Simon Bowles

Simon  Bowles

Lecturer in Nutrition at Sheffield Hallam University & PhD student at the University of Sheffield investigating the clinical response to high dose vitamin D supplementation in postmenopausal women.

Location Sheffield, UK


  • Yes, an excellent point. Some BAME groups tend to have much poorer uptake of supplements than Caucasians. @ChrisA

  • You’re very welcome.

    Thank you for your comments.


  • Ok, it's time for me to sign off from this run of the course. I am sorry if you had questions that I didn't manage to respond to. I do try to get round them all, but it's not always possible.

    Thank you all for your discussions over the last few weeks. It has been a pleasure interacting with you all.

    From reading the comments below, I am glad that most...

  • @CarysSwanwick Hi Carys.

    The confusion is my fault. I should have put the 'fractional' amount of calcium absorpbed decreases as dietary calcium intake increases.

    So, the more calcium intake the less of that calcium we absorb as a fraction. The less calcium intake, the more of that we relatively absorb.

    The body is clever and so upregulates our...

  • Louise - You might find this section from the BNF useful:

    Regarding your question about increases in protein intake. This is hotly debated. My only concerns about higher protein intake in older adults in the effect on kidney function (particularly where...

  • @MikeHatcher

    Mike, the review that you have posted is a very sensible one. I agree with it's conclusions.

  • I believe that in time we will identify both biological and environmental reasons for the disproportionate deaths seen in those from BAME backgrounds - it will not just be (if at all) to do with vitamin D.

    In Summary:

    Vitamin D, like other nutrients, should not be seen as a ‘magic bullet’ to beat COVID-19. The scientific evidence base is just not there...

  • The strongest evidence based research studies are randomised controlled trials. Indeed, the largest RCTs carried out to date for the prevention and treatment of non-bone health disease (e.g. Cancer, type 2 diabetes and cardiovascular disease) with vitamin D have shown null results - no beneficial effect on type 2 diabetes progression, no beneficial effect on...

  • e.g. The most important point related to COVID-19 that I will make is that the carrier proteins that carry vitamin D in the blood are what we call acute phase reactants. Acute phase reactants are inflammation markers that exhibit significant falls in concentration in the blood during inflammation. This is the case of albumin and vitamin D binding protein (the...

  • Arguments against a direct role of vitamin D in the prevention and/or treatment of COVID-19:

    1. The mechanisms for how vitamin D helps to fight viral infections, such as SARS-CoV-2, are simply based on speculations about presumed mechanisms from an extremely limited evidence base.

    2. We have been here before with vitamin D! A few years ago, perhaps...

  • Thank you so much for your comments on this part on the thread. I really liked reading them. You all make excellent points and I cannot tell you what is absolutely correct and what isn't. We just don't know enough at this stage, but in time we will. There are lots of studies now underway, particularly randomised controlled trials which are the strongest study...

  • @GuyCowley Yes, kippers are on average probably the best source. All oily fish contains vitamin D, but just how much can vary quite widely depending on geographical location.

  • A little bit off topic...but I have a very topical question for discussion.

    Does anyone have any thoughts on the recent reported link between COVID-19 and vitamin D?

    I’ll give you my thoughts (for those interested) at the end of the week. Please do post your thoughts below. There are no right or wrong answers, but I'm very interested to listen to...

  • The good thing about vitamin D is that it is actually very difficult to make someone toxic. You would have to take very high doses over a prolonged period of time.

    We have very efficient degradation pathways for vitamin D and excess is readily excreted.

    But, whether there is any additional benefit in taking amounts above the RNI is very much debatable.

  • @RichardVallis

    I can comment on some of those...

    Age - Older people actually have a better dietary intake of vitamin D (with and without supplementation) than younger adults. We have done work on this in Sheffield.

    Ethnicity - South Asians have a poorer dietary intake of vitamin D than Caucasian counterparts. They also have a poorer use of...

  • The RNI is set at 10 micro grams per day as this is the amount that is seen as enough to keep 97.5% of the population out of the deficiency threshold. So there will be a lot of people who don’t reach this level of intake but are still not deficient.

    This may be for reasons that you suggest, such as the contribution of sunlight from April to October and...

  • It does vary. It’s depends on where the fish is caught too!

    But generally oily fish is the only really significant dietary source of Vitamin D.

  • The RNI in the UK is set at 0.75g of protein per kilogram of bodyweight per day for adults.

  • Hi Martin. Although the thyroid gland and parathyroid glands are neighbours anatomically, they have very different physiological jobs to do and are unrelated.

    The thyroid glands generally help govern metabolism throughout the body, but the parathyroid glands (via parathyroid hormone) help govern calcium levels in the blood.

  • In short, for most people probably not. There may be certain circumstances where people might do something extreme (e.g going from being sedentary to becoming a competitive weight lifter or something). Or if some physiological abnormality was corrected.

    But generally, after around the age of 35 it’s then about maintaining what you have and in later years,...

  • Anne, I agree with your GP.

    That is the general rule!

  • Hi George.

    Yes, I'm very fussy with the use of 'facts'. I believe that, generally, if someone is presenting something as 'fact' they have very little understanding of science.

