Nutrition Research Highlights 2|2014
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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!
The avid reader may be well aware that we should limit dietary trans fats for the sake of our hearts and that frequent consumption of sugary foods and drinks increases the risk for dental caries (1). These are just a couple of examples where carbohydrates and fats have been implicated in the development of disease. Interestingly though, the third major nutrient in our diets, protein, largely has been spared this fate.
However, a recent study (2) hit the headlines with the claim that high protein intakes* are associated with higher risk of mortality from diabetes, cancer, and all causes. The researchers used dietary data and mortality statistics from 6 381 adults aged 50 and above who participated in the third U.S. National Health and Nutrition Examination Survey (NHANES III). Subjects were grouped by their daily caloric intake of protein into low (<10%), moderate (10-19%), and high (≥20%) consumers. Compared to the low protein group, the groups with moderate and high intakes experienced an increased risk of death from diabetes. Moreover, when subjects were divided by age (50-65 and 66+ years), higher cancer and overall mortality rates occurred in people with higher protein intakes in the 50-65 years group. On the other hand, higher protein intakes seemed to be protective for those aged 66+ years. The authors speculate that the growth hormone Insulin-like Growth Factor-1 (IGF-1)** partly mediates the progression of these age-related diseases. Studies in mice supported this hypothesis as cancer progression was significantly more complete and extensive on a high- vs. low-protein diet and was accompanied by higher levels of IGF-1 (2).
Although these new findings merit further investigation, the authors noted a number of limitations that put the extensive media coverage of the study in perspective. First, using single 24-hr diet recalls to estimate participants' dietary patterns for an 18-yr follow-up period at best is a very rough indicator of people's habitual diets. Even if we assume the diet patterns to be real, it does not mean that a high protein intake caused the reported deaths. People may have adopted a high- or low-protein diet because of an underlying condition or vice versa. Furthermore, the sample size and especially the number of diabetes-related deaths were too low to determine an association. As for the mice studies, the experimental diets may be criticised for their composition (e.g. casein as the sole protein source), and findings are not easily transferable to humans.
In summary, the study raises an interesting hypothesis about dietary protein, IGF-1 and age-related disease. However, further research is needed to clarify what is cause and what is effect, and to what extent this applies to humans. In the meantime, one should bear in mind that current recommendations for adults of all ages are to consume 0.83 grams of protein per kilogram of body weight (3), which translates to about 10% of daily calories from protein***. For comparison, actual European intakes average 12-20% of daily calories (3). (SSgB)
*** Calculated from a recommended 0.83 g of protein per kilogram of bodyweight (3); a 60 kg woman with a daily energy requirement of 2 000 kcal should consume approximately 50 g of protein, which corresponds to about 200 kcal, i.e. 10% of the 2 000 kcal daily requirement.
We have recently reported on the issue of childhood obesity in Europe and beyond, and that it requires a multi-faceted approach to achieve meaningful improvement of the current obesity levels. An important window of time for establishing eating habits is the first 24 months of a child's life—that is to say, when transitioning from liquid to solid family foods. This period is key to self-regulation of intake and acceptance of a wide variety of foods and flavours (1). However, traditional feeding practices during this critical period often encounter the situation of food affluence. Practices such as offering food as a first response to infant crying and distress, frequent feeding, offering large portions of preferred foods, and pressuring children to eat all made sense in a context of food scarcity but in a context of continuous availability of highly palatable, energy-dense, and inexpensive food the possibility of over-eating in many is pre-programmed (1). Given the importance of early-life exposures for long-term health and disease outcomes, infants and children below 2 years of age need to be protected from today's obesogenic environment*. A large concerted effort has started in the United States to systematically assess and improve the available knowledge base for developing evidence-based dietary guidelines from birth to 24 months of age (2). And in Europe? Less than a year after EU health ministers decided to prioritise the fight against childhood obesity, EU Member States** have agreed on an Action Plan on Childhood Obesity 2014-2020. Demonstrating their shared commitment to address childhood obesity and collectively keep track of progress, EU Member States set out priority areas for action. These action areas address all life stages from 0 to 18 years, including breastfeeding, early child and (pre-) school nutrition. They aim to promote healthier environments (e.g. home and schools), to restrict marketing and advertising of certain foods and beverages to children and to promote physical activity. (JW)
* Obesogenic environments refer to those environments which promote high energy intake and sedentary behaviour. The obesogenicity of an environment has been defined in the scientific literature as ‘the sum of influences that the surroundings, opportunities, or conditions of life have on promoting obesity in individuals or populations’ (3).
