Nutrition Research Highlights 3|2013
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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!
In these times of ever tighter public health budgets, strategies that help improve eating habits at minimal cost and effort are much sought after. Since habits form early on in life, the school environment seems an obvious choice for intervention. A team of researchers at Cornell University, USA, has now examined in a small field study in two New York school cafeterias whether students (grades 7-12) increased their fruit and vegetable intake when these foods were made more convenient, attractive and normative* (1). Previous experience had shown that forcing children to eat more healthily was likely to result in resistance and avoidance (2, 3) so the authors of this study aimed to influence choices without restricting them, an approach referred to as nudging or libertarian paternalism.
The three categories of convenience, attractiveness and normativeness comprised multiple interventions including fresh fruit located next to the cash register (convenience), nice colour photos of fruits and vegetables on lunch menus (attractiveness) and verbal prompts such as "No veggie? How about …?" by cafeteria staff (normativeness) (1). With these interventions in place, 13% more students (54% vs 47%) took a serving of fruit and 23% more students (44% vs 36%) took a vegetable serving. Figures for consuming at least one-half a serving of fruit and vegetable rose by 18% and 25%, respectively. Finally, 16% more students ate an entire fruit serving and 10% more an entire vegetable serving compared to before the intervention. All these changes were statistically significant.
Limitations of the study include its small sample size and lack of information about how school food intake was related to the pupils' total dietary and lifestyle patterns. However, considering that implementing the changes in the school cafeterias took only three hours and 50 US$, a larger scale follow-up should be feasible to further investigate this strategy's usefulness for improving children's eating habits. (SSGB)
*based on or prescribing a norm or standard (Webster's Dictionary).
Image: Healthy US School Meal Choices (Wikimedia Commons)
Different people eat very differently. Eating behaviour is affected by both personal factors (e.g. habits) as well as social or environmental (e.g. food availability, culture). But what about biology and our genetic profile? Is it in any way affecting the way we choose our food?
Family and twin studies have shown that there is indeed a genetic component to the intake of macronutrients (carbohydrate, protein, and fat) and this genetic contribution has been estimated to be as high as 70% in some cases. There are significant associations of common variations in our genes (also known as single nucleotide polymorphisms* or SNPs in short) with high intakes of energy and fat as well as obesity and increased risk of diabetes. Some examples are SNPs in genes like adiponectin or the FTO gene which has been associated with body mass index (BMI) and obesity in various cohorts (1). To link specific genes to particular dietary intakes, researchers undertake genome-wide association studies (GWAS) where they examine in large populations the statistical association between millions of different SNPs throughout all the genome and the type of food people consume (2).
In a very recent meta-analysis** of this type of studies (3) researchers assessed the food intake of 38,360 individuals retrieved from 12 large cohorts. Then, they related macronutrient intake to the genetic profiles of each individual. Simply put, their results demonstrate that genetics account for roughly 17% of protein, 20% of carbohydrates and 20-23% of fat intake. But how can we explain these associations between genetic variation and our dietary intakes? One illustrative example is the novel association between variations in chromosome 19, where the FGF21*** gene lies, and higher carbohydrate and lower fat intakes. As FGF21 has been proposed to have a role in the regulation of glucose and lipid metabolism (4) this could explain the differences seen in fat or carbohydrate intake. Interestingly, although this study did not confirm some previous associations, the FTO gene we referred to above (also called "obesity gene") struck back with more interesting data, this time linking variations in FTO with higher protein intake.
While these results support the view that our genes do affect our dietary choice, more data needs to be collected and analysed to conclusively demonstrate some of these associations and importantly understand the biological mechanisms underlying them. In addition, genetics can also illuminate differences in the metabolism of nutrients, individual needs and responses to food and nutrients. Eventually, one day it will be in everyone's reach to tailor our diets to our genes to maximise the benefits that good food can bring to each one of us! And that day seems to be drawing closer and closer… (AL)
Image: DNA (dream designs/FreeDigitalPhotos.net)
The recent report on sodium intake by the US Institute of Medicine (IOM) re-launched the debate on salt (sodium chloride) and salt-reduction initiatives (1). However, the report clearly backs up population-based efforts to lower excessive dietary sodium intakes (mainly from added salt in processed foods) based on all the evidence linking higher intakes of dietary sodium with an increased risk of cardiovascular disease. It does, though, put a question mark on the benefits of lowering dietary sodium intakes to below the values currently recommended in the US, i.e. below 2.3g (i.e. 5.8g salt) for everyone or for people above 51 years of age or with hypertension, diabetes or chronic kidney disease down to or even below 1.5g (i.e. 3.8g salt) as currently recommended by some medical or public health associations. Let's put the numbers into some context without going into the technicalities of the scientific debate: as an essential nutrient sodium has to be taken up regularly; it is needed for fluid and electrolyte balance and normal cellular function (2). Adequate dietary intake recommendations (i.e. a level at which the population at large is protected against deficiency and other negative health effects) range from 1.2 to 1.6g sodium (i.e. 3 to 4g salt) per day while upper limits (i.e. mainly to prevent high blood pressure and cardiovascular disease) range from 2 to 2.4g sodium (i.e. 5 to 6g salt) (2, 3). For comparison: current average daily intakes in Europe are much higher and usually range between 3.2 to 4.8g of sodium (i.e. 8 to 12g of salt). Importantly, dietary deficiency of sodium is very uncommon (1, 2, 4). Thus, dietary salt intake is clearly in excess and salt intake reduction efforts are undoubtedly needed, such as those pursued in the EU salt reduction framework (4) and re-iterated in the recent 66th World Health Assembly where an objective of "30% average reduction in salt intake" was agreed (5). Meanwhile, start today: use table salt mindfully at home, in particular when preparing food for children and read the labels on food packages while considering your daily need of 5-6g salt: you will be surprised how much added salt is in your food. (JW)
