portions National Institutes of Health recommended serving size soda is 20 ounces and contains 250 calories multiple people Portions and Servings: What's the Difference? Serving Size and Portions. National Institutes of Health portions Serving Size and Portions. Portion Distortion Quiz portion and a serving Serving Sizes and Portions Serving Sizes and Portions Serving sizes and portions, 2013. NIH. Keep Portion Sizes Small Comparison Chart. Comparison Chart. National Institutes of Health Comparison Chart. portions