15
Examination of witnesses
A/Professor Catherine Bondonno and Professor Gunter Kuhnle.
Q26 The Chair: Good morning, and welcome to the Environment and Climate Change Committee. If Members have relevant interests, they should be declared the first time they speak.
I warmly welcome our first panel and thank them for taking the time to be with us today to take us through how nitrate and nitrite in food and water impact on health. Before asking the first question, I ask each of our witnesses briefly to introduce themselves. I start with Professor Kuhnle.
Professor Gunter Kuhnle: Thank you very much, Chair. I am a professor of nutrition and food science at the University of Reading. My main research focus is on dietary assessment methods and nutritional biomarkers. I have worked quite a bit on nitrite and nitrate, mainly on the link with the development of colorectal cancer. I have been a member of an EFSA panel investigating additives. I am currently involved with the COT until the end of March, and I am currently working on an FSA/COT-funded project to do a systematic review on the risks of nitrite and nitrate as additives. I should add that I have also worked on a large EU-funded project to replace nitrite and nitrate in meat products.
The Chair: Before you start, Professor Bondonno, I thank you very much from joining us all the way from Perth in Australia.
A/Professor Catherine Bondonno: Thank you, and thank you very much for this opportunity to contribute to this important inquiry. I am a researcher at the Nutrition & Health Innovation Research Institute at the Edith Cowan University in Perth, Western Australia. My research focuses in depth on the complex health effects of dietary nitrate, both the positive and negative effects.
The Chair: My first question to both of you is designed to help set the scene. Nitrates and nitrites both occur naturally in vegetables and meat. Could you help us to understand what function these naturally occurring substances have in the body?
A/Professor Catherine Bondonno: In the body, nitrate is reduced to nitrite, and then to nitric oxide, which is an important signalling molecule in the cardiovascular system, central nervous system and immune system. There is a growing body of evidence that nitrate, through its effects on nitric oxide, improves cardiovascular outcomes, musculoskeletal health and exercise performance and, potentially, other diseases such as dementia.
If we look at what happens naturally in the body, ignoring nitrate and nitrite in food for a moment, nitrate and nitrite are also end products of nitric oxide metabolism. Nitrate and nitrite are recycled in the body through an enterosalivary nitrate-nitrite-nitric oxide pathway back into nitric oxide. Blocking that pathway results in effects on processes in the body that nitric oxide regulates, such as blood pressure.
The discovery of the pathway raised the possibility that nitrate from food could be an important source of nitric oxide, and there is now a growing and compelling body of evidence that dietary nitrate improves cardiovascular health and lowers risk of cardiovascular disease. The evidence for that positive effect on health now also extends to other diseases where nitric oxide has a role, such as dementia, as I mentioned.
The Chair: Excellent. Thank you very much.
Professor Gunter Kuhnle: Thank you. I think that I can add to that. The positive role of nitrite and nitrate is well understood; unfortunately, the negative side of nitrate and nitrite is also well understood. We have this Janus-type compound which on one hand can reduce the risk of cardiovascular diseases but on the other side can increase the risk of cancer. That is the aspect of the story that makes it really fascinating because we have those two separate approaches that you have to look into.
Catherine has already explained much of the role on the positive effect, so I shall talk about the negative effect. The problem with nitrite is that it can result in the formation of nitroso compounds, and many nitroso compounds are toxic—they are carcinogenic. Not all of them —that would be easy—but some of them are incredibly carcinogenic while others are not. But overall, as a group of compounds, they are considered to be carcinogens; they can cause cancer. It is this kind of balance: if you add nitrite to the food, is it good or is it bad?
The Chair: We will come to additives in the next question. To stay with nitrosamines, what are the conditions under which they are formed when you ingest naturally occurring nitrate and nitrite in vegetables? Let us separate out vegetables and meat.
Professor Gunter Kuhnle: They need acidic conditions. They can form in the acidic conditions in the stomach.
The Chair: And how do those acidic conditions arise in the body?
