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Are Onions Keto-Friendly? (& Substitutes)

On the ketogenic diet the goal is to keep your carbohydrate intake low enough. What about onions, are they keto-friendly?

Onions are a type of vegetable well-known around the world. While most people won’t eat onions just on their own, they play a role in many different dishes.

The net amount of carbs, which comes down to total carbs minus carbs from fiber, in raw onions is around 7.6 grams per 100 grams.

While it depends on the rest of your diet, for most people onions are keto-friendly in small amounts but you will likely have to exercise some portion control. In any case, there are vegetable substitutes for onions that are better for staying in ketosis.

When is a food keto-friendly

The goal of the ketogenic diet is to put your body into ketosis, a state where it starts mainly burning fat as a fuel (1). This comes down to more or less getting 55%-60% of your macronutrients from fat, 30%-35% from protein, and 5%-10% from carbohydrates.

For most people this comes down to eating around 20g – 50g of carbohydrates a day.

In reality, this number is different depending on a lot of factors. For example, people who exercise a lot may be able to consume more carbohydrates before getting kicked out of ketosis.

That being said that daily amount can be a good general guideline.

It is also common to exclude fiber from this amount since it doesn’t get absorbed into your body the same way as regular carbohydrates.

Carbs in onions

100 grams of onions contains the following amounts of carbs (2):

  • Total carbs: 9.3 grams
  • Of which fiber: 1.7 grams
  • Net carbs: 7.6 grams

Combined with the other foods in your diet the 7.6 grams of net carbs in 100 grams of onions can be enough to kick you out of ketosis.

One ounce of onion is about 28 grams and contains the following amounts of carbs:

  • Total carbs: 2.6 grams
  • Of which fiber: 0.5 grams
  • Net carbs: 2.1 grams

The number of net carbs in 1 ounce of onion, 2.1 grams, is slightly easier to fit into a keto diet. Whether or not onion is keto for you ultimately depends on your individual situation and the rest of your diet.

Other nutrients in onions

Other nutrients like fat, protein, vitamins, and minerals also still matter on the ketogenic diet.

100 grams of raw onions contains the following nutrients (2):

  • Calories: 40
  • Protein: 1.1 grams
  • Carbs: 9.3 grams
  • Part of the carbs that is fiber: 1.7 grams
  • Fat: 0.1 grams
  • Vitamin C: 12% of the DV (Daily Value)
  • Vitamin B6: 6% of the DV
  • Manganese: 6% of the DV
  • Folate: 5% of the DV
  • Potassium: 4% of the DV

And some other vitamins and minerals in smaller amounts.

On top of being slightly higher in net carbs, onions do not contain that many valuable nutrients per 100 grams compared to many other foods.

Substitutes for onions on keto

Onions are not the only option when you want to eat vegetables on the ketogenic diet. There are many vegetables that are more keto-friendly.

Some of the following substitutes may be better on the keto diet. These are the net carb values per 100 grams (4, 5, 6, 7, 8, 9):

  • Chicory: 0.9 grams of net carbs
  • Spinach: 1.4 grams of net carbs
  • Green leaf lettuce: 1.5 grams of net carbs
  • Celery: 1.8 grams of net carbs
  • Radishes: 1.9 grams of net carbs
  • Asparagus: 2.1 grams of net carbs

If you have trouble staying in ketosis but still have cravings for vegetables it may be smart to choose some of these substitutes over onions.

What is your goal with keto?

Even a small portion of onions added to certain daily diets can potentially put you just over the net carbs border, out of ketosis. Depending on the goal you have with keto this may or may not be a problem.

If your goal is to stay strictly in ketosis 24/7 you want to be careful about your carbohydrate intake.

If your goal is to lose weight and become healthier, onions can be a good food option even if they potentially put you at a carbohydrate level slightly above your ketosis level.