Instant Genius - Vitamin D, Dr Gail Rees

Episode Date: December 12, 2022

During winter months, over 15% of UK adults are estimated to have a vitamin D deficiency. But what exactly does vitamin D do in our bodies? And is it technically a vitamin anyway? Dr Gail Rees, senior lecturer in human nutrition at the University of Plymouth, reveals all. Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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It feels like a continuation. Explore your options at canesley manor.org, a non-profit month-to-month senior community within the Front Porch family. This podcast is sponsored by name, audio, and focal. Streaming has made music more accessible than ever, but true listening is about more than ease. It's about quality.

British audio experts name audio, alongside French acoustic specialist focal, combine handcrafted tradition with cutting-edge innovation and high-end materials, delivering digital precision with analogue warmth. So you can experience exceptional sound at home. Music just as the artist intended. Visit name audio.com to learn more. Welcome to Instant Genius, the Bitesize masterclass in podcast form. I'm Thomas Ling, digital editor at BBC Science Focus magazine. When it comes to vitamin D, you probably know two key things. your body can make it from sunlight, and two, a lot of people in the UK don't get enough of it during the winter. But why is it important for you to get your dose of vitamin D? Can you get too much of it? And is it technically a vitamin anyway?

To discuss all this and more, I'm joined by Dr Gail Reese, Senior Lecturer and Human Nutrition at the University of Plymouth. Hello, Dr. Reese. Thank you very much for joining me today. Thank you for inviting me. So I'm going to start from the beginning and ask, what actually is vitamin D? Vitamin D is a fat soluble vitamin that we can make in the body, but we also do need some orally or in our diet where you live in climates, where you don't have sufficient sunlight to make it all year round. So is it technically a vitamin, a hormone, a steroid? Understand that vitamin D's a bit of an outlier in the vitamin. community. That's right. We do still classify it as a vitamin, but usually vitamins we can't make in the body, but we can actually make vitamin D in the body through the action of sunlight on the skin.

We make it from a cholesterol derivative. So it's a bit unusual in that respect. So how exactly can we sort of make vitamin D from this cholesterol? So we have UVB light and the action of that on the skin surface changes a molecule, it's a derivative cholesterol, into a slightly different molecule, that we then metabolise in the body to make active vitamin D. It's a couple of metabolic pathways, but we make it from that cholesterol derivative. So what actually is a vitamin as a whole then? How would you describe a normal vitamin? A normal vitamin is an organic molecule. that we usually can't make in the body that we need in our diet for proper metabolic functioning, so for health and growth and energy release, etc.

Okay, a big question then. What does vitamin D do in the body? Its main function is to help absorb calcium and keep calcium at the proper level in our bloodstream. So it works at the gut so that we absorb. calcium from our food. It works at the kidney so that we excrete the right amount of calcium. And it also works at the bones so that we can release calcium from the bones or we can put calcium back in the bones. And we keep a very tight control of calcium in our bloodstream. That's the main function. But it does also have other functions like it's important in

immunity as well. So how does vitamin D bolster the immune system? It works. with some of the cells and the immune system. So it helps some of the specialized cells of the immune function differentiate into their specialist cells. So can that effectively protect you from different infections? Well, I think, you know, it's similar with other vitamins that you need an adequate level in your body to be able to do all of these functions.

But if you have an adequate level in your body, taking more won't necessarily protect you. So it won't protect you from infections by taking more vitamin D. But obviously if you're deficient in vitamin D, it could lead you open to not dealing with infections as your body should. Is there any evidence that if you have a sufficient level of vitamin D, that your immunity to diseases such as COVID can be bolstered? I'm not sure the evidence is that strong. There has been a fair amount of research in it that showed that people who experienced very severe COVID symptoms had low vitamin D levels. So I think the best advice really is just to make sure that you have sufficient vitamin D

orally, particularly through the winter where we don't make sufficient through the action of sunlight, just to make sure that you have enough so that your body can perform at its best in protection against infectious diseases. So you sort of touched on it there, but how can a person get vitamin D? I think most people would say you get vitamin D from sunlight. Yes, so we do synthesize vitamin D from the action of sunlight, as I explained, but only in the summer months. So, you know, about now in the winter, well, really from, I suppose,

September, perhaps through to April, May, we don't get sufficient sunlight to make vitamin D in that way. So we either therefore get vitamin D from food, but there's not that many foods that are a good source of vitamin D or through a dietary supplement, a tablet, which is what we recommend particularly through the winter months. So you mentioned there that some foods could be high in vitamin D. Which foods are these? So oily fish, salmon, sardines, pilchards, they're particularly high. but obviously a lot of people don't eat oily fish at all or don't eat very much. Other foods, eggs have some. Other fortified foods are quite a good source.