Professor Gunter Kuhnle: They would be in the stomach from the stomach acid. The stomach acid would create the acidic conditions. Then we have the amino groups from the proteins, and the nitrite can react with the proteins. It is a multi-step reaction, so the nitrite has to be activated to a nitrosating species, and then moves on.
The Chair: So that is the chemistry. What do I have to eat to create those conditions?
Professor Gunter Kuhnle: You have to eat nitrates and proteins. In general, of course, meat is incredibly protein rich.
The Chair: So just eating nitrates and proteins can give risk to those acidic conditions.
Professor Gunter Kuhnle: The stomach acid would cause acidic conditions anyway, unless of course you took proton pump inhibitors, which would raise the stomach pH. That would make things different. It is a little bit more complex because there is the enterosalivary cycle, whereby nitrate is excreted in your oral cavity and the microbiome in your mouth converts it into nitrite, which can give rise to nitric oxide, which we think is good, but it can also give rise to nitrosamines, which we think are bad. If you disrupt that with antimicrobial mouthwash, for example, that would not help.
The Chair: That is interesting. I shall bring in Lord Krebs then go to the second part of my question.
Lord Krebs: Actually, Lord Chair, I was going to ask something related to the second part of the question, so I shall let you ask it.
The Chair: We know that nitrates and nitrites occur naturally in vegetables and meat. Is there a difference in how they behave in the body, depending on the source?
A/Professor Catherine Bondonno: Yes, that is the current hypothesis: nitrate from vegetables forms nitric oxide because there are compounds in vegetables that prevent the formation of these harmful nitrosamines.
The Chair: So things like vitamin C.
A/Professor Catherine Bondonno: Yes, flavonoids and vitamin C in vegetables are some of the compounds hypothesised to stop the formation of nitrosamines and send nitrate down the beneficial pathway. Nitrate in meat together with amines and other conditions can lead to the formation of nitrosamines. Very much our working hypothesis is that the source of nitrate is important, but we are a few years away from getting any definitive answers here. There are a lot of studies, and we are working hard to answer that question, but that is the current working hypothesis.
The Chair: Would you like to add briefly to that, and then I shall move on?
Professor Gunter Kuhnle: If I can add that, if we consume meat with high amounts of nitrate and we add plant extracts, we see a reduction in the formation of these nitrosamines, so we can do the same thing that happens with vegetables. We can reduce the formation. If we add exactly those compounds, it prevents the formation of nitrosamines.
The Chair: Excellent. I am going to move on to Lord Krebs’s question and hope you will be able to bring in Lord Trees and Lord Duncan with supplementaries.
Q27 Lord Krebs: Thank you very much, Lord Chair. I should before asking my question declare a relevant interest that I am a scientific adviser to Marks & Spencer. My question is about why we add nitrites and nitrates to food and what are the main health concerns. Before I lead into that, perhaps you could pick up on the last bit of your answer to the Chair. If I eat a meal that is meat and two veg—we do not normally eat meat on its own, we eat it with vegetables—does that mean that the beneficial effect from the plant intake outweighs the possible disadvantage from the meat?
Professor Gunter Kuhnle: This is a very good question. It is very difficult to answer because it depends on the plants. In general, you would say that if you eat a sufficient amount of plants, yes. However, we conducted a study where we fed people about 100 grams of raw onions in a shepherd’s pie, and these 100 grams did not really make a huge impact, so you would probably have to eat a lot of vegetables.
Lord Krebs: Thank you. So why do we add nitrite and nitrate to food and what are the main health concerns as a result of the additives? Gunter, would you like to kick off?
Professor Gunter Kuhnle: The main reason in meat is to preserve the food. Nitrite is a preservative; it prevents the spoilage of meat, and it has been used for a long time to preserve meat. There is some argument about whether it was originally an impurity or not, but now it is used as a preservative to prevent the growth of bacteria. That is the main reason.
