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In Reply: We agree with Dr Wiklund and colleagues that it would be ideal to take into account local variations of magnesium concentration in drinking water in the calculation of magnesium intake. Unfortunately, in the Swedish Mammography Cohort we did not have information collected on water consumption. To accurately calculate magnesium intake from drinking water, we would also need to know not only area of residence of the participants but also how much water is consumed away from home and from other sources.

Because we did not take water consumption as a source of magnesium into account, our study underestimated the total magnesium intake for each participant in different degrees. If we assume that water consumption is 1 to 1.5 L/d, this underestimation would correspond to approximately 1 to 30 mg/d of magnesium according to values presented by Wiklund et al. This exposure measurement error in magnesium intake could . . . [Full Text of this Article]

Susanna C. Larsson, MSc
susanna.larsson@imm.ki.se

Alicja Wolk, DMSc
Division of Nutritional Epidemiology
The National Institute of Environmental Medicine
Karolinska Institutet
Stockholm, Sweden

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