Quinoa: plant protein powerhouse?

qunioaQuinoa is promoted as a high protein grain. True?

Quinoa is an ancient grain, native to South America where it’s been a staple food for centuries.  In the past few years it’s taken on new life in North American and beyond as a health food.  One of the main selling points: the protein content.  In a world now obsessed with sustainability and eating less meat, a high protein grain seems like a win-win.

I’m not a big fan of quinoa, mainly because I hate jumping on food fad bandwagons.  Quinoa is hyped as some kind of super food, sprinkled into chips and snack bars and cereals for the Health Halo marketing effect.  But it’s a whole grain, and if it’s high protein, so much the better.  But is it really “high” protein?

No.

If you’re looking for plant protein, legumes (beans) have almost twice as much as quinoa.  Quinoa is higher protein than corn or rice, about the same as whole wheat.  So where did this high protein Health Halo come from?  The best guess is it’s about protein quality, not quantity.

In my book “Feed Your Vegetarian Teen“, I discuss the issue of plant protein quality as related to meatless diets.  The building blocks of proteins are amino acids.  There are 22 varieties, of which 9 (or sometimes just 8) are considered essential for humans — we must eat them in food.  And ideally we’d eat them in a ratio that’s close to the ratio of amino acids in our body tissues.  And this ratio determines protein quality.  The closer a food protein is to that ratio, the higher the quality.  Egg, milk and soy are our highest protein quality foods.  Meats are also high quality.   And these all are also high protein quantity.  Plant proteins are lower quantity, and tend to be lower quality, because they’re low in one or two of the essential amino acids.

eaaratiochart

The chart above shows the human requirement ratio of each of the 9 essential amino acids.  For example, we need roughly twice as much leucine as isoleucine.  We need similar amounts of threonine and methionine.  Now compare those ratios to the ratio of those amino acids in different grain foods:

amino acid ratios in quinoa, rice and wheat

amino acid ratios in quinoa, rice and wheat

NOTE: this chart lists 8 essential amino acids, leaving out histidine.  I could not find any reliable data on histidine content of quinoa.  In fact my search for amino acid values for quinoa turned up several alleged sources with widely variable data.  Sometimes it looked like someone pulled numbers out of a hat.  The chart above uses data from the United Nations Food and Agriculture Organization.  Other sources reference data that is many years old, or relies on questionable values that have no source listed.  So sorting through this grab-bag of “data” turned into quite an adventure.

But the chart can give you an idea of why quinoa protein is considered higher quality than wheat or rice.  Look at the values for lysine, the third amino acid down.  The blue line (human requirement) is longer than the lines for rice (yellow) or wheat (orange).  That means rice and wheat are lower in lysine than is ideal for humans.  But the line for quinoa lysine (green) is higher than the blue line.  In fact, the green quinoa line is higher than all of the blue (human requirement) lines.  Meaning that the pattern of essential amino acids in quinoa protein is good for humans.

But of course that doesn’t mean anything about quantity.  If your protein intake was 65 grams a day, and you wanted to get all your protein from one food, you could cover that requirement by eating:

8 cups quinoa  at 1700+ calories

8 cups low fat milk at 975 calories

10 eggs at 750 calories

13 oz of tofu at 540 calories

13 oz roast chicken breast at 305 calories

So is quinoa a superior source of protein?  It’s higher quality than other grains, but it is not highly concentrated.  You’d still have to eat a whole lot of quinoa to get all your protein.  Which is why it’s a good idea for vegetarians and vegans to eat a variety of higher protein plant foods throughout the day — legumes, grains, nuts soy — to boost protein quantity and quality, and to avoid boredom.  8 cups of quinoa every day?  I don’t think so.

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