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  • Dr. Brian Lum

Why Do I Feel Sick When I Eat Sugar?

Updated: Feb 2, 2022

So, you've been sticking to your diet diligently for a month or two and decide to have a decadent 'cheat' dessert.

It could be a sundae or a slice of cake, but instead of a pleasant sugar rush, you start to feel queasy.

Nausea, sinus congestion, sluggishness, stomach cramping, gas, and bloating can all be the consequence of your momentary indulgence. So why can't your body handle a little detour off your healthy diet?

There can be many potential causes of feeling sick after eating sugar - but here are the ones I see most.

a cupcake. text overlay saying why do i feel sick when I eat sugar?

Potential Causes

1. Intestinal Infection

Sugar, especially refined sugar, can feed opportunistic 'bad bacteria'.

This bacteria can then overgrow, creating an imbalance and making you sick (this is called small intestinal bacterial overgrowth - or SIBO).

Read: Small Intestinal Bacterial Overgrowth (SIBO)

Sugar can also feed yeast overgrowth in your intestinal tract (one kind of this type of infection is called candida).

In both cases you may have an underlying infection but you may not feel any symptoms until you eat sugar.

This especially applies to those who stop eating processed sugar for an extended period of time and then start again - like when you are on a healthy diet and have a 'cheat meal.'

When you temporarily stopped the sugar, the body started to function better and the infection had less fuel.

Once sugar was reintroduced, symptoms flare up because the infection is roaring back to life.

Symptoms of an Intestinal Infection

  • Dizziness

  • Head 'Fullness'

  • Sinus Congestion

  • Nausea

  • Stomach Cramping

  • Abdominal Pain

  • Gas

  • Rashes or Hives

  • Bloating

2. A Blood Sugar Issue

If your body is not using glucose properly, an 'overload' of sugar into your body will cause chaos.

These problems can range from insulin resistance to pre-diabetes to type II diabetes.

Blood sugar problems stem from the body's inability to utilize glucose in the blood stream.

In the case of insulin resistance, the body's cells cannot incorporate glucose easily which causes glucose to build up in the blood. This process can eventually lead to type II diabetes.

Testing will be required to confirm a diagnosis - the good news is that many blood sugar issues can be corrected through diet and lifestyle changes.

Symptoms of a Blood Sugar Problem

  • Feeling Faint

  • Nauseous

  • Shakiness

  • Anxiety

  • Fatigue

  • Irritability

  • Feeling sick when you are hungry

  • poor quality sleep

  • feeling nauseous in the morning

3. Inflammation Or An Underlying Condition

If you have an underlying condition, like rheumatoid arthritis, Raynaud's syndrome or vascular disease - the inflammation that excess sugar causes may inflame an underlying condition.

This is why people can feel pain in their joints and have brain fog and digestive distress for days after they eat sugar. The inflammation lingers, causing a chain reaction of effects throughout the body.

Just as your diet can trigger pain, inflammation and disease - it can also hold the key to quelling these processes in the body.

A diet rich in whole foods - with lots of vegetables and fruits with grains and legumes for fiber and healthy fats like coconut and olive oils for their anti-inflammatory benefits - can create a great foundation to keep inflammation low.

Functional medicine testing can determine if you have any underlying conditions, if certain factors led to those conditions, and what specific interventions we can do to lessen symptoms and improve overall health.

4. Food Allergy/Sensitivity/Intolerance

Although a true sugar or fructose allergy is possible, it is more common for people to mistake a sugar intolerance for another kind of food intolerance (or one of the causes listed above).

A patient may notice that whenever they have Chinese takeout, toaster pastries and a certain kind of candies - they feel awful. All of those things have sugar so they assume it is sugar they are reacting to.

The problem is, processed food are loaded with ingredients you could be reactive to.

MSG, gluten, preservatives, dyes, and soy are all incredibly common allergens that are crammed into foods like candies, take-out foods and processed meals.

A functional medicine doctor can help you prune your diet of the likely culprits.

Once the trigger is identified, it is often necessary to avoid the dietary offender for a time while your body is healing - this will enable you to tolerate the food in moderation in the future.

A step you can start today if you find yourself highly reactive to sugar is to keep a food journal, you may notice that you feel fine with fruit but awful with corn syrup - these differences are very important in crafting a healthy, symptom-free diet.

Learn: How To Correctly Keep A Food Journal

Limitations of a 'Gut Healing Diet'

Despite the popularity of 'gut healing' diets like paleo - usually your body needs a healthy diet in addition to some targeted nutritional medicines to kick an infection for good.

An indication that your diet alone is not treating the infection adequately is when you have some sugar and have digestive symptoms - this shows that the infection is still dormant in your gut.

A healthy intestinal tract should be able to handle occasional sugar.

After all, it was available to our Paleolithic ancestors - the occasional fruit tree or bee hive would supply fantastic amounts of fuel.

Instead of staying on a restrictive diet permanently, treating your underlying infection can allow you to have an occasional indulgence without the consequences.

Many patients also find improved overall health when an infection is finally cleared - increased energy, better sleep, improved mood as well as the ability to occasionally enjoy sweets are all experienced by most after treatment.

For my patients, if they feel sick when eating sugar I confirm an infection using a specific testing

How Functional Medicine Testing Can Help

A starting point for many patients who react adversely to sugar is to check their Hemoglobin A1C and to do a comprehensive stool analysis.

Hemoglobin A1c

Hemoglobin A1C measures your average blood sugar for a span of 3 months.  The most accurate assess of blood sugar regulation.  Functional medicine levels should be approximately 5.2.  5.6 or higher is classified as prediabetic and 6.5 or high is type two diabetes 

Comprehensive Stool Analysis 

A Comprehensive Stool Analysis evaluates specific levels of your protective bacteria, identifies possible hidden gut infections, assesses your ability to digest food - excellent evaluation for anyone who wants to get rid of their symptoms quickly

The Fix: Functional Medicine

The first step will invariably be a trial period without the foods that are making you sick. Keep in mind that it may not necessarily be the sugar making you feel sick - it could be the other ingredients in your foods.

Thats why a food journal is a great idea. You can read more about what to put in your food journal in our article below.

Your Number One Tool If You Have A Food Allergy

A functional medicine appointment or online consultation can help you determine the cause of your symptoms - particularly if your condition is complex, and you have tried to eliminate sugar before without any real results.

Once the underlying cause is resolved then you may be able to go back to having the occasional sweet treat - and actually be able to enjoy it.

If you would like to speak to me to ask questions about functional medicine, chronic illness or how I can help you, please schedule a Free 15 Minute Consultation or call or text my office at 913-728-5291.

My clinic offers functional medicine appointments as well as manual chiropractic treatments. I do online consultations for those out-of-state or outside of the United States.


If you think that you may have a medical emergency, call your doctor or 911 immediately.  No action or inaction should be taken based solely on the contents of this information. Nor should you ever delay seeking medical advice or treatment due to the information contained on this Website.

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