The role of blood loss and diet in the aetiology of mild iron deficiency in premenopausal adult New Zealand women Anne-Louise M Heath 1 , C Murray Skeaff 1 , Sheila Williams 2 and Rosalind S Gibson 1, * 1 Department of Human Nutrition, University of Otago, PO Box 56, Dunedin, New Zealand: 2 Department of Preventive & Social Medicine, University of Otago, PO Box 56, Dunedin, New Zealand Submitted 2 November 1999: Accepted 17 February 2000 Abstract Objective: To investigate the role of blood loss and diet in the aetiology of mild iron deficiency (MID) in premenopausal New Zealand women. Mild iron deficiency was defined as low, but not necessarily exhausted, iron stores (i.e. serum ferritin ,20 mg/ L) in the absence of anaemia (i.e. haemoglobin $120 g/L). Design: Cross-sectional study of a volunteer sample of premenopausal adult women. Information on habitual dietary intakes (using a specially designed and validated computerised iron food frequency questionnaire), health and demographic status, sources of blood loss (including menstrual blood loss estimated using a validated menstrual recall method), contraceptive use, height and weight, haemoglobin, serum ferritin and C-reactive protein were collected. Setting: Dunedin, New Zealand during 1996/1997. Participants: Three hundred and eighty-four women aged 18±40 years. Results: The characteristics that were associated with an increased risk of MID were: low meat/fish/poultry intake, high menstrual blood loss, recent blood donation, nose bleeds, and low body mass index. The protective factors included shorter duration of menstrual bleeding, and multivitamin±mineral supplement use in the past year. Conclusions: There are a number of potentially modifiable factors that appear to influence risk of MID. Women with low menstrual blood loss may be able to decrease their risk of MID by increasing their meat/fish/poultry intake, while those with a higher menstrual blood loss may be able to decrease their risk by decreasing their menstrual blood loss, perhaps by changing their method of contraception. Women should be encouraged to maintain a healthy body weight, and those who choose to donate blood, or who experience nose bleeds, should have their iron stores monitored. Keywords Iron deficiency Risk factors Diet surveys Women's health Premenopausal women There is a growing interest in the presence of iron deficiency without any clinical or biochemical evidence of anaemia, and the extent to which it may be associated with adverse health consequences. Some reports have suggested that iron deficiency, without anaemia, may result in impaired cognitive function 1 and decreased work performance 2,3 . The early stages of iron deficiency are characterised by a gradual decline in the amount of iron stored in the liver, until eventually stores become completely exhausted. These changes are reflected by a progressive fall in serum ferritin from between 20 and 12 mg/L, to less than 12 mg/L, at which point the stores are considered to be exhausted. In this study of premenopausal women, we have defined mild iron deficiency (MID) as the existence of low but not necessarily exhausted iron stores (i.e. serum ferritin ,20 mg/L), in the absence of anaemia (i.e. haemoglobin $120 g/L). Women of child-bearing age are known to be more vulnerable to mild iron deficiency than post-menopausal women. In a recent national survey in the United Kingdom 4 approximately 40% of women aged 18 to 40 years had a serum ferritin level of less than 25 mg/L compared with only 12% of women aged 50 to 64 years. Anaemia from any cause (defined as haemoglobin ,125 mg/L) was present in 23% of the younger women, suggesting that at least 17% of these women had iron deficiency without anaemia. No comparable national prevalence data exist in New Zealand to date, but it is likely that many premenopausal New Zealand women Public Health Nutrition: 4(2), 197±206 DOI: 10.1079/PHN200054 *Corresponding author: Email rosalind.gibson@stonebow.otago.ac.nz q 2001 Nutrition Society