Dietary supplements are food products in concentrated form, e.g. as capsules or tablets, that are intended to supplement the diet. They are typically applied in times of increased nutritional needs or other circumstances in which the nutrient supply is inadequate.
The safety of these products is a high priority for the legislature in terms of consumer protection. Due to European legislation, a consumer can assume that products that are found legally in the European market and originate from reputable sources are safe.
Nevertheless, the media disseminate information on a regular basis that suggests that dietary supplements are dangerous or at least useless.
The German version of Wikipedia on "dietary supplement" or "nutraceuticals" also spread the opinion that the effectiveness is "difficult to prove" or the positive effect is "not supported by sufficient scientific evidence". Interestingly, one does not find these negative remarks in the English versions of the same terms, or the topics are at least presented in a more positive manner.
Among the goals of our professional society for nutraceuticals is the creation of clarity in the jungle of opinions on this increasingly important segment of food items. In this sense, the following remarks are intended to provide an overview.
The background of dietary supplements?
A key concept regarding dietary supplements is the following: on the one hand, the intake of nutrients can be deficient in a normal diet; on the other hand, there might be an increased need of nutrients in certain situations. In both situations, it is sensible to complement the intake of nutrients in the form of a concentrated mixture and thus compensate for a deficit or ensure optimal supply. Vitamin and mineral mixtures were the most popular forms of nutritional supplements for many years. In recent years, this range has been complemented by many other nutrient concentrates, such as fish oil products, prebiotics and probiotics , and various phytonutrients to name a few.
Dietary supplements are comprehensively regulated in Europe. For example, there are rules as to which substances are allowed in dietary supplements, what quantity of a nutrient can still be regarded as a foodstuff and therefore are differentiated from pharmaceutical products, and what advertising claims may be made for dietary supplements. Some of these regulations apply uniformly across the whole of Europe , while others (such as maximum levels) are regulated at the national level.
One of the most important aspects of legislation on dietary supplements is safety. One needs to be sure that these products have no harmful effects, even if they are taken for many years. According to our view, the legal basis for this is well developed. The result is that any products from reputable companies and sources that are approved for sale in Europe can be regarded as safe. Nonetheless, as is often the case with pharmaceutical products, dietary supplements from dubious sources may be suspect (such products are often sold via the Internet). However, this obviously does not constitute an argument against dietary supplements as such, but provides more of a reason to buy such products from reputable suppliers.
Benefits of dietary supplements
Two key questions
A key question in this context is the consideration of the amount of these nutrients that people ingest in their normal diet. Collection of such data is more complex than commonly assumed and the results of such studies must be interpreted carefully. However, there are general results from which one can draw concrete conclusions.
Some examples of critical nutrients can be found in the table to the right.
Another key question is whether there are particular population groups that do not receive enough micronutrients or which have greater needs than average. An overview of such groups can be found in the table to the left.
Isn't a normal diet enough?
A common argument against dietary supplements is that the food supply is very good nowadays and that nutritional supplements are quite unnecessary if one eats a balanced diet.
In principle, we agree with this statement. But, as one might say: "If only there was no ‘if’". In practice, however, not everyone eats a balanced diet. The real deficit lies here: the recommendations to eat at least five servings of fruit and vegetables a day or to eat saltwater fish at least once a week illustrate the problem. Surveys show quite clearly that only a small percentage of the population actually follows these recommendations, in spite of campaigns that have been running for decades such as “five-a-day”.
This discrepancy between dietary recommendations and people’s actual dietary habits is the reason for the insufficient intake and the existence of population groups at risk.
Sensible dietary supplements
From the facts presented so far the following consequences have been derived with regard to the question of useful dietary supplementation:
On the one hand, there are those nutrients that are regarded as being generally useful, and on the other hand, there are nutrients that, based on scientific findings, can be recommended for specific groups or situations.
Wide use of iodine (in most countries covered with iodised table salt), folic acid, vitamin D, omega 3 fatty acids (fish oil and other sources) and also to some extent fruit and vegetable concentrates appears to be justified.
