Anne J. Wanders

Effects of dietary fibre on subjective appetite, energy intake and body weight: a systematic review of randomized controlled trials.

Dietary fibres are believed to reduce subjective appetite, energy intake and body weight. However, different types of dietary fibre may affect these outcomes differently. The aim of this review was to systematically investigate the available literature on the relationship between dietary fibre types, appetite, acute and long‐term energy intake, and body weight. Fibres were grouped according to chemical structure and physicochemical properties (viscosity, solubility and fermentability). Effect rates were calculated as the proportion of all fibre–control comparisons that reduced appetite (n = 58 comparisons), acute energy intake (n = 26), long‐term energy intake (n = 38) or body weight (n = 66). For appetite, acute energy intake, long‐term energy intake and body weight, there were clear differences in effect rates depending on chemical structure. Interestingly, fibres characterized as being more viscous (e.g. pectins, β‐glucans and guar gum) reduced appetite more often than those less viscous fibres (59% vs. 14%), which also applied to acute energy intake (69% vs. 30%). Overall, effects on energy intake and body weight were relatively small, and distinct dose–response relationships were not observed. Short‐ and long‐term effects of dietary fibres appear to differ and multiple mechanisms relating to their different physicochemical properties seem to interplay. This warrants further exploration.

Effect of Animal and Industrial Trans Fatty Acids on HDL and LDL Cholesterol Levels in Humans – A Quantitative Review

Background Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower HDL cholesterol, raise LDL cholesterol, and increase the risk of coronary heart disease. The effects of conjugated linoleic acid and trans fatty acids from ruminant animals are less clear. We reviewed the literature, estimated the effects trans fatty acids from ruminant sources and of conjugated trans linoleic acid (CLA) on blood lipoproteins, and compared these with industrial trans fatty acids. Methodology/Principal Findings We searched Medline and scanned reference lists for intervention trials that reported effects of industrial trans fatty acids, ruminant trans fatty acids or conjugated linoleic acid on LDL and HDL cholesterol in humans. The 39 studies that met our criteria provided results of 29 treatments with industrial trans fatty acids, 6 with ruminant trans fatty acids and 17 with CLA. Control treatments differed between studies; to enable comparison between studies we recalculated for each study what the effect of trans fatty acids on lipoprotein would be if they isocalorically replaced cis mono unsaturated fatty acids. In linear regression analysis the plasma LDL to HDL cholesterol ratio increased by 0.055 (95%CI 0.044–0.066) for each % of dietary energy from industrial trans fatty acids replacing cis monounsaturated fatty acids The increase in the LDL to HDL ratio for each % of energy was 0.038 (95%CI 0.012–0.065) for ruminant trans fatty acids, and 0.043 (95% CI 0.012–0.074) for conjugated linoleic acid (p = 0.99 for difference between CLA and industrial trans fatty acids; p = 0.37 for ruminant versus industrial trans fatty acids). Conclusions/Significance Published data suggest that all fatty acids with a double bond in the trans configuration raise the ratio of plasma LDL to HDL cholesterol.

Trans fatty acids and cardiovascular health: research completed?

This review asks the question if further research on trans fatty acids and cardiovascular health is needed. We therefore review the evidence from human studies on trans fatty acids and cardiovascular health, and provide a quantitative review of effects of trans fatty acid intake on lipoproteins. The results show that the effect of industrially produced trans fatty acids on heart health seen in observational studies is larger than predicted from changes in lipoprotein concentrations. There is debate on the effect of ruminant trans fatty acids and cardiovascular disease. Of special interest is conjugated linoleic acid (CLA), which is produced industrially for sale as supplements. Observational studies do not show higher risks of cardiovascular disease with higher intakes of ruminant trans fatty acids. However, CLA, industrial and ruminant trans fatty acids all raise plasma low-density lipoprotein and the total to high-density lipoprotein ratio. Gram for gram, all trans fatty acids have largely the same effect on blood lipoproteins. In conclusion, the detrimental effects of industrial trans fatty acids on heart health are beyond dispute. The exact size of effect will remain hard to determine. Further research is warranted on the effects of ruminant trans fatty acids and CLA on cardiovascular disease and its risk factors.