Image: Speisesalz (Wikimedia Commons)
Most people have heard about fats, saturated fats and polyunsaturated fats (PUFAs) at one point or the other. But have you heard about "trans fats"? Trans fatty acids (TFAs) can occur naturally in low amounts in foods such as meat or dairy derived from ruminant cattle (ruminant TFAs, or rTFAs). However, the issue about TFAs is that they are also formed in an industrial process called partial hydrogenation and added to a variety of processed foods like biscuits or margarines (industrial TFAs or iTFAs) where their values can be as high as 50% of the total fat content of the food product. There is a clear association between high iTFA intakes and increased cardiovascular disease risk and therefore, the recommended intake is "as low as possible" (1). For this reason across Europe some governments and food producers have implemented measures to reduce the population intake of iTFAs. A recent article though alerts to yet another possible source of TFAs (2). Conjugated linoleic acid (CLA) is a fatty acid that is naturally present in small amounts in ruminant fat. It is chemically very similar to linoleic acid (LA), an essential polyunsaturated fatty acid present in many vegetable oils, but the small differences are its physiological properties. CLA is also produced industrially and marketed as food supplements to aid in weight management. This claim is however not supported by the European Food Safety Authority (3). The intake of CLA through supplements can be appreciable as the manufacturers recommend dosages up to 6 g/day (2) as compared to a typical intake of roughly 1g/day from naturally occurring rTFAs. There is much debate on whether CLA is a trans-fat like the others and the jury is still out on its health effects. However, given these uncertainties a word of caution is indeed warranted when consuming CLA supplements. (CMS)
Image: Supplements (Wikimedia Commons)
This month we attended the annual meeting of the International Society for Behavioural Nutrition and Physical Activity (ISBNPA) in Ghent, Belgium (1). It was a great opportunity to find out the latest developments in the field of nutrition and physical activity research. In a keynote lecture 'Wrong bodies? Or wrong culture and economy?' (2) Tim Lang emphasized the policy challenges faced when looking broadly at the ecological * dimensions of public health (1, 3). The 20th century saw great increase in food production and availability, but also the emergence of food mal-distribution and altered dietary behaviours, along with alarming environmental impacts of the food chain (2, 4). The belief of producing more food to alleviate hunger is now considered too old and simplistic and there is a need to integrate health, environment, social values, economy and quality, and to underpin all this with good food governance.
An appropriate way to deal with such concerns could be to use the 'ecological public health' approach and bring public health policy makers from different disciplines together to create a culture shift towards sustainable diets** (2). Another exciting area of research presented in the meeting is the use of modern technologies to measure eating behaviour and physical activity! Traditionally, researchers rely on participant's ability to estimate how frequently they exercise, the type and duration of activities they engage in, and the context or environment they exercise in using questionnaires (5). The same approach is used for diets but it is difficult for participants to record where, when, with whom and how much they eat (6). With the advances of digital technologies such as the internet, mobile computing and imaging devices, scientists are using these as alternatives or complementary tools to measure diet and physical activity behaviours. The ubiquitous use of smartphones, particularly among the youth, has sparked a range of new research opportunities in this area, such as the use of mobile applications to record dietary intake, built-in cameras to capture and analyse the food consumed, mobile GPS (Global Positioning System) and built-in accelerometers to track movements, locations and distance of travels and activities, as well as using social media to promote and prompt physical activities or particular diets. Other new technologies developed include SenseCam (7), a small digital camera with built-in accelerometer that is worn around a person's neck which passively and automatically takes photographs of their surroundings. This tool is currently used in different research groups to study how environments affect food choices and eating habits of individuals, as well as their physical activity behaviours. While it is still too early to tell how usable and effective these devices are in measuring behaviours across different populations, and whether the use of them will prompt a long term behavioural change, this is no doubt a very exciting arena!
The field of nutrition research is constantly evolving. At this stage now where there is a need to study lifestyle behaviours simultaneously e.g. physical activity and diet as well as their determinants, in order to fully understand why, how and what we eat impacts our health. This meeting prompted new discussions around sustainable diets and food systems and showcased new modern technology used on behavioural research. We have certainly enjoyed our time and learned many new and interesting things at the ISBNPA meeting, and we look forward to seeing the results of these lifestyle behavioural studies supporting public health policies in the near future. (TNM & TM)
*To comprehend the composite interactions between the physical, physiological, social and cognitive worlds that determine health outcomes in order to intervene, alter and ameliorate the population’s health by shaping society and framing public and private choices to deliver sustainable planetary, economic, societal and human health (3).
**Sustainable diets are those with a low environmental impact, which contribute to nutritional and food security and to a healthy lifestyle for current and future generations. Sustainable diets protect and respect biodiversity and ecosystems, are culturally acceptable, accessible, economically just and affordable, nutritionally balanced, healthy without posing any health risk, while still making it possible to optimize the use of natural and human resources (4).
Image: Cycling (Wikimedia Commons)
May - June 2013
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. Sandra Caldeira, Sandra Eisenwagen, Anastasia Livaniou, Tsz Ning Mak, Theodora Mouratidou, Carlos Martin Saborido, Stefan Storcksdieck genannt Bonsmann and Jan Wollgast contributed to this issue.
The views expressed here do not necessarily reflect the opinion of the European Commission.