The secondary reason is that it affects the mouthfeel, the taste, and it causes the nice pink colour of meat. It does this in a nice way that means that if you fry something, it goes grey or brown or whatever colour you fry it to, but the colour goes away, because nitrite binds to haemoglobin, and it causes the pink colour. The consumer wants that. We have tried meat that stays grey, and we have tried meat that stays pink, and consumers do not like that; if you fry a steak and it stays pink, you do not want that. If you sell meat products that are grey, people think they are spoilt. So we are used to that. That is something which, of course, one could change, but that is the secondary reason. So we preserve, but we also create the taste, the mouthfeel that we are used to with meat.
Lord Krebs: Thank you. Catherine, did you want to add anything?
A/Professor Catherine Bondonno: I think everything has been covered. In this discussion, it is also very important to note that nitrosamines can also be formed in our bodies. It is estimated that this formation accounts for up to 97% of nitrosamine exposure, so when considering all this, we need to consider both the nitrosamine formed in the meat itself and then what is happening in the body and what happens after intake as well.
Lord Krebs: Can I just go back to Gunter and check? Is it both nitrate and nitrite that have these antimicrobial plus colour-preserving properties?
Professor Gunter Kuhnle: It is generally nitrite. A way to get around the declaration of nitrite is to add nitrate in the form of vegetable salt, which is then reduced to nitrite, and you do not have to declare the nitrate. You have the clean label approach, and you still have it on there. It is nitrite that is preserving.
Lord Krebs: May I ask a supplementary?
The Chair: We have three other supplementaries. Please ask your question, but quickly for a brief response.
Lord Krebs: Very briefly, we have talked about the health concerns related to meat, but also touched on processed meat. This is to Gunter: is there a difference between the health concerns relating to processed meat and to fresh meat?
Professor Gunter Kuhnle: Yes. Most processed meat contains nitrite, but not all processed meat contains nitrites. Notable examples are Parma ham and English sausages, which tend not to have nitrite and are not preserved that way, so putting them all into one is an oversimplification. However, in general, yes, because with processed meat we have the ideal conditions. We have nitrite and protein at the same place, we put it in the stomach, add acid and get nitrosamines, whereas if we eat normal meat or meat without any nitrite, we would have to have another nitrate source. We generally have plenty of nitrite in our food. It is not the problem that we do not find nitrite and nitrates, but with processed meat, we bring them together, we have them at the same place, and they can react straightaway. That is one of the one of the problems.
The Chair: Thank you. Lord Trees, then Lord Duncan, then Earl Russell, but please keep you questions short.
Lord Trees: I thank you both for giving us the advantage of your knowledge. I am interested in the function of nitric oxide. You have mentioned the pros and cons in terms of cardiovascular disease, dementia and cancer. If I can remember my immunology, nitric oxide is also a potent mediator of a defensive immune response to infectious agents. So can you say a little bit about its role in combating infection and how that might be affected by the food we eat?
Professor Gunter Kuhnle: I have to pass on this because I am not an immunologist, and I would not want to say anything beyond that.
A/Professor Catherine Bondonno: I agree, I also do not feel confident. Certainly, in the food nitrate research field it is not something that is considered or looked at. We look at it mainly in terms of the cardiovascular and central nervous systems. There has been some work done to see if it has an effect on immune responses, but the evidence is little and there are very few studies at this stage.
The Chair: Could I request, Professor Bondonno, that if you know of any colleague who is qualified to comment on this, you could prompt them to send some evidence to the inquiry? We would be very grateful. It is going to be Lord Duncan, then Earl Russell, then we will move on to Question 3.
Lord Duncan of Springbank: This is a very quick question. Following on from your question, Chair, the trend, probably since the 1950s, of occurring nitrate and nitrite in meat and vegetables has presumably been monitored quite significantly. Are you able to provide us with the growth in the appearance of these particular elements?