    I'm particulaly fussy with my students when they write "it has been proven that..."

  • Hi Malcolm.

    You are absolutely right. It is almost an impossible task to quantify.

  • Hi Lou,

    Nutrient Reference Values are EU recommendations for the daily ntake of vitamins and minerals based on current understadning. The NRV replaced the Recommended Daily Allowance (RDA) for vitamins and minerals only back in 2014.

    NRV's are set for the purposes of food labelling and are EU guidance levels on the daily amount of vitamin or mineral...

  • @MikeHatcher

    Hi Mike,

    I am not aware of any studies that have quantified the effect of alcohol intake on calcium absorption in this way. Most studies have just reported an inverse association between alcohol intake and fractional calcium absorption and/or serum calcium.

  • I think for most people magnesium deficiency will not be a problem (around 85% of people in the UK have magnesium intakes at or above the reference nutrient intake of 300mg for males and 270mg/day for females). Magnesium is found in lots of different foods too.

    It also seems that magnesium intakes are better in older vs. younger people and better in...

  • Hi Carys.
    This is an interesting question. It is not an easy one to answer.

    Magnesium is important for bone health and enzyme activity. It is thought to have effects on osteoblasts, effects on hydroxyapatite crystal formation and also plays a role in the regulation of calcium homeostasis through interactions with PTH and vitamin D.

    I think there is a...

  • Hi Daniela.

    Thanks for your comment. Yes, unfortunately there is a genetic link too. We would say that there is a genetic susceptibilty to osteoporosis and so like lots of health and disease outcomes, we could say that we need to 'pick our parents well!' People with a slight consitution do seem to be at higher risk.

    However, just because a parent (or...

  • @gilliantennant We see lots of older people who are vitamin D deficient (well actually across all age groups). It certainly is likely due to lifestayke factors, such as not getting a healthy and varied diet and not getting unprotected sunlight exposure.

    Regrding injetions... It may be that there are malabsorption concerns and intramuscular injections are a...

  • Here are some other factors to consider for calcium absorption:

    - High sodium intake increases the amount of calcium that we excrete in our urine

    - High protein intake also increases urinary calcium excretion and was therefore thought to negatively affect calcium status. However, there is also research to suggest that high protein intake also increases...

  • Last week I mentioned (somewhere) that I would put up some more information about calcium absorption and bioavailability. There's an awful lot to summarise but here are some points about foods that may affect calcium absorption:

    - The fractional amount of calcium absorbed decreases as dietary calcium intake increases

    - As we age we absorb less calcium -...

  • Hi All,

    just some thoughts to add:

    DRVs (or dietary guidelines) are ‘recommended’ values and are therefore guidelines at a population level.

    There are many individual differences within a population (that extend beyond gender, age, ethnicity, disease status) and only now are we beginning to understand the potential importance of nutrient-gene...

  • People may find these British Dietetic Association Information on Osteoporosis and calcium and Vitamin D helpful:

    They also have other food...

  • @RichardNuttall

    Yes, it is used interchangeably and depends the country or institution really.

    There rule is 10 micrograms = 40IU.

  • Hi Sarah.

    There are actually lots of types of vitamin D in the body. The form of vitamin D that we predominantly get from the diet is the same as what we make in our skin - Vitamin D3.

    However, this vitamin D3 needs to be converted to the active form - this is done through two sequential steps. First the vitamin D3 is transported (bound to vitamin D...

  • Yes, Linda. We have done lots of work here in Sheffield on vitamin D levels in Obesity. People living with obesity do tend to have lower levels of vitamin D than normal weight counterparts.

    This is due to 'volumetric dilution'. Basically the vitamin D is still in the body, but it is just diluted by the higher body mass (particularly the higher fat mass...

  • There is so much that affects our ability to synthesise vitamin D in the skin. Vitamin D is specifically snthesised in the skin using UVB wavelengths of light.
    it is affected by:
    - Time of year: in the UK we cannot synthesis vitamin D in the skin between October to the end of March. The sun is never high enough in the sky.
    - Time of day: even in the summer,...

  • I really like this video from Prof. Powers. I think that she explain some very difficult concepts quite nicely. I think it is really good for people to see just how much work goes into creating intake guidelines for a particular nutrient and how thorough the process is. Of course, this does not mean that it is perfect!

  • Welcome to week 3 everyone. I am biased, but this is my favourite week! :)

    I will keep trying to get through as many questions/comments as I can. I am sorry if I have missed anyone's questions so far...there have been a really high number in this run, but I have tried to get through as many as I can.

    Thank you all so far for your interest and the role...

  • @JasmineMilnes

    Hi Jasmine.

    Yes, Men typically have a higher bone mineral density than women and so they will typically have a greater bone strength. Genetics and hormones play a role, including the higher muscle mass.

  • @SehrShahid I absolutely agree.

  • @CarysSwanwick Yes, absolutely right. Of course, nothing is certain and genetics play a role too, but what you say is correct.

  • @LOUISEWOODS Yes, and I think we see this kind of resistance in the National Child Measurement Programme too.