Conjugated linoleic acid and human health: a critical evaluation of the evidence

Purpose of review: This review critically evaluates studies investigating the effects of conjugated linoleic acid on human health, including effects on body composition, blood lipids, liver metabolism, insulin sensitivity and immune function. It focuses mainly on human intervention studies, but includes some reference to animal and cellular studies which provide insight into potential molecular mechanisms of action of conjugated linoleic acid. Recent findings: Human studies continue to report inconsistent effects of conjugated linoleic acid on human health. Some of these reports are based on overinterpretation of marginal effects of supplementation. Recent data suggest that the effects of the substance may be isomer dependent and that cis-9, trans-11 and trans-10, cis-12 conjugated linoleic acids have opposing effects on blood lipids and on metabolism in adipocytes and hepatic cells. Summary: Claims that conjugated linoleic acid is beneficial for health remain as yet unconvincing. Human studies investigating the effects of conjugated linoleic acid supplements have tended to use mixtures of isomers and have been inconsistent. More recent studies have attempted to use relatively pure preparations of single isomers and these studies suggest that the effects of conjugated linoleic acid may be isomer-specific. These recent data suggest a relative detrimental effect of trans-10, cis-12 conjugated linoleic acid on blood lipids. There appears to be little effect of conjugated linoleic acid on immune function and the effects on insulin sensitivity remain unclear.

Critical stages of the brewing process for changes in antioxidant activity and levels of phenolic compounds in ale

Samples were taken at each stage of brewing (malt, milling, mashing, wort separation, hop addition, boiling, whirlpool, dilution, fermentation, warm rest, chill-lagering, beer filtration, carbonation and bottling, pasteurization, and storage). The level of antioxidant activity of unfractionated, low-molecular-mass (LMM) and high-molecular-mass (HMM) fractions was measured by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfortic acid) radical cation (ABTS(.+)) and ferric-reducing antioxidant power (FRAP) procedures. Polyphenol levels were assessed by HPLC. The LMM fraction (<5 kDa) was responsible for similar to80% of the level of antioxidant activity of the unfractionated malt and beer samples. In the unfractionated samples, significant decreases (P < 0.001) in antioxidant activity levels were observed after milling and beer filtration, with the decrease after beer filtration being accompanied by a significant decrease (P > 0.001) in catechin and ferulic acid levels. Increases in antioxidant activity levels were observed after mashing, boiling, fermentation, chill-lagering, and pasteurization, in line with previous studies on lager. Additionally, increases in the level of antioxidant activity occurred after wort separation and carbonation and bottling and were accompanied by increases in levels of most monitored polyphenols. Data from the ABTS(.-) and FRAP assays indicated that the compounds contributing to the levels of antioxidant activity responded differently in the two procedures. Levels of ferulic, vanillic, and chlorogenic acids and catechin accounted for 45-61% of the variation in antioxidant activity levels.

Critical review of health effects of soyabean phyto-oestrogens in post-menopausal women

A consensus view of soyabean phyto-oestrogens in clinical interventions in post-menopausal women is presented that is based on data from the EU-funded project Phytohealth. The phyto-oestrogens, primarily genistein and daidzein, were given as soyabean-protein isolates, whole-soyabean foods or extracts, supplements or pure compounds. A comprehensive literature search was conducted with well-defined inclusion or exclusion criteria. For areas for which substantial research exists only placebo-controlled double-blind randomised controlled trials (RCT) conducted on healthy post-menopausal women were included. For emerging areas all available human studies in post-menopausal women were reviewed. In order to make cross comparisons between studies the doses of isoflavones were calculated as aglycone equivalents. There is a suggestion, but no conclusive evidence, that isoflavones from the sources studied so far have a beneficial effect on bone health. The consumption of whole-soyabean foods and soyabean-protein isolates has some beneficial effects on lipid markers of cardiovascular risk. The consumption of isolated isoflavones does not affect blood lipid levels or blood pressure, although it may improve endothelial function. For menopausal symptoms there is currently limited evidence that soyabean-protein isolates, soyabean foods or red-clover (Trifolium pratense L.) extract are effective but soyabean isoflavone extracts may be effective in reducing hot flushes. There are too few RCT studies to reach conclusions on the effects of isoflavones on breast cancer, colon cancer, diabetes or cognitive function. The health benefits of soyabean phyto-oestrogens in healthy post-menopausal women are subtle and even some well-designed studies do not show protective effects. Future studies should focus on high-risk post-menopausal women, especially in the areas of diabetes, CVD, breast cancer and bone health.

The effect of learning condition on perceptual anticipation, awareness, and visual search

The efficacy of explicit and implicit learning paradigms was examined during the very early stages of learning the perceptual-motor anticipation task of predicting ball direction from temporally occluded footage of soccer penalty kicks. In addition, the effect of instructional condition on point-of-gaze during learning was examined. A significant improvement in horizontal prediction accuracy was observed in the explicit learning group; however, similar improvement was evident in a placebo group who watched footage of soccer matches. Only the explicit learning intervention resulted in changes in eye movement behaviour and increased awareness of relevant postural cues. Results are discussed in terms of methodological and practical issues regarding the employment of implicit perceptual training interventions. (c) 2005 Elsevier B.V. All rights reserved.

Who knows best? Awareness of divided attention difficulty in a neurological rehabilitation setting

Objective: To explore whether patients relearning to walk after acquired brain injury and showing cognitive-motor interference were aware of divided attention difficulty; whether their perceptions concurred with those of treating staff. Design: Patients and neurophysiotherapists (from rehabilitation and disabled wards) completed questionnaires. Factor analyses were applied to responses. Correlations between responses, clinical measures and experimental decrements were examined. Results: Patient/staff responses showed some agreement; staff reported higher levels of perceived difficulty; responses conformed to two factors. One factor (staff/patients alike) reflected expectations about functional/motor status and did not correlate with decrements. The other factor (patients) correlated significantly with dual-task motor decrement, suggesting some genuine awareness of difficulty (cognitive performance prioritized over motor control). The other factor (staff) correlated significantly with cognitive decrement (gait prioritized over sustained attention). Conclusions: Despite some inaccurate estimation of susceptibility; patients and staff do exhibit awareness of divided attention difficulty, but with a limited degree of concurrence. In fact, our results suggest that patients and staff may be sensitive to different aspects of the deficit. Rather than 'Who knows best?', it is a question of 'Who knows what?.

Critical notices: subjective, intersubjective, objective

Book review of 'Subjective, intersubjective, objective' by Donald Davidson.

Critical studies: aspects of reason I

Book review of 'Aspects of reason' by P. Grice.