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

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