Professor Gunter Kuhnle: I am sorry, I cannot. The one bit of data I have, which I found interesting, is that additives are still the smaller amount of nitrate and nitrite that we consume. Most of what we consume is natural. They are all natural, obviously, but it is naturally occurring in vegetables and not added. The nitrite and nitrate that we get from additives—I have got the data because we just wrote something about it—is for everyone under 20%. For adults, it is up to 30% or so of the nitrate and nitrite we get. There are trends to try to reduce the amount of nitrite. It is not that people want to add as much as possible. There is the trend to reduce nitrate because the consumer is more health conscious, but there is also the idea that if we can reduce it, it might be better for the product. I am sorry, I cannot answer the specific question.
Earl Russell: Thank you both for your evidence. In terms of processed meats, in particular, in terms of avoiding the worst health impacts of nitrate and nitrite, is there enough research looking at whether other compounds could also be added to help prevent the bad pathways?
The Chair: I think that we are coming to that question later in the session. Let us move on to Lord Trees’s question.
Q28 Lord Trees: How robust is the evidence that nitrate in food and water affects human health? Is there a safe threshold for nitrate concentrations? Secondly, does the way in which food is grown or raised, if it is food of animal origin, affect the level of nitrate present in it and, consequently, the impact on health? Who would like to take that, Gunter?
Professor Gunter Kuhnle: Yes, there are risk assessments of nitrite and nitrate. It used to be done by EFSA, but it is now done by the Food Standards Agency. One of the projects I am currently involved with is to look at the latest evidence. For nitrate, the assumption is that, if you eat about 4 milligrams per kilogram of body weight daily, you can assume no harm over a lifetime, so that is the ADI. For nitrite, it is much lower, but, of course, nitrite is more potent. I have written it down; it is about 0.1 milligrams per kilogram of body weight. The interesting thing here is that meat would probably meet this. What does not meet it are the health drinks you can purchase that include extra nitrates. There are shots that I have seen you can actually buy here at the coffee shop that contain quite large amounts of nitrate, but the assumption is that because they contain other compounds, they are healthy and do not have an adverse effect on health.
Lord Trees: How do those daily maxima translate into the amount of food that people normally eat and the balance of their diet?
Professor Gunter Kuhnle: I am sorry; I will have to look into that and get back to you.
Lord Trees: Are we consuming anything like that amount regularly or daily?
Professor Gunter Kuhnle: I remember from reading the opinions that there is no risk that we are all above the threshold. That is an opinion; I could easily look at the data and tell you later, but I do not know what the actual proportion is. It is not very close to that, as far as I remember.
Lord Trees: Could you send us a note on that?
Professor Gunter Kuhnle: I will, and with an immunologist, I think.
A/Professor Catherine Bondonno: I just want to comment on that. We mentioned before that 70% to 80% of our nitrate intake comes from vegetables, and the current threshold is around 260 milligrams per day for an adult with a weight of 70 kilograms. The recommendations do not differentiate between sources, but that amount can be exceeded by having a serving of rocket; you can get more than that. We currently feel that having this limit for vegetables is instilling fear in people. We do not really see a problem with having a large amount of vegetables that exceed that amount. That is one thing that we worry about with that recommendation, when it does not differentiate according to source and there is such robust evidence now for nitrate from vegetables having a beneficial effect.
We have conducted a number of observational studies where we have measured habitual nitrate intake and looked at long-term health effects. The current average intake for most people is around 70 to 100 milligrams a day. Interestingly, this is the amount where we see beneficial effects. For people who have higher amounts, there is no added benefit of having nitrates; the effect plateaus out. However, when it comes to animal sources, it is still all unclear. There is a lot more research that needs to be done.
The Chair: At the moment, the ADI—the accepted daily intake—recommends about 260 milligrams for an average adult, but that can be exceeded by a portion of rocket, for example. I think I am hearing that it would be sensible to separate the ADIs for sources that are beneficial to the body from those that are not so beneficial.
Baroness Whitaker: To return to processed meat, do we know how significant it is as a cause of colorectal cancer because there are other causes? What is the extra burden? If the Government want to reduce colorectal cancer—I am sure they do—do they first of all say, “Lay off the bacon” or “More exercise and less alcohol”? Do you have any idea of the weight?
