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  • Writer's pictureDr. Brian Lum

Why Do I Feel Sick After I Eat?

Updated: Feb 2, 2022

While many are familiar with feeling nauseous after eating a whole bowl of halloween candy, or feeling tired after thanksgiving dinner - when these symptoms accompany a normal meal, it can be a sign that something is wrong.

Shakiness, dizziness, nausea, and fatigue are all signs that your body is struggling to digest and utilize the food you ate.

The reason behind these symptoms could be a blood sugar issue, a food allergy, or even a parasitic infection.

Finding out what is going on is crucial in stopping these symptoms and ensuring that you are digesting your food properly.

a group of friends having dinner. text overlay Why Do I Feel Sick After I Eat? Functional Healthcare Institute

1. Food Sensitivity & Intolerance

The most common cause of symptoms like nausea, racing heartbeat and fatigue is a food intolerance.

Food allergies are generally more serious and can cause symptoms like a numb mouth, severe stomach cramping, swollen tongue or feelings of breathlessness.

Food intolerances (also called food sensitivities) are more common than food allergies and are largely under diagnosed. Usually, the symptoms seem subtle because people have had a low level of inflammation almost constantly for months or years.

Low-grade inflammation caused by food intolerances can lead to symptoms like fatigue, brain fog, weight gain and migraines.

You can do an elimination test and keep a food journal to better isolate the food that you are reacting to.

Often, however, my patients have many underlying sensitivities due to toxin exposure, poor digestion or an autoimmune disease.

In this case, I would order testing so we can quickly isolate the offending foods, remove them from the diet and heal the patient's digestive tract.

2. Infection

A parasitic, fungal, bacterial or viral infection can all cause you to feel sick after you eat food.

In all of these cases, I can order testing to determine if you have an infection and what kind it is.

The strain, type and location of infection within the body will determine the most effective treatment, supplements and therapeutic foods for you.

One of the most common types of infections that produce symptoms after eating is small intestinal bacterial overgrowth or SIBO.

This happens when, due to things like antibiotic use, poor diet or food poisoning, undesirable bacteria overrun the small intestine.

Read more about SIBO

In the case of a parasitic infection, the eggs and larvae can become lodged in your liver and digestive organs, causing symptoms every time you eat.

Many times these types of infection do not have the 'classic' signs of infection like fever and chills. Underlying infections can last for months or years when left untreated.

Lesser-Known Symptoms Of Infection

  • Brain Fog

  • Stomach pain, cramping

  • Headaches

  • Migraines

  • Rectal Itching

  • Irritability

  • Fatigue

  • Lethargy

  • Skin Rash

  • Eczema

  • Rosacea

  • Autoimmune-like symptoms

  • Body temperature regulation problems

  • Blood sugar regulation problems

Specific Reactions

In some cases, feeling bad after you eat certain foods can indicate a specific underlying problem. In these cases, the food you are eating is giving fuel to an underlying infection.

Mold Exposure, Bacterial & Fungal Infection

You May Particularly React To:

Parasitic Infection

You May Particularly React To:

  • Pork

  • Garlic

  • Dairy

  • Eggs

  • Preservatives

3. A Gallbladder Problem

Another common problem is when your gallbladder is not producing enough bile to properly digest your food.

Bile contains acids that help break down food, particularly fat and fat-soluble vitamins.

When bile production is too low it leads to the malabsorption of essential nutrients.

Even if these patients were to take the 'right' supplementation to reverse deficiencies, their digestion is so impaired that they would not be able to absorb what they needed.

A common symptom of a gallbladder disfunction is pain near the shoulder blades as well as morning nausea.

The first thing I recommend to these patients is to start their day off with the juice of a half of a lemon in a glass of warm water. This has remarkable therapeutic effects.

In the short term they would decrease their dietary fat while we worked to reboot their digestive system.

Stool and blood testing can be ordered to look at bile acids.

4. Low Stomach Acid

Low stomach acid can be caused by things like poor diet, not eating during an optimal window during the day, and chronic stress.

When there is not enough acid to digest food it can prevent the body absorbing key vitamin and nutrients.

It can also lead to pieces of food festering in your digestive tract, creating gasses and providing food for 'bad' bacteria.

In these cases, the first step is to take a half of a lemon in water about 15 minutes before each meal to aid digestion.

I would then prune the diet from anything that is hindering stomach acid production and administer natural treatments to increase stomach acid.

Symptoms of Low Stomach Acid

  • Nausea when taking pills

  • brittle nails (indicating a lack of absorption of minerals)

  • acid reflux

  • bloating

  • stomach pain and cramping

  • Nausea after eating

5. Intestinal Sensitivity Syndrome

Inflammation and nerve sensitivity in the lining of the intestines can cause symptoms every time you eat.

Foods you would particularly react to are those high in fiber - like fruits, whole grains and vegetables.

This can be very confusing for some patients as they generally have very healthy diets but have severe digestive symptoms, as their symptoms progress they try to eat even healthier (more fiber), which causes more symptoms!

The primary factor behind this intestinal sensitivity is a fungal or bacterial infection.

Our first step would be to temporarily adjust the diet so as not to aggravate the digestive system further. We would then target and kill any infection that is causing the inflammation while soothing the nerves.

We would slowly then increase the amount of fiber in the diet to 'mechanically' get rid of the waste of the infection.

The Herbs Of Functional Medicine

While treatment will vary widely depending on diagnosis there are a few high grade herbal supplements and healing foods that are a part of many patient's treatment plan.

Always get these supplements from a functional medicine doctor as many supplements you see at the store and on Amazon are either of poor quality or are counterfeit items.

To achieve optimal benefit you need to have the right form, quality and dosage for you in a pharmaceutical grade supplement.

When killing a bacterial or viral infection, berberine, garlic, oregano and olive leaf extract are frequently used to great effect. One of these would generally be paired with other treatments so that they can work synergistically to kill infection and repair the damage.

Soothing the nerves of the digestive system is a big part of reducing symptoms and inflammation. Lemon balm and marshmallow root are frequently used.

Once the infection is effectively on its way out the door, I would slowly increase the amount of dietary fiber to escort debris out of the intestinal tract.

To repair intestinal lining, vitamin A, zinc and marshmallow root can be excellent companions to primary treatment.

Need More Help?

As with any advise you read, it is important not to self-diagnose if you are experiencing severe symptoms.

I have a worldwide consulting practice as well as an office in Kansas City, Kansas, USA.

If you have severe or long-term digestive symptoms, you can talk to me directly by scheduling a Free 15 Minute Consultation or you can 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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