Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Learning Portion Size Is Important When Choosing Proteins

Dear Doctor: Would you please explain what "grams of protein per pound of body weight" etc. actually LOOKS like on someone's dinner plate? I think a lot of readers would love to have a visual for how much protein we are supposed to be eating.

Dear Reader: We're so glad you've brought up portion size. Along with eating from a well-balanced range of food groups, it's the factor that has the greatest impact on nutrition, good health and weight control. And you're right -- there's definitely room for an "aha!" moment regarding portion size.

Protein is the major building block of our bodies. Bone, muscle, cartilage, hormones, antibodies, membranes, chemical messengers, skin and blood all need protein to function. As with so many areas of nutrition, how much protein we need is a subject of ongoing debate.

In our recent column about protein, we cited the figure of 0.36 grams of protein per pound of body weight, which is the current Recommended Dietary Allowance, or RDA. That's considered the minimum needed for all systems to function well. Newer research seems to be leaning to somewhat higher numbers. We'll keep an eye on that for you and report back if things change significantly.

As for what a protein portion looks like on the plate, it depends on what type of protein you're talking about. Poultry, fish, beef, pork, eggs and milk products fall into a category known as "complete proteins." That means they contain the essential amino acids, which are nine amino acids that our bodies need but cannot manufacture.

A serving of meat or fish is generally considered to be 3 ounces. That's about the size of a deck of playing cards. Depending on the type of meat or fish, you're getting about 20 to 25 grams of protein per 3-ounce serving. A 1.5-ounce serving of cheese has in the neighborhood of 10 grams of protein, depending on the type. That's about the size of an index and middle finger held together.

Most of the other natural sources of protein, such as dried beans, rice, legumes, seeds, grains and many vegetables, either lack one or more of the essential amino acids, or are low on them. These are considered to be "incomplete" proteins. However, as vegans and vegetarians can attest, these so-called incomplete proteins can easily be mixed together in delicious combinations that make up for their various deficits.

A serving size of cooked beans, legumes or grain is a half-cup, or about the amount that would fit into an empty cupcake wrapper. A loosely cupped hand holds about an ounce of nuts. A tablespoon of peanut butter is about the size of the first joint of your thumb. For a 3-ounce serving of tofu, which has 7 grams of protein, we return to the visual of a deck of playing cards.

Once you start paying attention, learning portion sizes becomes easier. Just be sure to take variables like fat, salt and carbs into consideration when choosing your proteins.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)