The effect of delivering dietary nitrate via different food matrices on blood pressure in normotensive volunteers

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Caroline Day completed the Summer Studentship at the Nutrition and Dietetics Department at King’s College London under the supervision of Dr Trevor George.  Caroline, myself and Harriet Smith also run Fight the Fads, a nutrition media platform that addresses and corrects misinformation in the media with evidence-based science. You can find FTF on Twitter and Instagram.
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Project Title: The effect of delivering dietary nitrate via different food matrices on blood pressure in normotensive volunteers

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About the project:

My project investigated the effect of the consumption of dietary nitrate, consumed in the form of both beetroot bread and beetroot juice, on blood pressure.

Increased vegetable consumption has been associated with a reduction in blood pressure and reduced risk of cardiovascular disease. Originally, this association was thought to be a result of the anti-oxidant properties of vegetables. More recently however the effect vegetable nitrate on blood pressure has been investigated. Vegetables including beetroot have a high nitrate content which after ingestion is reduced endogenously to nitric oxide, a potent vasodilator. Previous studies have found the consumption of beetroot juice is associated with a significant reduction in systolic blood pressure.  This could have important clinical relevance if the dietary nitrate in beetroot could be transferred to a commonly consumed food such as bread, which could then be used in the lifestyle management of hypertensive patients.red-beets-1725799_1920.jpg

Whist some studies have found that beetroot enriched bread products also reduced blood pressure in normotensive subjects, no studies had compared the effect of delivering nitrate via bread and juice using beetroot from the same source, so direct comparisons of the efficacy of each method of delivery have not been possible. My project aimed to create a novel beetroot bread product to establish if it was possible to create the same blood pressure lowering effect as when the same source of beetroot was consumed as a juice.

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My results demonstrated that the  both beetroot juice and beetroot bread lowered blood pressure in participants. After the consumption of beetroot bread, blood pressure remained lower for two hours longer than beetroot juice consumption.

What was the best aspect of your Summer studentship experience?

Having the opportunity and funding to design and implement your own research idea is an invaluable experience. I am considering expanding the study for my dissertation project next year, I have gained skills so many areas that I can take forward with me to make this process much smoother! Particularly in participant recruitment, project planning and data analysis.

What was the most challenging part of your studentship?

Learning to adapt when the project didn’t go to plan. Adding beetroot extract to a standard bread recipe presented many challenges. I had originally intended to maximise the nitrate content of the bread by using a concentrated beetroot juice extract. Unfortunately, the high sugar content of this extract killed the yeast in the standard bread recipe and my loaf ended up more like a cake. This then delayed the project as I had to source and trial other forms of beetroot extract. After two disappointing weeks of trial and error, and thirty loaves of unusable bread I finally found a recipe that worked. This has taught me that patience and flexibility are crucial skills for working in research!

What’s the one thing you learnt that is transferable to future work you might do?

My study was powered for 24 volunteers and only 9 were recruited, so the results do not have sufficient statistical power to draw conclusions even though a pattern was observed. Experiencing the difficulties of participant recruitment has been very useful as this is something I will need to do on a larger scale for my dissertation.

Tips for anyone who is interested in applying for the NS – SS or a similar fellowship:

When researching your project for the application process, I would recommend exploring a number of different project ideas. Speaking to researchers in different areas and thoroughly explore the literature. By doing this I gained a lot of knowledge in different research areas before deciding on my final topic, which helped both with the planning of chosen project and has sparked ideas for future research.

Would you be interested to do more research in the future and if so what topic(s) would interest you?

I am hoping to continue this project as part of my final year dissertation with a larger sample size. There is also the potential to test the bread products on participants with hypertension as all the studies to date have used normotensive subjects.

