Proceedings of the Rank Forum on Vitamin D.

The Rank Forum on Vitamin D was held on 2nd and 3rd July 2009 at the University of Surrey, Guildford, UK. The workshop consisted of a series of scene-setting presentations to address the current issues and challenges concerning vitamin D and health, and included an open discussion focusing on the identification of the concentrations of serum 25-hydroxyvitamin D (25(OH)D) (a marker of vitamin D status) that may be regarded as optimal, and the implications this process may have in the setting of future dietary reference values for vitamin D in the UK. The Forum was in agreement with the fact that it is desirable for all of the population to have a serum 25(OH)D concentration above 25 nmol/l, but it discussed some uncertainty about the strength of evidence for the need to aim for substantially higher concentrations (25(OH)D concentrations>75 nmol/l). Any discussion of 'optimal' concentration of serum 25(OH)D needs to define 'optimal' with care since it is important to consider the normal distribution of requirements and the vitamin D needs for a wide range of outcomes. Current UK reference values concentrate on the requirements of particular subgroups of the population; this differs from the approaches used in other European countries where a wider range of age groups tend to be covered. With the re-emergence of rickets and the public health burden of low vitamin D status being already apparent, there is a need for urgent action from policy makers and risk managers. The Forum highlighted concerns regarding the failure of implementation of existing strategies in the UK for achieving current vitamin D recommendations.

The relationship between alpha-tocopherol and phospholipid fatty acids in rat liver subcellular membrane fractions.

(1) A method was devised for the subfractionation of normal rat liver and for the subfractionation of the mitochondrial fraction into inner and outer membrane fractions. The purity of the fractions was assessed using marker enzyme measurements. (2) alpha-Tocopherol was measured in all the fractions by a sensitive HPLC technique. Profiles of phospholipid fatty acids were also determined by gas-liquid chromatography in all the fractions, and these values were calculated in terms of the percentage of each fatty acid in the total fatty acid of the fraction, as well as of the mass of each fatty acid per mumol of phospholipid phosphorus. Tocopherol values were expressed as the mass of tocopherol per g wet liver and per mumol of phospholipid phosphorus. (3) The results show that the mitochondrial and microsomal fractions were the major tocopherol-containing fractions, and both the inner and outer mitochondrial fractions contained substantial amounts of alpha-tocopherol. (4) The mitochondrial and microsomal fractions also had the highest levels of polyunsaturated fatty acids (PUFA) in their phospholipid fraction, especially 20:4 and 22:6, which were particularly localised in the inner mitochondrial membrane fraction. The high inner mitochondrial and microsomal PUFA levels were particularly apparent when the sum of all the unsaturated fatty acids with three or more double bonds was calculated. (5) Calculation of molar ratios of of some phospholipid fatty acids to alpha-tocopherol gave values of the order of several thousand to one. (6) It is concluded that the protective effect of each molecule of alpha-tocopherol must be exerted towards a large number of molecules of membrane unsaturated fatty acids simultaneously. This perhaps implies specific localisation of tocopherol in regions of membrane particularly liable to attack, such as might be expected to occur close to respiratory enzymes that can donate electrons to molecular oxygen.

The alpha-tocopherol and phospholipid fatty acid content of rat liver subcellular membranes in vitamin E and selenium deficiency.

(1) Rats were given a diet deficient in vitamin E and selenium, or diets supplemented with either or both of these nutrients. The livers were subfractionated by standard procedures, and the purity of the fractions was assessed by marker enzyme techniques. alpha-Tocopherol was measured and profiles of phospholipid fatty acids were determined. (2) All the organelles studied were severely depleted of alpha-tocopherol in the rats deprived of vitamin E: no organelle was particularly severely depleted. There was a large rise in the alpha-tocopherol content in organelles of rats deprived of selenium but given adequate amounts of vitamin E, suggesting an increased uptake or mobilization of tocopherol to compensate for the detrimental effects of selenium deficiency. (3) The following general conclusions were reached from the results of the phospholipid fatty acid analyses. (i) vitamin E deficiency caused a consistent fall in the polyunsaturated fatty acid (PUFA) content (13-66% of the control level); (ii) selenium deficiency alone caused no consistent effect on phospholipid PUFA in the fractions studied; (iii) double deficiency of vitamin E and selenium caused a consistent rise in the proportion of PUFA in the fractions studied, ranging from 11 to 311%. (4) The result given in 3(i) is consistent with peroxidative destruction of membrane phospholipid PUFA during vitamin E deficiency. The result in 3(iii) is paradoxical: a possible explanation is that during severe disruption of antioxidant defences, there is an overshoot in the increased incorporation of unsaturated fatty acids into the membrane phospholipids, or in the chain-elongation and desaturation process required for the formation of PUFA, which may require vitamin E and/or selenium for its regulation.

Food and nutrition: attitudes, beliefs, and knowledge in the United Kingdom.

