Can I Eat Onions on a Keto Diet?

  • By: kim
  • Date: September 23, 2018
  • Time to read: 8 min.

Yes, you can eat onions on a keto diet however you need to be very careful that you don’t overeat them, so you go over your daily carb limit and come out of ketosis. To keep within your daily carb limits I would always carefully weigh the onions before you eat them or add them to your recipes. Onions contain between 7g – 9g of carbohydrate per 100g or 31/2 ounces (depending on the source you use!).

Were would the cook be without onions? I should imagine that I add onions during cooking to about 80% of my cooked recipes. Unfortunately, I really have never got on well with raw onion, even the milder scallions or spring onions, unless a small component of a recipe like coleslaw. I find the taste overwhelming. However, my husband loves raw onions and will happily eat onions raw in salads.

Also, I’m going into sound so fussy here – I just can’t get on with pickled onions either, I suppose this is because it combines two foods I find unpleasant raw onions and vinegar. I do however keep trying these foods as I understand you can learn to love foods if you keep giving them a try.

Onion Culinary Uses

The onion has been used extensively throughout most world cuisines. For example, in Cajun cuisine, the well-named “holy trinity” that makes up the base of Cajun food recipes are onions, celery and bell peppers.

Also, onions are used throughout Asia. Onions are added to vast varieties of curries found in these regions.

In French cuisine, a mixture of diced vegetables called mirepoix made of onions, celery and carrots. The mirepoix forms the base of many dishes, from stews to soups. Of course, the French made a delicious soup called French Onion Soup were the onions are cooked slowly over a low heat until caramelization takes place, producing a dark rich and tasty soup.

Mexican cuisine uses onions as for example in traditional Mexican dishes like mole, enchiladas, and fajitas.

Types of Onion

Anyway, the proper name for the common onion we cook with is Allium cepa. There are other closely related vegetables to the common onion called shallots, spring onions or scallions.

Generally, onions can be placed into three groups, for yellow, white and red. The red onion has a mild flavor and can be eaten raw as an addition to salads. The white and yellow onions are the more common onions that we use in every day cooking. Other onion uses are onion powder this can be used as a spice, very useful in meat rubs.

Nutritional value of onions

Raw Onions per 100g or 3.5ozs

Calories in onion – 166kj or 40 kcal
Carbohydrates 9.24g
Sugars 4.24g
Fat 0.1g
Protein 1.1g

Onion health benefits

The benefits of onions are thought to include, protection against – colon cancers and stomach cancers, lowering blood pressure, protection against other cardiovascular diseases. Of course, I’m not a doctor so I would recommend doing your own research on this area.

Onions are generally tolerated very well in the human body there are few references to onion intolerance or allergy, but no doubt these do occur.

Onions and dogs

As I was researching this article, I was surprised when I came across numerous citations claiming onions are very bad for your dog’s health. Here is just one of them
As I have two Westies myself its great to have this information, as they are sometimes given table scraps.

Why do Onions make us cry?

We have all no doubt experienced the eye irritation onions can cause. The reason for this is that as you slice through your onion with your knife, you slice through the onions cell walls. This then causes enzymes to break down which results in sulphenic acid being generated. Another enzyme turns this acid into a gas which is the cause of the irritation. The gas then activates sensory neurons in the eye which then creates that familiar stinging sensation. As a reaction to the stinging, your eye produces tears, in an attempt to flush away the irritant.

How do you avoid crying when peeling and chopping onions?

Personally, I just get on with and put up with a few tears it just seems quicker that way. Also, the effects go away rapidly once you have finished chopping. I acknowledge however that people do find this unbearable.

I did a quick search around the web and I found the following remedies for onion tears, I can’t vouch for there effectiveness although covering your eyes should work effectively.

1. Apparently peeling and chopping onions under water prevent the gas from escaping into the air; I have never fancied doing this as it just seems too much effort.
2. Cover your eyes, for example, wear swimming goggles or a diving mask you may look stupid but no tears.
3. Could try chilling the onions in the fridge or freezer before chopping as a way of reducing the tears.
4. Use a very sharp knife.
5. Cut through the onion root part last as this bit of the onion has the highest concentration of enzymes.
7. Put lime juice onto the knife blade.
8. Breath through your nose. It may help to chew gum or place a cocktail stick between your teeth.
9. Try using a fan to blow the fumes away from your face.
10. Put white vinegar onto your chopping block this is supposed to neutralize the irritating chemicals.
11. Burn a candle nearby.
12. Many years ago I found that wearing contact lenses prevented my eyes from being affected when chopping onions, I don’t know if everyone has this experience.