Continue reading “The effect of delivering dietary nitrate via different food matrices on blood pressure in normotensive volunteers”

A pilot study to determine the effectiveness the Change 4 Life Sugar Smart App (SSA) has on influencing sugar consumption and further investigating the affect the App has on motivating healthier eating habits in healthy adults

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Johanna Bolinder completed her Summer Studentship at St. Mary’s University, London under the supervision of Liz Newling Ward. Johanna has her own website called Bolinder Nutrition and you can also find her on Twitter (@bolnutrition).

Title of project: A pilot study to determine the effectiveness the Change 4 Life Sugar Smart App (SSA) has on influencing sugar consumption and further investigating the affect the App has on motivating healthier eating habits in healthy adults.

About the project:

I looked at how habitual use of the Sugar Smart App (SSA) can influence healthy adults, to reduce their sugar intake and motivate them to make healthier food choices. The results of the pilot showed participants reduced their sugar intake by 32%, free sugar intake by 39.5% and overall energy (kcal) by 28.9% after using the Sugar Smart app daily for two weeks. I have since developed and shaped my dissertation from the results of the study, which I am currently researching.

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What was the best aspect of your Summer studentship experience?

The opportunity to get a running start on my dissertation was invaluable. I enjoyed the challenge that came with independent research. Although I was supervised (by Liz Newling – Ward, the programme director for Nutrition, St. Mary’s University), I was strongly encouraged to get out of my comfort zone and fully embrace, the ups and downs, that come with research as independently as possible.

What was the most challenging part of your studentship?

I worked during my research scholarship. I was offered a position at Jamie Oliver, working on his Food Revolution campaign. It was a dream of mine to work for Jamie, and I couldn’t say no. Instead I decided I could do both, research and work.  It was very demanding at times to juggle the responsibilities. However, it was completely manageable and it forced me to be slightly more disciplined in my time management and scheduling. Research comes with a lot of unforeseen challenges, you can prepare research in theory, however, in practice it usually pans out quite differently. I found it was during these times, research was difficult; you must have a can – do attitude and be flexible and creative when things do not go according to plan.screen-shot-2017-02-16-at-18-46-44

What’s the one thing you learnt that is transferable to future work you might do?

Time management will be the first thing that comes to mind, which in my opinion, is something you can never get too much experience in.  I also learned to work independently, and seek ways to reach conclusions on my own, without relying on professionals. Critical thinking, report writing and data analysis are also skills I am much more confident in.

Tips for anyone who is interested in applying for the NS – SS or a similar fellowship:

My best advice would be to just go for it. Pick a topic which interests you, then brainstorm with someone (nutrition related) whom you respect, and can give you honest feedback. Develop the research methodology, and don’t rush it.  This is such a golden chance, and you will not regret it. It sets you up for the future and you will gain confidence and momentum which you will need to complete your degree.

Would you be interested to do more research in the future and if so what topic(s) would interest you?

I would love to go on and do a PhD at some point in the future, possibly in something related to nutrigenomics which is another area of nutrition which fascinates me. However, right now I am ready to take my knowledge and experience and put it all into practice. I am currently looking for work within food tech, public health and/or industry for when I graduate this summer.

Continue reading “A pilot study to determine the effectiveness the Change 4 Life Sugar Smart App (SSA) has on influencing sugar consumption and further investigating the affect the App has on motivating healthier eating habits in healthy adults”

Inflammatory Bowel Disease and Additive Emulsifiers

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I completed my Summer Studentship at the Department of Nutrition and Dietetics at King’s College London, under the supervision of Professor Kevin Whelan and Dr Megan Rossi. On the side, I run Fight the Fads with Harriet Smith and Caroline Day. A nutrition platform that aims to remove the fear and confusion over nutrition often created by the social media. You can find FTF on Twitter and Instagram and you can also find me on my personal Twitter account

Project Title: Inflammatory Bowel Disease and Additive Emulsifier

About the project:

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The incidence of inflammatory bowel disease (IBD) is increasing (Hanauer, 2006) alongside dietary intakes of food additives resulting from societies’ demand for palatable convenience foods (Lerner and Matthias, 2015). Exploration into this association has uncovered a novel mechanistic pathway by which some food additives, specifically synthetic emulsifiers, may trigger colitis. (Roberts et al, 2013 and Csaki, 2011) Moreover, convincing evidence in support of this emerging hypothesis demonstrated that mice fed common emulsifiers, carboxymethylcellulose and polysorbate-80, at relatively low doses induced significant colitis in those predisposed to IBD (Chassaing, 2015). This landmark study, published in Nature, has raised serious concerns behind the safety of additive emulsifiers, warranting investigation in humans.

