Vitamin E: the natural difference
Vitamin E is unique amongst the vitamins as the usual synthetic form is different from the natural product, and this has an effect on the vitamin's biological activity
Vitamin E is unique amongst the vitamins as the usual synthetic form is different from the natural product, and this has an effect on the vitamin's biological activity
Synthetic and naturally-sourced vitamin E are not always chemically identical. It is the only vitamin which has a chemical and biological distinction between the natural and synthetic versions.
Recent consensus indicates that natural vitamin E is utilised by the body in preference to the synthetic isomers. In practice, this is seen as a more effective initial retention of natural vitamin E over the synthetic forms and, with time, by the presence of a consistently higher natural to synthetic ratio in many body tissues. What this means is that natural-sourced vitamin E has a higher bioavailability than synthetic.1 Also, with increasing consumer preference for naturally-derived foods, natural-source vitamin E is ideally placed to meet current consumer expectations.
Natural source vitamin E (D-α-tocopherol) is derived from vegetable oils, primarily from soya beans, corn, rapeseed and sunflower. The vitamin E found in nature is exclusively the RRR isomer, but the β, γ and δ-forms also exist.
Natural vitamin E is a single stereoisomer of tocopherol, but chemically-manufactured vitamin E (DL-α-tocopherol) is a mixture of eight diastereoisomers in equal proportions. Only one of these, i.e. 12.5% of the total mixture, is the same isomer as the natural product. The other seven isomers have lower biological activities.
There are four naturally-occurring tocopherols: α,β, γ and δ, usually referred to collectively as mixed tocopherols. α-Tocopherol is by far the main type of vitamin E found in the human body. Natural-source vitamin E capsules generally contain D-α-tocopherol and/or mixed tocopherols.
In the US, the Institute of Medicine (IOM) recommended recently that, for dietary purposes, vitamin E activity should be expressed as mg of D-α-tocopherol.1 However, commercial products are required by US law to be labelled in IU. IUs, recognised by the food chemicals codex, refer to the activity of the α-tocopherol form of vitamin E in pregnant rodents. While β, γ and δ-tocopherols carry significantly less IU activity, there is emerging evidence to suggest that they may confer additional health benefits.
The stereochemical differences between the different forms of vitamin E affect how it is treated by the body and, in turn, its biological availability. Numerous studies support the following differences between the two:
While not a revolutionary new discovery, increased scientific and media attention has led to vitamin E continuing to strengthen its appeal to health-conscious and proactive consumers in many countries around the world.
However, given the many differences in culture and traditional healthcare practice, the task of actually communicating the benefits of vitamin E to a European audience remains complex. The Spanish and Italians, for example, continue to rely on the advice of physicians for healthcare advice, whereas in the UK there is a growning trend towards developing a similar mass-market for vitamins and minerals to that seen in the US. There are currently widely-differing national regulations but within the European Union the process of harmonisation relating to vitamins and minerals is under way.
In terms of raising consumer awareness, the recent publication of a report from the US Institute of Medicine1 served an important dual purpose. Firstly, the report highlighted the many potential health benefits associated with higher intakes of vitamin E, such as helping to maintain cardiovascular health and supporting the immune system. Secondly, and perhaps more significantly, the report was the first to give scientific recognition to the difference in bioavailability between the natural and the synthetic forms.
This was the first time that a scientific consensus had concluded that there is a 2:1 difference in activity between natural vitamin E, listed on labels as D-a-tocopherols, and the synthetic DL-a-tocopherol.
Understanding how consumers perceive vitamin E and the reasons for supplemental incorporation into their diets are key areas of interest to many manufacturers. A study carried out by C&R Research8 provides a valuable insight in to consumer attitudes towards vitamin E. In terms of serious disease, the findings of this survey showed that the majority of interviewees took vitamin E for its health-promoting benefits in areas relating to heart disease, cancer and brain-functioning diseases such as Alzheimer's.
However, when it comes to identifying the difference between natural and synthetic vitamin E, many consumers are not familiar with the correct terminology and as a result may assume that they are taking natural when, in reality, it is synthetic. It is this specific communication that formed the focus of a high-profile, promotional test market campaign carried out in Chicago, IL, US, initiated by ADM in conjunction with Walgreens and GNC stores.
The campaign specifically focused on promoting the D-a (natural source) terminology and the difference in bioavailability between the natural and synthetic forms. Consumer research carried out prior to the campaign showed a clear lack of understanding; only 6.3% of respondents specifically looked for D-a on the ingredients label to ensure purchase of natural source vitamin E. However, of those who did buy the natural form, 39.4% mentioned that 'natural vitamin E is more effective than synthetic'. ADM reported a 20% increase in volume sales of its natural-source vitamin E as a direct result of this test market promotion.
In order to obtain the optimum health benefits associated with vitamin E, intakes in the range 200 and 800IU/day have been suggested.9 However, it is almost impossible to consume this amount from dietary sources alone. Additionally, foods containing relatively high levels of vitamin E are also high in fat, making it difficult for the health-conscious consumer to take in higher amounts without increasing fat intake. Supplements are therefore a very practical alternative.
Any form of vitamin E is beneficial but the argument for natural-source vitamin E in terms of bioavailability is becoming stronger as the amount of supporting evidence continues to increase.