A new food labeling guide for consumers is being launched at Canadian grocery chain Loblaw, but a consumer advocate and a doctor wish it was more refined.

Guiding Stars, which is being offered by Loblaw at its stores in Ontario starting today, said it offers shoppers at-a-glance nutritional ratings for foods to complement existing information such as the nutrition facts table on packages.

Nutritionists developed the system, which looks at more than a couple of specific ingredients. It was introduced at some U.S. supermarkets in 2006.

Products get credits for containing more vitamins, minerals, dietary fibre, whole grains, and omega-3 fats, while they get debits for containing saturated fat, trans fat, added sodium, or added sugars, Loblaw said.

"We worked with nutritional scientists to develop an algorithm where we credit for having more vitamins, minerals, whole grains, dietary fibre, and omega 3 fats, and debit for added sugar, added sodium, saturated and trans fat," said Alexis Williams, director of health for Loblaw in Toronto.

When a product has more stars, it has a better balance of credits and debits.

If a food has been rated and has no stars, that means it didn't meet the criteria for a star.

"Simple as 1-2-3," Williams said.

The nutritional guide is not influenced by price, brand or manufacturer and the ratings are displayed on shelf tags at the store, the grocer said.

Guiding Stars is not bad at helping consumers to make broad products decisions, said Bill Jeffery of the Ottawa-based Centre for Science in the Public Interest, but it's generally ineffective at helping consumers make more nutritious brand choices or encouraging food companies to make progressively more nutritious reformulations since comparable foods usually fall into the same star category.

Under Guiding Stars, a product could score 51 points and get three stars, but that's not necessarily comparable to a product that earns 74 points and also receives three stars.

Jeffery would prefer a rating system that combines traffic-light colouring with a scale from 1 to 100.

"The main thing is that whatever front-of-pack labelling schemes are used should be developed, tested and evaluated against public health benchmarks in a transparent way by a public health authority, not a food company," Jeffery said in an email.

Dr. Yoni Freedhoff, an obesity specialist at Ottawa's Bariatric Medical Institute, blogged about Guiding Stars.

Freedhoff considers Guiding Stars to be a step in the right direction, since it scores all foods, and he praises Loblaw for introducing it. Like Jeffery, however, he sees room for improvement.

Part of the problem is that food companies are permitted to put claims on the front of packaging that suggest consumers will become smarter or healthier.

"Unless there is either in addition to those messages a score of one to 100 where 100 is great and one is crappy, we need something to quickly navigate what we're buying in boxes," Freedhoff said.

Elena Holeton, a Loblaw customer in Toronto, said shopping for groceries can be confusing.

"It would be lovely if there was one strong, trustworthy, unified system," Holeton said.

Food companies also stand to benefit from Guiding Stars.

"Information provided by Hannaford Supermarkets, a U.S. grocer, shows that the Stars drive higher sales of food items receiving stars," the Guiding Stars website says.

"There are tentative plans for the Canadian program at Loblaw to be rolled out on a national scale next year as part of a broader health initiative."

Foods with fewer than five calories per serving such as bottled water, tea, and spices, are not rated.