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Ask the doctor: Our new plant-based diet is making my husband and son very flatulent. Help!


Changing your diet can lead to flatulence

Changing your diet can lead to flatulence

Changing what you eat can lead to excessive gas

Changing what you eat can lead to excessive gas


Changing your diet can lead to flatulence

We have decided to cut down on our meat consumption as a family and have it once a week. I have now been using beans and lentils and a lot more vegetables. The thing is, my husband and 13-year-old son have become so flatulent that the rest of us are struggling to be around them. It has been around three weeks and there is no let up. My son wants us to give up as he said there is no way he will go back to school in this state. My husband on the other hand thinks it is hilarious. Have you any remedies or ideas?

Although there is a list of potential underlying medication conditions that may cause increased intestinal gas, I will assume this is purely due to your recent dietary change. I commend you for making positive changes to your diet and trying to become more ‘flexitarian’ by reducing over-reliance on meat. This usually comes with some notable side effects as you and your family have noticed, but I feel the nutritional and health benefits from increasing fibre and sources of protein other than meat are well worth it.

A flexitarian diet is more flexible than going fully vegetarian or vegan and encourages more plant-based and minimally processed foods while allowing moderate consumption of animal products (meat, fish, chicken and dairy). The possibility of a few nutritional deficiencies such as vitamin B12, iron, calcium, zinc and omega-3 fatty acids can be easily addressed by taking the appropriate supplements. Vitamin C supplements will help absorption of iron from plant-based food.

Some facts about intestinal gas include:

⬤ The volume of gas in the intestinal tract is approximately 200ml in the fasting state or just after eating.

⬤ This is true of people who complain of excess intestinal gas and in those people who do not have any complaints.

⬤ The volume of gas passed per rectum varies from about 500ml to 1500ml per day.

⬤ The frequency of gas released varies between 10 and 20 times per day in healthy subjects.

⬤ Individuals who report excessive gas usually fall within this range of normal.

The main gases do not have an odour. Minor constituents of flatus, to which odour may be attributable, include sulphur-containing compounds, short-chain fatty acids, volatile amines, and ammonia. Hydrogen (H2) is both produced and consumed by faecal bacteria predominantly in the colon.

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In healthy individuals, certain foods with high concentrations of oligosaccharides (found in legumes), or resistant starches (wheat, oats, potatoes, and corn), cannot be completely digested by enzymes within the normal small bowel, leading to increased H2 production and increased flatus. Other foods such as beans, lentils, cabbage, onions, broccoli, brussel sprouts, celery, carrots, raisins, prunes, apples and fruit juices are known to increase intestinal gas.

I suggest carefully selecting ingredients that are consistent with a low FODMAPs diet. This stands for food low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. One of the best ways to understand this is to print from the internet a visual guide with a list of foods to avoid (red light) and foods which are low in FODMAPs (green light).

Much like the flexitarian diet, you do not have to be strict on this red-green light system but you will come to understand what food types disagree with you most. You may find one visit to a local dietician will provide you with enough tools to be able to tolerate your new healthier diet without having to put up with excessive intestinal gas.

Dr Jennifer Grant is a GP with Beacon HealthCheck

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