Consequently, aim of this project was to identify from the literature which emulsifiers have been associated with IBD and develop the methodology in order to quantify and qualify emulsifier intakes in patients with IBD, in order to compare them to the intakes of healthy controls and assess the health risk posed to potentially vulnerable groups. 

I conducted a literature review of published research relating to IBD and emulsifier consumption. Emulsifiers in the UK market were quantified using FoodMaestro®. Patients with IBD were recruited and completed a seven-day un-weighed food record. Three patients were analysed further using Nutritics® and their emulsifier intakes was quantified.

The literature results showed that Carrageenan (E407), Polysorbate 80 (E433) and Carboxy methyl cellulose (E466) is associated to IBD. Of the n=94,286 foods in UK Market, 30% contained any emulsifier. The distribution in food subcategories as organised by manufacturers varied greatly. Intakes of the three patients were not consistent, however sources were derived primarily from confectionary and processed meats.

The quantification of emulsifiers was limited as manufacturers are not obliged to provide the amount (mg) of emulsifiers used in food products in the same way as in carbohydrates (g). In addition, the European Commission allows the use of some emulsifiers as per quantum satis (= the amount required), without specifying an upper limit. I attempted to resolve this limitation by contacting manufacturers directly, liaising with the European Food Safety Authority and the Food Additives and Ingredients Association to obtain usage data. None of the information provided was adequate to quantify use of the three selected emulsifiers.

This is a very interesting area of research and additional studies with a larger sample size are required to be able to make any associations between intakes of additive emulsifiers and IBD in humans.

The best aspect of my Summer studentship experience:

Working alongside a team of leading professionals in the area of gut health was one of the best aspects of this project. I specifically enjoyed my meetings with my supervisors as they allowed me to organise my thoughts and experience how it is to be part of a research team. During the meetings I was able to get an insight on the way they work and the research they are conducting and understand how much hard work goes into completing a project. 

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International Congress of Dietetics ENDietS Conference – Granada, Spain 6th September 2016

A highlight of my SS experience was the opportunity to present the outcomes of my project at the International Congress of Dietetics, ENDietS conference in Granada Spain. This required me to prepare an engaging presentation that would present my eight-week project in a ten-minute presentation. I really enjoyed this experience and I understood how much hard work is required to deliver complex information in a simple and engaging way.

The most challenging part of my studentship:

Due to the nature of my project, I was constantly re-evaluating the aims of my project based on the available data. This at times was very challenging mentally and psychologically as I had to completely disregard work I had spent many hours completing. What this taught me though, was that nutrition research is not a straight forward process and it is these changes that evidently led me my results. 

The one thing I learnt that is transferable to future work:

The Nutrition Society SS was an invaluable funding opportunity that not only supported my interest in IBD, but provided me with first-hand insight into a career in nutrition research.  I was able to develop many research skills, including recruiting, re-evaluating goals, time management, data collection, food data analysis, planning a research presentation and presenting. These are skills that will be invaluable for my future academic development and in particular my dissertation next year.

Tips for anyone who is interested in applying for the NS – SS or a similar fellowship:

My top three tips would be:

  1. Take your time to explore several areas of interest. Try to read a paper each day to stay up to date and familiarise with different topics can be useful. Speak to your lecturers and express your interest, this will evidently allow you to decide on an area that will interest you. 
  2. When you decide on a topic – Make sure to be passionate about your topic. Not only does this mean you will learn new things about a topic of your interest it also means you will enjoy your project. This is essential, particularly if you will be spending long hours working on it…  
  3. Take your time to complete your application. A targeted, well organised and structured application is likely to be successful! Explore different funding opportunities and don’t give up if you don’t succeed on your first application. 

