Dr Alan Barclay
Why fermented foods and drinks are so good for our health.
Long before the invention of canning and refrigeration, people around the world fermented foods and drinks to preserve them for later use. Through trial and error over thousands of years, our ancestors worked out which bacteria and/or yeasts (microorganisms) would turn excess produce into delicious, nutritious foods and drinks they could enjoy all year round. Yoghurt, cheese, olives, pickles, bread, soy sauce, beer and wine are very common examples that many of us take for granted when we do our weekly supermarket shop, and often enjoy on a daily basis. Indeed, many traditional cuisines like the Mediterranean diet would not be the same without the broad range of fermented foods that are at its foundation.
One reason fermented foods are so beneficial to health is the development of organic acids such as lactic acid, acetic acid (vinegar), etc. These are by-products of the fermentation process when the bacteria/yeast metabolise the carbohydrate (sugars and starches) in the food or drink. These organic acids not only add distinctive flavours to the food or drink, they also lower the pH, making it difficult for other harmful microorganisms to grow.
In our stomachs, they slow down a food's rate of emptying into the intestine, which in turn slows the rate of digestion and absorption of the food's carbohydrates into the blood stream, lowering the overall GI.
In traditional breads (e.g., sourdoughs), the slow fermentation not only produces the organic acids that create that unique flavour, but the slow rise of the dough due to the production of gases (e.g., carbon dioxide), helps the bread develop the bubbly and chewy texture characteristic of a quality bread, as the gluten (protein in wheat) matrix slowly develops. This is why traditional sourdough breads have a low GI (54), even when they are made of refined white flour.
Yoghurt and fermented milk drinks like kefir, lassi, leben, and Yakult all have a low GI due to the unique proteins in milk that increase insulin production, milk sugar (lactose) which has a low GI of 46, and the lactic acid produced by the fermentation of the lactose by various strains of bacteria like of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophiles. While milk itself is low GI (20–34), the GI values of natural yoghurts (the fermented version of milk) are even lower, ranging from 10–19, depending on whether full cream or skim milk is used.
Research into the human microbiome is now providing additional insights into why fermented foods are beneficial to our health, keeping harmful bacteria at bay, and providing a range of organic acids to feed the cells that line our digestive tracts, to name but a few of the hypothesized mechanisms. So enjoying fermented foods and drinks daily is an important part of a healthy balanced diet.
Fermented foods that carry the GI Symbol include:
- Burgen Rye bread
- Burgen Fruit and Muesli bread
- Burgen Pumpkin seeds bread
- Burgen Soy-lin bread
- Burgen Wholegrain and oats bread
- Burgen Wholemeal and seeds bread
GI Symbol Program
Dr Alan W Barclay PhD, Chief Scientific Officer, Glycemic Index Foundation (Ltd): alan.barclay@gisymbol.com
www.gisymbol.com
GI testing
Fiona Atkinson, Research Manager, Sydney University Glycemic Index Research Service: sugirs.manager@sydney.edu.au
GI database
www.glycemicindex.com
