Nutrition Research Highlights 2|2012
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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 summarized as “News” items or presented as a “View”, comprising an analysis and expert opinion. Enjoy your reading!
Red meat was back in the spotlight last month as a recent study revisited the association between the consumption of red meat and the risk of cardiovascular diseases (CVD), cancer and 'all-cause mortality'* (1). The press office of the Harvard School of Public Health summarised the findings as ' One daily serving of unprocessed red meat (about the size of a deck of cards) was associated with a 13% increased risk of mortality, and one daily serving of processed red meat (one hot dog or two slices of bacon) was associated with a 20% increased risk'. The same study suggested that replacing red meat by other sources of protein (like nuts, legumes, whole grain, low fat dairy, white meat or fish) would decrease the risk of CVD deaths or 'all-cause mortality'. Red meat-associated mortality is a controversial topic and this controversy was also in the spotlight. Most nutritional studies of general dietary features such as meat consumption that involve large numbers of individuals (around 120000 in this case) are observational in nature. They report associations between a potential risk factor (e.g. red meat consumption) and an outcome (e.g. death). This is quite different from proving a cause and effect relationship between red meat consumption and CVD or cancer deaths. However, it has to be noted that questions such as this one are difficult to address through large well-controlled studies in individuals. The answers lies in bringing together different types of evidence that support, and lend plausibility to the associations observed. For example, there are ongoing mechanistic studies testing if and how exactly could red meat components like heme or fat promote cancer or CVD. While epidemiologists, nutritionists, bloggers or journalists fiercely defend their beliefs, others find themselves asking who's right and who's wrong. Answering whether 'eating red meat will kill you' is not straight forward but there are other issues related to red meat consumption that are not health-related but are still worth considering. An editorial (2) wittily entitled 'Holy Cow! What's good for you is good for our planet' alerts to the negative environmental impact of the animal agri-business and livestock consumption. There are several comprehensive studies on the topic, including one conducted by our JRC colleagues (3) that concludes that consumption of meat and dairy products contributes on average 24 % to the environmental impacts from the total final consumption** in EU-27. The environmental aspects considered range from ecotoxicity to nature occupation or consumption of non renewable energies. Some may ask whether this environmental damage is an unwelcome but unavoidable consequence of meat and dairy dietary needs in the EU? That does not appear to be the case as most Europeans seem to be eating well over (4) the WHO dietary recommendations regarding protein intake (roughly 50g of protein every day). There is room to decrease the consumption of animal protein at the EU level without affecting dietary protein needs and that reduction would likely bring about environment benefits and (directly or indirectly!) health ones as well. (SC)
* all-cause mortality refers to the total number of deaths in a population regardless of the causes
Image: Red Traffic Light (Wikimedia Commons)
It is well known that food plays a major role in health and disease. What is perhaps less obvious is that some dietary components have been associated with changes in behavior and mental health. We have previously discussed the effects of a deficiency in polyunsaturated omega-3 (n-3) fatty acids (PUFAs) that, in mice, led to anxiety and depression-like behaviour. This time we report on the potential effects of trans-fatty acids (TFAs) consumption in human behaviour. Trans fats can be found in many foods but especially in fried foods like French fries and doughnuts or baked goods including cookies and crackers and their consumption is known to have detrimental health effects on coronary heart disease (1). Current recommendations are to keep its intake as low as possible (2) and Denmark and Switzerland have banned them completely. A recent study (3) examined data from nearly 1000 individuals and focused on the relationship between TFA consumption and aggression, revealing an association between TFA consumption and each of the characteristics of aggression examined (e.g. overt aggression, conflict tactics, life history of aggression or self-reported impatience and irritability). The authors discuss that TFAs are known to inhibit the production of omega-3 PUFAs, which, apart from keeping laboratory mice happy, also appear to be protective against aggression in other studies (3). As noted by the authors themselves, there are some limitations of their work and further research is needed to firmly confirm their findings. In the meantime, if you are feeling easily annoyed, impatient and generally tense, maybe you 're just eating too many french fries? (PM)
Coffee is the most recognizable, widely consumed and readily available non-alcoholic beverage in the world, coming in many varieties and ways of preparations. Nutrionists are often called to answer questions like is coffee bad or good? Well… Caffeine itself has been evaluated extensively and is considered safe (1, 2) but coffee is not only caffeine. The potential risks and benefits on health of whole coffee consumption have been recently reviewed (3) and there are various studies reporting both negative (e.g. increased risk of chronic heart disease) and positive (e.g. reduced risk of developing Alzheimer or Parkinson's disease) health effects. The latest update examined the association between caffeinated and non-caffeinated coffee consumption and the risk of chronic disease development, including Type 2 diabetes, heart attack, stroke, and total cancer (4). This study by Floegel et al. examined more than 42,000 individuals and concluded that caffeinated filtered coffee consumption is not associated with increased risk of chronic heart disease. It even reports an association between coffee consumption and lower risk of type 2 diabetes. The reason why some earlier studies observed an association between coffee consumption and increased risk of chronic heart disease may be related to some unfavorable lifestyle behaviours that are often associated with coffee, e.g. smoking. On the other hand, coffee consumption in some cultures is linked to favorable lifestyle behaviors like an active social life (5). Floegel et al. also note some limitations of their study; for example, the study looked at the association of coffee consumption with type 2 diabetes, heart attack, stroke, and total cancer but did not consider individual diseases (like organ specific cancers) and therefore detrimental health effects from coffee consumption cannot be excluded. In addition, the study was conducted in Germany where most of the coffee consumed is filtered; the long term effects of non-filtered coffee (like instant coffee or espresso-like) are not well known, and some short term studies have shown that non-filtered coffee may increase serum concentrations of total and LDL cholesterol (5). In any case, next time you have a coffee break with your colleagues, you have a relevant topic to discuss! (PM)
1. Scientific Committee of Food report (14th series), 1983
Spring has arrived. Flowers are blossoming, birds are singing and building up their nests, and Easter just brought us plenty of colourful eggs. Across Europe, eggs are painted, searched for and consumed in many different ways during this festive season. But what about eating so many eggs, should we worry? Weren’t we told to limit our egg consumption because of the cholesterol content in egg yolk? Nutritional recommendations since the '60s and '70s strongly advised to limit egg consumption to a maximum of 3 per week and even less for people with increased blood cholesterol levels. Such recommendations were based on the high content of cholesterol and the correlation between high blood cholesterol levels and increased risk for cardiovascular diseases (CVD). However, studies published mainly in the last decade indicate that egg consumption does not significantly raise blood cholesterol levels and does not show a link with CVD risk (1). Moreover, as eggs contain relevant amounts of micronutrients, researchers increasingly plead for a ‘repositioning of the egg’ (2).
