How do you know if it’s low, medium or high GI?
Living in the USA, where would you suggest I look for GI information on our food? Or are foodstuffs pretty comparable? Any US sites you would recommend?’
Low GI eating often means making a move back to staple foods – fruit, vegetables, legumes (home-cooked or canned beans, chickpeas and lentils), wholegrains (pearl barley, bulghur), pasta, noodles, dairy foods (milk, yoghurt) – which naturally have a low GI, so it doesn’t matter which brand you buy. The top 100 low GI foods are listed in Low GI Eating Made Easy (US edition: Marlowe & Company) along with ideas for including them in your meals. When it comes to carb-rich processed foods such as breakfast cereals, bread, bakery items (cookies, cakes, muffins etc), you do need to know the GI of different brands as it can range from low to high and there’s no easy way to make an educated guess. To find the GI of your favourite brands you can:
- Look for an independently accredited GI symbol on the product
- Check the nutritional label – some manufacturers now include GI (but you need to be sure that an accredited lab tested the food. (See our note below on when to be wary.)
- Visit www.glycemicindex.com to search the database
- Contact the manufacturer and ask (hound) them to have the food tested by an accredited lab.
Not all claims are reliable. Why? Well, The GI rating of a food must be tested physiologically and only a few centres around the world currently provide such a testing service (see our list below). In fact the GI is defined by its internationally standardised method of testing in human subjects (we call this in vivo testing). You may hear about in vitro (test tube) methods, but these are simple short cuts, which may be useful for food manufacturers developing new products, but may not reflect the true GI of a food. Here’s a list of the accredited labs we know (in no particular order) that carry out GI testing following the internationally standardised method. Apologies to any we have left out – please send us your details so we can publish them in future editions of GI News.
- Sydney University s Glycemic Index Research Service (SUGIRS), Sydney, Australia (www.glycemicindex.com)
- International Diabetes Institute, Melbourne, Australia (www.idi.org.au)
- Glycemic Index Laboratories, Inc., Toronto, Canada (www.gilabs.com)
- Reading Scientific Services Limited (RSSL), Reading, UK (www.rssl.com)
- Leatherhead Food International, Surrey, UK (www.lfra.co.uk)
- Oxford Brookes University, Oxford, UK (www.brookes.ac.uk/bms/research/nfsg/index.html)
- Hammersmith Food Research Unit, Hammersmith Hospital, London, UK (www.foodresearch.co.uk)
- Glycaemic Index Otago, University of Otago, New Zealand (www.glycemicindex.otago.ac.nz)
When you see one of these symbols you will know that the food has been tested by an accredited lab.
The GI Symbol Program
This international symbol is a guarantee that the product meets strict nutritional criteria. Glycemic Index Limited is a non-profit company established to run the GI Symbol Program. Its members are: the University of Sydney, Diabetes Australia and the Juvenile Diabetes Research Foundation. For more information, visit www.gisymbol.com.
International GI Symbol
Sainsbury's and Tesco
In the UK, Sainsburys and Tesco are testing and labelling foods low and medium Gi across a range of products.
When you need to be wary
Sometimes a GI value may be too low to be true. If a manufacturer is promoting a carb-rich processed food with an ultra low GI, be wary before you buy. Processed foods such as breakfast cereals and breads and bakery products are very unlikely to have a very low GI. In fact, if the GI is less than say 50, we suggest that you ask the manufacturer for the name of the lab that tested it and the method that was used.