Martijn B. Katan

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 (pu200a=u200a0.99 for difference between CLA and industrial trans fatty acids; pu200a=u200a0.37 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.

Effect of fish oil on ventricular tachyarrhythmia in three studies in patients with implantable cardioverter defibrillators

AIMSnTo determine the effects of omega-3 polyunsaturated fatty acids (omega-3 PUFAs) from fish on the incidence of recurrent ventricular arrhythmia in implantable cardioverter defibrillator (ICD) patients by combining results from published trials.nnnMETHODS AND RESULTSnWe searched in the Medline, EMBASE, and Cochrane databases and performed a meta-analysis on all three available trials on fish oil and ventricular arrhythmia. Furthermore, we pooled individual data of two of these randomized, double-blind, placebo-controlled trials (Raitt et al. Fish oil supplementation and risk of ventricular tachycardia and ventricular fibrillation in patients with implantable defibrillators: a randomized controlled trial. JAMA 2005;293:2884-2891 and Brouwer et al. Effect of fish oil on ventricular tachyarrhythmia and death in patients with implantable cardioverter defibrillators: the Study on Omega-3 Fatty Acids and Ventricular Arrhythmia (SOFA) randomized trial. JAMA 2006;295:2613-2619). The main outcome was time to first confirmed ventricular fibrillation (VF) or ventricular tachycardia (VT) combined with death for the meta-analysis, and time to first spontaneous confirmed VF or VT for the pooled analysis. The meta-analysis (n = 1148) showed no convincing protective effect of fish oil (RR 0.90; 95% CI 0.67-1.22). The hazard ratio for the subgroup of patients with coronary artery disease at baseline (0.79; 0.60-1.06) tended towards a protective effect. The pooled analysis (n = 722) showed that time to appropriate ICD intervention was similar for fish oil and placebo treatment (log-rank P = 0.79).nnnCONCLUSIONnThese findings do not support a protective effect of omega-3 PUFAs from fish oil on cardiac arrhythmia in all patients with an ICD. Current data neither prove nor disprove a beneficial or a detrimental effect for subgroups of patients with specific underlying pathologies.

Dietary fructo-oligosaccharides and inulin decrease resistance of rats to salmonella: protective role of calcium

Background: We have shown recently that rapid fermentable fructo-oligosaccharides (FOS) decreased resistance of rats towards salmonella. It is not known whether inulin (which is fermented more gradually) has similar effects or whether buffering nutrients can counteract the adverse effects of rapid fermentation. Aims: To compare the effects of dietary inulin and FOS on resistance of rats to Salmonella enterica serovar Enteritidis and to determine whether calcium phosphate counteracts the effects of fermentation. Methods: Male Wistar rats (nu200a=u200a8 per group) were fed a human “Western style diet”. Diets with 60 g/kg cellulose (control), FOS, or inulin had either a low (30 mmol/kg) or high (100 mmol/kg) calcium concentration. After an adaptation period of two weeks, animals were orally infected with 2×109 colony forming units of Salmonella enterica serovar Enteritidis. Colonisation of salmonella was determined by quantification of salmonella in caecal contents. Translocation of salmonella was quantified by analysis of urinary nitric oxide metabolites in time. Results: Inulin and FOS decreased intestinal pH and increased faecal lactobacilli and enterobacteria. Moreover, both prebiotics increased the cytotoxicity of faecal water and faecal mucin excretion. Both prebiotics increased colonisation of salmonella in caecal contents and enhanced translocation of salmonella. Dietary calcium phosphate counteracted most of the adverse effects of inulin and FOS. Conclusions: Both inulin and FOS impair resistance to intestinal infections in rats. This impairment is partially prevented by dietary calcium phosphate. The results of the present study await verification in other controlled animal and human studies.