Best Ways to Store Onions

For cooking onions and shallots, these can be stored at or below room temperature, for example in a well-ventilated garden shed. Ideally in a single layer so that they don’t touch each other. Kept in the dark and cool the onions should last at least for a month possibly longer. The reason for storing the onions in a single layer is to avoid mold spreading from onion to onion. The onions must be kept frost free.

Onions can also be stored in a refrigerator, I always remove them from their plastic packaging and store in the bottom shelf in the salad drawer, I place them on a layer of kitchen paper and check regularly in case an onion has gone off and has gone slimy or moldy. Kept this way they will last a couple of weeks but I find they don’t keep well after this time.

Freezing Onions

It is possible to freeze onions but you need to remember like a lot of vegetables the freezing process will lead to deterioration, so don’t expect to have perfect slices of onion once defrosted. Frozen onions are great for adding to soups, stews and casseroles.

To freeze onions- be warned they do smell really strong when first placed in the freezer. Don’t put close to delicately flavored foods in the freezer.

  1. Chop the onions to the size you need personally I would leave in large chunks as too fine dice can turn to mush during the freezing process.
  2. Take a strong freezer bag and place onions in the bag in portion sized amounts. You can just fill one big bag but you will find the onions will clump together.
  3. Place in the freezer, aim to use within 3 months or so.

Keto Onion Recipes

How to make Low Carb French onion soup

Here is my French onion soup recipe, this delicious, but time-consuming. Instead of the bread croutons normally called for. Instead, use diced bacon and fry these until crispy and place on top of the soup. The Gruyere cheese goes over the bacon before going into a screaming hot oven to make the cheese bubble.

In the traditional recipe, a little bit of sugar is added to the onions to help with the caramelization. You can omit this if you are rigorous in omitting refined sugar from your diet, the onions contain sugars so they will cook down nicely without the sugar.


1 ½ lb  white onions – sliced thinly
1/2 tsp sugar optional
Glug of olive oil
2 ozs unsalted butter
4 garlic cloves crushed
2 ¼ pints 1.5 liter good beef stock
12 fl ozs  300ml white wine
2 tablespoons brandy (Cognac is best) – optional
Salt and pepper


8oz  225g Gruyere cheese grated
8oz  225g Cubed bacon
Dash of olive oil


  1. Take a heavy bottomed casserole dish; add the glug (about 2 tablespoons)of olive oil and the butter.
  2. Heat until the butter has melted then add the onions and garlic. Keep over a high heat for about 6 minutes, keep moving the onions and garlic around to prevent burning. The onions will complete this stage once they have turned a dark nut brown.
  3. Add the stock, white wine and salt and pepper, and then keep stirring bringing up any onion bits that has adhered to the bottom of the pan.
  4. Once the mixture has come to the boil, reduce the temperature down to a very low setting. Leave the soup mixture to simmer very gently for an hour.
  5. At this point adjust the seasoning, and add the brandy if required.
  6. While the soup has been cooking fry the diced bacon until crispy and grate the Gruyere cheese.
  7. Place the soup into bowls and sprinkle over the crispy bacon bits, followed by the grated Gruyere cheese. You can either leave the cheese like this or alternatively either place the bowls of soup into a screaming hot oven or place under a grill/broiler until the cheese is hot and bubbly. Make sure your dishes are heat resistant if you decide to do this last method.

Caramelized Onions and Shallots

For caramelized onions and shallots follow the first two steps of the French Onion Soup about. A great side dish to cold meats, sausages and burgers. For caramelized onion gravy add a small amount of beef stock to the onion mixture until the desired thickness is achieved.

Sauteed Onions or Fried Onions

Chop the onions into ½” dice.
Heat a large non – stick saute pan on the stove.
Add oil or an oil and butter mixture.
Add the onions or shallots to the pan.
Keep an eye on the onions to make sure that they don’t burn, turn the onion over every minute or so to cook evenly.
Sauteed onions are delicious with burger or sausages. Sauteed onions form the basis of many dishes e.g.stews.

Broiled Onions

You need the really large Spanish Onions for this dish. Cut ½” wide slices through the middle of the onions. Brush with olive oil, place under the broiler for about 5 minutes turning halfway through. These broiled onions are great with a steak, as a replacement for the fried onion rings.

can I eat onions on a keto diet

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