Thinking about the foods available to consumers in Europe, most people would argue that variety has increased over the last 50 years. Exotic fruits and vegetables can now be found on the shelves of most supermarkets throughout the year. Nearly every European city hosts trendy Asian, South American or African restaurants that serve delicious foods quite different from those our parents or grandparents were eating when, and if, they ever dined out. Yet, at the same time, some foods have been lost; there are certain cereals that are no longer cultivated and edible plants that are rarely eaten now. Furthermore, with the so called “westernisation of diets” taking place throughout the world, is the apparent variety in Europe a reality on a global scale? A new study (1) on global food supplies aims to answer this question. Results indicate that over the last 50 years, diets around the world have become more similar. On one hand, national per capita supplies increased and the 52 crop commodities analysed in the study increased in geographic spread as well. At the same time, food supplies worldwide also became more similar and rely on a limited number of crops (e.g. wheat, rice, maize and barley). This implies narrowing of the diversity of global agricultural systems and this trend may impact food security*. Clearly, the growing reliance worldwide on a limited number of crops underlies a loss of crop biodiversity and increases our dependence on these same crops and the vulnerability of the food system as a whole (e.g. climate or political instabilities in production regions). In addition, the loss of plant genetic diversity can also directly impact human nutrition and health (see here for an example in a previous article). The conclusions of this study highlight the complexity of food security and call for a reversal of this homogeneity trend and a diversification of agricultural systems. Under-researched crop species and great-grandparents’ cereals, vegetables and herbs may hopefully make their way to our tables one day! (SC)
* “Food security exists when all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life” (FAO definition)
Spring and summer are fast approaching, and many are looking forward to spending time out in the sun. In this issue, we focus on the importance of vitamin D, the 'sunshine vitamin' (1). It is a nutrient of concern worldwide; the public health nutrition aspects of vitamin D and bone health, including low vitamin D status (i.e. low circulating concentrations in blood), food fortification and supplement use, have long been a subject of interest (2). A recent series of articles last month (2, 3) revisited the topic, highlighting that deficiency from low dietary intake or low sun exposure is often seen across all age groups in Europe (4). Findings from a Europe-wide study HELENA-CSS* reported that approximately 40% of adolescents across Europe were vitamin D deficient (5), presenting with a vitamin D status below what is regarded as a safe level to ensure optimum bone health (<50nmol/l) (6). Of these, 15% were severely deficient with levels below 27.5nmol/l; such low levels can increase the risk of rickets** (in children) and osteomalacia*** (in adults) (5).
Vitamin D is essential for bone health, acting as a regulator of calcium absorption and calcium metabolism, which together with phosphorus is one of the main nutrients responsible for 'healthy, strong bones'. Therefore, it plays a central role in promoting peak bone mass attainment during childhood, adolescence and early adulthood and in maintaining bone mass throughout life (7). Achievement of a high peak bone mass is the best form of prevention against age-related bone loss, increased fracture risk and osteoporosis (8). Maximising peak bone mass attainment during childhood and adolescence is important, as 90% of bone mass is acquired by age 18 years (9), leading to improved musculoskeletal health both in current and future generations.
