Low Carb Diets For SIBO/ IBS - Get Adequate Nutrition

Low Carb Diets For SIBO/ IBS – Get Adequate Nutrition

When someone experiences Small Intestine Bacterial Overgrowth, there may be confusion on which diet to choose.  Many options are available, and it should meet the individual’s needs.

Current diets recommended may include diets such as the low FODMAP diet, low carb diet or the specific carb diet.  Each diet manipulates carbohydrate intake in a specific way to reduce symptoms 4.

In this article, we will walk you through the nutrition basics you need to know before implementing a lower carbohydrate diet so that you can avoid deficiencies and other health issues that come from malnutrition.

Why carbohydrates?  

carbs in SIBO

Carbohydrates are a hot topic these days.  Some may view them as completely unneeded by our bodies, yet this isn’t true.  Carbohydrates, simply put, provide our bodies with energy. The carbohydrates we consume are broken down into a simple molecule named glucose.

Glucose is used in our bodies to provide energy and fuel the brain… plus much more. If it is not fully used it is stored in the liver or muscles for later use in the form of glycogen. If not stored away, it is converted into body fat 5.

Not all carbohydrates are the same.  They can be broken down into two main categories based upon certain characteristics – complex and simple carbohydrates.  It is generally recommended to consume more complex carbohydrates than simple carbohydrates, with a few exceptions.

Fiber is a complex carbohydrate.  Fiber is used in the body as an agent to help remove unwanted substances from the body.  It is actually never digested while in the digestive system but passes through. Once it reaches the large intestine, some undergo fermentation and the remainder is removed from the body. Starches are another complex carbohydrate.

Starches are broken down into glucose throughout the digestive system beginning in the mouth. Simple carbohydrates are sugars found naturally in foods and those added to food. They are quickly broken down in the body for energy 3.

Nuts, seeds White breads, pasta, rice Fruits & fruit juices
Whole grains Potatoes Granulated sugar
Raw vegetables Pumpkin and winter squash Honey & molasses
Raw fruit, especially, Apples, pears & berries Corn and cornmeal Desserts
Bran White flour

How This Applies to SIBO

what is sibo

This all ties back to the question of a diet for SIBO.  Bacteria feeds upon carbohydrates. When fiber is fermented, further gas can be produced if there is a dysbiosis.  This is unwanted when bacteria are in a location that it isn’t supposed to be such as the small intestine.

Also, the increased bacteria can damage the small intestine’s ability to absorb carbohydrates. This leads to a desire to reduce carbohydrates as much as possible.

If someone chooses to follow a lower or specific carbohydrate diet, how is the body to be fueled for daily use?

As previously discussed, the major source of energy is provided through carbohydrates. When the body is not receiving the typical carbohydrate amount, fat is used as an energy source.  This process allows the body to use ketones produced from fat as energy instead of glucose from carbohydrates.  This process is called ketosis 1,2.  This process can happen naturally in certain medical conditions such as diabetes or stages of life such as pregnancy. Low carbohydrate diets using less than 50 grams of carbohydrates per day also drive the body into ketosis.

Not only are carbohydrates important for the body but proper calorie, protein, fat, vitamin, and mineral intake is needed as well.  As you adjust intake based upon carbohydrates you must remember the other nutrients too. The majority of adults need at least 1200 calories per day to perform basic daily functions such as breathing and sleeping.  Additional calories are needed for further activities such as exercise.

Providing at least the needed 1200 calories per day from a variety of foods to ensure you stay healthy plus provide nutrients such as vitamins and minerals to fuel the metabolic processes taking place within your body.  Ensuring at least 0.8-1.0 g of protein per kilogram of body weight will provide adequate protein. More protein may be needed for intense exercise.

Low Carb diets for SIBO/ IBS and How to Get Adequate Nutrition

Each type of low carb diet has different requirements and presents different nutritional benefits and challenges.  Let’s go over a few typically used in IBS and SIBO.

The Low FODMAP Diet


The Low FODMAP diet removes certain carbohydrates that promote fermentation.  Individuals go through a series of three phases when following this diet.  It is highly recommended that this diet be administered by a dietitian to ensure proper intake.

Phase 1:

Some view phase 1 as an elimination phase but according to Monash University 7 it is not.  It is a substitutionary type diet in which you choose a food that is allowed as a substitute for a high FODMAP food.  Keyways to stay healthy during this phase is to swap foods within the same food group.