Conducting research is a challenging project but one that will give you a lot insight into what it means to do research, organising your own time and being efficient so make the most out of this experience. While working on your project will be your main focus, make sure to speak to other researchers and learn about their areas of interest.

Good luck to everyone that wishes to apply for a research project this summer! 

Am I interested to do more research in the future?

As I have mentioned before I strongly believe research is the way forward in the nutrition science. Studying at KCL we are trained by leading scientist in the field of nutrition. Our training is based on the most recent evidence-based science and I would be definitely interested in conducting further research in the future. Currently, my interest is primarely on gut health, however the more I read on other topics I realise there are a large number of topics that interest me. Renal, oncology and cardiovascular health being some of them. 

Continue reading “Inflammatory Bowel Disease and Additive Emulsifiers”

The Summer Studentship Series

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The Nutrition Society (NS) offers a unique funding opportunity to a limited number of students to undertake a research project during the summer months. The Summer Studentship Series on Research Girl Today is a collaboration with all students that took part in the 2016 NS Summer Studentship (NS-SS).

The Nutrition Society received a large number of applications and eight projects were selected and funded for the summer of 2016. The variety of topics highlight the diversity in the areas of research related to Nutrition. The projects included:

Elisabeth Cresta – Title of Project: Inflammatory Bowel Disease and Additive Emulsifiers

Johanna Bolinder – Title of Project: A pilot study to determine the effectiveness the Change 4 Life Sugar Smart App (SSA) has on influencing sugar consumption and further investigating the affect the App has on motivating healthier eating habits in healthy adults

Caroline Day – Title of Project: The effect of delivering dietary nitrate via different food matrices on blood pressure in normotensive volunteers

Dove Yu – Title of Project: Estimating the dietary intake of “free sugars” in the teenage population in the United Kingdom

Hanna Walsh – Title of Project: Glycaemic response and satiety after consumption of gluten-free bread containing buckwheat

Cindi Bei – Title of Project: Interactions between TCF7L2 and MC4R gene variants with dietary factors on Type 2 Diabetes-related factors in the British population

Toni Spence – Title of Project: The relationship between the immune response in pregnancy, birth outcome and polyunsaturated fatty acids (PUFA)

I decided to ask everyone a couple of questions related to their projects and general experience, in an attempt to give you an idea of the variety of projects we completed and the interesting elements of each project. My hope is to inspire more students to do research and provide useful information and tips for those who may be interested in applying for the NS Summer Studentship or other similar research projects.

I firmly believe research is the way forward in nutrition and I hope the Summer Studentship series will inspire more of you to get involved in research projects.

I will be posting daily for a week and you will have the chance to read all about our experiences and hopefully get inspired to apply to do a research project.

The 2017 Nutrition Society Summer Studentship application is now open and you can find it here or by clicking on the Nutrition Society logo below:

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Please comment and let me know if you have found these series useful!

Many thanks,

Elisabeth

Continue reading “The Summer Studentship Series”

80 Days to the London Marathon!

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RUNNING THE LONDON MARATHON IN SUPPORT OF 

SPINAL RESEARCH UK

If you wish to sponsor me please visit Elisabeth’s Virgin Donation Page!

Day 1. Rest Day

Day 2. 11 km

Day 3. Rest Day

Day4. 11 km

Day 5. Rest day

Day 6. 25 km

Day 7.  Rest day

Day 8. Bikram Yoga class

Day 9. 5 k

Day 10. Bikram Yoga class

If you wish to sponsor me please visit Elisabeth’s Virgin Donation Page!

These 10 days were slightly more intense as they were packed with more university deadlines and Fight the Fads responsibilities. I am still very much enjoying training for the marathon and although sometimes I had to face the shivering cold (-1C in London on Day 4) I still have a smile on my face each time I wear my gear!

