Shopping for products that aren't genetically modified (GM) can be challenging, particularly in the United States where there are as yet no laws governing the labeling of products with GM ingredients. To make it a little easier on concerned shoppers, the US advocacy group Institute for Responsible Technology (IRT) this week launched a new website for consumers who want to avoid buying products containing genetically modified organisms (GMO) and gene-spliced food products.

While it's impossible to provide a complete list of GM foods marketed in the US, the new guide aims to take the guesswork out of avoiding GM food and features straightforward brand-by-brand comparisons of non-GM products and products likely to contain GM ingredients. It's been widely reported that most Americans would like to know if their food contains GMO ingredients and would avoid foods they knew contained GM ingredients.

But there are some basic rules of thumb in avoiding GM products and are applicable worldwide:

Buy 100 percent organic: Some organic products (with multiple ingredients), however, may contain non-organic ingredients, so it's best to stick to single ingredients. Because something says "organic" on it doesn't mean it doesn't contain GM ingredients. In fact, it could contain up to 30 percent GM ingredients, so be sure the labels say 100 percent organic.

Avoid processed foods likely to be made with ingredients from the "Big Four" GM crops: corn, soy, canola (for rapeseed oil), and cotton (for cottonseed oil).

Avoid sugar unless it's 100 percent cane sugar: GM beet sugar is one of the latest additions to the food supply; avoid aspartame, an artificial sweetener derived from GM organisms.

Look at what is (or isn't) on the labels: If a product is not labeled as being GMO-free, most likely it contains some GM ingredients.

The shopping guide also has a long list of so-called invisible GM ingredients that  can make their way into one's diet.

For more information, go to: http://www.nongmoshoppingguide.com

There are plenty of other websites with detailed information on GM foods and genetic engineering, some of which also provide downloadable shopping guides for consumers. Some of them include:

http://www.sustainablestuff.co.uk
http://www.seedsofdeception.com
http://www.truefoodnow.org
http://vivresansogm.org
http://guideogm.greenpeace.ca
http://www.non-gmoreport.com