Low FODMAP diet: Reducing fermentable carbohydrates in your diet

What are FODMAPs or fermentable carbohydrates?

FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) is a term to describe a group of fermentable carbohydrates. These carbohydrates are not absorbed or digested well in the small bowel, meaning they pass on into the next part of your bowel called the large bowel. The bacteria that is naturally living in the large bowel breaks down (‘ferments’) these carbohydrates. Some people are more sensitive to this process of fermentation and it can cause symptoms such as wind, bloating, abdominal (tummy) pain or discomfort and a change in bowel habit such as diarrhoea or constipation. These symptoms are often described as functional gut disorder or irritable bowel syndrome (IBS).

Which carbohydrates are fermentable?

The following types of carbohydrates are most commonly fermented in the large bowel:

Fructose - this is a type of sugar, mainly found in fruits and honey. It is also added to processed food products as a sweetener or to enhance flavour, appearance or texture.

Fructans – these are carbohydrates made up of lots of fructose sugars joined together. These are called fructo-oligosaccharides (FOS), oligofructose and inulin. Fructans are found in wheat products such as bread, pasta, breakfast cereals, and some vegetables e.g. onions and garlic. They are also added to some processed foods.

Galacto-oligosaccharides (GOS) – these are carbohydrates made up of lots of a different type of sugar called galactose. The main foods where you find GOS are beans and pulses.

Polyols – these are ‘sugar alcohols’ such as sorbitol and mannitol. They naturally occur in some fruits and vegetables and are also added as artificial sweeteners in confectionary such as sugar free chewing gum, mints and chocolate.

Lactose – this is a type of sugar found in dairy products for example cow, sheep and goat’s milk and products made with these milks.

How do I reduce fermentable carbohydrates in my diet?

To achieve the best possible improvement in your symptoms it is best to avoid all foods that contain: fructose, fructans, GOS and polyols for an initial period of four - six weeks.

For some people they may also need to avoid lactose as well; your dietitian will advise you of this. This is not a permanent diet but a temporary restriction and you will then gradually reintroduce these back into your diet - your dietitian will give you more information about this stage of the diet when you need it.

What can I eat on this diet?

The following table gives information on foods high in fructose, fructans, GOS and polyols to avoid along with suitable alternatives.

Please remember to check the ingredients lists on pre-packaged food labels to see if they are suitable (see ‘How do I check for suitable ingredients?’)

Lactose malabsorption

Only some people will have lactose malabsorption. Most people with lactose malabsorption can include small amounts of lactose without getting symptoms. It is not necessary to exclude all dairy foods. If you tolerate lactose or have had a negative lactose breath test you do not need to avoid dairy products.

Which ingredients should I look out for when limiting lactose in my diet?

The following ingredients contain lactose:

• Lactose
• Buttermilk
• Milk solids
• Skimmed milk powder
• Whey

Remember to also check suitable lactose free foods for other fermentable carbohydrates as above e.g. unsuitable fruit, FOS, inulin, oligofructose, fructose.

Will I get enough calcium if I limit lactose in my diet?

Calcium is an essential nutrient for healthy bones and teeth. By limiting lactose in your diet you may reduce your intake of calcium.

Aim to have at least three portions every day of alternative dairy products as above; choose calcium enriched types where possible.

Other good sources of calcium are tinned fish with edible bones, tofu, calcium-fortified wheat-free breakfast cereals and some drinking water.

How do I check for suitable ingredients?

Always take time to check the ingredients lists on food labels of pre-packaged products to help you determine if they contain fermentable carbohydrates.

The ingredients list for flavoured rice cakes can be seen below as an example; the fermentable carbohydrate has been highlighted.

Which ingredients should I look out for on food labels?

Avoid any foods that contain the following ingredients:

Also check the ingredients lists for any flavouring from unsuitable fruits

Ingredients containing wheat and barley as a minor ingredient such as thickeners, starches and flavourings, need not be avoided.

Can I drink alcohol and caffeine?

You can drink alcohol and caffeine if you know that you usually tolerate these as both caffeine and alcohol can exacerbate functional gut symptoms. Keep alcohol within recommended government limits of no more than 14 units a week, aiming to have 2 alcohol free days per week.

For more information on government recommendations on alcohol intake please ask your dietitian or visit NHS choices: Alcohol-units (opens in a new tab)

Medication

If you are taking medication that helps with your gut symptoms, for example anti-spasmodic or anti-diarrhoeal, continue to take these while on the low FODMAP diet.

It is important to check the ingredients of your medication, in particular looking for sorbitol or mannitol. Lactose may also be an ingredient but usually this amount of lactose is not a problem. Always check with your doctor before stopping any medication or if you want to change medication.

Constipation

Due to the restrictions of the low FODMAP diet, some people may find they experience constipation. To help relieve this is it important to ensure you take sufficient fluids and dietary fibre. The UK recommended dietary fibre intake for an adult is 30g per day but most people don’t manage this. Fibre is found in oats, grains, fruit and vegetables, nuts and seeds.

