The German National Nutrition Survey II (Nationale Verzehrsstudie II, NVS II) provides representative data of the vitamin and mineral supply in Germany. The 2012 Nutrition Report presents results of a new NVS II data assessment method (1). These results are usually presented in a summarised form giving the impression the German population is well supplied with vitamins and minerals.
This article critically scrutinises the interpretation of these assessment results, among other things the evaluation based on the statistical value ‘median’ and the resulting conclusions.
The nutrition survey determined the current food consumption by two 24-hours recalls. On two consecutive days 13,753 participants (men and women between 15 and 80 years of age) were surveyed in detail by telephone about their total food consumption of the last 24 hours. The nutrient intake was calculated on the basis of the current version of the German Nutrient Food Code and Data Base (Bundeslebensmittelschlüssel, BLS, version 3.02) (2). Afterwards, the detected nutrient intake of the participants was compared with D-A-CH Reference Values for Nutrient Intake established by the nutrition associations in Germany, Austria and Switzerland (3).
The median intake of vitamins and nutrients in men is higher than in women; only the intake of vitamin C is equal. In both men and women, the median intake of the reviewed nutrients is higher in the age groups 25 to < 65 years compared to younger and older age groups. Compared to D-A-CH reference values, the median intake of vitamins A, B1, B2 and B6 in both sexes falls within the range of D-A-CH reference values or exceeds them. The intake of vitamin B12 and niacin in men and women is significantly higher than the respective reference values. In contrast, both sexes approximately obtain the recommended median vitamin C intake. The median intake of vitamin E and folate is significantly lower than the reference values. Vitamin E equivalents are usually calculated to assess the vitamin E intake since different vitamin E compounds have varying levels of physiological efficacy as vitamin E. Vitamin E equivalents of the BLS are currently being compiled mainly based on ?-tocopherol and without consideration of other vitamin E compounds. Therefore, the calculated values represent a significant underestimation of actual vitamin E intake. Since dietary vitamin D intake through habitual diet covers only a small amount of the total vitamin D supply, the intake data are not suitable to determine its supply by comparison with D-A-CH reference values. Both men and women do not obtain the reference value for calcium, especially its intake in adolescents and seniors is significantly lower than the reference value. While men reach the reference value for iron, the intake in women is significantly lower. Especially young women reach only half of the recommended intake. Iodine intake in men and women falls significantly below of the reference value. However, salt iodisation and foods produced from or with iodised salt are not considered by the NVS II. In contrast, the recommended zinc intake is met in both men and women.
For the majority of vitamins and minerals, the median intake levels fall within the range of D-A-CH reference values. Exceptions include folate, calcium and iodine plus iron in women (see figure 1).
The intake of vitamins and minerals (except vitamin C) in men is higher compared to women. This can be explained by the higher food consumption of men. Energy and nutrient intake is influenced by the social status. The upper class shows a slightly higher energy and nutrient intake than the middle and working classes, which can be explained by their favourable choice of food. Nevertheless, in upper class the intake of folate, calcium and iodine as well as iron in women is also critically low. Neither men nor women reach the recommended folate intake. Men obtain 52 % and women 46 % of the recommended intake value. Regarding these results of nutrient intake, it must be considered that the vitamin and nutrient intake from supplements is not included. Furthermore, the status or rather the actual fulfillment nutrient demand of participants cannot be identified from these results of nutrient intake. Therefore, biochemical parameters in blood and urine tests have to be analysed. Values lower than the D-A-CH reference values allow no conclusions to be drawn about a nutrient deficiency because the reference values are derived in a way that the demand of approximately 98 % of the particular population is met or rather that a sufficient supply is given (1).
Regarding this new assessment of vitamin and mineral intake in Germany above mentioned, the German Nutrition Society (Deutsche Gesellschaft für Ernährung, DGE) determines that the median intake of most vitamins and minerals falls within the range of the reference values except folate, calcium and iodine plus iron in women. Here, the average intake levels (based on the statistical value ‘median’) are compared to the recommended intake levels. To qualify the assessment, one must be aware of the nature of the compared values. The intake levels recommended in the reference values for nutrient intake ensure an adequate nutrient supply among almost all people (about 98 %) of a healthy population. Healthy individuals whose intake meets these recommendations are, therefore, adequately supplied with approximately 98 % probability. Individuals who do not reach the recommended intake are not necessarily undersupplied. The likelihood to meet their individual nutrient requirement, however, decreases when their level is lower than the recommended value.
The median is a mean for distributions in statistics. In general, the median is a numerical value separating the higher half of a data sample, a range of values or a distribution, from the lower half at which the median is the middle value.
