Hannelore Daniel, PhD, Research Center for Nutrition and Food Sciences, Technische Universität München, Germany
“The uncertainties surrounding what quantities of vitamins should be consumed by an individual to promote optimal health are reflected, for example, in the dietary recom-mendations for vitamin intake provided by various national bodies and scientific com-mittees. Most interestingly, for some vitamins, the recommendations may vary up to 2.5-fold even between European countries with similar socioeconomic status. This is one of the results of a new review comparing mean dietary vitamin intakes based on food consumption data across a variety of countries. Based on their analysis of food intake data from the USA, the UK, the Netherlands and Germany the researchers came to the conclusion that the majority of consumers did not meet the recommended intakes. This gap is most pronounced for the fat-soluble vitamins and folate, and to a lesser extent for vitamin C. Of course, not reaching the recommended intake of a vitamin does not mean that there is a vitamin deficiency, as the recommendations always have a statistically defined safety margin. The key question of course, is whether this situation is something to worry about, and so to start campaigns to encourage increased vitamin intake, or whether we need to reassess the recommendations.
The assessment of food intake only provides a rough estimate of nutrient intake and this approach is beco-ming even more imprecise with an increasing spectrum of food items including products that contain extra vitamins which provide additional health benefits. In addition, supplement use is a critical factor, but the frequency of use is different in various population groups. For example, consumers who already enjoy a healthy diet tend to take supplements more frequently than those on a poor diet, who would actually benefit most from supplementation. It is also known that more women than men take supplements. So, diversifi-cation of lifestyles as well as the growing portfolio of food products makes dietary intake assessment more difficult than ever before.
The vitamin requirements of an individual are largely unknown and may depend on a plethora of factors such as diet, physical activity, time spent outdoors, age, smoking history, medication and very likely numerous other parameters. What has become obvious in the last decade is that variation in genes involved in vitamin absorption, distribution, metabolism and function also affects vitamin status. For example, a substantial amount of vitamin A in an average diet derives from beta-carotene. It has been found that genetic variations (polymorphisms) of a certain gene influence enzyme activity with subsequent effects on the conversion rate of dietary beta-carotene to vitamin A (2). Other examples for a genetic contribution are related to vitamin D metabolism (3), folate status and disease risk (4) and vitamin C status (5). Some of the reported polymor-phisms are quite frequent in the population, and it is possible that their presence has compromised earlier studies on vitamin supplementation which could not demonstrate a benefit for, or even worse, reported increased incidences of disease in the treatment groups. Thus, beyond the dietary intake of vitamins, genetic variation contributes to vitamin absorption, distribution, metabolism, status and function. In addition, at least for some vitamins, the gut microbiota may also contribute to the host vitamin status (6). Despite the fact that research in this area is booming, there are no recent efforts to validate and quantify the contribution of intes-tinal microbiota, for example, to vitamin synthesis or host metabolism.
Whereas in developing countries vitamin deficiencies are still a relevant cause for disease, developed socie-ties face the problem that diversification of lifestyles may create some subgroups at risk of intakes excee-ding safe levels while other subgroups may not meet the recommended values. This new study (1) will hopefully fuel new discussions on how much of each vitamin is really needed and how we can provide it. As population-based assessment methods and fortification trials may not be very helpful in this respect, we need to assess vitamin status at the individual level, an approach that is essential to supporting develop-ments in personalized medicine and nutrition. This is of course not trivial. For some vitamins, we still lack proper biomarkers that reflect status. However, the life sciences offer a plethora of new technologies and smart devices that can be used to analyze blood cells, plasma, urine or other bodily fluids and samples for defining new relevant biomarkers. So, let us revitalize the research on vitamins toward a second ‘golden age’ of nutritional science.“
Based on: Jürgen Stolz and Hannelore Daniel. A celebration of 100 years of vitamin research but time to revitalise the science. British Journal of Nutrition. 2012; 108(4):574–576.