Nutrition Research Highlights 1|2010
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This newsletter is published by the Nutrition & Health Group of the JRC’s Institute for Health and Consumer Protection. Regularly surveying the top nutrition and medical journals, we select the most recent news on nutrition research, relevant to current societal debates or policies. These are then summarised as “News” items or presented as a “View”, comprising an analysis and expert opinion. Enjoy your reading!
Consumption of nuts has been associated with reduced risk of coronary heart disease (CHD), diabetes and gallstone diseases and is linked to lower body weight and reduced risk of obesity (1). While further studies are required to firmly establish these health benefits, their protective effects on CHD are well established. Sabaté et al. have now pooled data from 25 nut consumption trials to assess the impact of nuts on hyperlipidaemia (2). Their meta-analysis shows that daily consumption of nuts improves blood lipid levels (e.g. reduces total cholesterol, LDL-c as well as triglycerides in those with initially high levels) in a dose-related manner. Nuts have a healthy nutritional profile and the effects observed in blood cholesterol are likely a consequence of their unsaturated fat content. They also contain fiber, vegetable protein, phytoesterols and other antioxidants but they are also energy dense and thus a high intake could contribute to obesity. The U.S. Food and Drug Administration has issued a qualified health claim in 2003 stating that "scientific evidence suggests but does not prove that eating 1.5 ounces of most nuts per day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease". On food labels, the claim is accompanied by a cautionary note: "See nutrition information for fat content". In Europe, EFSA is due to issue an opinion on the cardiovascular effects of nuts in the end of 2011. (SC)
Photo: Michael Coombes
This year the Albert Lasker Basic Medical Research Award was given to Douglas Coleman and Jeffrey Friedman for the discovery of leptin. This prestigious prize awards those "whose fundamental investigations have provided techniques, information or concepts contributing to the elimination of major causes of disability and death"(3). Leptin is a hormone that regulates appetite and body weight. Its discovery was followed by great hopes that a cure for obesity had been discovered. Obesity is however a harder issue to tackle and leptin per se was not the solution. Nevertheless, leptin is of great relevance in human metabolism and its therapeutic implications in lipodistrophies or diabetes cannot be dismissed. This award honours the excellence of Coleman and Friedman and we hope it also continues to inspire other researchers that followed on from their initial work to affirm the relevance of this molecule.
Leptin is a hormone that regulates appetite and body weight. Its discovery was followed by great hopes that a cure for obesity had been discovered. Obesity is however a harder issue to tackle and leptin per se was not the solution. Nevertheless, leptin is of great relevance in human metabolism and its therapeutic implications in lipodistrophies or diabetes cannot be dismissed. This award honours the excellence of Coleman and Friedman and we hope it also inspires all other researchers that followed on their initial work and persevered to affirm the relevance of this molecule. (SC)
Picture: Leptin and the regulation of energy balance. Reprinted by permission from Macmillan Publishers Ltd, doi:10.1038/ nm1010-1100©2010
Vitamin E (a collective name for particular tocopherols and tocotrienols) is seen by many as a health promoting factor. Vitamin E supplements are popular and claims such as "Helps support a healthy heart" are abundant in such products. These are worrying as randomised controlled trials have not shown protection against cardiovascular disease by vitamin E supplementation. Moreover, a previous meta-analysis has even suggested that a high dose of vitamin E increases the risk for all-cause mortality. Schürks et al (4) have just published a meta-analysis of randomised controlled trials on the effects of vitamin E on stroke. It encompasses 118765 individuals and suggests that while vitamin E supplementation reduces the risk for ischaemic stroke by 10%, it also increases the risk for haemorrhagic stroke by 22%. Overall, the study adds to the warnings against the pervasive use of vitamin E supplements. EFSA has also emitted a Scientific Opinion on Vitamin E related health claims (5) stating that a cause and effect relationship has not been established between the dietary intake of vitamin E and maintenance of normal cardiac function (PM).
