Women involved in regular exercise have some special nutritional needs.
Although the basic principles of sports nutrition are similar for men and women, females involved in regular sporting activity do have increased needs for certain nutrients, and may be more at risk of dietary deficiencies. The key nutritional issues for sportswomen include calcium, iron, weight control and eating disorders. CALCIUM INTAKE Calcium is a mineral that plays an essential role in growth, the development and maintenance of strong bones, muscle contraction and transmission of nerve impulses. Having adequate calcium during childhood and adolescence is important for developing an optimal peak bone mass by the mid 20's to early 30's. This then helps reduce the risk of osteoporosis or thinning of the bones. Some sportswomen are at risk of inadequate calcium intake and some also appear to be at risk of early osteoporosis due to an absent or irregular menstrual cycle. Recommended dietary intakes of calcium: - Girls (12 - 15 years): 1000 mg/day. - Girls (16 - 18 years): 800 mg/day. - Menstruating women: 800 mg/day. - Post Menopausal women: 1000 mg/day. - Pregnant/breastfeeding women: 1200 mg/day. - Sportswomen with absent/irregular menstrual cycle: 1000 to 1500 mg/day.
The best dietary sources of calcium are dairy foods, particularly the low fat alternatives. One cup of low fat `fortified' milk or one tub of low fat yoghurt provides between 350 to 400 mg calcium. One x 30g slice of reduced fat cheese has approximately 300 mg calcium, and one scoop (50 g) of low fat ice cream provides 70 mg calcium. Other good sources include soy products e.g., one cup of low fat, calcium enriched soy drink has 300 mg calcium, 100 g tofu provides 160 mg calcium, and 100 g of canned salmon with bones provides 300mg calcium. IRON INTAKE The mineral, iron, forms part of haemoglobin, which transports oxygen in the blood and is also an essential nutrient for energy production and immunity. Athletes appear to be at greater risk of iron deficiency, with female athletes who are regularly menstruating being at particular risk. Strenuous exercise may increase iron losses through the destruction of red blood cells and losses in sweat, as well as inadequate iron intake. Iron deficiency and subsequent iron deficiency anaemia are associated with reduced athletic performance, fatigue, dizziness, shortness of breath and increased susceptibility to colds and infections. A blood test which measures blood iron levels and body iron stores (ferritin) is required to diagnose iron deficiency. If body iron levels are depleted, an iron supplement in conjunction with increased dietary iron may be recommended. Recommended dietary intakes of iron: - Children (1 - 11 years): 6 to 8 mg/day. - Males (12 - 18 years): 10 to 13 mg/day. - Males 19 years and over: 7 mg/day. - Females (12 - 50 years): 12 to 16 mg/day. - Females 51 years and over: 5 to 7 mg/day. - Pregnancy: 22 - 36 mg/day. - Breastfeeding: 12 - 16 mg/day.
Iron is found in the diet in two main forms; haem iron and non haem iron. Haem iron is found in lean red meat, offal, poultry and seafood and is well absorbed by the body. Non haem iron is found in plant foods such as breakfast cereals, dried fruit, legumes (beans, peas, lentils, etc), green, leafy vegetables, bread and grains. This form is not well absorbed by the body, although its availability can be enhanced by consuming vitamin C-rich foods at the same meal. Tannins (found in tea), caffeine and phytates (found in wheat bran) on the other hand, can reduce iron absorption. The following foods provide approximately 2 mg iron; 50 g lean beef, 200 g lean chicken, 20 g liver, 2 florets broccoli, half cup spinach and between half to 1 cup breakfast cereal. WEIGHT CONTROL AND EATING DISORDERS Keeping body fat levels low is the aim of many female athletes and in some sports, leanness is particularly prized. Excess body fat can be detrimental to performance, however low energy intakes and extreme dieting behaviour will not achieve optimal performance. It is important that an active female who is concerned about her weight has formal body composition assessments and sets realistic body fat and eating goals with her sports dietitian. The risk of eating disorders, such as bulimia and anorexia appears to be increased in sports where a low bodyweight/fat is highly prized, such as gymnastics, dancing and diving and it is important to recognize the early signs and seek professional help as soon as possible. (See the Eating Disorders and Female Athlete Triad topics for further information.)
Ask your Pharmacist for advice. 1) An active woman with inadequate dietary intakes of calcium and iron may require nutritional supplements in addition to advice on improving dietary intakes. 2) Pregnant and lactating sportswomen are at particular risk of dietary inadequacies. 3) A sportswoman with a very low energy intake may require a low dose vitamin and mineral supplement to meet nutritional needs. Ask your Pharmacist for advice. 4) If a woman is displaying signs of an eating disorder, it is important to encourage her to seek professional help. 5) A sports dietitian or exercise physiologist can perform a combination of weight, skin fold and girth measurements which are recommended for assessing body fat levels.
NOTESAll information has been compiled by Lorna Garden, leading Sports Dietitian. For further information contact your state branch of Sports Medicine Australia for your local Women in Sport representative. For individual dietary advice, contact Sports Dietitians Australia on 03 9682 2442 for your nearest Sports Dietitian.