Effect of a High Intake of Conjugated Linoleic Acid on Lipoprotein Levels in Healthy Human Subjects

Background Trans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower high-density lipoprotein (HDL) cholesterol, raise low-density lipoprotein (LDL) cholesterol, and increase the risk of coronary heart disease. The effects of trans fatty acids from ruminants are less clear. We investigated the effect on blood lipids of cis-9, trans-11 conjugated linoleic acid (CLA), a trans fatty acid largely restricted to ruminant fats. Methodology/Principal Findings Sixty-one healthy women and men were sequentially fed each of three diets for three weeks, in random order, for a total of nine weeks. Diets were identical except for 7% of energy (approximately 20 g/day), which was provided either by oleic acid, by industrial trans fatty acids, or by a mixture of 80% cis-9, trans-11 and 20% trans-10, cis-12 CLA. After the oleic acid diet, mean (± SD) serum LDL cholesterol was 2.68±0.62 mmol/L compared to 3.00±0.66 mmol/L after industrial trans fatty acids (p<0.001), and 2.92±0.70 mmol/L after CLA (p<0.001). Compared to oleic acid, HDL-cholesterol was 0.05±0.12 mmol/L lower after industrial trans fatty acids (p = 0.001) and 0.06±0.10 mmol/L lower after CLA (p<0.001). The total-to–HDL cholesterol ratio was 11.6% higher after industrial trans fatty acids (p<0.001) and 10.0% higher after CLA (p<0.001) relative to the oleic acid diet. Conclusions/Significance High intakes of an 80∶20 mixture of cis-9, trans-11 and trans-10, cis-12 CLA raise the total to HDL cholesterol ratio in healthy volunteers. The effect of CLA may be somewhat less than that of industrial trans fatty acids. Trial Registration ClinicalTrials.gov NCT00529828

The association between dietary saturated fatty acids and ischemic heart disease depends on the type and source of fatty acid in the European Prospective Investigation into Cancer and Nutrition–Netherlands cohort

BACKGROUND The association between saturated fatty acid (SFA) intake and ischemic heart disease (IHD) risk is debated. OBJECTIVE We sought to investigate whether dietary SFAs were associated with IHD risk and whether associations depended on 1) the substituting macronutrient, 2) the carbon chain length of SFAs, and 3) the SFA food source. DESIGN Baseline (1993-1997) SFA intake was measured with a food-frequency questionnaire among 35,597 participants from the European Prospective Investigation into Cancer and Nutrition-Netherlands cohort. IHD risks were estimated with multivariable Cox regression for the substitution of SFAs with other macronutrients and for higher intakes of total SFAs, individual SFAs, and SFAs from different food sources. RESULTS During 12 y of follow-up, 1807 IHD events occurred. Total SFA intake was associated with a lower IHD risk (HR per 5% of energy: 0.83; 95% CI: 0.74, 0.93). Substituting SFAs with animal protein, cis monounsaturated fatty acids, polyunsaturated fatty acids (PUFAs), or carbohydrates was significantly associated with higher IHD risks (HR per 5% of energy: 1.27-1.37). Slightly lower IHD risks were observed for higher intakes of the sum of butyric (4:0) through capric (10:0) acid (HRSD: 0.93; 95% CI: 0.89, 0.99), myristic acid (14:0) (HRSD: 0.90; 95% CI: 0.83, 0.97), the sum of pentadecylic (15:0) and margaric (17:0) acid (HRSD: 0.91: 95% CI: 0.83, 0.99), and for SFAs from dairy sources, including butter (HRSD: 0.94; 95% CI: 0.90, 0.99), cheese (HRSD: 0.91; 95% CI: 0.86, 0.97), and milk and milk products (HRSD: 0.92; 95% CI: 0.86, 0.97). CONCLUSIONS In this Dutch population, higher SFA intake was not associated with higher IHD risks. The lower IHD risk observed did not depend on the substituting macronutrient but appeared to be driven mainly by the sums of butyric through capric acid, the sum of pentadecylic and margaric acid, myristic acid, and SFAs from dairy sources. Residual confounding by cholesterol-lowering therapy and trans fat or limited variation in SFA and PUFA intake may explain our findings. Analyses need to be repeated in populations with larger differences in SFA intake and different SFA food sources.

