M. Dhont

Estimation of dietary fat intake of Belgian pregnant women. Comparison of two methods.

Aim: To evaluate the validity and usefulness of a food frequency questionnaire (FFQ) which was designed to evaluate individual fat consumption for a Dutch population relative to 7-day estimated records (7d ER). The FFQ has been validated previously and was adapted to the Belgian situation. Methods: Longitudinal study in 26 healthy pregnant women; FFQ and 7d ER were obtained during the 1st and 3rd trimesters. Results: FFQ was validated with 7d ER. Fat and fatty acid intake estimated by the FFQ did not differ significantly (p < 0.01) from data obtained by the 7d ER except for 18:2n–6. Pearson correlation coefficient between the 2 methods ranged from 0.62 to 0.68. On average, 47% of the women were classified in the same quartile with the 2 methods and less than 2% in the opposite quartile. Total fat intake, calculated from FFQ, was on average 87.9 (SD 18.1) g/day. The mean intake of linoleic acid was 13.3 (SD 5.4) g/day and of α-linolenic acid was 1.4 (SD 0.5) g/day. The dietary intake of the saturated, monounsaturated and polyunsaturated fatty acids was respectively 34.7 (SD 10.0) g/day, 29.6 (SD 8.1) g/day and 15.7 (SD 5.9) g/day. Conclusion: The FFQ gives similar results for fat intake as the 7d ER and is thus considered an appropriate method for classifying individuals to the right part of the distribution of dietary fat intake.

Oxidative stability of low density lipoproteins and vitamin E levels increase in maternal blood during normal pregnancy.

In 24 healthy pregnant women, parameters related to the oxidative stability of low density lipoproteins (LDL) were determined at three times during pregnancy and shortly after delivery. The fatty acid composition of plasma phospholipids (PL) and the plasma concentrations of vitamin E, vitamin A, and β-carotene were assessed in the same samples. Total triglyceride (TG), total cholesterol, LDL-cholesterol, and high density lipoprotein (HDL)-cholesterol concentrations were also determined. The length of the lag phase of isolated LDL challenged with Cu2+ ions significantly increased with the progression of pregnancy. The oxidation rate and the amount of conjugated dienes formed increased and reached a maximum at 29–37 wk of pregnancy. Total TG, cholesterol, and LDL-cholesterol reached a maximum in the third trimester of pregnancy. β-Carotene remained stable, vitamin A decreased, and vitamin E significantly increased throughout pregnancy. Vitamin E plasma concentration correlated positively with the length of the lag phase. The increased levels of vitamin E could contribute to the higher resistance of LDL toward oxidation with progressing gestation, measured by the prolonged lag phase. Furthermore, vitamin E plasma levels correlated positively with TG concentration but not with LDL-cholesterol. The level of polyunsaturated fatty acids in PL decreased with the progression of pregnancy. No correlation was found between the fatty acid composition of plasma PL, nor with the cholesterol concentration, and the parameters studied related to the oxidative stability of LDL. The major finding of this study is the increased oxidative resistance of LDL with progressing gestation.

FA composition of cholesteryl esters and phospholipids in maternal plasma during pregnancy and at delivery and in cord plasma at birth.

The purpose of this study was to assess the FA composition of both cholesteryl esters (CE) and phospholipids (PL) in maternal plasma during pregnancy and at delivery and in umbilical plasma at birth. A longitudinal study of 32 normal pregnant women was carried out with three cutoff points during pregnancy (first, second, and third trimester) and at delivery. Few significant differences occurred in the FA profile of maternal CE: 18∶1n−9 increased, 18∶2n−6 dropped slightly, and 18∶3n−3 decreased with progressing gestation. In maternal PL, long-chain highly unsaturated FA concentrations dropped and were replaced by saturated FA as gestation progressed. Additionally, changes in saturated FA in PL occurred: Shorter-chain 16∶0 was higher whereas longer-chain 18∶0 was lower at delivery compared to early pregnancy. The FA profile of umbilical venous plasma was strikingly different from that of maternal plasma at delivery. Cord plasma CE contained more saturated and monounsaturated FA than maternal CE. The polyunsaturates 18∶2n−6 and 18∶3n−3 are lower in umbilical CE than in maternal CE whereas 20∶4n−6 and 22∶6n−3 are twice as high in umbilical CE. Cord plasma PL have a higher content of long-chain highly unsaturated FA than maternal plasma PL at delivery. In contrast to maternal plasma PL, 16∶0 was lower and longer-chain saturated FA were higher in cord plasma PL. The FA profile of umbilical plasma at birth shows preferential accumulation of 20∶4n−6 and 22∶6n−3, with low concentrations of 18∶2n−6 and 18∶3n−3 in CE and PL, indicating a preferential supply of the fetus with long-chain highly unsaturated FA needed for fetal development.

The composition of saturated fatty acids in plasma phospholipids changes in a way to counteract changes in the mean melting point during pregnancy.

It has been demonstrated that in pathological conditions with an increase in the calculated mean melting point (MMP) of phospholipid (PL) fatty acids (FA) there are changes in the composition of the saturated FA (SFA), which partially counteract this effect: shorter-chain SFA with lower melting points are increased, while longer-chain less fluid SFA are suppressed. The aim of this study was to determine whether there are differences in MMP during pregnancy and in the newborn and, if so, whether similar adaptive changes occur in the composition of the SFA The FA composition of plasma PL was determined in healthy women (n-16) twice during pregnancy (15–24 wk and 29–36 wk) and at delivery and in umbilical venous blood obtained at birth. The MMP of maternal PL was significantly higher at delivery compared to mid-gestation, due to a loss of highly unsaturated FA (HUFA) which were replaced by SFA. In addition, changes in the SFA occurred; 16∶0 with lower melting point was higher while 18∶0 with higher melting point was lower at delivery. MMP of PL FA in umbilical plasma was lower than in maternal plasma at delivery, which was due to higher HUFA content. In contrast to maternal plasma, 16∶0 was lower while 18∶0, 20∶0 and 24∶0 were higher in umbilical plasma resulting in a higher MMP of SFA, tending to raise the overall MMP. It can be concluded that, during pregnancy and in the newborn, the FA composition of SFA changes in a way to counteract changes in MMP induced by reduced and increased HUFA, respectively.

Number of women needed in a prospective trial to prove potential cardiovascular benefit of hormone replacement therapy.

Introduction Hormonal replacement therapy (HRT) may be beneficial for the cardiovascular system if hormones are given shortly after the onset of menopause. So far, no randomized trial has provided conclusive results. Materials and methods Based on Belgian population data, we calculated the number of women that should be included in a prospective double-blinded study to prove a potential cardiovascular benefit of HRT. Sample size calculations were based on the extrapolation of empirical observations made in three large databases from epidemiological studies carried out in Belgium during the past 20 years. Results The 10-year mortality varies with the age at which women are included in the observation. In the normal Belgian female population, the cardiovascular mortality risk is 0.85% and 1.58% for women aged 50–54 and 55–59 years, respectively. To prove that HRT induces a decrease of 10-year mortality of 30% in a normal population of 50–54-year-old women, 34 630 subjects would have to be included; for reductions of 20% and 10%, the numbers would be, respectively, 82 468 and 348 056. To prove a significant decrease in 10-year mortality starting with a normal population with an average age of 55–59 years, the numbers needed for hypothetical reductions of 30%, 20% and 10% would be, respectively, 18 514, 44 072 and 185 936. Conclusion If cardiovascular mortality is the study end-point, it is obvious that such a study will be a gigantic task. Taking cardiovascular morbidity as the end-point, such a study would be feasible.