Professor Gunter Kuhnle: This is a very good question. It is really complicated to disentangle all the different aspects. Most of the evidence we have showing that processed meat is linked to cancer is obviously observational, and there are additional confounding factors—who eats processed meat, who eats a lot of bacon and so on—which make it really difficult.
We know that nitrosamines can affect this and that they are a contributor to increased risk, but people who eat a lot of processed meat might eat much less fibre, and eating a low-fibre diet is a clear risk factor. If I had anything to say, I would probably say boost the fibre intake first because we all eat about 15 grams of fibre a day, when the recommendation is about 30. There are ways to process bacon that reduce the amount of nitrite.
Baroness Whitaker: We will come on to that.
Professor Gunter Kuhnle: There are ways, but I think bacon is a very complicated question. Of course, if people overindulge in it, it is different from a normal intake of bacon, whatever normal is. It is one of the many parts of the jigsaw puzzle that comes together, and it should not be the main and only focus.
A/Professor Catherine Bondonno: I just want to add to the comment about observational studies. It is clear from observational studies that processed meat is linked to an increased risk of colorectal cancer particularly but, as Gunter alluded to, in observational studies it is difficult to tease out what is actually causing that. Whether it is the nitrate and nitrite content in processed meat and whether that is related to nitrosamine formation, we can guess, but we are not 100% certain because there are so many other things in processed meat that are also linked to cancer, such as the polycyclic aromatic hydrocarbons and other compounds. The recommendation would be to lower processed meat intake, but we are still working out what in processed meat is actually causing that problem.
Professor Gunter Kuhnle: I just want to add that the observational studies have their limitations, but they are data. The group I worked with before managed to establish a pathway that linked bacon intake to specific mutations in colorectal tumours in about 200 people. This is—I would not say convincing—very encouraging that there is a clear pathway and clear impact. However, I think we both agree that it is difficult to say what one thing causes the problem.
Lord Duncan of Springbank: You mentioned that health drinks are one of the main sources. There would almost seem to be a contradiction in a health drink having a greater risk—I am going to use that word. The argument, presumably, is that the vegetables or fruit within them are an offset, but are you actually saying that that is potentially not correct and that there is a greater problem with health drinks than a health benefit?
Professor Gunter Kuhnle: I obviously do not want to say that anything is dangerous or something like that, as I cannot, but we can measure the formation of nitroso compounds. Colleagues of mine and I have done a study where we gave people these health drinks and then measured the formation of nitroso compounds in urine samples, and they do form.
Lord Duncan of Springbank: The risk then is that people would never take the health drinks because they are patently not healthy.
Professor Gunter Kuhnle: That is the big question: they improve your exercise performance and vascular health. That is what makes this topic fascinating, as there is not one direction. You cannot say that it is all good or all bad; it goes in two different directions.
Lord Duncan of Springbank: Perhaps the use of the word “health” in that context is not helpful.
Professor Gunter Kuhnle: I do not think they are marketed as “health drinks” because they would not be allowed to be. It is about exercise performance and things like that.
The Chair: Before I come to Lord Krebs, I have a couple of supplementaries of my own. I am trying to unpick the apparent discrepancy between the recommended ADIs and the risks associated with the different sources of nitrate. The WHO classifies processed meats as a group 1 carcinogen, yet that is not reflected in the advice given on ADIs. Is that correct? That is quite a large discrepancy, so can I have your personal views on it? Professor Bondonno, I know you are nodding, but I need to hear for the transcript that you are in agreement. Am I right in saying that that concerns both of you?
A/Professor Catherine Bondonno: I think I would like to see more evidence that the nitrate and nitrite in processed meat is causing the problem, but I agree that the ADIs for nitrate and nitrite need to be looked at according to source.
Lord Krebs: Just to follow up very briefly on Catherine’s comment that there are other components in fresh meat or processed meat that could be carcinogenic—and you mentioned polycyclic aromatic hydrocarbons that are formed in curing or cooking—there is also the contribution of heme to the formation of nitrosamine. Have any of the epidemiological studies succeeded in parcelling out the contribution of those different chemicals. You are shaking your head, but could you say no?
