Food supplements: Is there any scientific evidence for health claims?
For several decades now, the food industry has been offering a growing range of products claiming specific health benefits, including food supplements (DS), functional foods and super foods.
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Definition of terms
Another term often used to refer to such products is “food additives”. This is incorrect, however. Food additives, also referred to as E-numbers, are substances that are added to foods for engineering purposes, for example to extend their shelf life (preservatives) or add viscosity (thickeners).
By contrast, the products discussed below are of the kind that have, or are claimed to have, an added nutritional/physiological benefit owing to their ingredients or their very nature. Food supplements are products of no nutritional value in single-dose form (tablets, capsules, pills etc) that are enriched with vitamins, minerals or other substances. Functional foods are broadly defined as foods that in addition to providing basic nutrition possess characteristics that are claimed to have a positive long-term effect on vital physiological functions. These products are intended for use in improving bowel activity and cholesterol levels, reducing the risk of cardiovascular diseases and building stronger bones. Typical examples include probiotic dairy products or foods fortified with plant stanols or plant sterols.
Another concept that has gone mainstream in recent years is super foods. These are foods considered to be beneficial to health and well-being for the nutrients they contain by nature. They tend to be high in nutrients, whether vitamins, omega-3 fatty acids or secondary plant compounds, the latter being non-nutritional substances occurring naturally in plants. Typical examples of super foods are chia seeds, goji berries and kale.
Food safety laws vary by country and sometimes even within regions. Consumer protection is just one priority among several shared by food legislation around the globe. The example below is discussed to illustrate a case on which even scientific opinion is divided. The example refers to Swiss law and coordination with EU authorities but is representative of cases elsewhere.
On 1 May 2017, the new Foodstuffs Act (Lebensmittelgesetz) and the applicable ordinances will enter into force in Switzerland. Previously, any foods not mentioned in food safety legislation were subject to approval. Under the new act, such foods will be permitted if safe and meeting the legal requirements. Food supplements will now be governed by a separate ordinance regulating the addition of vitamins, minerals or other substances for nutritional or physiological purposes. The ordinance will also prescribe maximum levels that may be considered safe for daily intake. The term “functional food” is not explicitly regulated in law. Such products are regulated in terms of their health claims, which may be stated on product labels only if scientifically proven and approved. Any manufacturer planning to add a new type of substance never before used in foods will need to have it approved. To this end, the manufacturer will need to demonstrate that the substance is safe and suitable for use. To communicate the health benefit to consumers, the manufacturer will also need a separate permit to make health claims. Health claims for super foods, too, are subject to the regulations on health claims under the new Foodstuffs Act. A number of examples are discussed below.
At current count, more than 200 health claims are permitted under food legislation. These are claims regarding the health benefits of vitamins, minerals and certain other compounds occurring naturally in foods. They are identical to the EU claims evaluated by an EFSA scientific panel. The health benefits are deemed proven based on those evaluations. Such health claims are also subject to minimum standards. Where claims meet the legal requirements, they pose no health risk. A good example of this is one of the 15 claims permitted for vitamin C: “Vitamin C helps the immune system function normally during and after intense physical activity”. This claim may be made only for foods which deliver a daily intake of 200 mg of vitamin C. For the claim to be permissible, consumers must be informed that it is based on a daily intake of 200 mg in addition to the recommended daily dose of 80 mg.
In Switzerland, special attention is paid to the practice of iodising and fluoridating table salt. Here, permitted claims include not only health claims but also medicinal claims such as “iodine will prevent goitre if taken daily in sufficient amounts” or “fluoride prevents cavities”.
There is a growing body of scientific research that shows the links between diet, food ingredients and the positive or negative effects thereof on human health. Ingredients obtained through special manufacturing processes, such as red yeast rice or secondary plant compounds such as caffeine, synephrine, carotenoids, flavonoids, plant sterols or plant stanols, have long been the focus of scientific research and of makers of food supplements and fortified foods. The levels of secondary plant substances that typically occur in edible plants are harmless. Intake of such substances is limited by the quantity of the edible plant that can reasonably be consumed at any given time. The equation changes, however, where such substances are extracted from the plants and used in making foods or food supplements fortified with these extracts. More often than not, there is insufficient research into these substances in pure form and few if any studies on their effect, beneficial or otherwise, on health. To ascertain their safety for use, extensive intervention studies would need to be run. By extracting them from the plants, it is possible to use these substances in concentrations that by design are more consistent with pharmacologically active substances than with nutrition. As such, they generally should be considered pharmaceutical drugs. This is illustrated in a number of examples below, some positive, some negative.
