IF YOU'RE big on supplementing your diet with anti-oxidants, vitamins and minerals, it pays to know what you're popping into your mouth, and why. Given that drugstore shelves are practically heaving with supplement brands, how do you tell a good nutritional supplement from another?

Canadian biochemist Lyle MacWilliam has found a way to do this. His book - NutriSearch Comparative Guide to Nutritional Supplements - is now in its fourth edition. In it, Mr MacWilliam, a former member of parliament in Canada, lays out the scientific explanations for supplementation.

And most importantly, he has also drawn up a 'Blended Standard' that gives the daily 'optimal' intakes for supplements for them to be effective.

You want optimal, because it's a means of preventing degenerative disease, says Mr MacWilliam. 'The Recommended Dietary Allowances (RDA) define the lower limits of intake that are necessary to avoid acute nutritional deficiencies - which set the standard 60 years ago, as they were developed during World War II.'

Mr MacWilliam was in town earlier this week, invited by Usana Health Sciences.

The Blended Standard - derived from the daily intakes suggested by 12 independent nutritional authorities - is the yardstick he uses to compare the value and benefits of supplements. It covers 47 nutrient categories - 19 vitamin and vitamin-like factors, 13 minerals, five phyto-nutrient complexes, three omega fatty acids and seven other nutritional factors.

What developments have there been in the nutritional supplement field since the third edition of the guide? Supplements are going the combination way as more companies package anti-oxidants together with minerals, herbal products and essential fatty acids, Mr MacWilliam notes. 'People are finding that they have a broad spectrum of need and you can't fit it all into a tablet.'

And there's now more science behind factors that accelerate ageing - such as chronic inflammation and glycation, he says. 'We're now seeing that chronic inflammation is an important component for the onset of degenerative disease. There's scientific evidence to show that about 50 per cent of cardiovascular disease is a direct result of undetected inflammation in the body. More degenerative disease processes involve both oxidative stress and inflammatory reactions in the body. Osteoporosis, for example, can be kick-started by inflammatory processes in the gut.'

Generally speaking, the inflammatory process is closely linked to diet, he says. 'If you eat a diet that's high in saturated fats and in refined sugars - anything that increases your glycemic load has an inflammatory component - or a diet high in shellfish, this leads to a production of a whole series of inflammation-promoting chemicals.'

But that process can be 'turned off' by eating a diet that's high in essential fatty acids such as fish oil, according to Mr MacWilliam. 'Fish oil is probably one of the most profound anti-inflammatory agents you can find, so is olive oil and flaxseed oil. These Omega-3 fats - fish oil, flaxseed oil - 'turn down' the thermostat on inflammation response. Which means that you can adjust the level of inflammation in your body by adjusting the level of good fats and bad fats.'

Another new area is the understanding of glycation, a process in which sugar 'binds' with proteins and 'gums' them up, causing them to become 'denatured' or changed in shape. 'Those proteins once damaged can't function properly. What we know now is that glycation accelerates with age,' he points out.

Ageing cells tend to accumulate a lot of this molecular garbage which cannot be readily removed, he says. 'Glycation is like roasting a turkey and it turns brown. (One way to put it is that) our bodies are like low-temperature ovens with a 76-year cooking cycle.' This process is very damaging, because the 'roasted' protein-sugar complexes are very inflammatory and they produce a lot of oxidative stress.

Factors like inflammation and glycation control form part of the 18 health support criteria that an optimal nutritional supplement should address, according to Mr MacWilliam. (Visit www.NutriSearch.ca to find out more). Other recent inclusions are gamma tocopherol profile and ocular health.

A notable exclusion is iron, he adds, as even low levels of supplementation can increase the risk of iron toxicity.

As for recent negative media reports on supplementation, the guide highlights flaws in some of these - studies that cast doubts on Omega-3 fats, glucosamine and chondroitin, calcium and vitamin D, and the Johns Hopkins vitamin E report.

'There's a lot of disinformation as a result of inaccurate reporting, which is both the fault of the media and the newsmaker,' Mr MacWilliam says. 'Some investigations are just bad science, improperly conducted, poorly reported and inadequately reviewed.'

The guide rates some 2,000 nutritional supplements - most of which are available in North America rather than Asia - and gives them from zero to five stars based on how they match up to the Blended Standard.

Top-rated products include formulas from Creating Wellness Alliance, Colgan Institute, Douglas Laboratories, TrueStar Health, Usana Health Sciences, Life Extension Foundation, Allergy Research Group, HealthyWize, NSI, Rejuvenation Science, Source Naturals, Sawnson Lee and Vitamin Research Products and Ortho Molecular Products Alpha Base.

Some of the brands retailed here which received 0.5 to 3 stars include specific multi-vitamin formulations from 21st Century, GNC, One-A-Day, Pharmanex and Nikken Kenzen.

Lifestyle, diet and nutritional supplements - those three are pillars for optimal health, says Mr MacWilliam.

NutriSearch Comparative Guide to Nutritional Supplements will be available next month at ResearchBooks Asia, which has outlets in Novena Square2, Biopolis, Medibooks SGH and Medibooks KKH