Iron needs in teenage girls are high once they start menstruating and a good supply of foods rich in iron are needed to replace menstrual losses. This is particularly important for girls who consume a poorly planned vegetarian diet or restrict their food intake to control weight. The 2014 National Diet and Nutrition Survey reported that 46% of 11-18 year-old girls had very low intakes of iron, with low haemoglobin status in 7%, an overt sign of iron deficiency anaemia. Iron needs in teenage girls can be supported by regularly eating foods such as red meat, eggs, pulses, cocoa, green vegetables and fish. The amount of iron available for absorption when the food is eaten is termed bioavailability. See post on how to maximise your iron intake.
The start of menstruation also marks changes in bone growth as more calcium is taken up by bone. Delayed menstruation (after age 16) has a negative impact on bone growth and increases the development of osteoporosis later in life. This is not uncommon in eating disorders and should be taken seriously.
Teenage girls who become pregnant are especially nutritionally vulnerable. They should begin taking a vitamin supplement containing Vitamin D and folic acid as soon as they realise they are pregnant. Iron needs during pregnancy are alleviated by the stopping of periods and by increased absorption of iron through the gut. However if they do not eat well, with a good range of foods and nutrients, then a full vitamin and mineral supplement suitable for pregnancy is advisable.
Teenage girls can be especially nutritionally vulnerable and benefit from dietary assessment and an opportunity to discuss their needs in one to one appointments. I do this in my teenage nutrition clinic.