After a year writing the criteria, Walmart on Tuesday unveiled a "Great for You" packaging icon for foods that meet minimum nutritional value standards and company goals for reducing sodium, sugar, saturated fats and transfats. The nation's biggest food retailer joins chains like Publix and Sweetbay Supermarket, which for years have used shelf tags to direct shoppers to what they consider healthier eating choices. Walmart plans to print its label on up to 25 percent of its thousands of Great Value store brand products, the nation's largest food brand, as they are reformulated by 2015. Walmart's name won't appear on its packaging icon and the company will not charge a licensing fee to other branded products to use the label if they meet the criteria, meaning the rules could become a national standard. Grocers developed their own healthy food guidelines because government attempts have been mired in political infighting between nutritionists and food companies angling for a marketing advantage.