For certain situations and specific target groups, minerals such as calcium, magnesium, iron, zinc and possibly selenium may be useful.
An often-discussed topic is supplementation with so called antioxidants, that protect against aggressive oxygen radicals. Vitamins A, C, and E are known for their antioxidant effect, but fruits and vegetables with their additional countless phytochemicals are particularly rich in antioxidants.
There is also valid scientific evidence for interesting substances such as pre- and probiotics, glucosamine and chondroitin, certain amino acids, plant sterols and stanols, and certain fibres.
This list provides a few important examples, and is not intended to be comprehensive.
A differentiated approach to food supplements
A question of quantity
Generally, certain rules have to be followed with dietary supplements, otherwise negative effects may occur. This applies to almost everything we may take in. As Paracelsus said centuries ago: "It is the dose that makes things poisonous" . It is well known that certain vitamins can even have exactly the opposite effect at high doses . For example, studies of smokers who were given high quantities of beta-carotene showed that the risk of cancer in
creased rather than decreased.
Establishment of so-called "tolerable upper intake levels" (UL) for vitamins and minerals is important in this context. A UL means daily quantities that can be consumed regularly without any risk of harm (see table).
These ULs are not suitable for determining the amount of a nutrient in a dietary supplement, but only provide an indication which quantities of nutrients should not be exceeded per day. These levels, however, are so high that it is difficult to exceed them by taking dietary supplements as defined above.
In this connection we would like to mention foods that are fortified with vitamins and minerals. By consuming these kinds of foods (like fortified juices, breakfast cereals, etc.) on a regular basis and in high amounts one may easily lose oversight of the nutrients ingested. Here dietary supplements with clearly defined amounts of nutrients have certain advantages.
Nutrients in nature are hardly ever found in isolated form
A problem, which has already been addressed above, is the administration of single nutrients. This is the usual practice in medicine and pharmaceutical research, where one normally combats diseases with single substances. It was thought that this principle could also be used with nutrients, a
nd major vitamin trials were planned and conducted accordingly. It was reasoned that a diet rich in fruit and vegetables could reduce the risk of certain diseases. Blood tests also showed that people with high blood levels of certain substances, such as beta-carotene, were less likely to suffer from these diseases. The "logical" thing to do was to administer beta-carotene at higher doses, according to the motto "The more, the better", in the hope of achieving the same effect, but the result of this is well known by now (see above).
We now know that this approach does not work and the interrelationships between biological systems are much more complex than imagined at the time. Nevertheless, we currently see a somewhat similar "logic", not with vitamins, but with phytochemicals. Products containing phytochemicals are derived from sources such as green tea, grapes etc. and are sold as "botanicals". As used to be the case with vitamins, they are given at doses much higher than would ever be reached in a normal diet. This can be problematic, especially when highly concentrated extracts and high doses of single compounds are involved. Comprehensive safety information on these substances is not yet available, so it is difficult to estimate possible effects. However, several individual reports of adverse effects are already under discussion.
How good are synthetic nutrients?
There is no single answer to this question. In some vitamins (such as vitamin C) there is virtually no chemical difference between the synthetic and natural forms, so that their effects are essentially identical. But we have to keep in mind that in nature these vitamins are always accompanied by other substances that have synergistic effects.
However, the situation with vitamin E is quite different. Vitamin E is not a substance with just a single unique structure. For example, the synthetic vitamin E that was used in large trials was a mixture of left- and right-handed forms ; however, in nature it only occurs as the right-handed form . The question is: what does the body do with the form that it cannot use? There is no clear answer to this question, and some critics suggest that it could be harmful. More recently, it has become possible to synthesise the naturally occurring form of vitamin E, and most commercial products only contain this form.
Another issue is that vitamin E occurs naturally not only as alpha-tocopherol, but also as beta, gamma and delta forms. And in addition to tocopherols, there are also tocotrienols (and even other versions) - again in four different forms. This means that vitamin E occurs naturally in at least 16 different forms, although only one of these is present in most dietary supplements. It is obvious that the natural forms are preferable, and the trend is to use these forms .