A/Professor Catherine Bondonno: I am sorry. It is very difficult to tease this out, but they are highly correlated. When we look at nitrate from vegetables we can tease it out, because we have our low-nitrate and high-nitrate vegetables, so we can tease out the relationship and make sure or show that it is probably the nitrate in vegetables that is having the effect. With processed meat, because we do not have that and because the intakes are so low, it is really difficult to tease that out.
The Chair: Is there scientific work ongoing to tease out the conflicts or differences that still exist in opinion?
A/Professor Catherine Bondonno: Yes, there are clinical trials currently being conducted.
The Chair: Could you give us more information about that, maybe in writing? That would be really appreciated.
A/Professor Catherine Bondonno: Yes, certainly.
Professor Gunter Kuhnle: One could potentially distinguish between nitrite and nitrate from meat and nitrite and nitrate from plants, because one comes mainly from added nitrate from South America and the other comes from the Haber-Bosch fertiliser production. They differ in their stable isotope ratios, so one could measure this but, when we looked into this last, the methods were incredibly tiresome, because it required a lot of detailed analysis. In theory it would be possible, and it would be really interesting, but it would be complicated.
The Chair: That brings me on to another supplementary. Professor Sutton, who is our special adviser here, would like to know—and you mentioned fertiliser inputs—given the current levels of nitrate in salad vegetables, whether farming methods to reduce those levels would be beneficial for health or not.
Professor Gunter Kuhnle: It is very difficult to say, if you look only at the health effect and not at the further environment. As Catherine said, the problem is that the health effect of nitrate in vegetables is more complicated than with meat, simply because of all the by-products that come in. Reducing it would definitely be sensible. Catherine’s group has published a great paper looking at the range of nitrates and nitrites in vegetables, and it is huge, depending on production method. You can eat a rocket salad that has no nitrite or has huge amounts of nitrite, and you do not know. But bringing that to a normal level would probably be good.
Of course, one thing that we have not looked at is that nitrite also has other adverse effects, especially in children. High amounts of nitrate can cause methaemoglobinaemia. Excessive amounts of nitrate are probably not a good thing to consume.
The Chair: I am going to move on to Baroness Whitaker, and I hope that we can pick up some supplementaries if we have time. We have a second panel, and I do not want to keep them waiting too long.
Q29 Baroness Whitaker: We have touched on ways to preserve and protect meat other than nitrates. What are the alternatives? How widely are they used? Have there been any negative health effects from them that you know of?
Professor Gunter Kuhnle: I have been part of a project that used them, and I am biased so I would say that our work was very good. There are things that you can add, instead of nitrite; you can add phenolic compounds, vitamin C and antioxidants, to create a similar preservative effect—and not only that but it also reduces the formation of nitrosamines. That is something that should be public knowledge. It is non-proprietary, so people could just use the extract.
There is a proprietary approach—you probably all know about “Naked Bacon” from Finnebrogue in Northern Ireland, which has looked at exactly that issue. In our discussions with them, we found that, for reasons that were completely non-science related, they never followed up on this. But they used a similar approach; the product that they add is proprietary, so we do not know what it includes, but they label it “flavouring”. It is very likely to be some plant extracts, which do exactly the same thing that nitrate does: they prevent the growth of bacteria and keep a certain amount of mouthfeel. But one thing that they have not achieved is the change of colour; to mimic the change of colour with nitrate is almost impossible, because it is that pink. But it is possible, and it would not be too difficult for companies to do that. The main problem is that it is a little more expensive, and in a market where you have small margins it is difficult.
Baroness Whitaker: And are there any possible negative health effects?
Professor Gunter Kuhnle: We have not seen any negative health effects to consumers—it is just a little more expensive.
Baroness Whitaker: Apart from being more expensive, is the process more complex and time-consuming, or is it just because the substance costs more?
