Is That Really a Protein Source?

“I couldn’t live without peanut butter.  It’s such a huge source of protein for me.”   The comment was heard years ago, yet it makes me cringe to this day. 


Yes, peanut butter does contain some protein, but “huge source” is an exaggeration.  You may have heard other plant-based foods referred to as similiarly large-scaled protein foods.  Let’s take a look at a few contenders and see how they measure up.


Peanut Butter

I too would die without peanut butter.  You can’t go wrong with a good old PB&J, and my oats would be sad without their creamy companion.  I even use it as a topping for Greek yogurt.  The list goes on!  While peanut butter may help meet protein requirements in a mixed-source (plant and animal) meal, it doesn’t stand alone as a protein source.  Here’s why: a 2 T. serving of peanut butter contains 16g of total fat.  Fat contains 9 calories per gram.  16 x 9 = 144 calories, meaning that out of 190 total calories in this serving of peanut butter, 75% of them come from FAT.  The same serving contains 8g of protein.  Protein contains 4 calories per gram.  So, with only 32 of 190 calories coming from protein, peanut butter is clearly a food that should be viewed as a fat, not a protein.


Black Beans

Black beans – along with chickpeas and cannelinis – are a staple pantry item for me and my family.  I love having an easy, versatile source of fiber at the ready.  But is it a great source of protein?  Not quite.  A half-cup serving of canned black beans provides 22g of carbohydrate versus 8g of protein.  Carbohydrate and protein each provide 4 calories per gram, so I’ll save you the math here: it’s clear that black beans contain nearly three times as much carbohydrate as they do protein.  Even accounting for net carbs after accounting for dietary fiber, black beans still contains twice as many grams of net carbs as they do protein.  They’re a great companion to other protein-containing foods, but, again, not a stand-alone protein source.


Chicken Breast

Love it or hate it, our feathered friends are an EXCELLENT source of protein.  Here’s why: a 3oz. serving provides roughly 26g for a measly 140 calories.   In fact, 75% of those calories are provided by protein. 


Now let’s put it all together…

To get 26g of protein, you could eat…

3oz. of chicken breast (about the size of a deck of cards),


1 ½ cups (3 servings) of black beans,


6 T. + 1 tsp. peanut butter


If you choose the peanut butter option, you’ve also consumed approximately 50g of fat – and if you’re a woman between the ages of 31 and 50, that’s nearly two-thirds of your recommended fat allotment for the day. 

Choose the beans, and you’re consuming 18g of fiber along with the protein.  Now, fiber is important, but you’ll serve your digestive system best by spreading intake throughout the day.  This is especially true if your diet is currently lacking in this department.


So, there you have it - winner, winner, chicken dinner!  Remember, a 3 oz. portion is the size of a deck of cards – leaving plenty of room on your plate for colorful vegetables, cheese, and a whole grain.  Stay tuned for more on how animal sources of protein can fit into a plant-based eating pattern.