Summary in aid of photos…

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Day 4 – 11km (4.58 min/km) View of Tower Bridge
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On Day 4, I managed to run my fastest 10km run in the shivering cold (-1 C) !!!

Day 25 – Part of me choosing new routes for my long runs each week is to keep me motivated and to ensure I explore new areas of London. However, this week involved running by a familiar route and listening to old nostalgic tunes. I headed off from Southwark to Hyde park run by Warwick Avenue, Primrose Hill, Regents Park and back to Southwark…I started the run at 7 am on Saturday morning and I managed to complete it on a pace of 6:23 min/km.   

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Day 6 – 25 km run on a 6:23

With this week being busier I managed to fit in a quick 5 k run on Day 9 prior to heading to university to present a case study as part of our Diet Therapy class, then filming with Charlotte Stirling-Reed and Jenny Rosborough for the Fight the Fads petition to legally protect the title Nutritionist, followed by an amazing event organised by the Rooted Project on Gut Health. Prof Whelan as always delivered an amazing presentation and he was joined for the question panel with two of my favourite nutrition experts, Dr Megan Rossi and Dr Laura Thomas

 

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Post yoga selfie 🙂

This week I also took up two very early morning (6:45 am!!! Yay to motivation) 90 minutes hot yoga classes at Hot Yoga Society. Yoga helps me relax but also is a good way to stretch tenses muscles from long runs 🙂 I was initially worried a 90 minute class would be too much for me but I ended up enjoying it!

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TUNE OF THE 80 DAY UPDATE

Thanks a lot for taking the time to read my marathon update! As it is February 1st, I hope we all have a productive month!

Elisabeth

Continue reading “80 Days to the London Marathon!”

90 Days to the London Marathon!

 

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Training Summary

Day 1. 10 K

Day 2. Rest day

Day 3. 23 k

Day4. Define class by Ashley Yeater

Day 5. 10 k + 2.5 km @Midnight Runners

Day 6. Rest day

Day 7. 10k Run

Day 8. Rest day

Day 9. 24 km

Day 10. Bikram Yoga (60 minutes)

*Detailed update starts on Day -13, 1st January 2017…

My marathon training started on the other side of the Atlantic…all the way at Los Angeles, CA, on a visit to my best friend during the festive season! I managed to start my training with two runs, a 10k (5:30min/km) and a 12k (5:57 min/km). Running from Santa Monica to Venice Beach, apart from the beautiful view the warmer temperature made them really enjoyable!

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Somewhere between Venice and Santa Monica, CA

January 9th – 15th 

Coming back to London, I decided I would have to face the rain and frost but at least I would enjoy running in favourite city! Last week started with two 10km (5:41 min/km, 5:50 min/km) runs on Wednesday and Friday, followed by a 23 km (6:10 min/km) run on Sunday with my running buddy, Giulia!

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Giulia and I on 19 k of our 23 k Sunday run…still smiling!

Giulia, (a very soon to be Dietitian from KCL!) is running the Rotterdam Marathon on the 9th April, which is two weeks before the London Marathon. We have decided to keep each other accountable and train together! On our long run we passed through Tower Bridge, the London Eye, Westminster and headed to Battersea Park were we did two laps and then headed back. The view on the early Sunday evening was beautiful and made us feel like we were part of the La la Land crew!

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Albert Bridge, Chelsea – London

January 16th – 22nd

This week started with a DEFINE class by Ashley Yeater. DEFINE is definitely one of my favourite classes. It combines elements of dancing, ballet and strength exercise! Stay tuned as I will be posting more about this class on my next marathon update.

On Tuesday evening, I joined the Midnight Runners crew! Tuesday runs involve a 10 km run with stops every 2 km for group exercises! There were around 170 runners on Tuesday, which motivated me to keep on going! As if that was not hard enough, I decided to run to the meeting point from home to add an extra 2.5 km. I am not going to lie, the exercises were tough…but by the end I managed to log a 12.5 km (5:50 min/km) run for the week and also strengthen my muscles! 😉

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Midnight Runners – Tuesday, 17th January 2017, spot me on the right with my friend Alice!

