The importance of vitamin D has been often highlighted in recent years. A new study published in Dec 2015 by the University of Sheffield has found a significant link between vitamin D and the severity of irritable Bowel Syndrome (IBS) symptoms, and perceived quality of life. The trial on 51 IBS patients found that 82% had insufficient vitamin D Levels. With supplementation there was good improvement in patient vitamin D levels, however improvements in IBS symptoms were not significant. A similar study in the same year also showed such results with a deficiency in 82% IBS patients, compared to 31% in the control group. Researchers from both studies have recommended possible screening and further explorations of vitamin D for symptom management in IBS.
Given the nature of IBS it is not unreasonable to conclude malabsorption as a consequence of the condition. This is probably not isolated and will inevitably include other nutrients. The use of vitamin D in IBS followed by symptom improvement has been documented in a case study where the patient reported taking daily 2000-4000 IU (50-100 micrograms) vitamin D3 supplement. The dosage varied with the season, with higher doses in the winter months. Over a period of 3 yrs there was significant improvement to near normal bowel habits, with relapses only occurring if supplementation was stopped. Additionally, there was also resolution of co-morbid symptoms of depression and anxiety. Such studies give reason to consider vitamin D’s role in the treatment of IBS.

Vitamin D is a fat soluble vitamin that is naturally occurring in some foods, but our body should be able to produce enough vitamin D if there is sufficient exposure to ultraviolet B (UVB) rays in sunlight. Despite this many people do not get enough sun to generate adequate vitamin D. This is particularly in winter and resident in the northern latitude where the sun rays are not strong enough to stimulate production in the winter. Skin melanin content, sunscreen, window glass, cloud cover and atmospheric pollution also blocks UVB rays. Complete cloud cover or atmospheric pollution can reduce UVB rays by 50%. With age the ability to manufacture vitamin D decreases.

IBS is a chronic condition causing stomach cramps, diarrhoea and/or constipation profoundly affecting the individual’s quality of life. One in five people develop IBS. The cause of IBS is poorly understood, and generally there are multiple factors. Most hypothesis include; changes in the intraluminal milieu, immune function, neuromusclular dysfunction and brain-gut axis deregulation. Intestinal microbiota are also suspected of playing a role in bacterial infection, antibiotic use and ongoing low-grade inflammation resulting in the onset of IBS. Aside from the absorption of calcium and regulation of calcium and phosphorus to help build strong bones and teeth, scientists have also highlighted the importance of vitamin D in cell growth, inflammation and healthy functioning of the neuromuscular and immune system. Vitamin D receptors have been identified on immune cell, and together they reduce levels of inflammatory proteins (cytokines), increase antimicrobial proteins thus enabling our innate immune system to fight infections more effectively. One study reported that people with low vitamin D levels had double the risk of getting flu. Scientific research on the epithelial small intestine in mice shows that after leaving the thymus intraepithelial lymphocytes (immune cells) directly seed in the intestinal epithelium. Here they interact with cytokines, nutrients (including vitamin D) and antigens to guide gene expression and cell function. This cell function requires communication through constant cell-to-cell contact which also tunes its antigen sensitivity.

Notably like vitamin D deficiency and the prevalence of multiple sclerosis (MS) is also higher in the northern hemisphere. From an MS research perspective vitamin D deficiency is an important consideration. Pathologically in MS there is degeneration of axons and neurons. Researchers have demonstrated that the biologically active form of vitamin D gives the body protection against T cell mediated killing of human neurons in laboratory cultures. Similarly, in mice vitamin D autoimmune experiments have resulted in axonal loss. This may throw some new insight on how vitamin D deficiency can affect immune and neuromuscular function in IBS. In a  cross-sectional study on the protective effects of vitamin D on 3,121 adults aged 50yrs or less (96% men) underwent a colonoscopy and found the 10% had at least one advanced cancerous lesion. Participants with highest vitamin D intake (>645 IU/day) had a significantly lower risk of lesions. However, a cancer and vitamin D study on 36,282 post-menopausal women of various races and ethnicities found there was no significant difference in the incidence of colorectal cancer over 7 yrs between the intervention and control groups.

Vitamin D is not routinely prescribed for IBS and there are no recommended vitamin D daily target levels set for adults. Safe daily intake levels are 25 micrograms in children and 50 micrograms in adults (12-70yrs). Optimum levels for good health varies depending on age and stage of life. Considering the reported case study for IBS the therapeutic dose may be closer to 50-100 micrograms daily. This can be added to by increasing the intake of vitamin D rich foods e.g. oily fish (salmon, sardines, and mackerel), eggs, organ meats and vitamin D fortified foods. Further enhancement in the summer months by exposing bare skin to the midday sun (April –Oct), 10-15 min for people with fair skin; 30 min in Asians; and 120 min in African or Afro-Caribbean is helpful. There is no danger of vitamin D toxicity from sunlight as it is effectively  gotten rid of by the body. Toxicity is mostly through supplementation sources, symptoms are non-specific e.g. anorexia, weight loss, headache, nausea, vomiting, heart irregularities resulting in subsequent damage to the heart, blood vessels and kidneys.

 

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