What is a Low-FODMAP Diet? Benefits and Side Effects

If you’re suffering from gastrointestinal problems like Irritable Bowel Syndrome, it’s time you try the low-FODMAP diet. Developed at Monash University in Australia, this diet identifies and eliminates the foods that can trigger symptoms of IBS like bloating, pain, nausea, and constipation. Read on to learn more about the low-FODMAP diet and how to follow it.

What is the low-FODMAP diet?

A low-FODMAP diet eliminates or restricts foods that are high in FODMAPs. FODMAP stands for Fermentable Oligosaccharides, Monosaccharides and Polyols. These short-chained carbohydrates and sugars are not absorbed by the body well and can result in bloating and abdominal pain. If you eat too much, they stay in your gut and ferment. FODMAPs include –

  • Fructose – Fruits, high-fructose corn syrup, honey, agave
  • Lactose – Dairy products
  • Fructans – Wheat, onions, garlic
  • Galactans – Legumes like beans, lentils, and soybeans
  • Polyols – Sugar alcohols, and fruits with pits like apples, avocados, cherries, figs, peaches, or plums.

The principle behind the low-FODMAP diet is to give your gut a chance to heal, especially if you have irritable bowel syndrome. People with IBS can use this diet as part of their treatment.

How does low-FODMAP diet work?

The low-FODMAP diet aims to understand which FODMAPs you can tolerate and which ones you should eliminate from your diet. This helps you to follow a nutritionally balanced diet that only restricts those foods that trigger the IBS symptoms. The low-FODMAP diet should be followed under the supervision of a registered dietician. The low-FODMAP diet involves three phases – Restriction, Reintroduction, and Personalisation.

1. The restriction phase

This phase involves identifying all high-FODMAP food in your diet and removing them. This phase of the low-FODMAP diet can last from two to six weeks. Replace these high-FODMAP foods with low-FODMAP foods and see if there is a change in your symptoms. Some people may see an improvement in the signs in the first week; others may take more time. When you see a noticeable improvement in the IBS symptoms, you can move on to the next phase.

2. The reintroduction phase

During this phase, you slowly start reintroducing the foods that you identified as high-FODMAP and eliminated in the first phase. This process is essential to identify the FODMAP foods that you are intolerant to. Each FODMAP subgroup should be reintroduced separately. A trained dietician can help you with which foods to reintroduce and in what amount. You must also take a break between the reintroduction of different foods so that there is no crossover effect. It takes most people six to eight weeks to complete this phase.

3. The personalization phase

Once you have all the data about which FODMAP groups trigger IBS symptoms for you and which don’t, you can move on to the personalization phase. Your dietician can now help you to establish a long-term personalized FODMAP diet. You must also remember that tolerances can change over time. So, you must try to introduce foods that you couldn’t tolerate earlier, after a few months.

Foods you can eat

  1. Vegetables – Alfalfa sprouts, bean sprouts, bell peppers, carrots, green beans, bok choy, cucumbers, lettuce, tomato, turnips, potatoes, parsnips, olives, chives, ginger, eggplant, bamboo shoots, and zucchini
  2. Fruits – Strawberries, grapes, honeydew melon, cantaloupe, banana, blueberries, kiwi, lemon, lime
  3. Dairy that is lactose-free and hard cheeses
  4. Beef, pork, chicken, fish, eggs
  5. Soy products like tofu and tempeh
  6. Grains – Rice, oats, rice bran, oat bran, quinoa, cornflour, and sourdough spelt bread, gluten-free bread, and pasta
  7. Non-dairy milk – Almond milk, coconut milk, rice milk
  8. Drinks – Water, tea, and coffee (with non-dairy milk), fresh fruit juice
  9. Nuts and seeds – Almonds, Macadamia nuts, peanuts, pine nuts, walnuts, pumpkin seeds.

Foods to avoid

  1. Vegetables – Onion, garlic, cabbage, broccoli, cauliflower, snow peas, asparagus, artichokes, leeks, celery, beetroot, sweet corn, Brussels sprouts, mushrooms.
  2. Fruits – Peaches, apricots, nectarines, plums, prunes, mangoes, apples, pears, watermelon, cherries, and blackberries
  3. Beans and lentils
  4. Dried fruits and fruit juice concentrate
  5. Wheat and rye – Bread, cereals, pasta, pizza, crackers
  6. Dairy products that contain lactose – milk, yogurt, cottage cheese, soft cheese, custard pudding, ice-cream
  7. Nuts – Cashews, pistachios
  8. Sweeteners – Honey, agave, high fructose corn syrup, sorbitol, xylitol, maltitol, mannitol, isomalt
  9. Drinks – Alcohol, sports drinks, coconut water

Benefits of a low-FODMAP diet

The low-FODMAP diet is not a fad diet. It is highly beneficial for people with IBS. Here are some of the benefits that you can expect from following the low-FODMAP diet.