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 (pu200a=u200a0.001) 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

Effect of low doses of n-3 fatty acids on cardiovascular diseases in 4,837 post-myocardial infarction patients: Design and baseline characteristics of the Alpha Omega Trial

BACKGROUNDnWeekly fish consumption has been related to a lower risk of fatal coronary heart disease (CHD) and incident stroke in populations with a low fish intake. This relation has mainly been attributed to n-3 fatty acids in fish, that is, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It is at present unclear whether alpha-linolenic acid (ALA), a n-3 fatty acid from vegetable origin, could also be protective against cardiovascular diseases (CVDs). There is a need for food-based trials to establish the efficacy of low doses of n-3 fatty acids in CVD prevention.nnnOBJECTIVESnThe aim of the study was to evaluate the effect of an additional daily intake of 400 mg of EPA + DHA and 2 g of ALA on CVD morbidity and mortality in free-living subjects with a history of myocardial infarction.nnnDESIGNnThe multicenter Alpha Omega Trial is a randomized, double-blind, placebo-controlled trial with a 2 x 2 factorial design. Between May 2002 and December 2006, we enrolled a total of 4,837 men and women aged 60 through 80 who experienced a myocardial infarction within 10 years before entering the study. Subjects were randomized to 1 of 4 margarine spreads that were enriched with EPA + DHA and/or ALA, or placebo. Compliance was monitored via tub counts and assessment of n-3 fatty acids in plasma. Subjects were observed for 40 months for the occurrence of fatal and nonfatal CVD.nnnRESULTSnThe cohort was on average 69 years old at the start of the study and comprised 22% women. Subjects had their (last) myocardial infarction approximately 4 years before enrollment. Mean body mass index was 27.7 kg/m(2), and 17% smoked. Average serum total and high-density lipoprotein cholesterol were 4.7 and 1.3 mmol/L, respectively, and 85% used statins. Mean blood pressure was 142/80 mm Hg, and most subjects were on antihypertensive medication (88%). Diabetes mellitus was reported by 17% of the subjects, and 7% reported a history of stroke. The overall mortality rate during the trial period was 23 per 1,000 person-years, with approximately 40% due to CVD.nnnCURRENT STATUSnFollow-up of the patients was completed in November 2009, and findings will be reported in the second part of 2010.

Nitrate in foods: harmful or healthy?

Nitrate and nitrite are considered hazardous, and there are legal limits to their concentration in food and drinking water. Nitrate from fertilizer accumulates in vegetables and fruit, and largescale livestock production yields huge amounts of manure rich in nitrate that seeps into groundwater. Therefore, keeping nitrate concentrations below legal limits is a struggle for farmers. In this issue of the Journal, Hord et al (1) challenge these limits. Other authors have already pointed out that the evidence for adverse effects of nitrate is inconsistent and that nitrate may actually be beneficial (2, 3). Hord et al (1) go one step further: they claim that nitrate and nitrite should be considered as nutrients. Many food components are beneficial at low and harmful at high intakes. Hord et al (1) claim that nitrate is beneficial at intakes now considered toxic. What do we know about the health effects of nitrate and nitrite? The World Health Organization (WHO) first set an upper limit for nitrate in food in 1962 (4). It was based on a brief report from the US Food and Drug Administration (5), which stated the following: ‘‘sodium nitrate has been fed to rats at levels up to 10% in the diet for their lifetime. Other than some depression on growth at levels above 1% of nitrate, no adverse effects were noted in these animals. Two dogs were fed 2% sodium nitrate in their diet for a period of 105 and 125 days, respectively. No adverse effects were noted’’ (p 136). The WHO calculated from this that daily intakes of 500 mg of sodium nitrate/kg body weight were harmless to rats and dogs. This figure was divided by 100 to yield an Acceptable Daily Intake for humans of 5 mg sodium nitrate or 3.7 mg nitrate per kg body weight, which equals 222 mg for a 60-kg adult. That figure has stood ever since. In the United States, concerns have focused on nitrate and methemoglobinemia in infants. Bacteria in the mouth and gut convert nitrate into nitrite, and nitrite reacts with hemoglobin to produce methemoglobin, which is no longer able to carry oxygen. In the early 1950s, methemoglobinemia and cyanosis were seen in infants fed formula made with contaminated well water. The effect was ascribed to the high nitrate content of these wells (3). The US Environmental Protection Agency (EPA) therefore set a Maximum Contaminant Level for nitrate of 44 mg/L (equal to 10 mg nitrate-nitrogen/L or 10 ppm) (6). The nitrate in the offending wells came from fecal contamination. It is now thought that methemoglobinemia was not caused by nitrate but by fecal bacteria that infected the infants and produced nitric oxide in their gut. Nitric oxide can convert hemoglobin to methemoglobin. The key role of intestinal infection rather than nitrate was confirmed by an experiment in 1948, in which infants who were fed 100 mg nitrate kg d did not develop methemoglobinemia. When they were fed bacteria from contaminated wells, however, methemoglobinemia did develop (3). This suggests that the nitrate concentrations commonly encountered in foods and water are unlikely to cause methemoglobinemia. The other concern about nitrate is cancer. Nitrate and nitrite themselves are not carcinogenic, but nitrite formed from dietary nitrate might react withdietary amines to formcarcinogenic nitrosamines. Such effects have been shown in animal experiments, but their relevance to humans is uncertain because of the high doses and the specific amines used in these animals. In observational studies, intake of nitrate or nitrite from diet or drinking water is not associated with cancer in humans (3, 4). An effect of exogenous nitrite on cancer also seems less likely because large amounts of nitrite are formed endogenously. Fasting saliva contains ’2 mg/L, and after consumption of an amount of nitrate equivalent to 200 g of spinach, the nitrite concentration in saliva may rise as high as 72 mg/L (7). That is much higher than the EPA standard for drinking water of 4.4 mg nitrite/L or the WHO Acceptable Daily Intake of 4.2 mg nitrite/d. Thus, evidence for adverse effects of dietary nitrate and nitrite is weak, and intakes above the legal limit might well be harmless. This is not unusual in regulatory toxicology. Many chemicals and contaminants might well be safe at intakes above their legal limit. Authorities willingly accept that possibility; erring on the safe side with many chemicals is justified if it keeps just one true carcinogen out of the food supply. But the trade-off changes when excessive caution deprives us of beneficial substances, as claimed by Hord et al for nitrate. In that case, the evidence for harm needs to be weighed against the potential benefit. But what is the evidence that nitrate and nitrite are beneficial?