So margarine is fortified. Obviously, we don't eat a loss of margarine, hopefully. And some breakfast cereals are fortified, but you'd need to check the packet. In some countries, they fortify dairy foods with vitamin D. And in the UK, we don't do that. So our milk isn't fortified with vitamin D. Only a few sort of products aimed at children might be fortified with vitamin D. But on the whole, our dairy foods aren't fortified. So obviously in winter, people aren't getting enough vitamin D because of the sunlight. Is it simply that the sun isn't out enough in daytime? Yes. I mean, it isn't strong enough for us to make sufficient vitamin D. So even if it's a sunny day and you've got your sleeves rolled up, you still wouldn't make sufficient vitamin D from that sunlight.

How much sunlight do you need to absorb your daily dose of vitamin D? Well, not that long. So 10, 15 minutes would be fine on a, you know, short amounts on a daily basis is fine. Is that the same in winter as well? So if you had a water work that was sort of 10 minutes, and it was a sunny day. Have you got your dose of vitamin D there? No, because in winter we don't have strong enough sunlight, so it wouldn't work during the summer months, which is why we recommend a supplement.

So even if people might not know that they are deficient in vitamin D, it's probably best to err on the side of caution over the winter months and just take a supplement anyway? Absolutely, yes. That's what I would recommend. And as I say, it's particularly important for those at risk. groups who don't get very much sunlight during the summer months. What would you say to people who are thinking that if they can't get enough sunlight in the winter, they could turn to something like a sunbed instead? I would not recommend that people use a sunbed. It's not good for the skin. It's much safer just to take a small vitamin D tablet daily and that will give you all the vitamin D that you need without exposing your skin to extra UV light that could potentially be dangerous.

Okay, what happens if you don't get enough vitamin D? How do you know if you're vitamin D deficient? Well, you probably wouldn't know anything at first. You wouldn't experience symptoms until your levels of vitamin D go very low. And then there's classical signs. So for young children, they can develop rickets. Before they develop rickets, they might. might have mysterious bone breakages, so it be very likely to break a bone when they fall over. For adults, you might experience muscle pain or pain feels like it's from your bones. And that could be a signal that you're low in vitamin D. I mean, unless you have your levels measured, it's quite difficult to determine. How is it that vitamin D supports bone health?

Vitamin D is needed to absorb calcium from your food. So if you can't absorb calcium from your food, you release calcium from your bones so you can lose bone density. And that's how you can get breakages. And in very young children, the classic look of rickets is the bowed bones where they bend outwards. And that's because of the weight of the child on the bones. The bones haven't got enough density to support the weight of the child. So you were saying that for particularly adults, they might not know if they are vitamin D deficient or not. How easy is it to get tested? I guess your GP would need to have reasonable cause to test your plasma levels of vitamin D, which they could do. But the easiest thing to do would be to look at what you're eating, to make sure, you know, if you're choosing a fortified cereal, choose one with vitamin D.

or simply just take a vitamin supplement that provides that the adequate dose is 10 micrograms a day. So you can find relatively cheaply vitamin D tablets of that dose in the supermarket or a pharmacy. Is there a link between vitamin D deficiency and mental health conditions such as depression? Again, that has been explored. It's quite difficult to relate one deficiency, let's say, to, to a mental health problem that could have many different causes. But it does make sense to make sure that the diet is adequate in all micronutrients to ensure good physical and mental health. So it would be worth making sure that people take that supplement to ensure that they've got an adequate dose.

So take it you are recommending that most people in the UK take a supplement over winter. Yes, that's the current advice from the government. Registered nutritionists and dietitians agree with that. So we do recommend that everybody takes the 10 micrograms over the winter period. But it is particularly important for certain groups of the community, like pregnant women or women who are breastfeeding. It's also important for people who cover themselves up during the summer. So some people might cover their skin for religious reasons or because they burn easily.

So for people that are usually covered all year round, it's really vital that they take a vitamin D supplement because they won't be making vitamin D sufficiently during the summer months as well. Does the colour of somebody's skin influence how much vitamin D they can absorb from the sun? Yes. So darker skin tones make less of vitamin D through the action of sunlight exposure. So for those people as well, it would be worth taking a vitamin D. vitamin D supplement, particularly during the winter, but you might even consider taking one all year around in our climate. So you're recommending that people take 10 micrograms of vitamin Ds per day. Can all of that be absorbed in tablet form if you were to take a tablet that was, for instance, 10 micrograms? Yes, most of it will. As I mentioned, it's fat soluble. So taking it with some food with a meal, particularly if it's got fat in it, will help the absorption of that vitamin D.

