Nutritional Anemias - Causes and Prevention

Anemia is a common blood disorder in which the body lacks adequate red blood cells to carry oxygen to tissues. The reduced oxygen delivery results in fatigue and weakness, and can severely interfere with exercise capacity and performance. Causes of anemia include inadequate dietary intake, poor absorption of nutrients,  blood disorders, or lack of red blood cell production from the bone marrow. Nutritional anemias are usually detected with blood tests that assess the size and number of red blood cells.
Symptoms of anemia include:

• Weakness
• Shortness of breath 
• Chest pain
• Dizziness
• Irregular heartbeat
• Pounding in the ears
• Headache
• Pale or yellow skin​

        Certain nutrients play an important role in the function and integrity of red blood cells. Iron-deficiency anemia is the most common nutritional anemia and not only decreases athletic performance, but also impairs immune function and results in physiologic dysfunction. Hemoglobin is an iron-rich protein in red blood cells that attaches to oxygen and carries it to body tissues. When iron stores are inadequate, hemoglobin levels become too low to transport sufficient oxygen, resulting in iron-deficiency anemia. Most often, dietary choices explain most of a negative iron balance, but it is also possible that a higher iron turnover rate occurs due to intense exercise. Diagnosis of anemia is confirmed by a blood test indicating a hemoglobin value less than 13.5 gm/dl in men or less than 12.0 g/dl in women. 
        Iron is important at any age, but particularly during stages of rapid growth. The high demands of dance training make dancers susceptible to iron deficiency because iron is lost in sweat. Menstruating females are at additionally elevated risk of developing anemia. The average adolescent should consume 6-8 mg of iron each day and dancers and athletes should aim for 9-12 mg per day to help distribute additional oxygen to working muscles and account for any iron that is lost through sweat. 
        The second and third most common nutritional anemias are related to folate and vitamin B12. Vitamin B12 deficiency anemia is unique in that it causes neurological problems and can take years of inadequate supply before symptoms develop. Inadequate levels of B12 are sometimes caused by poor absorption due to a lack of intrinsic factor (the protein that transports B12 to its absorption site in the gut) or a stomach disease. Folate deficiency manifests quickly and is typically a result of a poor diet or alcohol abuse. Folate needs are approximately 200-400 mcg/day and needs increase to 500-800 mcg/day during pregnancy and breastfeeding. Deficiencies of copper, zinc, and vitamins C, A, and B6 can also contribute to anemias.
        Eating a balanced diet can help you avoid both iron and vitamin-deficiency anemias. There are two kinds of iron found in foods. Iron that is found in animal products (e.g., beef, chicken, eggs)  is called heme iron, and the body can absorb 15-18% of heme iron. In contrast, the body only absorbs approximately 5% of non-heme iron, which is found in plant foods such as grains, dark leafy greens, dried fruits, and nuts. Vitamin B-12  is found in meat and dairy. Citrus, green leafy vegetables and legumes are rich in folic acid. A daily multivitamin can also help fill in any gaps in nutrient intakes from food and help prevent nutritional anemias. Be aware that iron supplements can result in toxic levels of the mineral and should only be used if instructed by a physician.
References:
John Beard, Brian Tobin, Iron status and exercise, The American Journal of Clinical Nutrition, Volume 72, Issue 2, August 2000, Pages 594S–597S, https://doi.org/10.1093/ajcn/72.2.594S

Faramarz Naeim, Chapter 23 - Disorder of Red Blood Cells: Anemias, Editor(s): Faramarz Naeim, P. Nagesh Rao, Wayne W. Grody, Hematopathology, Academic Press, 2008, Pages 529-565, ISBN 9780123706072, https://doi.org/10.1016/B978-0-12-370607-2.00023-5.