Professor Gunter Kuhnle: It is a slightly different process, because it would not use salt; it would use herbs. We have not tested whether you can inject it into the meat. Well, we tried it, but most of it was non-injectable, if I remember correctly. But it would not be difficult; it would be a change in the production line. I do not know why it was not continued; it fizzled out, like so many great ideas.
Baroness Whitaker: Should more research be done or can we just recommend it?
Professor Gunter Kuhnle: I think it could be used. There was interest in doing that, but it just never took off.
The Chair: Just to stay on this point, before I bring in Lord Krebs and Lord Ashcombe, we understand that to date these plant extracts used for the purpose of food preservation have not been approved by the EU or the UK food standard agencies as food additives, and they cannot be used in foods labelled “nitrate free”. Is that something that you think should be looked at again and reassessed?
Professor Gunter Kuhnle: I think that it is something that it would be really good to assess in a more comprehensive way. It is good that companies go on the market and produce it, but it would be good to have a wider uptake. The British Meat Processors Association was part of our project, so in theory it has all the details on how to do it. That is the frustrating aspect.
The Chair: Is it something that Governments could usefully do?
Professor Gunter Kuhnle: It would be good to look into that and see how we could not necessarily remove it completely but reduce it. We have reduced it by about 50% and found virtually no nitrosamine formation.
Lord Krebs: My question, Lord Chair, basically follows up on yours. I assume that for some reason this proprietary formulation used by Finnebrogue does not come under the normal food regulations. How is that?
Professor Gunter Kuhnle: It is labelled as “flavouring”.
Lord Krebs: In a way, it is a device to avoid coming under the regulations—to label it as “flavouring”.
Professor Gunter Kuhnle: That is outside my expertise, but that is presumably what it is.
Lord Ashcombe: You mentioned that using a phenolic compound is potentially more expensive than using nitrates. Can you give us a clue as to how much more expensive it is, because that is obviously of concern to the public when buying food?
Professor Gunter Kuhnle: I am sorry; I cannot remember. When we did the study, we did consumer trials, testing it, and it was not massively more expensive—but I would have to look at the data—and that was 2015, so prices will have changed. Then of course it was experimental extracts, and they were waste-stream products from making grapeseed oil with the leftover. It could be scaled up to drop the cost. This was an experimental product that was more expensive, but I am sure that one could come to a better cost profile.
The Chair: Do you have anything to add, Professor Bondonno?
A/Professor Catherine Bondonno: No, this is not really my area. I am aware of celery powder and rosemary extract being used. Celery powder is just an alternative source of nitrate. There is the potential that you might get a reduction in nitrosamine reduction with that, but we would need to look at the health effects.
The Chair: Any supplementary evidence you have of where further scientific work has been carried out to establish the beneficial or non-beneficial effects of plant extract nitrates or nitrites would be helpful to the committee. Thank you very much.
Q30 Lord Rooker: Good morning, and thank you very much for your expertise. My question is quite simply about water. What are the health risks associated with nitrate in water? If you can list the risks, how can they be avoided?
Professor Gunter Kuhnle: The main risk of nitrate in water is the formation of methaemoglobinaemia in children. Children cannot process the nitrate properly, so it can bind to haemoglobin and they will lose the ability to carry oxygen. That is probably the most immediate risk because it would have an immediate impact.
Of course, high amounts of nitrate in water would also increase the risk of colorectal cancer because it leads to the formation of nitrosamines. We have measured this: we fed people high and low amounts of nitrate in drinking water, and you can easily measure in urine the formation of nitrosamines.
We were trying to investigate the way this can be treated in a large study at EPIC Norfolk. We worked with Anglian Water at the time, which measured the nitrate content in its public water supply zones every couple of weeks or so. Once it reaches the threshold, it is treated and the nitrate can be removed quite easily. That also means that if you look at drinking water nitrate concentration, it is completely variable. So you might have a year of nitrate in your house: it goes up, it goes down, it goes up, it goes down because, first, the nitrate comes mainly from farmland and, secondly, the way the water supply is treated, when they treat it and what the threshold for treatment, so it is difficult to say what the nitrate level is. You could legislate a lower threshold for treatment, but I do not know whether this would have other impacts. I do not know whether this is relevant to the health impact for cancer; Catherine knows more about that.