If you experience constipation:

• Have at least five portions of suitable fruit and vegetables per day
• Aim for 1.5-2litres (8-10 cups/glasses) per day of fluids, ideally water. It may help to keep a bottle of water with you throughout the day, not including caffeine or alcohol
• Oats are a good source of fibre and can be eaten daily e.g porridge/ oat cakes/flapjacks
• If having wheat-free bread opt for the brown/high fibre/multiseeded types
• Add 1 tbsp linseeds or oat/rice bran to foods e.g breakfast cereals - it is important to have an additional 300mls of fluids (per tbsp of supplement). The quantity can be gradually increased if needed.
• Kiwi fruit (1-2 per day) or psyllium husk (can build up from 1tsp to 1tbsp/day) can also be added to your diet
• Increase fibre slowly into your diet as a sudden increase may cause IBS-like symptoms.

Probiotics and prebiotics

There is some evidence that probiotics can help certain people with IBS abdominal pain symptoms. However, it is advised to wait until after you have completed the low FODMAP diet before trialling probiotics. Prebiotics are often found in medications and some foods, again it is advised to avoid these whilst on the low FODMAP diet.

Vegetarian or vegan diets

It is advised to cut out pulses and legumes and to use other low FODMAP protein sources such as tofu, QuornTM, seeds, nuts, dairy and eggs as preferred.

If legumes and pulses can’t be avoided try to limit it to small amounts of tinned legumes as these may be better tolerated or to portion sizes stated in protein section. Ensure the rest of the diet is strictly low FODMAP.

How can I follow a healthy, balanced diet that is low in fermentable carbohydrates?

• Fruit and vegetables Aim to eat five portions of suitable fruit and vegetables every day. It is best to eat a variety of different types to get a variety of vitamins and minerals from your diet. Have only one portion of fruit at a time. There is no upper limit to the amount of the ‘suitable’ vegetables you can have at once.
• Starchy foods such as wheat-free bread & pasta, rice, and potatoes, should make up about a third of your diet. Spread them throughout the day and have something from this food group at each meal.
• Protein foods Aim to eat two portions of suitable meat, poultry, eggs or vegetarian protein foods every day. One portion is about 100g or two eggs.
• Milk, dairy and dairy alternatives Aim to eat three portions per day. One portion is 200mls milk (one glass), 125-150g yoghurt (one small pot), 30g cheese (one small matchbox size).
• Fatty and sugary foods. For a healthy diet you should try to eat fewer foods that are high in fat and sugar, however if you are unintentionally losing weight then these can be helpful. Choose unsaturated fats such as polyunsaturated fats (sunflower oil/soya oil/fish oil) or mono-unsaturated fats (olive oil/rapeseed oil/nuts (except pistachio) in preference to saturated fats (animal fats) where possible.

Home cooking

Processed and ‘ready’ meals and foods such as sauces and soups often contain fermentable carbohydrates. Therefore cooking from scratch using fresh ingredients at home may make it easier to follow a diet low in fermentable carbohydrates.

Spend a good amount of time planning the diet before you start.

Suitable meal ideas

Eating out

Eating out can be challenging when you are following a diet low in fermentable carbohydrates. You may experience symptoms after eating out as it is difficult to avoid all problem ingredients.

The following tips may help you to choose suitable options:

• avoid eating batter and coatings or if possible scrape them off
• ask for sauce or gravy to be served separately
• choose meals without sauces and dressings
• gluten-free options are useful but check for other ingredients such as onions and garlic
• opt for plain fish/meat/poultry/eggs with salad or vegetables or baked potato with a suitable filling and salad
• if possible, try and look at the menu before eating out or contacting the restaurant ahead of time to see if they can make you a special meal

What about foods that are not listed?

The fermentable carbohydrate content of all foods is not yet known. You can discuss the suitability of foods not listed with your dietitian but if in doubt then avoid the unknown food.

What should I do after I have followed the diet for four- six weeks?

Your Dietitian will aim to see you again after an agreed period on the diet to monitor your progress and any relief from your symptoms.

If your symptoms have improved you can start to gradually reintroduce some fermentable carbohydrates. Your dietitian will talk you through how to do this.

If your symptoms have not improved sufficiently your Dietitian might check that you have successfully removed all FODMAPs from your diet and might either recommend that you continue to follow the diet for a further period of time or discuss alternative dietary restrictions.

If the low FODMAP diet has not significantly improved your symptoms then it may be helpful for your next appointment if you keep a food and symptom diary for 5-7 days. Write down what you have been eating and what gut symptoms you have been having, ensuring you note the time of all meals, drinks and snacks and your gut symptoms.

How do I contact my dietitian if I have any questions?

Dietitian

Contact Number

Contact Email _____________________________________________