A High Intake of trans Fatty Acids Has Little Effect on Markers of Inflammation and Oxidative Stress in Humans

Consumption of industrial trans fatty acids (iTFA) increases LDL cholesterol, decreases HDL cholesterol, and is strongly associated with a higher risk of cardiovascular disease (CVD). However, changes in circulating cholesterol cannot explain the entire effect. Therefore, we studied whether iTFA and conjugated linoleic acid (CLA) affect markers of inflammation and oxidative stress. Sixty-one healthy adults consumed each of 3 diets for 3 wk, in random order. Diets were identical except for 7% of energy provided by oleic acid (control diet), iTFA, or CLA. At the end of the 3 wk, we measured plasma inflammatory markers IL-6, C-reactive protein, tumor necrosis factor receptors I and II (TNF-RI and -RII), monocyte chemotactic protein-1 and E-selectin, and urinary 8-iso-PGF(2α), a marker of lipid peroxidation. Consumption of iTFA caused 4% lower TNF-RI concentrations and 6% higher E-selectin concentrations compared with oleic acid (control) and had no significant effect on other inflammatory markers. CLA did not significantly affect inflammatory markers. The urine concentration of 8-iso-PGF(2α) [geometric mean (95% CI)] was greater after the iTFA [0.54 (0.48, 0.60) nmol/mmol creatinine] and the CLA [1.2 (1.1, 1.3) nmol/mmol creatinine] diet periods than after the control period [0.45 (0.41, 0.50) nmol/mmol creatinine; P < 0.05]. In conclusion, high intakes of iTFA and CLA did not substantially affect plasma concentrations of inflammatory markers, but they increased the urine 8-iso-PGF(2α) concentration. However, it is unlikely this plays a major role in the mechanism by which iTFA increase the risk of CVD. However, more research is needed to fully understand the implications of these findings.

Intake of individual saturated fatty acids and risk of coronary heart disease in US men and women: two prospective longitudinal cohort studies.

Objectives To investigate the association between long term intake of individual saturated fatty acids (SFAs) and the risk of coronary heart disease, in two large cohort studies. Design Prospective, longitudinal cohort study. Setting Health professionals in the United States. Participants 73 147 women in the Nurses’ Health Study (1984-2012) and 42 635 men in the Health Professionals Follow-up Study (1986-2010), who were free of major chronic diseases at baseline. Main outcome measure Incidence of coronary heart disease (n=7035) was self-reported, and related deaths were identified by searching National Death Index or through report of next of kin or postal authority. Cases were confirmed by medical records review. Results Mean intake of SFAs accounted for 9.0-11.3% energy intake over time, and was mainly composed of lauric acid (12:0), myristic acid (14:0), palmitic acid (16:0), and stearic acid (18:0; 8.8-10.7% energy). Intake of 12:0, 14:0, 16:0 and 18:0 were highly correlated, with Spearman correlation coefficients between 0.38 and 0.93 (all P<0.001). Comparing the highest to the lowest groups of individual SFA intakes, hazard ratios of coronary heart disease were 1.07 (95% confidence interval 0.99 to 1.15; Ptrend=0.05) for 12:0, 1.13 (1.05 to 1.22; Ptrend<0.001) for 14:0, 1.18 (1.09 to 1.27; Ptrend<0.001) for 16:0, 1.18 (1.09 to 1.28; Ptrend<0.001) for 18:0, and 1.18 (1.09 to 1.28; Ptrend<0.001) for all four SFAs combined (12:0-18:0), after multivariate adjustment of lifestyle factors and total energy intake. Hazard ratios of coronary heart disease for isocaloric replacement of 1% energy from 12:0-18:0 were 0.92 (95% confidence interval 0.89 to 0.96; P<0.001) for polyunsaturated fat, 0.95 (0.90 to 1.01; P=0.08) for monounsaturated fat, 0.94 (0.91 to 0.97; P<0.001) for whole grain carbohydrates, and 0.93 (0.89 to 0.97; P=0.001) for plant proteins. For individual SFAs, the lowest risk of coronary heart disease was observed when the most abundant SFA, 16:0, was replaced. Hazard ratios of coronary heart disease for replacing 1% energy from 16:0 were 0.88 (95% confidence interval 0.81 to 0.96; P=0.002) for polyunsaturated fat, 0.92 (0.83 to 1.02; P=0.10) for monounsaturated fat, 0.90 (0.83 to 0.97; P=0.01) for whole grain carbohydrates, and 0.89 (0.82 to 0.97; P=0.01) for plant proteins. Conclusions Higher dietary intakes of major SFAs are associated with an increased risk of coronary heart disease. Owing to similar associations and high correlations among individual SFAs, dietary recommendations for the prevention of coronary heart disease should continue to focus on replacing total saturated fat with more healthy sources of energy.

The effects of bulking, viscous and gel-forming dietary fibres on satiation.

