Need protein? Popeye has the answer.

I read a fantastical assertion that vegetables have more protein than a burger. It wasn’t a reliable source, but it got me thinking and I did some research. Obviously it’s not so hard to get a healthy diet of protein, but is a vegetable diet really that much different than a meat diet for protein intake? Maybe there are some new perspectives to present to those hard-case protein lovers out there.

Physicians Committee on Responsible Medicine (PCRM) are a reputable group of doctors who have such publications as the Power Plate for overal diet and the Protein Myth to educate the public.  They were my first stop. The Protein Myth site provides the two most important piece of information: it’s not that hard to get a good diet of protein and protein overload is dangerous for a variety of reasons. Given this understanding of our nutritional needs, we should understand that protein-loading is intrinsically problematic.

But the purpose here is to compare protein content for meat vs vegetable products. The PCRM site and many others list only protein for a certain serving, like 15.2g of protein for 1 cup of black beans. That allows for serving-size comparisons, but it would be interesting to see what this great protein deficiency is. To find a good answer to this question, I turned to nutritiondata.com, a relatively reliable and unbiased site with a lot of great information.

protein content for selected foods - click for larger view

The first thing to understand is that having between 10% and 30% of calories from protein is acceptable, with 15% being appropriate for a person of average size and activity level. The chart shows a steady diet of kale and broccoli will meet an average person’s protein needs. hallelujah!  With spinach tipping the scales at 30%, we vegans don’t even need to turn to tofu. It’s true that fish (cod) tops the scale in all categories, but seitan (wheat gluten) is in the next pack right beside “healthy” staples like turkey and egg whites. The best thing about vegetable protein sources is that they bring so many other nutrients, not just protein.

At the bottom of the list with composite scores under 10% were nuts, potatoes, oats, and fatty (25%) beef. So vegans beware, having nuts for protein may not be worth the cost of high fat content. Meat eaters remember that not all meat is lean enough to be a good protein source.

One may also ask about amino acids. The protein quality indexes were better for lean meats, but aside from brussels sprouts, vegetables showed no low quality scores. Also important to review are amino acid mixes. Essential amino acids are those the body needs to take in rather than synthesizing from other nutrients. Nutrition data gives a rating of 1-5 for each essential amino acid, but few foods had any acids contents rated less than 5.

On the one hand, results were predictable with seitan and tofu at the top. But readers may be surprised to see spinach and asparagus beating out black beans and quinoa. Having nuts near the bottom may also be a surprise. In the end though, stay vegan. Protein-loading itself is a bad idea, so it’s not really necessary to find a protein source. But for basic protein needs, vegetables provide just the right amount. Look for those perfect foods, what Nutrition Data rates as “5” on their nutrition rating – spinach, asparagus, broccoli, kale, brussels sprouts, also known as vegetables. yum.

 

Notes on Methodology

This “study” took about an hour and isn’t intended to be scholarly, but it is accurate to the best of the information presented. Please post any ideas, comments, or information you might find.

I used nutritiondata.com to do this analysis. The Nutrition Data (ND) site is a for-profit publication that draws from USDA and FDA databases and adds its own proprietary analyses to the mix. Of these tools, I used Caloric Mix (Carb-Fat-Protein totalling 100%) and Nutrition Rating (overall nutrition value on a 5-point scale, called “ND Rating” on their site).

Lastly, I pulled from their “protein quality” index which also lists amino acid quality. From all this, we can review what kinds of foods have protein quantity, protein quality, and whether the food source (aside from protein) is particularly healthy.

Nutrition Data also provides the nutrition label, which allows for calculation of the percent of calories from protein (4 calories per gram of protein) to compare with their Caloric Mix from protein. I chose Caloric Mix since the nutrition label is more likely to introduce rounding errors, for example 3 grams of protein in asparagus may be 2.5 or 3.4, which makes a big difference in the final calculation.

To determine the Composite Score, I multiplied together Protein Caloric Mix, Protein Quality/100, and Nutrition Rating/5. This means that the protein density (caloric mix) of the food could be improved or reduced based on the quality of the protein and by the nutrition quality of the food as a whole. Because these are functioning on percentages, there is a valid comparison of within the context of this scoring system, but the metric has no objective meaning. However, within this context, it should provide a fair assessment of what food item should be chosen for protein, from a purely nutritional standpoint.

The foods chosen for comparison were intended to provide a small but representative sample of foods generally chosen as protein sources. I would be interested to see what other food sources might be chosen and reviewed. Note that the item names given are not exact duplicates but should be clear enough to allow readers to find the corresponding entries on Nutrition Data.

Recommended protein intake is generally 0.8 g / kg of body weight, and up to 1.5 g/kg. Caloric intake varies based on activity level and metabolism. But to get percent of calories from protein, we need only understand that 1g of protein is 4 calories. By graphing 0.8g-1.5g/kg, weights between 100 and 250 lbs, and caloric intake of 1500 and 3000 cal/day, the recommended percentage is between 10% and 30%.