Radical action

Related tags Antioxidant Apple

Every supplement worth its salt is packed with antioxidants, but will popping pills really keep cancer at bay? Paul Hart reports

Antioxidants are currently under scrutiny as a panacea for health, vitality and anti-ageing: but the generalised ORAC (Oxygen Radical Absorbance Capacity) approach to them is being superseded by an interest in compounds with specific physiological effects.

Many dietary supplements and functional foods are presented to consumers for their claimed potential antioxidant (AOX) activity - and doctors advise plentiful fruit and vegetable consumption in order to increase intake of antioxidants - but how are they beneficial to health and where can you find them?

Oxidative disease theory

Highly reactive free radicals, or reactive oxygen species (ROS), are by-products of normal cell metabolism and their production is accelerated in inflamed tissue, or during sport. ROS are unstable: capable of reacting with DNA; oxidising protein and initiating lipid peroxidation in membranes; and degrading complex polysaccharides in joints.

Long-term cumulative oxidative damage, if unrepaired, is considered to be an important factor for chronic diseases such as arteriosclerosis, arthritis, cataracts and age-related macular degeneration; and is thought to be responsible for the deterioration in health often associated with ageing.

Other environmental factors which increase oxidative stress, include exposure to cigarette smoke; pollutants; ionising radiation (sunshine); and over eating.

In healthy individuals, the body's antioxidant systems counteract the effects of free radicals by halting disruption and repairing damage. But studies have shown that its natural defences may be swamped if, for example, a diet low in essential antioxidants or low in plant antioxidants is followed. And it is thought certain plant antioxidants may lower the risk of cardiovascular disease by reducing arterial wall LDL (low density lipoprotein) oxidation; or reduce the risk of embolism by inhibiting initial platelet aggregation.

While epidaemiology provides evidence of association, the ultimate goal is to demonstrate cause and effect via antioxidant rich extracts, in controlled long-term clinical trials.

Essential ACE AntiOxidants

Essential antioxidants include the vitamins A, C and E and minerals; all important factors for the proper function of antioxidant systems. These small molecules are all readily absorbed and act at the cellular or enzymic level. Vitamin A, or carotene, chiefly provides the light-sensitive pigment in the retina. However, taking supplements over and above the RDA (recommended daily allowance) has not been found protective and as it can even indicate an increase in mortality, the UK Food Standards Agency's suggested upper level has been set at 7 mg/day.

Vitamin C, obtained from citrus fruits, has a varied RDA. In the US it is 90mg, whereas in the UK it is 40mg, indicating that establishing intake levels, beyond a minimum, is not a simple matter.

The primary function of Vitamin E is to prevent oxidation of polyunsaturated fatty acids and low-density lipoprotein. Antioxidant minerals include selenium and zinc, which is contained within the key free radical disposing enzyme (superoxide dismutase).

However, antioxidant supplements to reduce the risk of cancer or heart disease have demonstrated little evidence of long-term protection or increased life expectancy in well nourished populations. An article in New Scientist (August 2006: Issue 2563) headlined: The Antioxidant Myth: a Medical Fairy Tale was largely critical of claims made about supplements - which are no substitute for a diet rich in fruit and vegetables.

Super fruits:

It began with blueberries, last year it was pomegranates, and this year it's the turn of açai. Juices, smoothies, marketing hype, via lifestyle supplements, all provide considerable goodwill for antioxidant intake. Consumers are encouraged to imbibe new, exotic fruits - never mind the food miles.

Açai is rich in antioxidants, essential omega-3 and 6 fatty acids and minerals. Pulp from the palms arrives as thick slurry, therefore dilution is inevitable.

Typical usage levels are less than 20%, so despite large front-of-pack billing suggesting the contrary, overall antioxidant levels depend largely on the base juice (grape, apple).

ORAC values are frequently cited by ingredients suppliers for the fruit or extract - and small companies may lack resources to translate these into a meaningful value per portion.

With the emphasis on clear labelling, surely this should be attended to right away? Prunes may lack sex appeal, but have a very good ORAC score - drying may serve to enrich dry-weight value, but dried prunes have no more antioxidant than the plums from which they were dried!

However, water-soluble flavonols are more readily absorbed than very highly polymerised dark polyphenols.

