Vital for health
The market for dietary supplements is booming. But consumers risk being overwhelmed by innovative products, research and technical jargon without understanding the relative benefits of individual products, says Dr Michelle Jones of ADM Natural Health and Nutrition
The market for dietary supplements is booming. But consumers risk being overwhelmed by innovative products, research and technical jargon without understanding the relative benefits of individual products, says Dr Michelle Jones of ADM Natural Health and Nutrition
The market for dietary supplements and nutritional products is currently estimated to be worth around US$500bn (Euro 512bn) annually and rising.1 Yet with an increasing number of new products hitting the shelves, the sector could risk being a victim of its own success.One of the buzzwords in health and nutrition in recent years has been antioxidants. These have been credited with many seemingly unrelated beneficial effects for conditions such as stomach ulcers, infertility and symptoms of menopause. It is hardly surprising, therefore, that there is a certain level of misunderstanding and scepticism around the subject.
Antioxidants are part of the body's self-defence system against the undesirable effects of oxidative free radicals. Free radicals are highly reactive, unstable molecules that are produced by the body for use in normal biological processes but can also be present as environmental contaminants such as cigarette smoke.2 Although they are used beneficially as part of the body's normal defence mechanisms against infections, if present in excess or where the body's immune system is impaired, they may be involved in potentially harmful reactions resulting in undesirable longer-term consequences.2 As a result, free radicals have been implicated in the development of a number of degenerative conditions including heart disease, macular deterioration and a wide range of age-related disorders.3 There is a need therefore to ensure adequate levels of antioxidant vitamins and other dietary antioxidants are consumed by adopting appropriate dietary practices, which may also include supplementation with antioxidant vitamins.
The most important dietary antioxidants include the vitamins A, C and E, carotenoids and other plant-derived components (phytochemicals). One of the most popular vitamins with antioxidant capability is vitamin E; the only vitamin for which there is a chemical and biological distinction between the natural and the synthetic forms. Worldwide sales are predicted to grow by around 5% per year to reach $556m (€574m) by 2004.4 Vitamin E is a lipid-soluble antioxidant that was discovered at the University of California at Berkeley in 1922 in the laboratory of Herbert M. Evans.3 Since it is fat-soluble, vitamin E is present in areas of the body where fat-like substances predominate, such as in cell membranes. It is obtained commercially from the processing of vegetable oil crops such as soya beans, maize, rapeseed and sunflower, and is also found in small quantities in foods such as sweet potatoes, avocados and nuts. But foods with relatively high levels of vitamin E are often high in fat, making it difficult for health conscious consumers to take in adequate amounts without increasing fat intake. Supplements are an alternative solution.
The vitamin E found in nature is correctly known as RRR-α-tocopherol (commonly known as d-α-tocopherol), but other natural forms known as β-, γ- and δ-tocopherol also exist. The synthetic form is an equal mix of eight isomers and is correctly referred to as dl-α -tocopherol.
Recent studies indicate that the natural form of vitamin E is utilised by the body in preference to the synthetic form because of greater initial retention.5 What this means in practice is that natural-source vitamin E has a higher bioavailability than the synthetic alternative.
elevated cholesterol
Although the mechanisms of action for vitamin E are not yet fully understood, there is a growing body of evidence to support the benefits of its regular, long-term consumption. It is a popular subject of scientific research with interest in its potential for benefit in such diverse areas as: acne, miscarriage and muscular dystrophy.5 Atherosclerosis is one of the leading causes of death in Westernised populations6 and as such, factors contributing towards the maintenance of cardiovascular functions are of major medical interest. Elevated blood cholesterol levels, known as hypercholesterolaemia, are implicated in the aetiology of atherosclerosis. One hypothesis suggests that under conditions of 'oxidative stress' a type of cholesterol known as ldl-cholesterol, may become oxidised during the early stages of atherosclerosis development.7 This form of oxidised cholesterol may lead to the development of plaques in the artery and development of atherosclerosis.
The oxidative stress mechanism also provides an explanation of why research into higher dose supplementation with vitamin E has demonstrated benefits in relation to measures of antioxidant action under conditions of oxidative stress,6 but little or no effect when no oxidative stress is present.8 It is thought that oxidative stress may be a factor in the observed increase in progression of coronary atherosclerosis in cardiac transplant patients. Recent data from intervention studies in transplant patients who were given a mixture of antioxidant vitamins (C and E) was supportive of a benefit in maintaining vessel wall integrity in the group compared with the control group (no additional vitamin).9 Diabetic patients are also known to be at greater risk of developing premature atherothrombotic complications, and it is thought that oxidative stress may be a contributory factor to this.
There is very active current research aimed at determining whether diabetics do have higher oxidative stress compared with non-diabetic individuals, and if so, whether vitamin E can provide an 'antioxidant defence'.10-14 Results from recent research into measures of oxidative stress and into thrombotic complications in Type 2 diabetes suggest that in these patients vitamin E intake may be positively associated with improved antioxidant status and may also be beneficial in relation to markers of thrombosis status.10,12 In Type 1 diabetics, some research results are indicative of benefits from high dose vitamin E supplementation in relation to erythrocyte membrane peroxidation,13 whereas other research would suggest that Type 1 diabetics are not at risk of oxidative stress and may therefore not benefit from higher vitamin intakes.14 Clearly, this is an area where more research is needed.
There is also an increasing amount of research data to support the involvement of α-tocopherol in the functioning of a number of cellular components that are involved in the atherosclerotic process. These areas are not necessarily antioxidant in character, but involve vitamin E as an important component of certain enzyme pathways.15 Some of the degenerative conditions that develop in later life can be related to pro-oxidant action and impairment of the immune system. Through its antioxidant properties and involvement in certain enzyme pathways, vitamin E may play a role in supporting the body in its fight against these degenerative effects.
A number of interesting scientific studies investigating the effects of antioxidants including vitamin E in areas such as life expectancy16 and cognitive function in the elderly17 are currently underway in a number of research locations; positive interim results have been reported.
potential benefits
New research findings18 suggest that diets rich in vitamin E, both from foods such as sweet potatoes, avocados and nuts, and from fortified foods such as beverages and cereal bars, may help combat oxidative stress in the skin. Foods containing antioxidant ingredients, such as vitamin E, offer skin protection by helping to maintain the skin's natural defences against the damage and wrinkling that may be caused by exposure to certain UV radiation.
The potential benefits associated with antioxidants, and particularly vitamin E, are very encouraging. Research to date is positive and further study into this area will continue to increase our understanding of the effects of antioxidants in the human body.