A/Professor Catherine Bondonno: I can certainly comment on cancer. The contamination of drinking water by nitrate and its potential link to cancer has been a public health concern for 40 years now, yet our understanding is far from complete. Most of the evidence for water nitrate is for a higher risk of colorectal cancer, bladder cancer and gastric cancer. The World Health Organization concluded in 2016 that the current evidence does not support an association between water, nitrate and colorectal cancer. However, there is a growing body of epidemiological evidence showing that there is potentially an association. Of particular concern is associations with nitrate levels below the regulatory limits. A recent meta-analysis, the latest one, showed a 40% increase in risk with high versus low nitrate exposures.
The limitation of observational studies is that you cannot really look at factors that may influence nitrosamine formation within the body which, as I mentioned early in the session, is where 97% of our exposure comes from. There is a potential for there to be subgroups within the population who are potentially at a higher risk of cancer. These are people with a low vitamin C intake and a higher red meat intake. We need to conduct studies that look at these factors.
It also worth mentioning that nitrate in water could simply be a marker of other contaminants. I do not think we can conclusively say yes or no yet. I know that a lot of work is being conducted in this area, and a number of cohort studies are being done to look at that because nitrate content in water could be a marker of heavy metals, bacterial contamination, chlorination by-products, pesticides et cetera. We need to look at this and whether lowering water nitrate intake improves other things in water as well, and then you would have beneficial effects. It might be worth lowering water nitrate intake for that reason, but a lot more work still needs to be done in this area.
Lord Rooker: One thing that people are told is to drink plenty of water. There does not seem to be any caveat on that from government. By the way, in our footnotes as part of our research note, there is a reference to the possible exposure of water in neural tube defects. Is there any evidence for that? If so, how would it affect a woman planning to become pregnant? As you know, the tube closes at 27 days when most women might not know they are pregnant. How would you avoid that risk, if there is such a risk?
A/Professor Catherine Bondonno: I have not heard of that. That is interesting; I will have to look at that. I know that nitrosamines have more neurodegenerative effects at lower levels than carcinogenic effects. Whether it is related to that, I do not know.
Lord Rooker: I am worried now because the other witness is looking at our bottles of water.
Professor Gunter Kuhnle: Some waters declare how much nitrate is in them. We always use Buxton water in studies because it is incredibly low in nitrate, but it is not declared on these.
The Chair: We are against the clock, so I apologise, but this is an important question. I want to look at the international dimension a bit because a couple of years ago, in 2023, France recommended a 20% to 25% reduction in nitrate additives. Could you say a little about the work that went into that recommendation, why France is doing that and whether it is an outlier?
A/Professor Catherine Bondonno: Are you talking about nitrite additives in processed meat?
The Chair: It says, “In July 2022, France’s food safety agency reported the link between cancer and exposure to nitrites in processed meats, leading to speculation of a nitrate ban”. There was a halfway house: in 2023, the French Government recommended a 20% to 25% reduction in nitrite additives.
A/Professor Catherine Bondonno: I still stand by the fact that we do not fully know. From my standpoint, I think we should reduce processed meat intake rather than vilifying what is in the meat products until we know for sure.
The Chair: Could I ask both of you whether you have reduced your processed meat and red meat intake?
Professor Gunter Kuhnle: I do not eat huge amounts, but I have not reduced it.
A/Professor Catherine Bondonno: I think the evidence is strong for processed meat, but the evidence is not yet there for red meat intake. We certainly do not know about combining red meat intake with vegetables, as was mentioned earlier, and what is happening in the body. Again, those studies are being conducted.
The Chair: With that, can I say a huge thank you to both our witnesses? Professor Bondonno made the extra effort, all the way from Perth, Australia. I know it is much easier online but, nevertheless, the time difference is always a bit of a challenge. Thank you very much, both of you.
