Effect of monounsaturated fat in the diet on the serum carotenoid levels

Epidemiological data suggest that populations with higher serum/ tissue levels of carotenoids have a lower risk of coronary heart disease (CHD), possibly due to the antioxidant capacity. Lycopene, a carotenoid mainly found in tomatoes, has been suggested to have the greatest antioxidant capacity of the carotenoids found in fruits and vegetables. Carotenoids are fat-soluble compounds and their absorption from the diet into the body may depend on the amount of dietary fat ingested. For years there has been debate about what energy source should replace the saturated fat in the diet, to give the optimum serum lipid profile to reduce CHD risk. Studies have compared monounsaturated fat rich diets with high carbohydrate, low fat diets and have found that both diets decrease serum cholesterol and low-density lipoprotein (LDL) cholesterol levels. Results for high-density lipoprotein (HDL) cholesterol and triglycerides have been inconsistent. However, it is of interest to study the effects of different diets on lipid oxidation, as this may also influence CHD risk. Studies have investigated the effect of different amounts of total fat on the serum levels of carotenoids especially beta-carotene and lutein, but to our knowledge no study has looked at the effect of different amounts of fats on the serum lycopene levels, and whether this could subsequently affect the oxidation of LDL in vitro. XIV Two separate randomised crossover dietary intervention studies were conducted; one in healthy men and the other in healthy women aged 20 to 70 years. The aim was to compare the effects of monounsaturated fat rich (MUFA) diet (38% of energy from fat) and high carbohydrate low fat (HCLF) diet (15% energy from fat) with controlled lycopene content, on serum lycopene levels. Main sources of lycopene in the diets were canned tomatoes and tomato soup for the study in women (lycopene content -15.9 mg/day) and tomato paste and tomato soup for the study in men (lycopene content - 20.2 mg/day). Serum lipids and lipoproteins levels and in vitro oxidation of LDL particles were also measured. Compared to the baseline levels there was a significant increase in the serum trans lycopene and total lycopene levels after MUFA diet for the study in women. Comparing the levels at the end of the two diets no difference was observed. In the study in men serum trans, cis and total lycopene levels increased after the MUFA and HCLF diet periods. There was no significant difference in trans; cis and total lycopene levels at the end of two diets. Thus, high levels of monounsaturated fat in the diet do not appear to increase lycopene absorption and serum levels compared to very low fat diet. There was however a better serum lipid profile after MUFA diet compared to HCLF diet. Lag phase for the in vitro oxidation of LDL particles was also longer on the MUFA diet. The lack of difference in antioxidant levels would indicate that this was due to the different fatty acid component of the diet.