In a questionnaire distributed to 5000 women volunteers as part of the SU.VI.MAX study - a long-term study of the effects of nutritional supplements and vitamins on a variety of medical conditions - more than half of the respondents declared they were concerned by hair loss, and more than 10 per cent described their hair loss as severe.
From a testing population of 3,759 non-menopausal women it was found that 48 per cent suffered from iron deficiency or iron depletion.
In order to verify their results, researcher cross-referenced data concerning hair loss and iron reserves. They were able to show that non-menopausal women in the category "severe hair loss" had significantly lower iron reserves than women who did not suffer from excessive hair loss.
The amount of ferritin in the blood indicates how much iron the body has in reserve. A level of ferritin above 40µg/l is considered normal. A level of ferritin between 15µg/l and 40µg/l is described as iron deficient and a level below 15µg/l is described as iron depletion.
The researchers were able to estimate the risk of severe hair loss caused by variations in the levels of ferritin. For example, a woman with a ferritin level of 70µg/l (the average level) whose ferritin level falls to 40µg/l has a 28 per cent greater risk of severe hair loss.
Lack of iron has long been suspected of contributing to hair loss, but previous experiments did not lead to definite answers because of the insufficient number of subjects studied. The large testing population involved in the SU.VI.MAX study allowed researchers to provide conclusive evidence that iron deficiency and iron depletion are factors in hair loss.
The scientists point out however that certain types of hair loss may result from a number of causes - hormonal imbalance, medical side effects, nutritional imbalance, psychological factors - and that losing one hundred strands of hair per day is normal.