A comparison of mean intake levels (median = 50th percentile) with recommended intake levels (98th percentile) has only a limited value regarding groups of people as, in fact, only equal percentiles may be compared with each other (4).
The chosen diagrams in the figures of the 2012 Nutrition Report suggest only visually that the intake levels of most nutrients and vitamins are met or even exceeded. For example, the median of vitamin C meets exactly the reference value. This means that 50 % of people lie below and 50 % above the value. The method chosen here is not suitable for an accurate assessment of an individual vitamin and nutrient supply. Hence, a vitamin C supply may also be insufficient among individual cases and also among groups of people. If the actual median intake, as in the case of folate, falls already significantly below of the reference levels, it concerns both men and women and all age groups. Then, approximately 90 % of men and women of older age do not reach the recommended intake levels (5). Consequently, the comparison presented here may at the best give direction for a supply assessment. Statements such as “basically everybody is well supplied” or “vitamin deficiency – not in Germany“ published in the media are based on too simple conclusions. Compared to former nutrition surveys, not more than a tendency towards a balanced diet may be documented in this case. The nutrient supply of the population assessed on the basis of recommendations of the DGE for an optimal diet is not satisfying (6). And the diagrams containing a completely unsuitable scale must be regarded in this context as highly misleading.
To assess what supplements contribute to the nutrient intake, the intake of individual nutrients was observed in people who take the respective nutrient supplement – calculated on the basis of BLS version 3.02. People are indicated as supplement users if they reported having used a supplement in at least one of the 24-hours recalls. During the survey no differences were made between food supplements or medicinal products containing nutrition, which are in part only available on prescription or in pharmacy. The calculation of nutrient intake from supplements is carried out by means of a supplement data base containing about 2,700 supplements maintained by the Max Rubner-Institut (MRI), the Federal Research Institute of Nutrition and Food in Germany (7). The percentage of people who used supplements on one of the days of the survey is 24.3 %. Both men and women taking nutritional and vitamin supplements in combination reach the highest percentage. Men and women most commonly use vitamin C and E supplements. And magnesium and calcium are the most commonly used minerals. Women prefer these nutrients more than men.
The median intake levels of supplement users meet or rather exceed the respective D-A-CH reference value for almost all nutrients received from foods and supplements (except iodine) (see figure 2).
Referring to the respective D-A-CH reference value, the nutrient intake from foods and supplements ranges between 103 % (men) and 105 % (women) regarding calcium and 377% (men) and 337% (women) regarding potassium. Potassium, however, is thereby basically supplied from foods. The total median intake of vitamins B1, B2 and B6 as well as vitamin C is about double the D-A-CH reference value, for niacin it is three-times higher. The dietary intake of folate usually lies lower than the D-A-CH reference value, but an additional folate intake from supplements results in a total nutrient intake above the D-A-CH reference value in both men and women. The dietary intake of calcium (men, women) and iron (women) also is lower than the recommended value, but increases by taking supplements so that men and women meet (calcium) or exceed (iron) the D-A-CH reference values. The median dietary intake of vitamin E in combination with supplements lies above the reference value. Men exceed the value by 60 % and women by 72%. In this context it must be considered that the calculated dietary intake values of vitamin E present a significant underestimation of the actual vitamin E intake. Men and women using supplements containing iodine reach a total intake of 151 mg/day and 160 mg/day, respectively. These values are, however lower than the corresponding D-A-CH reference value. The median dietary intake of vitamins B1, B2, B6 and B12 as well as niacin, potassium, magnesium and zinc in supplement users already falls within the range of the D-A-CH reference values. In addition, men reach the recommended value for iron and women the recommended value for vitamin A (1).
The new assessment method NVS II clearly shows that a habitual diet does not prevent nutrient shortfalls of folate, calcium and iodine as well as iron in women. These can be covered by food supplements.
The assessment also shows that people with a good nutrient supply achieved through a balanced diet very often use food supplements. These people may significantly exceed the recommended levels of vitamins and minerals. However, as this assessment includes not only food supplements but also medicinal products with often higher dosed nutrient levels used in medical conditions, the actual intake level through food supplements is lower.
The European Food Safety Authority (EFSA) specified the Tolerable Upper Intake Levels (UL) for vitamins and minerals (8). Only a small percentage of supplement users exceed the tolerable upper intake level of most nutrients, however, a higher percentage exceeds the corresponding level for vitamin A and magnesium (by 12.7 % and 15.7 %) (see table 1). It has to be advised against uncontrolled supplementation. But the term “oversupply” must be clarified first.