Tea offers a regular intake of polyphenols, though green tea is much richer than the standard black variety.

Cranberries have also long been associated with health benefits. Cranberry proanthocyanidin is uniquely structured and acts as an anti-adhesion component which prevents bacteria attaching where infections may develop, for example in the urinary tract. They also contain a high proportion of antioxidants.

The French food safety authority (AFSSA) has approved a claim that states: cranberry powder and juice 'helps reduce the adhesion of certain E-coli bacteria to urinary tract walls'.

Ocean Spray reckons two 8oz juice servings is a sufficient regular intake for this benefit. CPC Ingredients provides chocolate and cocoa extracts, enriched as required with any of the natural flavonols and procyanidin oligomers: theobromine, phenylethylamine or tyramine.

For antioxidant applications 12% polyphenols are recommended and for weight loss applications 8% theobromine is promoted. Hundreds of phytochemicals could have antioxidants, so there's a huge gap for exploitation between crude extracts and purified compounds with health benefits.

Specialist groups such as the Royal Botanic Gardens, Kew's Sustainable Uses of Plants Group can help manufacturers to profile plants for novel compounds and provide authentication on extract quality and standardisation. Meanwhile, work continues on chemo-protective phenols from brown rice that inhibit human cancer cell growth.

Glanbia Nutritionals' OliveActive contains 35% hyroxytyrosol, which has a low molecular weight, is water soluble and is stable to heat and pH. A mere 7mg per day is typical of Spaniards' maximum daily intake. But there's no monopoly on any one antioxidant from olives - verbascocide is the active in Indena's Oleaselect, which also produces extracts from bilberries, green tea, and oligomeric procyanidins (OPCs) from grape seed.

Grape extracts are also a rich source of compounds. Berkem's Powergrape is being promoted for sports use, and will be on show at Vitafoods.

A preliminary clinical study showed post-exercise reduction in biomarkers of oxidative stress.

Alcoholic extracts recently made headlines for improving the antioxidant potential of strawberries. Naturex uses ethanol to extract water soluble Rosemarinic acid, which it claims provides a strong antioxidant at competitive cost that protects products against colour and flavour loss - it also has the potential to fortify the resulting product quoted ORAC value.

Lyc-O-Mato is a standardised lycopene complex extracted from tomatoes. The entire phytonutrient complex present is active, including the antioxidants, lycopene, phytoene, phytofluene, beta-carotene and tocopherols.

Clinical studies show it reduces blood pressure and plaque deposition in arteries; it also reduces cell damage and protects skin reddening when exposed to sunlight. It survives processing and 15mg per serving is typical: more convenient than eating five tomatoes!

Similarly, Coressence chief executive Richard Wood argues that sweet, modern apple varieties only provide a fraction of the flavonols that were available 50 years ago: between five and 30 modern apples would be required to match intake. Coressence owns global breeder's rights to high-flavonol apple varieties standardised by the UK Institute of Food Research.

Evesse, its apple extract, is rich in soluble monomer epicatechin, which relaxes the vascular system, thus allowing smoother blood flow to help reduce arterial deposition and platelet clumping. Stable to low pH and pasteurisation, Evesse works well in drinks.

A health claims dossier will be submitted this July, based on epidaemiology and clinical trials.

Are you getting enough?

In practice few people achieve the recommended intake of five (80g) portions of fruit and vegetables a day. The benefits of high antioxidant plant-derived foods are, therefore, apparent for the broad nutrient profile they provide.

However, the intake of antioxidant supplements or concentrated extracts of specific molecules may be justified where there is proven evidence of desirable health outcomes.

There is a wealth of food plants in nature and issues of safety and quality are largely secondary to efficacy: we'll be hearing much more about that in future.

Paul Hart is general manager of nutrition consultancy Nutraceuticals. Contact him at: paul.m.hart@btopenworld.com

EU RDAs for essential antioxidant micro-nutrients

Essential Nutrient RDA

Vitamin A 800 mg RE

Vitamin C 60 mg

Vitamin E 10 mg

Zinc 15 mg

Follow us

Featured Jobs

View more


Food Manufacture Podcast

Listen to the Food Manufacture podcast