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Diet Modifications for Gastrointestinal Symptoms: It’s personal, but in a good way

No two gastrointestinal (GI) tracts are alike. I bet you’ve never heard an article with that opening line. But it’s true, the hollow organs that make up your GI tract–mouth, esophagus, stomach, small intestine, large intestine, and rectum–can differ slightly in structure and functionality from person to person. These organs determine how well food can be digested and absorbed. The amount of acid your stomach produces, the absorptive capacity of the epithelial cells in your small intestine, and the kind and quantity of bacteria in your large intestine, are examples of how digestive capabilities are dependent on several elements. The presence of functional bowel disorders, such as constipation, diarrhea, IBS, use of NSAIDs, antibiotics, or other medications, digestive motility, and level of inflammation from GI diseases (ulcerative colitis or Crohn’s) can impact the types of food that one can tolerate. Personalizing nutrition to the individual is key for preventing and managing symptoms of GI conditions in addition to symptoms of chronic disease.

Ordovas et al. defines personalized nutrition as “an approach that uses information on individual characteristics to develop targeted nutritional advice, products, or services [i].” A one-size-fits all paradigm does not apply to nutrition. It is why government officials and health-care professionals offer nutrition “guidance” rather than concrete protocols or meal plans. Personalization of nutrition interventions is necessary to maximize “the benefits and [reduce] the adverse effects of dietary changes for the individual [i].” Basically, nutrition intake that doesn’t align with an individual’s needs can do more harm than good.

How Digestion Influences Our Nutrition Needs

Oftentimes gastrointestinal function, or lack thereof, determines how well someone digests and absorbs (the nutrients of) certain foods. Functional GI-disorders (FGID) are due to disorders of the gut-brain axis–how your brain sends signals to the nerves in your gut. The symptoms of FGID can be incredibly bothersome to the person experiencing them; symptoms include, but are not limited to, constipation, diarrhea, pain, bloating, and difficulty swallowing [ii]. For this reason, symptom management via personalized nutrition interventions can vastly improve a person’s day to day wellbeing and comfort-level.

Let’s talk about some of these disorders and how different dietary interventions can help or hurt symptoms of them.

Constipation is Not Simply a Matter of Lack of Fiber

There are many reasons why one might experience constipation, including lack of fiber, irritable bowel syndrome (IBS), gastroparesis (slow-motility), opioid-induced constipation (OIC), and pelvic floor dysfunction (PFD). Even if you eat a high fiber diet, it’s still possible to get constipated if you create more stool than your body can excrete in a day.

The dietary interventions for constipation will differ slightly depending on the cause of constipation. For example, if you have PFD, fiber and laxatives can worsen symptoms. But if you have IBS-related constipation or gastroparesis-induced constipation, then over-the-counter laxatives, and increased fiber intake (food or supplements) can help. Two opposing solutions for the same apparent problem!

Gastroparesis-induced constipation is common in individuals with chronic high blood sugar or diabetes, meaning high blood sugar can cause a slowing down of the GI tract, which can lead to constipation.

Generally, it is recommended that a high fiber and low glycemic diet is followed if you have diabetes. However, a high fiber diet can exacerbate gastroparesis since fiber takes longer to digest and there is already slowed motility. The solution to this double whammy of high-blood sugar induced gastroparesis and gastroparesis-induced constipation is to modify the texture of high fiber, low-glycemic foods. For example, pureed parsnips and fennel are more easily digested since their particle size is reduced prior to digestion.

To add another level of diet puzzlement, I mean personalization, high fiber, low glycemic carbohydrates are often not well tolerated by those who have irritable bowel syndrome (IBS). The diet of someone with IBS versus someone with diabetes will differ according to personal tolerance and acceptability.

Personalization is Key for Managing Symptoms of Irritable Bowel Syndrome

IBS side effects include severe pain, bloating, and bowel changes after ingesting certain short-chain carbohydrates, known as FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols). IBS is a type of functional bowel disorder (FBD), which is just a fancy way to describe a condition where there is no apparent inflammation or structural issue with the intestines [iii]. All treatment protocols and dietary changes are made according to symptom presentation.

Management of IBS requires a high level of diet personalization. One person with IBS might be able to consume disaccharides, such as lactose, but not foods containing polyols, such as cauliflower. In addition, quantity of FODMAPs must be personalized. Tolerance of certain foods can vary according to dose. For example, someone could experience no adverse symptoms after eating half a clove of garlic, but one whole clove could cause bloating, gas, and pain. But thankfully, personalization of dietary management can resolve or reduce many of the unpleasant symptoms of IBS.

Indigestion: The Infamous IBD

According to recent data, more than 20% of the population experiences indigestion, known as dyspepsia in the medical world [iv]. Non-ulcer or -GERD induced indigestion can be a result of going too long in between meals (or not having any intake for an extended period), eating high volume or high fat meals, and drinking alcohol (particularly on an empty stomach). Dietary interventions include consuming more frequent meals, eating smaller low-fat meals, and avoiding alcohol on an empty stomach.

Like IBS, management of dyspepsia (aka indigestion) requires modifying quantity of food intake [v]. Smaller, more frequent meals can manage symptoms of dyspepsia but could exacerbate symptoms in someone who has constipation [vi]. It is recommended for those with constipation to eat larger, but fewer meals throughout the day. Large, bulky meals trigger the gastrocolic reflex, which controls the movement of the lower intestinal tract after a meal [vii].

However, as mentioned above, if your constipation is a result of gastroparesis, smaller meals might be your best bet. And herein lies the moral of this incredibly drawn-out story: understanding what is causing your digestive ailments (or any ailment for that matter) can aid in personalizing your diet for symptom alleviation, and your healthcare team can help. Nutrition is nuanced! A recommendation that might be appropriate for one condition could exacerbate another. So don’t be afraid to get personal with your diet–your gut and the rest of your body will thank you!


[i] Ordovas JM, Ferguson LR, Tai ES, Mathers JC. Personalised nutrition and health. BMJ. 2018;361:bmj.k2173. Published 2018 Jun 13. doi:10.1136/bmj.k2173

[ii] Fikree A, Byrne P. Management of functional gastrointestinal disorders. Clin Med (Lond). 2021;21(1):44-52. doi:10.7861/clinmed.2020-0980

[iii] Aboubakr A, Cohen MS. Functional Bowel Disease. Clin Geriatr Med. 2021 Feb;37(1):119-129. doi: 10.1016/j.cger.2020.08.009. Epub 2020 Nov 2. PMID: 33213766.

[vi] Francis P, Zavala SR. Functional Dyspepsia. [Updated 2021 Apr 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554563/

[v] Mahadeva S, Goh KL. Epidemiology of functional dyspepsia: a global perspective. World J Gastroenterol. 2006;12(17):2661-2666. doi:10.3748/wjg.v12.i17.2661

[vi] Definition & Facts of Indigestion. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/digestive-diseases/indigestion-dyspepsia/definitionfacts#:~:text=Indigestion%20is%20a%20common%20condition,the%20United%20States%20each%20year.&text=Of%20those%20people%20with%20indigestion,are%20diagnosed%20with%20functional%20dyspepsia.

[vii] Malone JC, Thavamani A. Physiology, Gastrocolic Reflex. [Updated 2021 May 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549888/

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