Based on a NOAEL (No Observed Adverse Effect Level) of 250 mg magnesium per day and an uncertainty factor of 1.0, an UL of 250 mg magnesium per day can be established for readily dissociable magnesium salts (e.g. chloride, sulphate, aspartate, lactate) and compounds like magnesium oxide in nutritient supplements, water or added to food and beverages. This UL does not include magnesium normally present in food and beverages. An uncertainty factor of 1.0 is justified in view of the fact that data are available from many human studies involving a large number of subjects from a spectrum of groups in different stages of life including adults, pregnant and lactating women and children. In addition, the NOAEL is based on a mild, transient laxative effect without pathological sequelae, which is readily reversible and for which considerable adaptation can be developed within a few days (8). Exceeding the level of 250 mg of magnesium does not present any health risk, only mild indigestions may occur. Usually, it is indicated on the package of high-dose food supplements.
The recommended vitamin A intake almost meets the corresponding UL. According to the Federal Institute of Risk Assessment in Germany (Bundesinstitut für Risikobewertung, BfR), there is a significant health risk of adverse effects associated with the use of food supplements. Among various age groups the 97.5 percentile of retinol intake lies above the UL. Furthermore, evidence from various studies must be taken seriously which indicates that excessive dietary or supplemented vitamin A intake may reduce bone mineral density. However, there is no literature reference of hypervitaminosis A in Germany (9).The high vitamin A intake must be examined critically, because beta-carotene (provitamin A), the precursor to vitamin A, is usually used in food supplements and not retinol, retinyl acetate or retinyl palmitate. The NVS II does not differentiate between vitamin A and beta-carotene. Those retinol equivalents in terms of beta-carotene in food supplements are stated as vitamin A or retinol equivalent in the nutrition table/dietary table according to the regulation for food supplements. This is relevant insofar as the Scientific Committee of Food (SCF) explicitly excluded carotenoids (including beta-carotene) when determining the UL of 3,000 µg RE (in terms of retinol or retinyl esters), stating that: “The toxicity of carotenoids differs from that of retinoids, and the risks of high intakes of carotenoids are not linked to the adverse effects of retinoids.” (10) It is not evident whether these facts were considered in the NVS II when assessing the exceeding of the tolerable upper intake levels of vitamin A.
The results show that the recommended folate intake in the majority of individuals is not attained through diet alone. This applies to the general population. It is especially important for pregnant and lactating women or those who could become pregnant. The DGE strongly recommends that women who could or want to become pregnant should, in addition to consuming dietary folate, take a folate supplement of 400 µg per day (3). Folate may not only prevent serious foetal malformations, it has also, beyond its actual nutrient efficacy, health benefits for all people (e.g. decrease of homocysteine level) (11). So, higher folate levels exceeding the real nutritional basic function also benefit preventive effects. An excess of 100 % of the recommended level is not equivalent to an overdose, not to mention health risk. The highest level which should possibly not be exceeded is 1,000 µg of folate per day (8, 12).
Current scientific findings suggest that low folate levels may decrease and high doses may increase the risk of cancer development. The last conclusion arose in recent studies in which the cancer growth increased in patients suffering from colorectal cancer taking unphysiologically high doses of 1,000 µg folate (13). However, these results do not apply to healthy individuals and the suboptimal folate supply in Germany. Nevertheless, folate has its advantages and disadvantages. On the one hand, most of the German population is undersupplied with folate and deficiency during pregnancy may cause serious foetal malformations. On the other hand, a too high intake may be risky in individual cases. The folate intake from food supplements up to 400 µg (plus intake through habitual diet) is far below the theoretical risky levels. So, there is definitely no health risk at such dose. Following consultation with a doctor, pregnant women are also recommended to take iodide and iron supplements.
Another example for an appropriate supplementation is vitamin D. Especially in winter, there is a greater need for taking a vitamin D supplement in elderly. Results of a dietary survey showed that more than a half of seniors living in nursing homes did not reach the reference value of vitamin D (14). In Germany over 60 % of the population has a vitamin D deficiency and up to 80 % residents in nursing homes (15).
When aging an insufficient supply of vitamin B12 through diet becomes of particular importance. Due to the fact that there is no deficiency of alimentary vitamin B12, as an insufficient production of gastric juice and intrinsic factor (IF) secretion, often caused by gastritis and by medicines reducing the vitamin B12 absorption, was not taken into account for a long time. It may be concluded that up to 43 % of elderly are deficient in vitamin B12 (16).
The use of food supplements may be appropriate for people with intensive physical activities (sports), one-sided diets (such as a vegan diet), long-term weight reduction diets as well as chronic, heavy alcohol or tobacco use.
The NVS II concludes that nutrient supply shall be assessed on an individual basis. An appropriate intake of individually chosen substances in an adequate dose should be taken greater account when using food supplements.
erschienen in: Agro FOOD Industry Hi Tech, March/April 2014, pp. 50-53