While cholesterol gave eggs a bad reputation, it does play different essential roles in the human body. Most recent studies that took into consideration other factors such as diet and lifestyle, find that egg consumption per se is not related to either blood cholesterol levels or CVD risk (1, 3). Saturated fat intake has been identified as an important confounding factor* (think about bacon & eggs) that was driving the association between egg intake and high blood cholesterol levels (4).In one intervention study where people were given 3 eggs per day (up to 640 mg of additional cholesterol) for 1 month only slight increments of blood cholesterol levels were seen (5), staying well below levels that are considered as 'increased' (> 5 mmol/L, equal to 200mg/dL) according to both European and American heart associations. Large prospective cohort studies also indicate that in healthy individuals even long-term (10-20 years) egg consumption up to 6 eggs a week, is not associated with higher mortality and CVD risk (3). A word of caution – the same study also shows that diabetics do seem to have an increased risk for CVD with a higher consumption of eggs although the underlying mechanism is unknown (3).
As already mentioned, beyond their cholesterol content, eggs have a well-balanced composition of substances and contain high quality proteins (6), lipids (including cholesterol), vitamins and minerals. Based on the criteria for health claims on foods (Regulation (EC) No 1924/2006), eggs can be 'claimed' a 'source of’ (≥15% RDA/100g) vitamin A, B2, D and E, folic acid, phosphorous, iron, zinc and iodine, and ‘rich in’ (≥30% RDA/100g) vitamin B12, biotin and selenium as well as monounsaturated fatty acids and protein. Eggs do also contain significant amounts of choline. This makes an egg by default a very valuable resource of nutrients. In fact, egg consumers seem to have higher intakes of micronutrients than non-egg consumers (7).
Knowing that egg consumption is not a high risk factor for CVD, as believed previously, and on top delivers several macro- and micronutrients in significant amounts, gives reason to think about how eggs would fit in a healthy diet. According to an editorial (8) that reflected on how the diet should be adapted to lower the risk for type 2 diabetes and CVD, the priority is to reduce the intake of 'simple carbohydrates' (refined grains and sugars) and replace them by whole grains and unsaturated fats, and/or healthy sources of proteins. The composition of eggs, especially the richness in both high quality protein and unsaturated fat, makes them fit well in such a diet. This is, of course, under the assumption that eggs actually 'replace' another food with a more unhealthy composition, processed meat for example. Eating eggs instead of other (animal) protein sources has additional value as they have a smaller impact on natural resources.
Although there is still some scepticism in accepting the more recent study outcomes regarding egg consumption and CVD risk, some national authorities are beginning to adapt their nutritional recommendations. These range from taking out the restriction of egg consumption in the UK (9) to specifically advising to increase egg consumption in the US (10). Recommendations are instead focussing on minimizing the intake of saturated fat in order to lower blood cholesterol levels.
Another issue that was recently highlighted in the media were eggs exceeding the maximum level of contaminants like dioxins and polychlorinated biphenyls (PCBs). Nevertheless, even if highly contaminated eggs were consumed over a long period, there are no concerns of health risks, according to the German Federal Institute for Risk Assesment (11).
All in all, an egg is a valuable food in terms of its nutritional content and the change in our understanding of the links between dietary cholesterol, blood cholesterol levels and CVD risk underlies the current shift in recommendations regarding egg consumption. Easter or not, eggs are a welcome presence at our breakfast, lunch and dinner table so feel free to enjoy them! (RG)
* In statistics, a confounding factor correlates with both a dependent and an independent variable. If not taken into account, there is a risk to make a 'false positive' conclusion for a causal relation between independent (e.g. ' food intake') and dependent (e.g. 'disease outcome') variables.
Image: Easter eggs (Wikimedia Commons)
Nutrition Research Highlights is a bi-monthly publication prepared by the Nutrition Team of the DG-Joint Research Centre, Institute for Health and Consumer Protection. The Nutrition team is comprised of Sandra Caldeira, Raymond Gemen, Petros Maragkoudakis & Jan Wollgast.
The views expressed here do not necessarily reflect the opinion of the European Commission.
© European Union, 2012. Reproduction of articles (excluding photographs) is authorised, except for commercial purposes, provided that the source is mentioned.