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We reviewed the evidence from human intervention studies for the health effects of probiotic bacteria, ie, live bacteria that survive passage through the gastrointestinal tract and have beneficial effects on the host. Of the 49 studies reviewed, 26 dealt with the prevention or treatment of diarrheal disease, 9 with the prevention of cancer or of the formation of carcinogens, 7 with the lowering of serum cholesterol, and 7 with the stimulation of the immune system. The most widely studied probiotic bacteria were Lactobacillus GG (22 studies), Lactobacillus acidophilus (16 studies), Bifidobacterium bifidum (6 studies), and Enterococcus faecium (7 studies). Intake of Lactobacillus GG consistently shortened the diarrheal phase of rotavirus infection by 1 d. However, evidence for the prevention by Lactobacillus GG and other probiotics of diarrhea due to viral or bacterial infections was less strong. Effects of probiotics on the immune system are inconclusive because of the variety of outcome variables reported. Cholesterol lowering by L. acidophilus was shown in some but not all studies; cholesterol lowering by E. faecium seems to be transient. Two studies of one research group showed a smaller recurrence of bladder tumors in patients after treatment with Lactobacillus casei; these results await confirmation. The production of mutagens after a meal might be reduced by the concomitant intake of probiotics, but the relevance of this finding is unclear. In conclusion, consumption of foods containing Lactobacillus GG may shorten the course of rotavirus infection. Other health effects of probiotic bacteria have not been well established. Well-designed placebo-controlled studies with validated outcome variables are needed to determine the health effects of probiotics.

Abstract-We tested whether trans fatty acids and saturated fatty acids had different effects on flow-mediated vasodilation (FMD), a risk marker of coronary heart disease (CHD). Consumption of trans fatty acids is related to increased risk of CHD, probably through effects on lipoproteins. Trans fatty acids differ from most saturated fatty acids because they decrease serum high-density lipoprotein (HDL) cholesterol, and this may increase the risk of CHD. We fed 29 volunteers 2 controlled diets in a 2ϫ4-week randomized crossover design. The "Trans-diet" contained 9.2 energy percent of trans fatty acids; these were replaced by saturated fatty acids in the "Sat-diet." Mean serum HDL cholesterol after the 3 trans fatty acids (TFAs) constitute 4% to 7% of dietary fat intake. A high intake of TFAs is associated with an increased risk of coronary heart disease (CHD). 4 -6 One probable cause is the effect of TFAs on serum lipoproteins. Like saturated fatty acids, TFAs increase the concentration of serum LDL cholesterol. 7,8 Moreover, and unlike saturated fatty acids, TFAs decrease serum HDL cholesterol (HDL-C). [7][8][9][10][11] This might be harmful, inasmuch as there is increasing evidence that HDL-C is inversely related to CHD. 12,13 We investigated whether the intake of trans fat would indeed increase the risk of CHD more than the intake of saturated fat by comparing the effects of these fats on endothelial function, a surrogate cardiovascular end point. 14 -16 We assessed endothelial function as flow-mediated vasodilation (FMD) of the brachial artery, because this is a noninvasive measurement that correlates well with known risk factors [17][18][19][20][21][22] and other markers of CHD. [23][24][25] Moreover, 2 longitudinal studies show an association between FMD in the past with future CHD events. 26,27 The diets were given for a minimum of 3 weeks, a time period long enough to establish changes in serum lipids 28 and FMD. 21 We hypothesized that FMD would be lower after the diet rich in trans fat than after the diet rich in saturated fat because of the expected difference in serum HDL-C. Methods SubjectsThe Medical Ethical Committee of Wageningen University approved the study aim and design. Each volunteer signed an informed consent form. We recruited 39 nonsmoking men and women and assessed their health by using a questionnaire; we eliminated 1 person because of use of medication, 2 because of missing information, and 1 because of poor veins for venipuncture. All subjects had normal concentrations of serum cholesterol and triglycerides and normal amounts of protein and glucose in their urine. We excluded 2 subjects because we could not obtain clear ultrasound images of their brachial arteries. One other subject withdrew before the start of the study; in the end, 32 subjects were enrolled. They all completed the study. Study DesignWe provided 2 controlled diets for 4 weeks, each in a randomized crossover design. The diets consisted of conventional food items supplemented with special margarines and were given i...

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