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For more information, visit the group homepage (NutriTrace@NUS) : http://www.fst.nus.edu.sg/research/ResearchGroup/Walczyk/home.html

Research Interests

Human Mineral and Trace Element Metabolism

Mineral and trace element deficiencies remain a major challenge to public health on a global scale. Iron deficiency and anemia, as the most prominent example, still affect one third of the world's population with its adverse effects on work performance, immune function and morbidity and mortality of mother and child around birth. Links between diet and health need to be better understood and translated into effective strategies for improving nutritional status, not only to save healthy life years but also to reduce growing burdens on health care systems.

Fig. 1: Elements in the diet that are needed for normal body function

Focus of my research is the development and application of stable isotope techniques for a better understanding of human element metabolism in health and disease. Radioisotopes have been used as tracers since decades in human studies but radiation hazards increasingly limit their use for research applications. Stable isotopes offer new perspectives as they do not decay and can be used without ethical concerns in humans. However, there full potential has not been exploited yet which I am trying to pioneer in my research:

1) Element absorption and bioavailability: by isotopic labeling of an element in the diet or a chemical compound, its bioavailability can be determined. Such information is needed for

• design and evaluation of food fortification programs or dietary supplements
• evaluation of physiological factors influencing element bioavailability
• identification of nutrient/nutrient and nutrient/non-nutrient interactions for improving nutritional status through dietary advice.

Fig. 2: Factors influencing element bioavailability, i. e. the amount of an element in the diet that can be absorbed and utilized for physiological function

2) Isotopic labeling of the body: Stable isotopes do not decay and can be basically traced over years in the human body. After equilibration with the native element in the body, the fate of the tracer can be used to determine element turnover and element losses for

• evaluation of potential strategies for improving mineral and trace element status

• measurement of actual element requirements in the individual for maintaining nutritional status.

3) Isotope effects in the human body: Isotopic abundances of an element are not constant. They can be altered through element transport provided that element transport is mass-sensitive and non-quantitative. Deciphering the isotopic signatures that each individual bears in his or her body tissues may provide new insights into the mechanisms of element homeostasis and conditions of impairment.

Representative Publications

Denk E, Hillegonds D, Vogel J, Synal A, Geppert C, Wendt K, Fattinger K, Hennessy C, Berglund M, Hurrell RF and Walczyk T (2006). Analytical and Bioanalytical Chemistry, 386, 1587-1602.

Tuntipopipat S, Judprasong K, Zeder C, Wasantwisut W, Winichagoon P, Charoenkiatkul S, Hurrell RF and Walczyk T (2006), Chili, but not turmeric, inhibits iron absorption in young women from an iron-fortified composite meal. Journal of Nutrition 136, 2970-2974.

Walti MK, Walczyk T, Zimmermann MB, Fortunao G, Weber M, Spinas GA and Hurrell RF (2006) Urinary excretion of an intravenous Mg-26 dose as an indicator of marginal magnesium deficiency in adults. European Journal of Clinical Nutrition, 60, 147-154.

Krayenbuehl PA, Walczyk T, Schoenberg R, von Blanckenburg F and Schulthess G (2005), Hereditary hemochromatosis is reflected in the iron isotopic composition of blood. Blood, 105, 3812-3816.

Walczyk T, Tuntipopipat S, Zeder C, Wasantwisut E and Hurrell RF (2005), Iron absorption by human subjects from different iron fortification compounds added to Thai fish sauce. European Journal of Clinical Nutrition, 59, 668-674.

Walczyk T and von Blanckenburg F (2005), Deciphering the iron isotopic message of the body using multicollector-ICP-MS. International Journal of Mass Spectrometry, 242, 117-134.

Bohn T, Walczyk T, Davidsson L, Pritzkow W, Klingbeil P, Vogl J and Hurrell RF (2004) Comparison of magnesium stable isotope techniques to determine magnesium absorption in humans using urinary monitoring, faecal monitoring and erythrocyte analysis. British Journal of Nutrition, 91, 113-120.

Walczyk T, Davidsson L, Rossander-Hulthen, Hallberg L und Hurrell RF (2003), No effect of vitamin A on iron absorption in humans, American Journal of clinical Nutrition, 77, 144-149.

Walczyk T, von Blanckenburg F (2002), Natural iron isotope variations in human blood. Science 29, 2065-2066.

Walczyk T (2001), The potential of inorganic mass spectrometry in mineral and trace element nutrition research. Fresenius Journal of Analytical Chemistry, 370, 444-453.