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The latest dietary guidelines recommend increased consumption of vegetables, fruits and nuts; weekly consumption of beans and fish; zero intake of alcohol; reduced meat and salt consumption; water, milk or yoghurt, filtered coffee, and 3-5 daily cups of tea rather than soft drinks and fruit juice; and replacing butter with vegetable oils and soft margarine. The glycemic index is considered not useful. The totality of the guidelines can lower blood pressure substantially. Effects on LDL cholesterol may be limited because the guidelines ignore the saturated fat content of foods, and treat all dairy products as equal. Interpretation of the effects of foods in terms of their constituent parts is mostly dismissed; this is a worrisome development in an otherwise valuable report.

A re-analysis of the Sydney Diet Heart Study (Ramsden et al., BMJ 2013) suggested that a diet high in linoleic acid increased the risk of coronary heart disease. The authors ascribe this to a lack of the omega-3 fatty acid, alpha-linolenic acid, in the oils and fats consumed. This argument has some weaknesses. Mortality in the linoleic acid group was 38 cases versus 27 in the control group (or 35 versus 28, or 39 versus 28; sources differ). The difference was significant in the current, though not in the original, publication. Conceivably, application of multiple statistical models led to chance significances. Additionally, the fats consumed by subjects in the intervention group were high in trans fats, which may have increased risk. Finally, a large recent clinical trial failed to show any benefit of linolenic acid. The conclusion is, therefore, that this re-analysis provides insufficient evidence to justify changes in current dietary recommendations.

Souvenaid (Nutricia, Zoetermeer, the Netherlands) is a medical food for the dietary management of early Alzheimer's disease. The mix of nutrients in this drink is suggested to have a beneficial effect on cognitive function; such implicit health claims for medical foods are not checked by government agencies. Souvenaid has been investigated in three clinical trials. The first trial showed that Souvenaid produced a significant improvement in delayed verbal recall, but not in other psychological tests. The second and largest trial showed no effect on any outcome. The third trial showed no significant effect at 12 or 24 weeks, but a significant difference in the 24-week time course of the composite memory score. None of these outcomes was clearly specified as a primary outcome at trial registration. In conclusion, there is no convincing proof that Souvenaid benefits cognitive function. Better scrutiny of the efficacy of medical foods is warranted.