In a study of 1700 members of the UK general public in 1992 in which face-to-face interviews were conducted, factors thought important in a healthy diet were (in descending order) more fiber, less sugar, less fat, less salt, and more starchy foods. Of common nutritional terms there was most confidence in explaining the meaning of fiber and least in the meaning of monounsaturated fatty acids. Most nutritional information came from the media but the credibility of this information was low. Fifty-three percent said that a conversation with their general practitioner (GP) was a source of advice they trusted. In a survey of 150 GPs and 50 practice nurses in 1992, lack of confidence was found to be common concerning the meaning of several nutritional terms, especially extrinsic sugars, NSP (nonstarch polysaccharide), and trans fatty acids. GPs were confident they could explain the link between diet and heart disease but were not sure about the value of starch in the diet. Both GPs and practice nurses were dissatisfied with their training in nutrition, both before and after registration. General practice staff thought that personal ill health was the most important motivator for dietary change among their patients. They thought that apathy and dietary conservatism were the most common barriers to people changing their diet. However, the public positioned lack of knowledge as the biggest obstacle. Surveys reported here showed that people's knowledge of sources of fat, calcium, and iron is often unreliable.

Vitamin D: An overview of vitamin D status and intake in Europe.

In recent years, there have been reports suggesting a high prevalence of low vitamin D intakes and vitamin D deficiency or inadequate vitamin D status in Europe. Coupled with growing concern about the health risks associated with low vitamin D status, this has resulted in increased interest in the topic of vitamin D from healthcare professionals, the media and the public. Adequate vitamin D status has a key role in skeletal health. Prevention of the well-described vitamin D deficiency disorders of rickets and osteomalacia are clearly important, but there may also be an implication of low vitamin D status in bone loss, muscle weakness and falls and fragility fractures in older people, and these are highly significant public health issues in terms of morbidity, quality of life and costs to health services in Europe. Although there is no agreement on optimal plasma levels of vitamin D, it is apparent that blood 25-hydroxyvitamin D [25(OH)D] levels are often below recommended ranges for the general population and are particularly low in some subgroups of the population, such as those in institutions or who are housebound and non-Western immigrants. Reported estimates of vitamin D status within different European countries show large variation. However, comparison of studies across Europe is limited by their use of different methodologies. The prevalence of vitamin D deficiency [often defined as plasma 25(OH)D <25 nmol/l] may be more common in populations with a higher proportion of at-risk groups, and/or that have low consumption of foods rich in vitamin D (naturally rich or fortified) and low use of vitamin D supplements. The definition of an adequate or optimal vitamin D status is key in determining recommendations for a vitamin D intake that will enable satisfactory status to be maintained all year round, including the winter months. In most European countries, there seems to be a shortfall in achieving current vitamin D recommendations. An exception is Finland, where dietary survey data indicate that recent national policies that include fortification and supplementation, coupled with a high habitual intake of oil-rich fish, have resulted in an increase in vitamin D intakes, but this may not be a suitable strategy for all European populations. The ongoing standardisation of measurements in vitamin D research will facilitate a stronger evidence base on which policies can be determined. These policies may include promotion of dietary recommendations, food fortification, vitamin D supplementation and judicious sun exposure, but should take into account national, cultural and dietary habits. For European nations with supplementation policies, it is important that relevant parties ensure satisfactory uptake of these particularly in the most vulnerable groups of the population.

Nutrition and health claims: the role of food composition data.

Regulation on nutrition and health claims number (EC) No. 1924/2006 came into force in the European Union (EU) in 2007. The Regulation aims to ensure that claims are truthful and do not mislead consumers. It also aims to stimulate innovation to produce healthier food products in the food industry. Nutrition claims are defined in an annex to the Regulation that states the wording of permitted claims and the conditions of use. The scientific support for potential health claims is being assessed by the European Food Safety Authority (EFSA), but consideration of other aspects and the final decision to accept or reject a claim lies with the European Commission. The final list of approved health claims was due to be published in early 2010, but work is behind schedule, and therefore decisions are being published in batches; the first batch of Article 13 claims based on generally accepted science was published in October 2009. Food composition data are vital in making accurate claims on food as the amount of the nutrient or food component in question must be defined. It is also important that the composition of a particular food or food category has been sufficiently defined in order for a health claim pertaining to this to be approved. In addition, to prevent claims being made on foods with a less healthy profile, nutrient profiles are being developed that will specify threshold amounts of saturated fat, sodium and sugar present in any product bearing a nutrition or health claim, and thus the composition of a food will be critical in determining whether it is eligible to carry a claim. Therefore, the access that the European Food Information Resource (EuroFIR) will provide to pan-European food composition data will be of great importance in making the Regulation workable. EuroFIR has been actively involved in EFSA's work on nutrient profiles, supplying data that have been used to develop the current profiling model. It is hoped that the EuroFIR Network and the not-for-profit organisation EuroFIR AISBL (Association Internationale Sans But Lucratif, that has been established to take forward EuroFIR's work) can continue to provide guidance to stakeholders as the Regulation develops.