In response to an American study looking at whether there is any link between calcium supplementation with or without vitamin D and bowel health, Dr Carrie Ruxton, an advisor to the Health & Food Supplements Information Service notes:
“Calcium and vitamin D are essential for bone health. NICE advises a daily intake of 700-1200mg of calcium for the prevention and treatment of osteoporosis. Whilst average intakes of calcium fulfill the Reference Nutrient Intake (RNI) for calcium of 700mg daily, the NDNS shows they fall short of the recommendation of 1200mg daily for preventing osteoporosis. In addition, 8 per cent of women and 19 per cent of teenage girls have intakes below 450mg which is classed as a risk for deficiency.
“This latest study set out to find out whether taking calcium and vitamin D supplements reduced the risk of one specific type of large bowel polyp – the serrated polyp, which is less common than the more usual adenomatous polyp.
“The researchers analysed findings from a US trial involving patients aged between 45 and 75 who had a history of polyps and were due to have a follow-up test (colonoscopsy) in 3 to 5 years. In other words, these were people with pre-existing large bowel disease. This was also a secondary analysis of a trial designed for other purposes, not a specific trial looking at the safety of supplementation. Secondary analyses are well known for throwing up chance findings which are clinically meaningless.
“In terms of study design, the patients were randomly split into groups to receive either daily calcium supplements, daily vitamin D supplements, both or neither for 3 or 5 years until their colonoscopy. Of note is that during this period of time, there was no effect of calcium or vitamin D on the risk of serrated polyps.
“Observation of the patients was continued for 3-5 years after the treatment had ended. During this phase when the patients were no longer taking the supplements, the researchers found increased risks of serrated polyps among those who had been taking calcium alone and among those taking a combination of calcium and vitamin D. Of further note is that no association was found between vitamin D alone and risk of serrated polyps.
“Given that calcium and vitamin D are essential for bone health, this study should not be used to dissuade people from taking these nutrients in a supplement form when required. Indeed, Public Health England recommends that everyone in the UK needs an average daily vitamin D intake of 10 micrograms and should take daily supplements in autumn and winter to prevent deficiency. Calcium supplements may benefit people at risk of poor bone health and fracture.”
 Crockett SD, Barry el, Mott la, et al. Gut epub ahead of print: March 1, 2018. doi:10.1136/ gutjnl-2017-315242 .
 Polyps are small growths in the lower part of the large bowel. They are non-cancerous, but some could eventually turn into cancer if they are not removed.