1. Reduced IBS symptoms

Irritable bowel syndrome (IBS) is a chronic condition that causes cramping, abdominal pain, bloating, gas, diarrhea, or constipation. The low-FODMAP diet can eliminate or lower these gastrointestinal symptoms in people with IBS.

According to a review of several studies by the University of Sydney, the low-FODMAP diet is highly effective in reducing the various symptoms of IBS (1). IBS can be broken down into different subtypes like IBS- D (diarrhea), IBS-C (constipation), IBS-M (mixed), and IBS-U (neither). A low-FODMAP diet can reduce the symptoms of all the IBS subtypes (2).

2. Long-term relief

The low-FODMAP diet provides long-term relief from symptoms of IBS. During a study, 103 patients of IBS followed a dietician-led low-FODMAP diet. Fifty-seven percent of these people reported satisfactory relief of symptoms one year after following the low-FODMAP process (3).

3. Improved quality of life

Besides lowering the symptoms of IBS, the low-FODMAP diet improves the quality of life of people with IBS. According to a 2019 study, people on a low-FODMAP diet experienced (4) –

  • Significant reduction in anxiety, fatigue, and depression
  • Decreased dysphoria and improved body image
  • Increased happiness and vitality
  • Enhanced social and sexual function


Small Intestine Bacterial Overgrowth (SIBO) is a serious condition in which the bacteria in the small intestine grow out of control. SIBO is three to five times more common in people with IBS. In fact, bacterial overgrowth is responsible for IBS symptoms (5). A FODMAP diet can nourish the gut bacteria and reduce bacterial overgrowth and control SIBO.

Side effects of the low-FODMAP diet

1. Nutritional deficiency

Foods rich in FODMAPs are also rich in several vitamins and minerals. When you eliminate such food from your diet, you run the risk of deficiencies in calcium, iron, zinc, folate, and vitamin D. While you may discard many foods from your diet in the first phase, many of them are reintroduced in the second phase.  Always consult a dietician when you go on a low-FODMAP diet to ensure that your nutritional deficiencies do not persist.

2. May harm gut flora

A healthy and nutritious diet is essential for healthy gut flora. Some types of beneficial bacteria like Bifidobacteria feed on FODMAPs. The low-FODMAP diet can result in a decrease of the Bifidobacteria population in the gut. When beneficial bacteria ferment small carbohydrate molecules in the gut, they produce short-chain fatty acids like butyrate. These fatty acids nourish the cell lining in the large intestine. This shows that some FODMAPs are essential for optimal intestinal health (6).

3. Difficult to follow

Low-FODMAP diets can be challenging to follow on your own. Lack of knowledge or information can cause problems. Eating out can also be stressful as many restaurants do not have any low-FODMAP options available.

4. Expensive

Low-FODMAP diets can be costly. In many cases, you have to replace staple food items with more costly options like exotic fruits, amaranth, quinoa, or buckwheat to avoid nutritional deficiencies.

How much does a low-FODMAP diet cost?

A low-FODMAP diet can be moderately pricey. You need to hire a dietician, which can be expensive. Depending on the region and years of experience, a dietician can charge from $150 to $350 per hour. A low-FODMAP diet can also add to the cost of the food bill. Lactose-free milk, gluten-free bread, spelt, quinoa, etc. can add to the cost.

Can the low-FODMAP diet help in weight loss?

Though this diet does help in reducing bloating in the belly, it does not necessarily help in weight loss. If you swap wheat for FODMAP-free potato chips, you will not lose weight.

Can you exercise while following the low-FODMAP diet?

Yes, you can exercise while following the low-FODMAP diet. Moderate exercise helps in weight loss and keeps your heart healthy.

Can vegetarians follow low-FODMAP DIET?

Yes, vegetarians can follow a low-FODMAP diet. However, since most vegetarian sources of proteins like legumes are high in FODMAPs, it can be a bit challenging. You can opt for low-FODMAP vegetarian protein options like tofu and tempeh. You can also include a small portion of canned legumes in this diet.


Final thoughts

A FODMAP diet is a three-phase diet that helps to lower the symptoms of irritable bowel syndrome. It also provides long-term relief, improves quality of life, and reduces small intestine bacterial overgrowth. However, not everyone with IBS benefits from this diet. Since food rich in FODMAPs are also rich in vitamins and minerals, this diet can lead to nutritional deficiencies. A low-FODMAP diet can also harm the gut flora.

This diet may be challenging to follow, so you must consult a dietician to help you follow this diet and to ensure that you get enough nutrition while following this diet.


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