The objective was to determine the effects of dietary fibre with bulking, viscous and gel-forming properties on satiation, and to identify the underlying mechanisms. We conducted a randomised crossover study with 121 men and women. Subjects were healthy, non-restrained eaters, aged 18-50 years and with normal BMI (18.5-25 kg/m²). Test products were cookies containing either: no added fibre (control), cellulose (bulking, 5 g/100 g), guar gum (viscous, 1.25 g/100 g and 2.5 g/100 g) or alginate (gel forming, 2.5 g/100 g and 5 g/100 g). Physico-chemical properties of the test products were confirmed in simulated upper gastrointestinal conditions. In a cinema setting, ad libitum intake of the test products was measured concurrently with oral exposure time per cookie by video recording. In a separate study with ten subjects, 4 h gastric emptying rate of a fixed amount of test products was assessed by ¹³C breath tests. Ad libitum energy intake was 22 % lower for the product with 5 g/100 g alginate (3.1 (sd 1.6) MJ) compared to control (4.0 (sd 2.2) MJ, P< 0.001). Intake of the other four products did not differ from control. Oral exposure time for the product with 5 g/100 g alginate (2.3 (sd 1.9) min) was 48 % longer than for control (1.6 (sd 0.9) min, P= 0.01). Gastric emptying of the 5 g/100 g alginate product was faster compared to control (P< 0.05). We concluded that the addition of 5 g/100 g alginate (i.e. gel-forming fibre) to a low-fibre cookie results in earlier satiation. This effect might be due to an increased oral exposure time.

Satiety and energy intake after single and repeated exposure to gel-forming dietary fiber: post-ingestive effects

Background:Viscous or gel-forming dietary fibers can increase satiety by a more firm texture and increased eating time. Effects of viscous or gel-forming fibers on satiety by post-ingestive mechanisms such as gastric emptying, hormonal signals, nutrient absorption or fermentation are unclear. Moreover, it is unclear whether the effects persist after repeated exposure.Objective:To investigate satiety and energy intake after single and repeated exposure to gelled fiber by post-ingestive mechanisms.Design:In a two-arm crossover design, 32 subjects (24 female subjects, 21±2 y, BMI 21.8±1.9 kg m−2) consumed test foods once daily for 15 consecutive days, with 2 weeks of washout. Test foods were isocaloric (0.5 MJ, 200 g) with either 10 g gel-forming pectin or 3 g gelatin and 2 g starch, matched for texture and eating time. Hourly satiety ratings, ad libitum energy intake and body weight were measured on days 1 (single exposure) and 15 (repeated exposure). In addition, hourly breath hydrogen, fasting glucose, insulin, leptin and short-chain fatty acids were measured.Results:Subjects rated hunger, desire to eat and prospective intake about 2% lower (P<0.015) and fullness higher (+1.4%; P=0.041) when they received pectin compared with control. This difference was similar after single and repeated exposure (P>0.64). After receiving pectin, energy intake was lower (−5.6%, P=0.012) and breath hydrogen was elevated (+12.6%, P=0.008) after single exposure, but not after repeated exposure. Fasting glucose concentrations were higher both after single and repeated exposure to pectin (+2.1%, P=0.019). Body weight and concentrations of insulin, leptin and short-chain fatty acids did not change during the study.Conclusions:Gelled pectin can increase satiety and reduce energy intake by post-ingestive mechanisms. Although the effects were small, the effects on satiety were consistent over time, whereas the effects on energy intake reduction were not.

A high intake of conjugated linoleic acid does not affect liver and kidney function tests in healthy human subjects.

Conjugated linoleic acid (CLA) is consumed widely as a supplement. It causes hepatomegaly in animals, but toxicological data in humans are limited. We therefore studied the effect of a high daily intake of CLA on liver and kidney function in healthy subjects. Twenty subjects received 14.6 g cis-9,trans-11 CLA and 4.7 g trans-10,cis-12 CLA isomers a day for 3 weeks. Liver and kidney function was measured at 0, 3, 7, 10, 16, and 21 days. Mean values of all tests remained within normal limits. Lactate dehydrogenase (mean+/-SD) increased from 290.9+/-43.6 to 322.5+/-60.7 U/L (p=0.04) on day 21. One subject exceeded the upper limit of normal of 450 U/L on day 21, to 472 U/L and another showed an isolated elevation to 555 U/L on day 7. Gamma-glutamyltranspeptidase increased from 12.1+/-5.9 to 13.5+/-6.2U/L (p=0.002). No one exceeded the upper limit of 50 U/L for men and 40 U/L for women. A daily intake of 19.3 g CLA for 3 weeks does not produce clinically relevant effects on markers of liver and kidney function in healthy volunteers.