Wednesday I took the day off from running. Did some foam rolling in the morning and then headed to uni for lectures and library studying! 

Thursday was a busy day. Started with work from home, headed to uni for a 3 hour class on the management of obesity, followed by a Nutrition and Dietetics Society event. On my way home I ran 10 km (5:49 min/km). Back home, as I was stretching and foam rolling, I tuned in to BBC2 Horizon to watch Giles Yeo talking about Clean Eating.

The final run for the week was on Saturday, a 24 km run (6:21 min/km). Giulia was away this weekend so I knew this would be a tough run, however, the sun was shining and the blue sky filled me with happiness and motivation to run! I have decided to vary the routes of my long runs so that the training is more exciting. As I had never visited Greenwich Park I decided to explore that side of London. The run there was very good, however I realised how hilly it was only when I reached the park and at that point I had run only 11 k. With  13 km left to run I slightly panicked…Reaching 20 km I thought I would pass out but thankfully with you in mind I picked myself up and completed the run! Following the run I had a lovely lunch with my father, which gave the chance to refuel! 

 

Currently, I am trying to decide on a half marathon race. If you are also a runner (cyclist, swimmer etc.) and can’t decide which race is for you, make sure to check out Racecheck, a great resource for finding races in the U.K. and abroad. On Racecheck you can read athletes reviews in order to pick the race that best suits you!

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DIET

In terms of my diet I haven’t really changed much, however, I am making sure I drink lots prior to my runs and I have noticed I have a bizarre new craving for milk post my long runs. I say bizarre, as I am the type of person who would never consider drinking milk on its own unless I was forced to…

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My brother made sure a steak with potato and sweet potato, mixed vegetables and a green salad were waiting for me when I got back from my Midnight Runners run on Tuesday! What else could one wish for?!

I am looking into protein supplements and whether protein shakes is something I want to consider, but haven’t reached any conclusions yet. As I look more into what works for me I will be updating you! I will most likely be asking the expert opinion of dietitians before making any changes.

 

 

 

 

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I would like to thank my dad- John, Vangelis, Eirini, Freya, Masha, Michael and Teresita and Takis for their generous donations!

If you wish to sponsor me please visit Elisabeth’s Virgin Donation Page!

All donations will be greatly appreciated and will contribute to the development of the research on spinal injuries.

I am hoping to complete the marathon in 4h30m! I know this training will be really hard for me and I need your help! To keep me accountable, I plan to post an update of my training every 10 days, so stay tuned for the next post on 80 Days till the London Marathon!

100 days till the London Marathon!

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It has been a while since I posted something on Research Girl Today. Last year I decided I would run my first ever marathon in 2017 and dear, oh dear how has time flown by…It’s officially 100 days till the London Marathon!

I decided to run the London Marathon in support of Spinal Research UKThe implications of injuries on the spinal cord are often severe and irreversible. You can find a summary of spinal injuries by respective sections of the spinal cord in the image below (Spinal Research, 2017).

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The effects of spinal injuries by location. (Body art by Zoe Light)
Note: The notation of the vertebra is not in the exact anatomical position.

Sadly, I have seen the impact spinal cord injuries had on a close friend, whose life is still affected everyday despite having surgery four years ago for Scoliosis (curvature of the spine).

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If you wish to sponsor me please visit Elisabeth’s Virgin Donation Page!

All donations will be greatly appreciated and will contribute to the development of the research on spinal injuries.

I was lucky to have a great superwoman friend, Alice Green, who gave me a training plan for this marathon (Big thank you Alice!). I hope to post about Alice’s inspirational story in a future post.

I know this training will be really hard for me and I need your help! To keep me accountable, I plan to post an update of my training every 10 days, so stay tuned!

