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Could a supplement of vitamin D help improve your quality of life if you have IBS?

Vitamin D is sometimes called the sunshine vitamin (it’s not actually even a vitamin but a hormone, but let’s just call it vitamin D for now!) 

The first thing to note, is that people with IBS or SIBO may be more likely to have low levels of vitamin D, compared to healthy controls.  

Is IBS linked to vitamin D deficiency?

If you’ve got long standing IBS or SIBO you could be more likely to have certain vitamin deficiencies.

This is due to potential absorption issues in your small intestine. For example, Vitamin A, D, E and K are fat soluble, which means they need fat from our diet to help them get into the cells.

The second reason for vitamin deficiency in IBS is diet restriction. You might be eliminating certain foods from your diet such FODMAPs, or high fat foods to avoid symptoms. This can lead to issues with nutrient availability over time. 

Vitamin D and SIBO (Small intestine bacterial overgrowth)

When there is an excess of bacteria in your small intestine the bacteria can interfere with dietary fat absorption. This could affect your vitamin status.  (BTW if you want to read more about SIBO I’ve written article previously such as What is SIBO?)

A study from 2019 showed that people with IBS who were low in Vitamin D felt better at the end of a 12 week supplementation trial. Their levels of Vitamin D rose from inadequate to adequate through large once a week dosing (50,000iu taken under professional control). At the end of the study participants felt better in themselves. 

This result hasn’t always been replicated. Another study found there was no improvement in quality of life after taking a moderate dose of vitamin D (3000iu) for 12 weeks. 

Quality of life scores could be influenced by mood. When we feel more positive we can better manage symptoms, and you feel more resiliant. We know that depression and low mood can also be influenced by vitamin D status.

golden yellow background, gel yellow capsules in a sun shape, words Vitamin D for IBS & SIBO in brown

How to top up vitamin D

Basically unless you’re going on holiday in the winter, if you live in the UK you need to supplement! 

Vitamin D is mostly created through our skin, when we are exposed to direct sunlight. During autumn and winter months in the northern hemisphere you will need to supplement to get a sufficient intake. This is mostly because there really isn’t enough sun exposure to convert to vitamin D.

Also, there is only a limited amount you can get from food. You might get around 10% of your vit D requirements if you eat oily fish regularly, but there isn’t a reliable source from our diet.  

The NHS recommends supplementing with vitamin D throughout the winter months (October to April). You should also supplement during the summer if you always cover your skin, rarely go outside in the sun or always wear high factor sun cream. 

Will supplementing help my digestion? 

If your levels aren’t low, then supplementing may not actually improve your digestive symptoms. However in the UK, it’s likely your levels could be low. On average 30–40% of people are deficient between January–March. After the sunshine exposure we (hopefully) get in the summer months this drops to 2–13% of the UK population who could be deficient (July–September). 

Ensuring you have adequate vitamin D can be a helpful check when dealing with a gut condition. Vitamin D receptors are expressed in the gut, and it’s thought that having sufficient levels might help protect the integrity of the gut (preventing ‘leaky gut’). 

We know that low levels of vitamin D is common in people with Inflammatory Bowel Disease, and low vitamin levels may precede an IBD flare up.

silhouetted finger and thumb holding a gel capsule up to the sun, against a blue sky.

IBS and osteoporosis

It’s not just your gut health that could be affected. If you have a low vitamin D level you could be at risk for bone fractures or osteoporosis.  Vitamin D helps us use calcium to make stronger bones, teeth and support our heart health.

If you’re avoiding dairy because it gives you bloating, diarrhoea or gas then you need to ensure you’re getting alternative sources of calcium, and also obtaining adequate vitamin D to maximise the calcium you do consume. 

Vitamin D is also really important for our immune health by supporting T-Reg cells which turn off the inflammatory cascade. Low levels of vitamin D can be implicated in autoimmune conditions, potentially linked to this action in the immune system.

How much should I take for IBS? 

I’d advise getting your levels checked before you supplement so you know whether you need a maintenance dose throughout the winter, or whether you need to boost your levels up from a deficient level. 

The NHS guidelines are to take 400iu per day, but this is on the low side of a useful dose. Even if you don’t get your blood levels checked first most people can take around 1000iu per day with no issues.

More isn’t better

It’s definitely not advisable to start taking huge doses like the 50,000iu from the research studies without medical supervision. You shouldn’t even take high doses such as 5000iu for prolonged periods. You can have too much of a good thing! Because it’s fat soluble vitamin D can be toxic at high doses. More isn’t always better.

Hi I'm Anna Mapson, registered Nutritional Therapist.

I help people with IBS and SIBO get control of unpredictable gut symptoms to find long term relief from painful and embarrassing IBS without restrictive dieting.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • develop better digestion and more energy

Find more about my 3 month 1:1 Gut Reset programme

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