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Focus on onions

Focus on onions

The humble onion — a food that’s everywhere, but never the center of attention. Onions add flavor, and are a common ingredient in soups, casseroles, pasta sauces, sandwiches, salads, marinades, dressings, dips and as a condiment. Correct me if I’m wrong, but the one place you’re not likely to find onions is in a dessert.

Despite being everywhere, onions have a disagreeable reputation. Along with garlic, they’re blamed for bad breath. Sliced onions bring stinging tears to the eyes. And some people cannot eat onions due to intestinal distress. Ironically, the cause of that intestinal distress is also an argument for eating more onions. Read on.

Onions and digestion

Onions are a concentrated source of fructans, a unique type of carbohydrate. Fructans are chains of fructose molecules. The chains vary in length. A fructan with 10 or more fructose molecules is referred to as inulin.* Specific enzymes in the human gut break fructose molecules off the fructan chain during digestion. Some people do not produce much of the necessary enzyme. When they eat onions, the fructans are not completely broken down. Undigested fructans end up in the large intestine, where gut microbes ferment them.

And that can cause problems. Fructan fermentation draws water into the large intestine and produces gas, leading to bloating and diarrhea. Other foods, notably wheat, are also high in fructans and can cause the same digestive upset. Some people mistake their reaction to wheat as gluten sensitivity, when in fact it’s the fructans.

Not everyone reacts badly to fructans, so eating onions is one way to promote healthy gut microbe populations. The fructans in your diet are feeding the beneficial microbes. And as I’ve noted many times, a healthy gut microbe population benefits your immune function, and may impact brain function. There’s evidence that flavonoids in onions may inhibit the growth and spread of cancer.


There isn’t a great deal of nutritional difference between different varieties of onion. One cup of chopped onion has roughly

  • 60-65 calories
  • 15 grams carbs
  • 1.7 grams protein
  • 2.7 grams fiber
  • almost no fat
  • 11-12 mg vitamin C
  • a variety of B vitamins and small amounts of most minerals

The more important health benefit of onions seems to be from the fructans and flavonoids. To benefit your gut health, if you don’t have issues digesting onions, I encourage you to include them in your meals.

I have a couple of recipes that are heavy on onions. One is for onion soup. Classic French onion soup is delicious, with caramelized onions, rich beef broth, toasty bread and melted cheese (traditionally Gruyere, not mozzarella). You can make it vegetarian by using a vegetable broth. You can serve it without the bread, if you’re watching carbohydrate intake. The key is to use lots and lots of onions, slowly sautéed to a rich caramel color.

Onion Soup

February 21, 2023
: makes about 1 quart
: 1 hr
: easy

Making this soup isn't difficult. It just takes time. The onions need to brown and then the soup needs to simmer for an hour or more to develop the flavor


  • 2-3 TB light olive oil or peanut oil
  • 1 quart vegetable or beef stock
  • 1/2 cup dry white wine or beer
  • 1+ lb sliced onions (about 4 cups)
  • 1 TB flour
  • 1/4 tsp sugar
  • 1/4 tsp salt
  • 2 TB brandy
  • grated Gruyere cheese
  • optional: toasted slices of French bread
  • Step 1 Heat the oil in a heavy duty sauce pan over moderate heat. Add the onions and saute for about 10 minutes.
  • Step 2 Add the salt and sugar, and continue to cook, stirring to avoid sticking. The onions should gradually turn a caramel color. Do not burn. Add a splash of water if they stick to the pan. This could take 30-40 minutes.
  • Step 3 Sprinkle the flour over the onions and stir.
  • Step 4 Whisk in a cup of the stock and bring to a simmer. Gradually add the rest of the stock, whisking after each addition.
  • Step 5 Add the wine and brandy.
  • Step 6 Reduce heat and simmer for 1+ hours. Add more stock if the liquid reduces too much.
  • Step 7 Season with salt to taste and black pepper.
  • Step 8 Serve topped with grated cheese. If you want a more substantial meal, place toasted bread on top of the soup, top with the grated cheese and broil briefly to melt the cheese.
  • Step 9 If you just want a warm and rich soup, serve without cheese or bread.


onion frittata

Onion Frittata

My other go-to onion dish is a very simple frittata, accompanied by raw vegetables or sauteed broccoli or a tossed salad.

This is a one-pan dish. I start by sautéeing chopped/sliced onion in olive oil in a small frying pan (photo). You should have enough onion to cover the bottom of the pan.

Whisk 2 eggs in a bowl. When the onion is soft, but not browned, pour the eggs over the onion. Moderate the heat and allow the eggs to cook. The top will be slightly runny. Turn off the heat. Top with 2-3 thin slices of cheese (your choice). Broil briefly to melt the cheese and finish cooking the eggs.

Slide out of the pan onto a plate. Garnish with raw vegetables and a sprinkling of chopped parsley or basil.

You can find lots more information about onions, including recipes, at the National Onion Association website. 

*Inulin occurs naturally in many plant foods. Purified inulin is also added to many processed foods to boost fiber content.