There’s good news for vegetarians with IBS as Australian researchers have identified a wider range of plant-based low-FODMAP food sources and also the best processing methods to make previously off-limits vegetarian foods tolerable.

The one in 10 people who follow a vegetarian or vegan diet face major difficulties with a low FODMAP diet because many of the foods they need as sources of protein, iron and vitamin B12 – such as legumes, nuts,  and soy products – are high in FODMAPs (fermentable oligo di mono-saccharides and polyols).

In a bid to widen the food options for vegetarians, Professor Caroline Tuck and colleagues from the department of gastroenterology at Monash University set out to investigate levels of FODMAPs in 35 foods popular in plant-based diets. They also tested how processing foods using methods such as pickling, canning and cooking might reduce FODMAP levels.

Publishing their results in the Journal of Human Nutrition and Dietetics, Professor Tuck and colleagues say they have identified and clarified  a wider range of vegetarian food options that are low in FODMAPs content. While some types of soy were high in FODMAPs, they showed that soy cheese, tempeh, pea-protein isolate and rice-protein isolate, were low FODMAP and therefore suitable for the diet in people with IBS.

Other nutrient-rich vegetarian foods found to be low FODMAP included macadamia milk (a source of calcium via fortification), dulse and kelp noodles (a source of iodine), and tempeh (a source of iron and zinc).

Their tests also showed how some methods of food preparation could reduce the FODMAP content of vegetable products, by taking advantage of the high water solubility of FODMAPs.

Pickling was found to have the most striking result, able to bring down FODMAP levels enough in garlic, beetroot and onion for these foods to be classified as ‘low FODMAP’.

Canning was also effective for lowering FODMAPs in red kidney beans – enough to place them in the low FODMAP range.

The tests also showed that FODMAP levels were reduced by 43% in red lentils after five minutes of cooking followed by straining.

“We propose that the water solubility of FODMAPs and the likely leaching of FODMAPs into the pickling liquid is the mechanism by which the FODMAP content is reduced, additionally it has been proposed that pH, time, water ratio and temperature may also influence the carbohydrate content following pickling,” the authors concluded.

By expanding the FODMAP database to provide more food sources of key macro and micro nutrients, the findings would help vegetarians and vegans who follow a low FODMAP diet to better adhere to dietary guidelines, Professor Tuck and colleagues suggested.

The variability in FODMAP content seen with plant-based foods depending on product, food processing and cooking methods, also highlighted the importance of individual tolerance testing in individuals with IBS, they added.

The study includes a sample FODMAP meal plan for vegetarians:

• Breakfast: 1/4 cup low FODMAP muesli

250 lactose free milk topped with 10 fresh or frozen raspberries/vegans substitute cow milk for calcium fortified macadamia milk (new) and wheat grass drink (new)

Snack: 10 almonds

• Lunch: Sandwich made with two slices gluten free bread or spelt sourdough bread, 20g cheddar cheese (vegan use soy cheese) 60g pickled beetroot (new), 95g sprouted mung beans, low FODMAP salad ingredients (lettuce, tomato, cucumber)

Snack: 1 cup fresh grapes

• Dinner: Stir fry made with 100g false chicken (new) 113 g kelp noodles (new) 95 g sprouted mung beans (new) 45 g pickled onion (new) low FODMAP vegetables, one egg / vegan use egg replacer (new)

Snack: 170g lactose free yoghurt/ vegans use coconut yoghurt (new)