With winter behind us and summer approaching, patients with Inflammatory Bowel Disease (IBD) are wondering whether it is a good idea to go out in the sun while taking medication.

It should be borne in mind that most of the vitamin D in our bodies comes from ultraviolet radiation from the sun, followed by the intake of vitamin D-rich foods. In Crohn’s disease, for example, 60-75% of patients are vitamin D deficient. In the case of Ulcerative Colitis, 55% of patients are deficient.

The entire population should always take preventive measures to avoid damage from exposure to the sun, but, in addition, people who are being treated with certain drugs should take into account the characteristics of these drugs, as their properties or effects may be altered.

This is why IBD patients, in particular, should avoid overexposure to the sun, while still achieving appropriate vitamin D levels.

  1. Vitamin D and IBD

Vitamin D promotes the absorption of calcium, a mineral that is very important for maintaining healthy bone structure. That’s why adequate sun exposure helps our body to provide itself with the necessary levels of vitamin D. In addition, vitamin D may have beneficial effects on the progression of IBD.

Vitamin D not only regulates calcium metabolism, but also plays a crucial role in the modulation of the immune system with potential beneficial effects on the course of IBD. Through its anti-inflammatory, immunoregulatory and epithelial actions, it helps to control disease activity and improve clinical outcomes.

In IBD, vitamin D plays a number of roles, including:

  • Immunoregulation: Vitamin D reduces the activity of pro-inflammatory T cells (Th1 and Th17), and promotes regulatory T cells (Treg), which help maintain immune tolerance in the gut and control inflammation.
  • Reduction of inflammatory substances or cytokines: Inhibits the production of TNF-α, IL-6 and IL-17, which are elevated in active IBD flares.
  • Strengthening the intestinal barrier: Improves intestinal epithelial integrity by increasing the expression of cell-binding proteins, thus preventing the entry of bacteria and antigens that exacerbate inflammation.

Clinical studies have found that adequate levels of vitamin D are associated with:

  • Reduced clinical disease activity.
  • Lower relapse rate in patients in remission.
  • Reduced need for hospitalisation and surgery.
  • Improved patient-reported quality of life.

For example, a randomised clinical trial published in the Journal of Crohn’s and Colitis (2013) showed that vitamin D3 supplementation (up to 5,000 IU/day) in patients with Crohn’s disease helped maintain remission and reduce inflammatory markers.

It is recommended to maintain serum 25(OH)D levels above 30 ng/mL in IBD patients. Therefore, oral supplementation is often necessary, especially in winter or in patients with impaired absorption or low sun exposure.

  1. IBD medications and sun exposure

Some studies have suggested that increased sun exposure may be associated with a lower risk of developing Crohn’s disease. In particular, a prospective study in France found that women with higher sun exposure had a significantly lower risk of developing Crohn’s disease, although the same association with ulcerative colitis was not observed.

However, some IBD drugs are photosensitisers. This means that they can produce photosensitivity reactions, resulting in abnormal skin damage caused by the interaction between a photosensitising chemical agent (some drugs) and solar radiation.

Ultraviolet (UV) radiation is highly associated with the development of skin tumours and photosensitivity reactions to drugs. In the case of tumours, radiation accumulates over the course of our lives in what is called the skin memory. The risk of skin tumours increases in patients treated with immunosuppressive drugs, especially those treated with thiopurines.

  1. Sun prevention measures.

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  • Avoid exposure to the sun at peak hours (from 12:00 to 16:00), as this is the time when there is maximum UV radiation.
  • Wear clothing to protect yourself from the sun such as hats, T-shirts or sunglasses.
  • Avoid the famous tanning booths.
  • Apply creams with a very high protection factor (preferably 50+) and with UVA and UVB filters.
  • For sunscreens to be effective you should use enough sunscreen to cover the entire surface of the body.


It is important to remember areas such as the ears or scalp.

  • Apply the creams on dry skin, as the water droplets have a magnifying effect, thus increasing the risk of burns.
  • Apply sunscreen 30 minutes before sun exposure.
  • Replenish the sunscreen after each prolonged bath or every two hours.
  • Use water-resistant creams and, if bathing for more than 20 minutes, reapply them after bathing.

  1. The sun and the little ones


Vitamin D deficiency is common in the paediatric IBD population and is associated with increased disease activity. It is therefore critical to monitor and correct vitamin D levels as part of the comprehensive management of IBD in paediatric patients.

An observational study in children with Crohn’s disease found that approximately 19% were vitamin D deficient and 38% were vitamin D insufficient. This deficiency is attributed to factors such as intestinal malabsorption, chronic inflammation, reduced sun exposure and dietary restrictions associated with the disease.

At the Australian National University, researchers have reported that children who are exposed to the sun for half an hour a day reduce their risk of developing Inflammatory Bowel Disease (IBD) by 20 per cent.

Despite this, we need to be sun-smart and protect ourselves and our children from the sun’s rays with the measures mentioned above.

However, it is worth going outdoors, having a drink on a terrace… but always safely and with photoprotective creams on your body.

References

  • Infosalud. (2019, 31 de mayo). Media hora de sol podría disminuir el riesgo de enfermedad inflamatoria intestinal en niños. Infosalus.com. Recuperado de https://www.infosalus.com/salud-investigacion/noticia-media-hora-sol-podria-disminuir-riesgo-enfermedad-inflamatoria-intestinal-ninos-20190531105229.html
  • Asociación Española de Enfermos de Crohn y   colitis Ulcerosa (ACCU) / EII LAFE. (s.f.). Tomar el sol y la medicación en la EII. Recuperado de https://eiilafe.com/tomar-sol-medicacion-eii/
  • EducaInflamatoria. (s.f.). Actividad física y exposición solar. https://educainflamatoria.com/actividad-fisica-y-exposicion-solar/
  • Gisbert, J. P., Chaparro, M., Rodríguez, C., Bermejo, F., Barreiro-de Acosta, M., & Esteve, M. (2019). Exposición solar y enfermedad inflamatoria intestinal: más allá de la vitamina D. Gastroenterología y Hepatología, 42(8), 480–488. https://doi.org/10.1016/j.gastrohep.2019.04.006
  • Prévost Jantchou, Francoise Clavel-Chapelon, Antoine Racine, et al., High Residential Sun Exposure Is Associated With a Low Risk of Incident Crohn’s Disease in the Prospective E3N Cohort, Inflammatory Bowel Diseases, Volume 20, Issue 1, 1 January 2014, Pages 75–81
  • Raúl Vicente Olmedo-Martín,, Inmaculada González-Moleroc, Gabriel Olveirac, et al: Sunlight exposure in inflammatory bowel disease outpatients: Predictive factors and correlation with serum vitamin D. Gastroenterol. Y Hepatol. 2019 (42) 10: 604-613.
  • Durá-Travé, Teodoro, Gallinas-Victoriano, Fidel, Chueca Guindulain, María Jesús, & Berrade-Zubiri, Sara. (2015). Deficiencia de vitamina D en escolares y adolescentes con un estado nutricional normal. Nutrición Hospitalaria, 32(3), 1061-1066.