopes of becoming leaner, especially for sports like running and gymnastics which emphasize a sinewy physique. That creates a situation in which iron deficiency is almost assured, because the average British and American diet often contains only five mg per 1000 calories. With the recommended dietary allowance for iron set at 15 mg per day for women, female athletes would need to eat about 3000 not their usual 2000 calories per day to take in enough iron. Many female athletes also prefer a vegetarian diet, which may be low in iron or may contain a form of iron which is difficult for the digestive system to absorb.
For females, the biggest LOSS of iron occurs during menstruation, with about one-half milligram of iron slipping away each day in the menstrual flow (and more if menstruation is heavy). Women who lose more than 60 ml (about two ounces) of menstrual blood per day are particularly susceptible to iron deficiency. Amenorrhoea (the absence of menstruation), which is more common in female athletes than in the population at large, would seem to lower the chances of iron deficiency, but studies indicate that amenorrhoeic women are actually at greater risk, possibly because their total intakes of calories and therefore iron, are often lower than normal.
Strangely enough, a fairly significant amount of iron can be lost in the faeces. The problem is particularly acute for runners, with up to 85 per cent of runners testing positive for blood in their stools following a strenuous run. In fact, women who run more than about five to six miles per day lose twice as much blood in their faeces, compared to sedentary women. Use of aspirin or non-steroidal anti- inflammatory medications can magnify these iron losses.
Something about exercise also seems to impair the absorption of iron across the walls of the small intestine. Iron-deficient runners, for example, may absorb only 16 per cent of dietary iron, compared with 30 per cent for iron-deficient, sedentary people.
Iron problems can have a big impact on performance. Anaemia, by reducing the oxygen carrying capacity of the blood, can eat away at maximal aerobic capacity (V02max), lower endurance, and increase fatigue. However, it’s not yet clear whether iron deficiency (without actual anaemia) can curtail exercise capacity. Several studies with runners have shown that apparently non-anaemic but iron-deficient athletes who take iron supplements do improve their performances and lower lactateproduction during exercise. However, many of these runners may have actually been mildly anaemic (although their haemoglobin levels were still in the normal range, the readings were probably lower than usual for many of the athletes. A female athlete with a usual haemoglobin level of 14 might have experienced a drop to 13, for example, which is still in the normal range for the overall population but below normal for her). If haemoglobin levels don’t actually decline during iron deficiency, many experts contend that the effects on performance will be minimal. The problem, though, is that deficiency, if not corrected will often lead to anaemia.
Ferritin levels of greater than 20 ng/ml represent adequate iron stores, while ferritin in the 12- 20 range indicates that iron stockpiles are minimal. Readings below 12 ng/ml show that iron stores in the bone marrow have become completely depleted (deficiency is present), and that anaemia may be just around the corner.Technically, anaemia is present if haemoglobin levels fall below 12 g/dl or if haematocrit plunges below 36 per cent. However, remember that ‘normal’ readings for these two variables may in fact not be normal. A female athlete with a haematocrit of 37 per cent is in the normal range, for example, but if her usual haematocrit is 42, she would actually be mildly anaemic, and her athletic performances would suffer.
Sometimes, low haemoglobin and haematocrit don’t represent real anaemia. That’s because one of the key physiological adaptations produced by physical training is an expansion of blood volume. For example, a very moderate but regular jogging programme can boost blood plasma by 5 per cent, and the training schedule of a top-level endurance athlete can augment blood plasma by 20 per cent. This upswing in blood volume although beneficial to the endurance athlete, (it increases the amount of blood which can flow to the muscles and skin during exercise; the enhanced skin flow promotes better body cooling) artificially lowers haemoglobin and haematocrit readings, fooling some doctors into thinking that anaemia is present. However, this ‘pseudoanaemia’ is unlike true anaemia because iron levels are normal. In addition, pseudoanaemia does not respond to iron supplementation.
Since iron deficiency is so common, it’s wise for female athletes to have their iron stores checked at least yearly, preferably before the competitive season begins. The treatment to reverse anaemia usually calls for iron supplementation, with a typical dosage of 50 to 100 mg of elemental iron three times a day (150-300 mg total per day). Such an intake should raise haemoglobin by at least 1 g/dl within four to six weeks, but the treatment often continues for six to eight months in order to reestablish normal ferritin concentrations. In the case of iron deficiency, the typical dose is 50 to 100 mg of iron per day, with supplementation continued until ferritin moves above 20 ng/ml.
Because of superior absorption, the ferrous, not the ferric form of iron, appears to be a better supplement. Ferrous sulphate, which is fairly inexpensive, is usually taken in an actual dosage of 325 mg three times a day for the treatment of anaemia. Experts advise iron supplementers to avoid the sustained release or enteric-coated iron tablets, which may decrease absorption. Also, it’s wise to decrease gastrointestinal side effects by increasing the dosage gradually from once daily to three times per day as tolerance increases, and it makes sense to take the supplement along with vitamin C, since the latter enhances iron absorption. Absorption of iron is especially enhanced if the vitamin C-iron combination is taken on an empty stomach (although Gl upsets may also increase).
How can you be sure you’re taking in enough iron? If your regular diet tends to be a bit low in iron, consider ingesting a daily multivitamin which contains at least 15 mg of iron. Also, try to include more iron-rich foods in your diet. Lean meat, poultry, and fish are excellent sources of iron, and the iron found in such meats is more readily absorbed than the iron in supplements or non-meat foods. If you are a vegetarian, some good high-iron comestibles include iron-enriched grains, dried fruits, spinach, tofu, and beans.
As mentioned, you should always take in your high-iron foods along with a rich source of vitamin C. In addition, eschew the practice of wolfing down iron with foods which inhibit its absorption: those foods include tea, wheat bran, and high-calcium products such as milk, antacids, and calcium-phosphate supplements. One final ‘trick’ for getting more iron is to do a lot of your cooking in an iron saucepan. Using an acidic sauce (like tomato sauce) in your iron pan can help to convert your meal into a rich lode of iron.
(‘Helping Active Women Avoid anaemia, ‘ The Physician and Sports Medicine, vol. 23(5), pp. 35-48, 1995)