12.3. Dietary carotenoids may decrease the risk of cancer

 Public examination of a doctoral dissertation in the field of clinical chemistry

Doctoral candidate: MSc Jouni Karppi

Time and venue: 12.3.2011 at 12 noon, Kuopio University Hospital, Auditorium 2

Carotenoids are colourful compounds, present in fruits and vegetables, synthesised by plants and micro-organisms. About 10% of these are important dietary precursors of vitamin A. Carotenoids act as antioxidants and possibly decrease in-vivo lipid oxidation. Lipid oxidation is known to be a risk factor for atherosclerosis. Carotenoids are thought to be responsible for the beneficial properties of fruits and vegetables in preventing human diseases, including cardiovascular diseases and cancer. In recent years, the antioxidant properties of carotenoids have become a major focus of research. The aim of this thesis was to develop a high performance liquid chromatographic (HPLC) method for determination of carotenoids from blood plasma and to study the role of carotenoids in lipid oxidation and cancer.

We developed and validated an HPLC method for analysis of carotenoids (lutein, zeaxanthin, β-cryptoxanthin, lycopene, α-carotene and β-carotene) that appears to be simple, quick and repeatable. Serum concentrations of carotenoids, except for lycopene, tended to increase in men and women as they became older, indicating an increase in the consumption of fruits and vegetables from the late 1980s to the beginning of the 2000s. The decrease in lycopene concentrations found in both sexes during follow-up years suggests that elderly people may not consume as many tomatoes and tomato products as do young people.

We investigated the effects of astaxanthin supplementation (8 mg/d) on lipid oxidation in healthy men and its safety as a supplement. When supplemented as capsules, astaxanthin was efficiently absorbed from the intestine into the blood circulation and was well tolerated. An almost significant decrease was found in 15-hydroxy fatty acid concentration after astaxanthin supplementation for three months. The serum low density lipoprotein (LDL) content of conjugated dienes is an in vivo lipid oxidation marker. We observed that in addition to gender, lycopene, lutein and β-carotene were the most powerful determinants for serum LDL conjugated dienes in Eastern Finnish men and women. A diet rich in vegetables and carotenoids can decrease in vivo LDL oxidation and thus slow down atherogenesis. We also studied the association between the serum concentration of lycopene and the risk of cancer. Men with serum lycopene concentrations higher than 0.19 µmol/l had a 45% lower risk for total cancer than did men with lycopene under 0.08 μmol/l. However, lycopene was not associated with prostate cancer in this population.

In conclusion, serum/plasma carotenoids may decrease lipid oxidation in vivo. In addition, high serum concentrations of lycopene may decrease the risk of cancer in middle-aged Finnish men.

The doctoral dissertation of Master of Science Jouni Karppi, entitled Measurement of carotenoids and their role in lipid oxidation and cancer will be examinedat the Faculty of Health Sciences. The opponent in the public examination will be Docent Georg Alfthan of the National Institute for Health and Welfare, and the custos will be Docent Kristiina Nyyssönen of the University of Eastern Finland.

Photo available for download at http://www.uef.fi/uef/vaitoskuvat

Contact: Jouni Karppi, tel. 050-5847631, jouni.karppi@uef.fi

Publishing year: 2011

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