Serving size vs. portion size

By Barbara Quinn

The Monterey County Herald

What is the difference between a serving size and a portion size? Plenty. A serving size is a specific measure of a food. A portion is the amount of that food that happens to be on my plate. Why should we care? Understanding serving sizes is one key to help manage our growing national waistline.

For example, one serving of milk is defined by nutrition experts as 8-ounces or 1 cup. Two cups (16 ounces) would be two servings and so on. Most adults need two servings or 2 cups of a calcium-rich food such as milk, yogurt or fortified soy beverage every day for optimal health. On the other hand, a portion of milk – what one actually consumes at a meal – might be a whole other animal.

Case in point: On a recent road trip, we stopped at a popular restaurant for breakfast. I ordered a glass of milk with my meal.

“Do you want the medium or large size?” the waiter asked.

After thinking it somewhat odd that “small” was not even an option, I asked, “How big is the medium?”

“Sixteen ounces,” she said. “And the large is 32 ounces.”

So. my dietitian brain calculated, a medium portion at this restaurant provides two servings of milk – my daily quota. And the belly busting 32 ounces – a whole quart - could easily feed a family of four.

Why does this matter? Large portions add extra nutrients, and they also add extra calories. One cup (8 ounces) of low fat milk, for example, contains about 300 milligrams of calcium, 120 calories and as much protein as an egg. A 32-ounce portion weighs in at almost 500 calories, a day’s supply of calcium and close to a daily quota for protein. We need to know the difference.

Not that we always have to consume standardized serving sizes. I just need to know that – if I consume a 16 ounce portion of milk – I have just met my daily goal of two servings of a high calcium food.

Nutrition guidelines also tell us to consume two to three servings of a protein-rich food each day. And this recommendation comes with the understanding that one serving is equivalent to 3 ounces of cooked meat, fish, tofu, poultry or the like.