Remember when you could enjoy a particular food in the past, but not so anymore without any stomach issues? That is the journey of ageing — apart from getting some wrinkles here and there, our digestion goes through changes as well. This change is known as food intolerance, an occurrence that can affect anyone at any age but increases as we get older. This is due to slower emptying of the stomach and microbial imbalance in the small intestine that come naturally with age.

Over 20% of the population in developed countries experience some form of food intolerance. A common one I see in Asian countries like Singapore is lactose intolerance, which comes with symptoms like diarrhea and abdominal cramps upon consuming dairy. In fact, about 65% of people do not digest lactose as well as soon as after infancy!

Allergy or intolerance?

Many people confuse food tolerances with food allergies because they share similar symptoms. However, both conditions are quite different, especially the impact of their onset.

A food allergy involves the immune system and occurs when the body mistakes a foreign ingredient —usually a protein— as harmful and attacks it by producing high levels of an antibody known as immunoglobulin E. What this means is that the patient goes through a slew of reactions, including:

  • Rashes or hives
  • Nausea
  • Stomach pain or cramps
  • Diarrhea
  • Swelling
  • Irregular heartbeat or difficulty breathing
  • Anaphylactic reaction – the most severe life threating reaction

A food intolerance, on the other hand, stems from a digestive issue. As mentioned, food intolerances happen more often as you age as your digestion slows down, which allows more time for bacteria to ferment in your gastrointestinal tract. Apart from dairy, some common sensitivities I see are dried fruits, canned goods, and monosodium glutamate (MSG) found often in Chinese food and chips.

When triggered, food intolerance presents itself with symptoms like:

  • Nausea
  • Diarrhea
  • Heartburn
  • Stomach pain
  • Headaches
  • Irritability or nervousness

As you can see, the symptoms more or less mirror that of food allergies, except food intolerances are rarely ever life threatening.

Below, I have a simple summary of the difference between food allergies and food intolerances.

Food Allergy Food Intolerance
What it affects & how it onsets Affects the immune system, may affect multiple organs,
may be life threatening, symptoms often appear quickly
Affects only the digestive system,
less serious and symptoms take a while to onset
Who does it affect? Usually diagnosed in childhood and carries through adulthood,
although it may develop at any age depending on when the
person is first exposed to the food
Usually developed in adulthood
What is it triggered by? Usually triggered by specific food like fish, nuts, soy, milk,
wheat, and eggs. Can be triggered even by a small amount
Usually triggered by multiple types of food
groups like fructose, galactans, gluten, lactose,
artificial sweeteners, and fermented food

Autoimmunity and food intolerance

We know that gluten can trigger celiac disease in genetically predisposed individuals, but are those with other autoimmune diseases more prone to food intolerance? Based on what we’ve studied so far, those with autoimmune diseases tend to have more food intolerances. Among the most reactive foods are wheat, cow milk, gliadin, casein, egg whites and rice. The good thing is that so far, we have not got many reactions from food like vegetables and fish (excluding shellfish) and meat.

How to manage food intolerance

A food tolerance can be tricky to pinpoint because you can still eat a small portion of a problem food without causing any trouble. What I make my patients do is to keep a detailed food diary and write down what they eat for every meal, including snacks and portion size. I get them to document the symptoms for every food.

Try to maintain this diary for 2 to 4 weeks and review it. You should be able to find a connection between symptoms, certain foods, and portion sizes. Once you pinpoint some food that coincides with your symptoms, try eliminating one ingredient at a time or adjust your serving sizes. This way, you can still enjoy your favorite food without experiencing symptoms.

For patients, whose problem food is a source of important nutrients, I make sure they find an adequate replacement. Take lactose intolerance for example. You can still get in plenty of calcium through lactose-free milk, almond milk, or other plant based milk fortified with calcium.

Overall, if managed well, food intolerance is nothing much to fret about and there are many ways to work around it without compromising on your quality of life!


  1. Coucke F. (2018). Food intolerance in patients with manifest autoimmunity. Observational study. Autoimmunity reviews, 17(11), 1078–1080.
  2. Di Costanzo, M., & Berni Canani, R. (2018). Lactose Intolerance: Common Misunderstandings. Annals of nutrition & metabolism, 73 Suppl 4, 30–37.