It has been recently reported that salt sensitivity of blood pressure is strongly associated with insulin resistance in lean but essential hypertensive patients (6), and that abnormal glucose metabolism may be causing high blood pressure (HBP) via a series of biochemical and hormone-regulated mechanisms (6). This led us to a discussion on the many causes of HBP and consequently on salt and the current focus on salt reduction initiatives (e.g. EU framework for national salt initiatives (7).
HBP is a major risk factor in the development of ischaemic heart disease, stroke and renal disease. While sodium is an essential nutrient, high dietary sodium intake, mainly in the form of excessive sodium chloride (table salt) consumption is thought to contribute to HBP (8). However, HBP is also associated with other metabolic syndrome conditions such as overweight/obesity, impaired glucose metabolism and dyslipidaemia. Importantly, it is estimated that 60-70% of hypertension is attributable to adiposity (9) through mechanisms such as insulin resistance, sodium retention, altered vascular function and others (6). Based on these numbers, are population-wide salt reduction initiatives the most effective way forward to reduce HBP and improve cardiovascular health?
There is a long history of scientific debate on the effectiveness of salt reduction on lowering HBP and cardiovascular morbidity and mortality (10, 11). A reason for this debate may be that only 30- 50% of hypertensive individuals are salt sensitive (12). The percentage is even lower for the normal blood pressure population. On the other hand, individuals with diabetes, kidney disease, metabolic syndrome as well as the elderly or sedentary persons tend to have increased salt sensitivity of blood pressure. Other dietary compounds are also important determinants of salt sensitivity: adequate potassium, calcium, and magnesium (rich in unprocessed foods) intake reduces, while excessive chloride (rich in processed foods) intake enhances blood pressure response to sodium (8, 12, 13). Therefore, epidemiology studies comparing diets rich in unprocessed foods, like fruits and vegetables with diets rich in processed foods, do not clearly identify salt as the only HBP determinant. In addition, certain dietary regimes (e.g. Mediterranean diet) may also lower blood pressure through salt-independent mechanisms (12). Thus, such dietary strategies, together with moderate alcohol consumption, physical activity and no smoking should be the main target for public health intervention (14). So, while we wait for further research to clarify the concrete role of salt in HBP, what can we expect from salt reduction campaigns?
Undoubtedly, salt sensitive individuals with HBP will benefit from salt reduction initiatives. However, it is debatable whether salt reduction will benefit the general population and some researchers have highlighted potential health risks caused by reducing salt levels below 4.0-4.5g per day (11). Nevertheless, avoiding excessive salt intake can benefit the consumer (12). In Europe, current daily salt intakes (8-11g) are clearly above recommended intake (5-6g). Approximately 75% of the sodium in our diet comes from processed foods, while only 25% derives from naturally occurring sodium in fresh foods or salt added by the consumer (8).
Thus, current salt reduction strategies, such as the EU framework for national salt initiatives (7) aiming to gradually reduce the salt content of targeted processed foods by 16% (from 2008 to 2012) will certainly not put European citizens at risk of excessive daily sodium reduction and will benefit those salt sensitive individuals with HBP at the widest possible reach. Importantly, excessive salt intake is also thought to increase a person's susceptibility to carcinogens, such as nitrosamines or the bacterium Helicobacter pylori and therefore, salt reduction can possibly reduce cancer risk (8).
In conclusion, the most effective way to improve cardiovascular health is through adhering to a healthy diet and lifestyle. Every public and private effort should aim at facilitating the population in this endeavour (14). Diet and lifestyle ultimately remain a question of personal choice. However, salt reduction of processed foods will benefit the public across a wide section of society, particularly those salt sensitive individuals who are not able or willing to adopt a healthy diet and lifestyle. (JW)
Nutrition Research Highlights is a bi-monthly publication prepared by the Nutrition & Health Group of the DG-Joint Research Centre, Institute for Health and Consumer Protection.The Nutrition team is comprised of Sandra Caldeira, Petros Maragkoudakis & Jan Wollgast.
The views expressed here do not necessarily reflect the opinion of the European Commission.
© European Union, 2010. Reproduction of articles (excluding photographs) is authorised, except for commercial purposes, provided that the source is mentioned.