Omega-6 polyunsaturated fatty acids and coronary heart disease

Most polyunsaturated fatty acids in the diet are of the omega-6 (n–6) type. These lower serum LDL cholesterol and, in clinical trials, the risk of heart disease. In this issue of the Journal, Jakobsen et al (1) illuminate the relation between fatty acids and heart disease from the observational side. They pooled data on diet and the incidence of heart disease in 340,000 people from the United States, Scandinavia, and Israel. The non-US cohorts made up 17% of subjects but 40% of the coronary events. The reason is probably that the Scandinavians and Israelis were mostly men, whereas 80% of the Americans were women. Jakobsen et al’s (1) article focuses on the effects of replacing one macronutrient by another. Macronutrients present an issue not seen with vitamins, minerals, or drugs. Vitamins or drugs travel to a particular target in the body, exert their action, and are excreted. The fatty acids, sugars, and amino acids produced from macronutrients likewise affect target tissues but also provide calories. Adding a macronutrient to an existing diet will increase body weight, which will distort the effect on heart disease risk. Therefore, scientists study what happens when one kind of macronutrient isocalorically replaces another type. It is a matter of semantics whether the effect of such a replacement is ascribed to the macronutrient coming in or going out. The Jakobsen et al (1) study is phrased in terms of such replacements. It shows that subjects with a low intake of saturated fatty acids and a concomitantly higher intake of carbohydrate suffered the same rate of coronary heart disease over the following 10 y as subjects who ate more saturated fatty acids and less carbohydrate. This agrees with the effect of replacing saturated fatty acids by carbohydrates on blood lipids: LDL and HDL cholesterol both fall, and the serum total-to-HDL cholesterol ratio remains unchanged (2). High-carbohydrate, low-fat diets also show little benefit for weight loss. The Jakobsen et al study therefore adds to growing doubts about whether such diets prevent heart disease. Remarkably, subjects with a high intake of monounsaturated fatty acids (oleic acid) experienced significantly more coronary events than did those with a high intake of saturated fatty acids. Before we discard our olive oil bottles, we need to recognize that the major sources of monounsaturated fatty acids in the United States and Scandinavia were dairy, meat, and partially hydrogenated oils. A high intake of fat from these foods typifies an unhealthy lifestyle. Correction for confounders such as smoking, body mass index, and activity cuts the excess risk associated with high monounsaturated fatty acid intake in half, and therefore monounsaturated fatty acids may have acted as a surrogate for other risk factors. In countries in which olive oil is the main source, a high monounsaturated fatty acid intake is associated with lower rates of coronary heart disease. Nonetheless, these data raise some concern about the advice to eat a Mediterranean diet. The low rate of coronary heart disease in Crete 50 y ago, when olive oil was a staple food, is suggestive, but such population comparisons do not constitute evidence-based medicine. The only experimental evidencewe have on monounsaturated fatty acids comes from studies of blood lipids and other biomarkers.Therearenoclinical trialsofmonounsaturatedfattyacids. In animal experiments, monkeys experienced as much atherosclerosis on diets rich in monounsaturated fatty acids as when consuming diets rich in saturated fatty acids (3). Extrapolations of such studies to humans are problematic, but it does stress that the scientific basis for monounsaturated fatty acids is incomplete. Jakobsen et al (1) found that a low intake of saturated fatty acids and a proportionally higher intake of omega-6 polyunsaturated fatty acids was associated with a significant reduction of coronary heart disease. Confounding was again a problem: diets low in saturated fatty acids and high in polyunsaturated fatty acids are rich in vegetable oils, polyunsaturated margarines, lean meats, and low-fat dairy. That is what health-conscious people eat. Indeed, correction for smoking, body mass index, and other risk factors diminished the effect from a risk reduction by 31% to a risk reduction by only 13%, if 5% of energy from saturated fatty acids was replaced by that from polyunsaturated fatty acids. Is this 13% due to residual confounding by imperfectly measured aspects of a healthy lifestyle, or is it real? Other types of research help us to decide. The first type consists of metabolic trials of diet and blood lipids. These show that replacing 5% of energy from saturated fatty acids with polyunsaturated fatty acids reduces the serum total-toHDL cholesterol ratio by 0.17 (2). In prospective observational studies, such a reduction in the total-to-HDL cholesterol ratio is associated with a reduction in heart disease risk of 9% (4).

