Journal Name:
Nutritional Biochemistry
Article Title:
Both dietary 18:2 and 16:0 may be required to improve the serum LDL/HDL cholesterol ratio in normocholesterolemic men
Date Written:
1995
Volume:
Number:
6
Page:
179
Author(s):
Sundram, K.; Hayes, K.; Siru, O.
Article:
Diets high in saturated fatty acids (SFA) elevate plasma concentrations of both total and low-density lipoprotein (LDL) cholesterol. Research in both animals and humans indicates that not all SFAs are equivalent in their cholesterol raising ability. In several studies stearic acid (18:0) did not appear to be cholesterolemic, and thus is considered to be neutral in this regard. The term "saturated fat was then considered to encompass three SFAs - 12:0, 14:0, and16:0. However, research has since demonstrated that palmitic acid (16:0) may also be neutral in regards to its effect on serum cholesterol values. The objective of this study was to examine the neutrality of a 16:0-rich diet, compared to a diet rich in oleic acid (18:1), or an American Heart Association (AHA) Step 1 diet in normolipidemic males."
Twenty-three normolipidemic males participated in this double blind crossover study. The study comprised four periods totaling 15 weeks. Participants began the study with a 3-week control period consuming their habitual diet. In period 2, participants consumed their habitual diets in which two-thirds of the energy from fat was replaced by a blend of fat based on the AHA Step 1 diet, in which total fat was restricted to 30% of energy and SFA, MUFA, and PUFA contributed approximately 10% energy each. For periods 3 and 4, the fat substitution was an oleic acid rich diet based on canola oil (CO) and a plamitic acid rich diet based on palm olein (POL) and was consumed in a cross-over design. Each experimental diet period was four weeks in length, providing approximately 31% energy as fat and < 200mg/ cholesterol/day. The percent energy from each dietary fatty acid was strictly controlled to compare low 16:0, high 18:1 (CAN), or high 16:0, low 18:2 (POL) intake with that of a balanced intake of each (AHA). Fasting blood samples were obtained at baseline, and at the end of each dietary period for subsequent analysis of serum lipid values.
Serum total cholesterol (TC) and LDL-C were unaffected by the different dietary fatty acid manipulations, despite significant shifts in % energy derived from PUFAs, MUFAs, and SATs. Serum HDL-C was significantly elevated (17%) in response to the AHA diet compared with either the CO or POL diets, both of which produced identical HDL-c values following the 4-week dietary comparisons. The AHA diet also resulted in a significant (14%) reduction in the LDL:HDL cholesterol ratio compared to the other two diets. Compared to the AHA diet, the CAN diet significantly elevated triglycerides (TG) by 22%. No significant differences were observed between the POL and CO diet for any serum lipid parameter.
These data support previous clinical studies in which the effect of palmitic acid on TC and LDL:HDL ratio was found to be comparable to that of MUFAs in normolipidemic men and women consuming a moderate fat load (<31%) low in myristic acid (14:0) and cholesterol. These researchers also noted that a definite intake of PUFAs and SFAs may be necessary to maximize HDL-C levels under these conditions.
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