Red yeast rice:
Fermentation with Monascus purpureus, a yeast, yields a red food colourant but also various pharmacologically active by-products such as monacolins, monankarines, ankalactone and citrinin. Monacolin-K is identical to lovastatin, a potent active ingredient in cholesterol-lowering prescription drugs. Citrinin is nephrotoxic, or harmful to the kidneys, and so food supplements are not permitted to contain more than 2 mg/kg of the substance. Red yeast rice is usually sold via the internet in capsule form and marketed with claims to lower cholesterol. In most cases, the fact that it is a drug and not a harmless food supplement is not made clear to consumers. Its potential side effects are those of any statin (headaches, muscle pain, etc). Regrettably, the EFSA issued a positive opinion on red yeast rice with monacolin-K, which demonstrates the limitations of assessing health claims. Although the active ingredient monacolin-K does effectively lower cholesterol, the substance per se was not assessed for its risks. In light of such risks, the health claim was not included in the list of permitted health claims in Switzerland.
Caffeine combined with synephrine:
Caffeine and synephrine are typical secondary plant ingredients. Caffeine occurs naturally in foods such as coffee, tea or guarana. Synephrine is found in citrus fruits. Food supplements which contain these substances in pure form are marketed online mainly, as combination “fat burners” and also “100% plant-based”. Often, product labels do not list these substances by name, camouflaging them instead as guarana extract combined with bitter orange extract. They boost the metabolic rate and stimulate the cardiovascular system. This can present serious health hazards such as insomnia, raised blood pressure, palpitations or even a heart attack. In some cases, certainly, the combination has been found to be fatal.
Carotenoids are responsible for the yellow to red range of colours in fruits and vegetables. Beta-carotene, lycopene and lutein are ingredients in many food supplements sold in supermarkets and online and more often than not are marketed using wildly exaggerated health claims of eliminating free radicals, boosting the immune system, protecting DNA, etc. No positive scientific opinion has been issued for beta-carotene, lycopene or lutein due to the absence of studies that demonstrate a positive effect. On the contrary, it has been shown that high doses of beta-carotene can increase the risk of developing lung cancer.
This class of substances covers a large number of plant compounds. Due to their antioxidative properties, flavonoids eliminate free radicals both in vitro and in vivo. To date, the flavonoids found in cacao are the only kind whose health benefits have been proven in an intervention study. For this reason, a health claim to this effect was approved in 2013 and 2015.
Plant sterols and plant stanols:
This class of substances is similar in structure to cholesterol and occurs mainly in vegetable oils. Studies have shown that consuming more plant sterols will lower plasma LDL cholesterol levels. The food industry has capitalised on this evidence, isolating plant sterols and plant stanols and using these to fortify a range of foods such as margarines, dairy products and other fatty foods. As mentioned above, these are typical examples of functional foods. For these products, it is permitted to claim that they are “proven to lower/reduce cholesterol. High cholesterol is a risk factor for coronary heart disease”. Functional foods are beneficial only to people whose cholesterol levels are slightly elevated. For children and pregnant women, however, or for individuals who are on medication to reduce cholesterol, these fortified foods are a health risk.
The safety of food additives is ensured in the case of vitamins, minerals, omega-3 fatty acids or secondary plant ingredients that have been assessed as safe and if they are taken in the recommended daily doses. Scientific evidence of their benefits is provided in accordance with the regulations on health claims under food safety laws. In regular food retail channels, moreover, such products are subject to random checks by the enforcement agencies and so pose no risk to consumers. Caution, however, is advised on products sold via the internet with hyperbolic health claims, whether food supplements, fortified foods or super foods. Often, products contain not only legal additives but, for profit, are laced with illegal substances that pose a serious health risk. The bottom line is that consumers should first educate themselves on any additives they may be unfamiliar with.
1. Eichholzer M, Camenzind-Frey E, Matzke A, Amadò R, Balmer PE et al. (eds.). Fünfter Schweizerischer Ernährungsbericht [Fifth Swiss nutrition report; unavailable in English]. Bern, Swiss Federal Office of Public Health, 2005.
4.Verordnung des EDI betreffend die Information über Lebensmittel (LIV) [ordinance of the Swiss Federal Department of Home Affairs regarding information on food; unavailable in German]
5. Federal Office of Consumer Protection and Food Safety, 10117 Berlin, Germany; press release of 3 January 2017: Schlankheitsmittel versprechen viel helfen aber nur wenig [weight-loss products overpromise and underdeliver; unavailable in English].
6. Commission Regulation (EU) 2015/539 of 31 March 2015 authorising a health claim made on foods, other than those referring to the reduction of disease risk and to children's development and health and amending Regulation (EU) No 432/2012