Transferrin saturation is a test which helps determine the iron status of an individual using the ratio of serum iron concentration and total iron binding capacity (TIBC) expressed as a percentage.[1]
Transferrin is a glycoprotein produced by the liver. It can bind to iron and acts as an iron carrier in the blood. Transferrin levels increase when iron deficiency is present and decrease when an individual’s iron status improves or if there is malnutrition.[2]
Too much or too little iron can have negative health consequences on the human body. Inherited conditions such as hereditary haemochromatosis cause an inappropriately increased absorption of iron which can lead to iron accumulation within tissues and potential organ damage. A high amount of iron, a high Ferritin and a low transferrin saturation will confirm haemochromatosis. The liver is the organ which is predominantly affected as well as the heart, skin, pituitary gland, joints and pancreas, particularly as transferrin is made in the liver. Symptoms can include hyperpigmentation of the skin, joint pain, arthritis, diabetes, liver cirrhosis and inflammation. Other causes of high iron levels include iron overload which may result from excessive blood transfusions. In early life, iron overload can lead to growth failure and the inability of the thyroid gland to function properly. The central nervous system can also be affected by iron overload and is usually found alongside conditions such as Alzheimer’s Disease and Huntington’s Disease. Iron overload is also associated with a higher risk of developing cancer.[3]
Low levels of circulating iron and a low transferrin saturation, on the other hand, can be indicative of iron deficiency anaemia. Low levels can be caused by:
During the early stages of iron deficiency anaemia, there may be no physical symptoms. However, as the condition progresses/worsens signs may include:
Your iron status can be improved or maintained with diet and adequate exercise.
Good sources of dietary iron include:
Haem iron:
Non-Haem Iron:
Plant-based sources of iron such as dark green leafy vegetables, nuts, seed, pulses and fortified cereals may be absorbed better in the presence of vitamin C.[6] Try eating fortified breakfast cereals alongside a glass of orange juice or swap chips for a jacket potato with a side of green leafy veg – be sure to eat the skin of the potato.
You should also refrain from drinking tea with your meals as this can affect iron absorption. Instead, you should drink it between meals to ensure you absorb iron effectively.[7]
Women who are menstruating or pregnant may need to increase their iron intake. During your period you lose blood which contains vital iron and you should look to replace this through dietary sources or supplements.
Both too much and too little iron can influence energy levels and could affect your ability to exercise. Low iron can also influence how well and quickly your muscles repair themselves after exercise.[8] Iron deficiency anaemia may also be more common in athletic groups and may need iron supplementation.
[1] Worwood, M., May, A, M and Bain, B, J. (2017). 9 – Iron Deficiency Anaemia and Iron Overload. In: Dacie and Lewis Practical Haematology (Twelfth Edition).
[2] Litchford, M, D. (2008). Chapter 8 – Nutritional Issues in the Patient with Diabetes and Foot Ulcers. In: Levin and O’Neals The Diabetic Foot (Seventh Edition).
[3] Papanikolaou, G and Pantopoulos, K. (2004). Iron Metabolism and Toxicity. Toxicology and Applied Pharmacology: 202, pp 199-211
[4] Lopez, A., Cacoub, P., Macdougall, I, C and Peyrin-Biroulet, L. (2015). Iron Deficiency Anaemia. The Lancet
[5] British Dietetic Association. (2017). Food Fact Sheet: Iron. Available at: https://www.bda.uk.com/foodfacts/iron_food_fact_sheet.pdf
[6] Lane, D, J, R and Richardson, D, R. (2014). The Active Role of Vitamin C in Mammalian Iron Metabolism: Much More than Just Enhanced Iron Absorption. Free Radical Biology and Medicine: 75, pp 69-83.
[7] Zijp, I, M., Korver, O and Tijburg, L, B, M. (2000). Effect of Tea and Other Dietary Factors on Iron Absorption. Critical Reviews in Food Science and Nutrition: 40(5), pp 371-398.
[8] Beard, J and Tobin, B. (2000). Iron Status and Exercise. The American Journal of Clinical Nutrition: 72(2), pp 594S-597S.