However, it is not easy to ensure we are meeting our requirements for vitamin D (see the highlighted text below for some tips). It is the only vitamin we obtain primarily from a non-dietary source; very few foods contain it and in very small amounts (10). Among these are oily fish (salmon, fresh tuna, mackerel and sardines), cod liver oil and egg yolk. So, what can we do to ensure we are doing the best for our bones? A combination of good dietary and lifestyle habits can help us solve the trick. A diet containing lots of calcium-rich foods (e.g. dairy products, green leafy vegetables such as broccoli) and foods containing vitamin D, combined with spending enough time outdoors in the sun is a start. If time in the sun is combined to exercise, in particular impact loading exercise, such as jumping or running, we are on the right track to strengthening our bones (6, 11).
Vitamin D and sunshine facts
- Skin production of vitamin D is maximised, if exposure to sunlight occurs when the sun reaches its highest point in the sky (at midday) (15).
- At latitudes >40o N (anywhere above Rome for example) the incline of the sun does not allow vitamin D production during winter (2, 4).
- Factor 15 sun-cream can block up to 98% of sunlight absorption (14)
- Darker skin and clothing can also reduce sunlight absorption (2).
Spending 10 minutes a day in the sun between 10am and 3pm is sufficient to meet daily vitamin D requirements (16) however, make sure you do apply sun cream after this short period in order to protect your skin from too much exposure.
At the population level, policy makers should focus on the development of feasible public health measures to increase vitamin D status across all population groups, in order to prevent bone diseases such as osteoporosis or other conditions associated with low bone mass (fracture risk, osteomalacia) (3). Three options have currently been explored with varying degrees of success. Firstly, aiming to increase intake of foods containing vitamin D seems to be the least favoured measure to counteract deficiency, because very few foods are a natural source of the vitamin and are consumed in low amounts (4). Therefore, supplementation has also been considered, although its use is still widely debated. Supplements have been shown to increase intake at an individual level across different ages, gender and ethnic groups. However, at a population level, their use still remains low and do not seem to be an effective strategy (12). Thirdly, there is a need for stronger evidence assessing the impact of food fortification on vitamin D status, prevention of deficiency and implications for health (13). Nonetheless, mandatory fortification of certain food products has already been implemented in countries such as the USA and Canada, and although the current fortification level is still insufficient to meet requirements, it has managed to somewhat raise intake levels across the adult population (4). Therefore, through the development of appropriate fortification strategies it may be possible to use a variety of mainstream foods, such as milk, juice or cereals, to target the population as a whole and to help prevent vitamin D related health issues rather than to treat them (4).
Currently, variation exists between Member States' vitamin D intake recommendations and is therefore challenging to develop effective public health measures relevant to the entire European population.The European Food Safety Authority (EFSA) is currently revising dietary reference intakes for vitamin D at European level. Higher, if not adequate status of vitamin D would have a positive impact on healthy growth, development and ageing for current and future generations (4). As it stands, the best advice to achieve it is to eat well, enjoy the outdoors and be active. (FM)
* Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) is a multi-centre study focussing on lifestyle and nutrition. The HELENA-CSS was performed in adolescents aged 12.5 to 17.5 years in ten European cities (Athens, Heraklion, Dortmund, Ghent, Lille, Pecs, Rome, Stockholm, Vienna and Zaragoza) between October 2006 and December 2007 (5)
** Rickets is a disorder of the skeleton affecting bone structure and growth in children, whereby cartilage fails to mature and mineralise. This results in soft bone, arched limbs and compression of bone tissue. It is associated with inadequate intakes of vitamin D and/or calcium (6).
*** Osteomalacia affects the adult population and presents when newly formed bone tissue is not mineralised appropriately. It is associated with low calcium and vitamin D intakes, resulting in increased bone resorption and reduced bone formation (6).
March– April 2014
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, Anastasia Livaniou, Tsz Ning Mak, Theodora Mouratidou, Flaminia Mussio, 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.
© European Union, 2014. Reproduction of articles (excluding photographs) is authorised, except for commercial purposes, provided that the source is mentioned.