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.

The Effect of Sugar-Free Versus Sugar-Sweetened Beverages on Satiety, Liking and Wanting: An 18 Month Randomized Double-Blind Trial in Children

Background Substituting sugar-free for sugar-sweetened beverages reduces weight gain. A possible explanation is that sugar-containing and sugar-free beverages cause the same degree of satiety. However, this has not been tested in long-term trials. Methods We randomized 203 children aged 7-11 years to receive 250 mL per day of an artificially sweetened sugar-free beverage or a similarly looking and tasting sugar-sweetened beverage. We measured satiety on a 5-point scale by questionnaire at 0, 6, 12 and 18 months. We calculated the change in satiety from before intake to 1 minute after intake and 15 minutes after intake. We then calculated the odds ratio that satiety increased by 1 point in the sugar-group versus the sugar-free group. We also investigated how much the children liked and wanted the beverages. Results 146 children or 72% completed the study. We found no statistically significant difference in satiety between the sugar-free and sugar-sweetened group; the adjusted odds ratio for a 1 point increase in satiety in the sugar group versus the sugar-free group was 0.77 at 1 minute (95% confidence interval, 0.46 to 1.29), and 1.44 at 15 minutes after intake (95% CI, 0.86 to 2.40). The sugar-group liked and wanted their beverage slightly more than the sugar-free group, adjusted odds ratio 1.63 (95% CI 1.05 to 2.54) and 1.65 (95% CI 1.07 to 2.55), respectively. Conclusions Sugar-sweetened and sugar-free beverages produced similar satiety. Therefore when children are given sugar-free instead of sugar-containing drinks they might not make up the missing calories from other sources. This may explain our previous observation that children in the sugar-free group accumulated less body fat than those in the sugar group. Trial Registration ClinicalTrials.gov NCT00893529 http://clinicaltrials.gov/show/NCT00893529

Saturated fat and heart disease

Saturated fats contain single bonds between carbon atoms which causes the fat to be ‘saturated’, or to be linked to as many hydrogen atoms as possible. Sources of saturated fat include: butter, coconut oil, palm oil, lard, full-fat dairy products, pies, pastries, cakes and biscuits and the visible fat on meat.1 Due to the association between saturated fat and increased low density lipoprotein (LDL) cholesterol levels, most public health bodies recommend limiting saturated fat intake in order to reduce the risk of heart disease.1,2