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Fat soluble vitamins, i.e. vitamins A, D, E and K, play an important role in growth and development. Both inadequate and excessive intake of these vitamins may lead to adverse health effects.
Inadequate intake can result from an unbalanced food consumption, whereas the consumption of supplements and foods fortified with fat soluble vitamins might pose a risk for excessive vitamin intake. This study evaluates the intake of fat soluble vitamins in Belgium taking into account all sources i.e. foods, fortified foods and supplements.
A key challenge in nutrition policy is to provide the population with a sufficient level of micronutrients without risk for excessive intake. A well-balanced and healthy diet is essential for disease prevention. Fat-soluble vitamins are essential nutrients to support growth and development, bone metabolism and resistance to diseases. Both inadequate and excessive intakes might lead to adverse health effects.
In the last decades, socio-economic advances have negatively influenced the dietary patterns in industrialised countries. Energy-rich but micronutrient-poor diets are to blame for unbalanced nutrient intake and cause the onset of many chronic diseases. On the other hand, there is a concern for excessive nutrient intake due to the increased consumption of fortified foods and supplements. This is especially the case for fat-soluble vitamins, since excessive amounts are stored in the adipose tissue.
This study presents the first evaluation of fat-soluble vitamin intake in Belgium taking account of all sources:
- fortified foods
We conducted the study in the general Belgian population and 4 specific subgroups who are more vulnerable to adverse health effects of these vitamins:
- in infants
- pregnant women
- lactating women.
The evaluation of the intake of fat-soluble vitamins requires accurate food consumption and food composition data. Since fortified foods and supplements greatly influence the intake distribution of fat-soluble vitamins, it is a prerequisite to take account of these additional sources in the intake evaluation. At the onset of the study, we conducted a market research to make an inventory of the supply of supplements and foods fortified with vitamins A, D, E and K available on the Belgian market. We used these data to compile a food composition database and to develop an online food frequency questionnaire. Food consumption data of the Belgian national food consumption survey were used to evaluate the intake of fat-soluble vitamins in the general Belgian population. In addition, we collected food consumption data for the specific subgroups for the purpose of this study. The respondents were recruited in collaboration with Belgian child health consultation centers and obstetric clinics. We collected food consumption data by means of online food frequency questionnaires which were adapted to the specific diets of the target populations. The food list of these questionnaires was based on the market inventory and the top 90% food groups that contribute to the intake of fat-soluble vitamins.
The collected food consumption and food composition data allowed us to calculate the intake of fat-soluble vitamins. Vitamin E and K intake in Belgium was deemed adequate. Nonetheless, there was a risk for inadequate intakes of vitamins A and D in different subgroups of the Belgian population:
- inadequate vitamin A intake resulted from insufficient consumption of vegetables and dairy products, which are the main food sources of vitamin A.
- inadequate intake of vitamin D was related to a limited intake from fortified foods and supplements. This is especially concerning when sun-induced dermal synthesis of vitamin D is limited.
The results also showed a risk for excessive vitamin A intake from the consumption of liver(products) and a risk for excessive vitamin D intake related to the consumption of high dosed supplements.
The study revealed that current policy recommendations were insufficient to eradicate inadequate intake of fat-soluble vitamins in the Belgian population and protect the population from excessive intake.
Conclusions and policy advice
The fortification of foods with vitamin D at national level is considered an efficient strategy to improve the vitamin D status of a population. However to be effective, this fortification strategy requires a thoughtful selection of the food vehicles. An optimisation model was developed in order to select the appropriate food vehicles as well as the vitamin D fortification level that would allow for an optimal vitamin D intake within the Belgian population without compromising safety. Several fortification scenarios were deemed adequate to efficiently improve vitamin D intake but when taking account of technological and regulatory aspects and the healthiness of the food vehicles, the fortification of bread and milk was considered the most optimal scenario.
However, to optimize the vitamin D status in all subgroups of the Belgian population, consumption of vitamin D supplements will still be needed in subgroups with additional needs (such as the elderly) or subgroups with differing eating patterns (such as infants). The results of this study emphasised the importance to set uniform supplement recommendations and revise the maximum allowed concentration of vitamin D in supplements and fortified foods, taking into account the proposed fortification strategy.
Fortification with vitamin A is not recommended considering the limited benefit in vitamin A intake and the small safety margin between the recommended intake and safe upper intake level. Promoting a healthy and well-balanced diet is considered the best approach to reach adequate levels of vitamin A intake in the Belgian population. To achieve this goal, food policy actions should be directed to enable the food environments and guide consumers towards healthier food choices.
Furthermore, we evaluated the benefits and risks of current fortification and supplementation practices. The results indicate that current supplement recommendations were not safe to protect consumers from excessive intakes of fat-soluble vitamins. Also, voluntary fortification with fat-soluble vitamins was mostly applied to unhealthy foods. This emphasises the need to revise the current fortification and supplementation recommendations with respect to fat-soluble vitamins.