The main objective of this study is to elucidate whether different dietary fatty acids (SFA, PUFA, butter fat and margarine fat) in a high fat load will have different effects on PBMC gene expression profiles. Secondary objectives are to elucidate the effects of these fat loads on individual plasma free fatty acid profiles, triglycerides and cholesterol levels.

Nutrition plays a key role in the development of metabolic disorders like cardiovascular disease and the metabolic syndrome. Nutrients that can contribute to the risk of developing such diseases are fatty acids (FAs). It is known that fatty acids mediate their metabolic effects via changes in gene expression, through binding and subsequent activation of the transcription factor peroxisome proliferator-activated receptor (PPAR). In addition, it is known that unsaturated fatty acids are better ligands for PPAR than saturated fatty acids. Peripheral blood mononuclear cells (PBMC) express PPARalpha and are relatively easy to isolate from whole blood. We previously showed that the gene expression profiles of these cells can reflect free fatty acid increases during fasting. The question still remains whether dietary FA can influence gene expression in a similar way and, if so, whether different dietary FA result in different gene expression changes and subsequent activation of other pathways.

Inclusion Criteria:

• Healthy Caucasian men
• age between 18 and 30 years

Exclusion Criteria:

• Allergic to fish oil
• Allergic to margarine
• Allergic to cow milk or dairy products
• Current or recent (<4 weeks) use of fish oil supplements or more then four times fish/week; 24.35 g of EPA-DHA of fish per month (800 mg/day) as judged by the questionnaire.
• Body mass index (BMI) < 18 or > 25 kg/m2
• Urine glucose concentrations outside normal ranges (low to non-detectable)
• Fasting blood glucose outside the normal range (3 - 5.5 mmol/L)
• Tobacco smoking
• Taking medication that may influence the study results
• Received inoculations within 2 months of starting the study or planned to during the study
• Donated or intended to donate blood from 2 months before the study till two months after the study
• Diagnosed with any long-term medical condition (eg., diabetes, hemophilia, cardiovascular disease, anemia, gastrointestinal disease)
• Vegetarian