Representation in the media
As regards the alleged "danger" of dietary supplements
It may sound surprising, but recurring media reports instill the belief that food supplements are associated with health risks.
The starting point for many (if not all) media reports on the dangers of supplements is that the major vitamin trials have, for the most part, produced disappointing results, and even evidence of harmful effects in some cases. Without exception, the media reports always refer to the same vitamin trials. However, the inexperienced reader is given the impression that these are new scientific discoveries.
Scientific research is, however, very complex, and in the vast majority of cases is not differentiated and presented in a balanced way by the press. Therefore, we would like to list some points that question the validity of many studies on dietary supplements:
- Studies that were carried out on people who were ill or at high health risk (e.g. smokers and asbestos workers) cannot be regarded as trials of preventive measures. The results cannot be transferred to the healthy population.
- Most of the studies used isolated micronutrients, such as individual vitamins. However, in nature these substances are found in combination with many other vitamins and nutrients. It is now known that the interaction of nutrients contributes significantly to their health benefits .
- It must be made clear that in many studies the vitamins were often given in very high doses. The amounts often exceeded what would be usually ingested with a healthy diet (see above "A question of quantity"). ((Link setzen))
In this context, it is striking that even positive results are presented in a uniformly negative way. An example is the SU.VI.MAX study, carried out in over 13,000 adults in France , which showed that by taking a combination of vitamins and minerals men had a reduced risk of cancer by 31% while the overall mortality rate was reduced by 37% after 7.5 years of intake. However, more often than not, reports only mentioned that there was no effect in women. For this reason the study was mostly represented by the media in a negative way. The explanation of this result is relatively simple:
the measured output values of nutrients were significantly higher among women. They were even on the level that the men reached only after supplementation. Therefore, an increase in nutrients would have no further effect among female participants.
The statement that dietary supplements are superfluous or even harmful is therefore untenable. When micronutrients are in short supply, as is often the case in the European population, dietary supplements may have important health benefits.
As regards the alleged uselessness of supplements
We have already shown (above) that dietary supplements are beneficial if used properly.
Scientific opinions from the European Food Safety Authority (EFSA) have provided negative headlines on food products. As part of new legislation for the promotion of food products within the European Union , the EFSA has received the task to provide scientific assessments on many food products, including dietary supplements. Of the thousands of applications submitted regarding health claims, 70-80% were rejected by the EFSA due to negative assessments. The EFSA did not consider in these cases that a corresponding health benefit would be demonstrated by taking these nutrients. This unfortunately leads to the conclusion of the general uselessness of dietary supplements. This is a fallacy for the following reasons:
- These applications are for a very large number of food products and nutrients; only some of these are dietary supplements.
- In fact, the vitamins and minerals that get most of the headlines received the most positive assessments by EFSA.
- Many of the EFSA‘s negative opinions are not shared at all by distinguished scientists, so they are clearly contrary to some well-established expert opinions.
- Many applications were rejected on purely formal errors and not due to lack of benefit.
- It is also important to note that studies conducted on people with pre-existing health problems were not approved for the assessment. The target group of the regulation is the healthy general population. But a very important target group for dietary supplements is also people with health problems, such as those with chronic disease.
In a nutshell
Our answer to all the critical Press statements can be summarised as follows:
dietary supplements that contain single and isolated nutrients and are ingested in high doses should be regarded skeptically. The negative media reports refer almost exclusively to these types of products. However, it is negligent to question the benefits of dietary supplements or to present them as harmful on account of false conclusions and individual questionable examples.
In sharp contrast to a one-sided negative view of dietary supplements is the opinion of the Harvard School of Public Health, one of the world's most prestigious University Institute on Public Health: "A daily multivitamin is a good ‘nutrition insurance policy’. Some extra vitamin D may add an extra health boost" . Based on scientific data we can fully agree with this opinion. In addition, however, a detailed and differentiated approach in the individual case is necessary.
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