So that should be sufficient. How big of a problem is vitamin D deficiency in the UK? We do see it in sections of the community. I don't have a figure for you, but I think some of it certainly goes undiagnosed. People don't realise they have low levels and may only be tested after several broken bones or as I said, aches and pains that can't be attributed to anything else. So I think there's a lot of people that have underlying levels. We've done some research at the university,

and we looked at people who were overweight or living with obesity, and just about all of the people we tested in the winter went into a marginal deficiency. Is this different in the UK to other countries? A lot of other countries recognise. that their population are at risk of vitamin D. So some of the Nordic countries where obviously there's less sunlight available for longer periods of time would be more used to supplementing with vitamin D or some sort of fish oil that's got vitamin D in it.

They're also perhaps bigger oily fish eaters than we are. Some countries that are very sunny, like Australia and countries in the Middle East, recognize that they also have vitamin D deficiency in their populations simply because either people cover themselves up or avoid sunlight because it's too hot. Are there more reasons why a lot of people in the UK could be deficient of vitamin D? As I said, there are sections of the community who do cover themselves up or older people who are housebound and don't get regular sunlight during the summer months. So in order not, if you don't supplement during the winter, you're relying heavily on the levels that you manage to reach during the summer.

So your levels in the summer will go up if you get sun exposure and then they gradually decline or through winter. So you need to be at quite a high level not to reach deficiency in the winter. And I think there's several reasons why we perhaps don't get so much. sunlight in the summer now. We're very aware of the problems of too much sunlight on the skin, the risk of skin cancer and burning. So we do cover up more than we used to, particularly we're careful with children, which is important. We don't want too much sun exposure. We use sunscreens and hats and things, which is all important. So we may be reaching lower levels of vitamin D than we used to. We also spend quite a lot of time indoors. We've got jobs indoors. Children are playing

indoors and there's perhaps less outdoor activity for some people than perhaps in the past. Can you take too much vitamin D? Can you supplement yourself too far? Well, with all vitamins, it's not good to take more than the recommended dose. There's very little evidence on toxicity of vitamin D. But if you take a high dose, you know, much higher than the recommended level every day, you know, it's never good to take too much of one vitamin. And you could cause issues. It's very rare. I mean, it would have to be a high dose for a prolonged period of time. But you can then increase the absorption of calcium more than you would want from the diet. So there's no need to take more than the 10 micrograms unless you've been diagnosed as being deficient or needing more

by your GP or other health professional. So what would happen if you did take too much and you had too much calcium in the body? What could be the impact there? Calcium is very tightly regulated in the body and vitamin D helps with that. But you could store calcium, develop calcium stones in the kidney, for example. That's a possibility. It's not very common. People don't usually take too much vitamin D. And as I said, it would have to be for a prolonged period of time. I think you're saying at a very, very high doses, you can take too much vitamin D. Is that different to other vitamins? So can you take too much vitamin C, for instance? Vitamin C is different because it's a water-soluble vitamin. So if you take too much, you just lose it in the urine. You don't store it in the body. If you take very high doses of vitamin C, you won't absorb all of it and you could give yourself some nasty side effects like diarrhea.

Are there any other supplements that people should be taking over the winter months? Generally, if your diet is varied and it's reasonably healthy, vitamin D is the only one we recommend to most people. Different sections of the community would need different advice. So pregnant women or women thinking about pregnancy would be advised to take folic acid. So 400 micrograms a day in the preconception period up until the end of the first trimester. So that's important. Pregnant women might need other support as well. And they'd be advised on that by their healthcare professional.

And older people might need further support as well, depending on their medical condition and their diet. So what are the largest unknowns about vitamin D at the moment? That's a good question. I think different countries do recommend different amounts of vitamin D. So other countries recommend a higher level of supplementation and some recommend a lower level. And it's quite difficult to be precise about it because there's so much variation in how much sun exposure people get.

just within one country and between countries, that it's difficult to be precise about how much should be taken. But we know in the UK that the 10 micrograms a day is sufficient for just about everybody, as I said, unless you've already been diagnosed as deficient. So if people are looking to get a vitamin D supplement and they type vitamin D into their favorite search browser, they might be met by a choice of getting vitamin D2 or vitamin D3. What exactly are there? What's the difference there? There's slightly different molecules. They both can be metabolized in the body to the active form of vitamin D, but they're not equal in strength. So vitamin D3 has a better potency.

And it is vitamin D3 that you usually find in supplements at the rest of. required level. But vitamin D2 is still useful. So if you have a choice, is it better to have both or go with vitamin D3? Yeah, there's no need to have both. Vitamin D3 would be the one that's perhaps easiest to get in supplement form and in the range of foods. And it's what's used usually for fortifying food as well. Fantastic. Well, Dr. Reese, thank you very much for joining us. You're welcome. That was Dr. Gail Wies. Senior lecturer in human nutrition at the University of Plymouth,

talking all things vitamin D. Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus magazine, which you can find on sale now in supermarkets and newsagents, as well as your preferred app store. You can, of course, also find us online at sciencefocus.com. This podcast is sponsored by name, audio and focal. The texture and emotional depth of music can be lost through digital sources or poor signal.

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