For example, if you usually have asparagus for dinner, swap it for another green vegetable such as kale.  As much as possible, aim for variety to ensure proper intake of vitamins and minerals. Phase 1 usually takes 2-6 weeks to complete.

Phase 2:

is the reintroduction phase.  This phase usually takes 6-8 weeks.  Documentation is key during this time.  While working with a dietitian, foods that were substituted in phase 1 are now reintroduced in specific amounts.  SIBO symptoms, mood swings, and mental clarity should be noted when these foods are reintroduced. Waiting 3-5 days in between each food introduction is very important.

Lastly, Phase 3 begins.  

At this point, you and your dietitian have evaluated your documentation and pin-pointed foods that were problematic to you.  The good news is that foods that did not cause problems in phase 2 can now be permanently added back to your diet. Only the documented foods causing difficulty should be removed from your diet 7.

It is suggested this diet not be combined with other diets.  It should also be administered by a dietitian who can help to ensure nutritional adequacy.  FODMAP foods can be tricky so be aware of some hidden sources such as sugar-free gum, broths, flavored nuts, and some gluten-free products.

The Ketogenic Diet

keto diet

The keto diet is another option.  This is a very low carbohydrate diet and requires certain percentages for each macronutrient.  As a diet first introduced to help children with epilepsy, this diet has been around for quite a while just with little tweaks and different names along the way.

The goal is to bring the body into ketosis by reducing carbohydrates to less than 50 grams per day. Ketosis is typically achieved within 2-3 days 2. To stay healthy while following this diet there are a few things you should keep in mind.

  • Make sure you don’t completely eliminate all carbohydrates.  Healthy low carbohydrate vegetables are still very important to ensure proper vitamin and mineral intake as well as to prevent constipation.  Keep these low carb veggies on hand:

5 Veggies with 5 carbs or less per 1 cup serving:

  1. Zucchini
  2. Spinach
  3. Cauliflower
  4. Cabbage
  5. Celery
  • Removing food such as milk, fruits, and vegetables can reduce the intake of certain minerals such as calcium and potassium.  These minerals can be replaced through low carb vegetables as well as nuts, seeds, and full-fat yogurts.
  • Be aware of mood swings, muscle weakness, and fatigue which may be a sign of a nutritional deficiency.
  • The keto diet is not intended for long-term use.  When ending this diet, carbohydrates should be added back very slowly.

Specific Carbohydrate Diet


Lastly, the specific carbohydrate diet may be chosen.  This diet removes grains from the diet as well as reduces sugar and lactose.  Food allowed and not allowed are shown below 6.

When following this diet and completely removing whole food groups, supplementation should be considered.  The removal of all grains can reduce the intake of energy-producing B vitamins.

Grains also contribute to fiber that must be maintained through fruit and vegetable intake.  Low iron may occur and should be replenished by legumes and meat sources. Calcium should be evaluated due to the removal of dairy products. Calorie and protein intake should also be considered.

Food restriction of any kind to individuals who are currently underweight or have unintentional weight loss can be very problematic and highly monitored.

Vegetables Canned vegetables
Certain legumes Chickpeas, soy, chickpeas
Fresh meat & poultry Processed meats
Nuts, nut butters, peanuts & natural peanut butter All grains
Oils: coconut, oil, soy, corn Oils: canola
Condiments: mustard, vinegar Condiments: (commercial) ketchup, mayo, margarine, balsamic vinegar
Dairy: natural cheeses and homemade yogurt Dairy: milk, ice cream, whey, creams, fresh cheeses, processed cheese
Fruits & pure fruit juices All simple sugars: table sugar, molasses, candy, chocolate
Honey (in moderation) Starchy vegetables: potatoes, yams, parsnips,

Restriction Gone Too Far

bad probiotic products

As with any diet that restricts certain foods, the potential to take the diet too far is always present.  Extreme weight loss or low body weight with food restrictions can be very dangerous. Be aware of certain signs of nutrition deficiency such as extreme fatigue, weakness, headaches, muscle cramps, constipation, and skin problems.

Individuals with conditions such as diabetes should consult their physician before considering these diets. It is always recommended to speak with your healthcare provider when trying a new dietary plan. This should be done with a low carbohydrate as well.


In conclusion, small intestine bacterial overgrowth is a very complex condition.  A low carbohydrate diet may prove to be beneficial to those who must combat this difficult condition daily.  As research is conducted and recommendations made, it will be imperative to properly plan and consistently evaluate your nutritional status along this journey.

Read a full review of the different SIBO Diets.

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