 

Build up your Fibre intake

What is dietary fibre?

Dietary fibre is used to describe the majority of the carbohydrates that enter the colon, such as non-starch polysaccharides, resistant starch and indigested oligosaccharides. This fraction of carbohydrates cannot be digested in the small intestine and is fermented by bacteria of the colon, producing short-chain fatty acids (SCFA, acetate, propionate and butyrate) and gases (carbon dioxide, hydrogen and methane).

Tips to increase fibre intake ?

  1. Increase your bean intake. All beans are good sources of fibre, whether baked beans, beans like kidney beans in chilli or beans in salads. Half a tin of black beans (200g –> 120g drained weight) is about 8 g of fibre. As well as beans, chickpeas and lentils are rich in fibre, high sources of protein and low fat.walnuts
  2. Wholegrain and wholemeal. Skip white bread and pasta, look out for wholegrain and wholemeal on the labels. Brown or wholegrain rice? Choose wholegrain rice over white rice, white rice doesn’t offer as much fibre.
  3. Nuts: Choose almonds, pecans, and walnuts as they have more fibre than other nuts.SA1TMVCPF8
  4. Fruit and vegetables:Consume at least your 5-a-day portions and the crunchier, the better. A medium-sized apple alone is 2g fibre. If fresh fruit isn’t available, dried fruit can offer a good alternative to boost your fibre intake but beware of the sugar content. A 50g portion of dried figs is 4g fibreYVDRQAGWOP.

5.Choose bran based cereals. As a rule of thumb, a high-fibre food will contain more than 6g of fibre per 100g. A 30g bowl of Bran Flakes delivers 4g of fibre. As an alternative try porridge, which is made from oats and is a great source of fibre.

How much fibre should we consume?

The Recommended Daily Intake for fibre in the United Kingdom until recently was 18 g/day and in Australia it is even higher, recommending daily consumption of 25-30 g. Following Australia this recommendation was raised in July 2015 to 30g/day (SACN report on Carbohydrates and Health).  In the UK most people are not consuming enough, with the average intakes being 12.8 g/day for women (19-64 years) and 14.7 g/day for men (19-64 years) (6). A number of studies have shown that an increase in the intake of dietary fibre has been associated with the treatment and prevention of a number of multifactorial diseases, such as colon cancer, obesity and diabetes and coronary heart diseases.

The role in promoting health:

In order to fully understand the role of fibre in the promotion of health it is useful to outline the effects SCFA and gases have in the body.

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Table 1: The products of fermentation in the colon and their effect on the body.
  1. Colonic Health

As fibre enters the colon water flows in by osmosis, which increases faecal bulk and makes it softer. This results to the laxative effect, which is associated with a decrease in the transit time, increase in faecal bulk and an increase in the frequency of defecation (1) (See Graphs 1,2).

Graphs 1 (left), 2 (right): The inversely proportional relationship between stool weight and colon cancer incidents and the proportional of non-starch polysaccharides and stool weight (7).
Graphs 1 (left), 2 (right): The inversely proportional relationship between stool weight and colon cancer incidents and the proportional of non-starch polysaccharides and stool weight (7).

The decrease in transit time reduces the time toxins are in contact with colonocytes, hence reducing carcinogenesis in the colon, an effect originally introduced by Burkitt (1969) (8). A high fibre diet also contributes to the decrease of diseases related to constipation and abdominal pressure, such as diverticulitis (1). A number of prebiotic health effects have been associated with the balance of gut microflora and in particular with that of bifidobacteria (9) (See Figure 1).

Fig.1 Health benefits associated with bifidobacteria.
Fig.1 Health benefits associated with bifidobacteria.

As mentioned above, butyrate is the preferred substrate for colonocytes and is used in microbial growth. The SCFA produced by the microbial fermentation reduce the pH of the colon, which prevents the growth of pathogenic organisms in the colon (10). The reduced pH of the colon increases the bioavailability of calcium and that leads to greater mineral density (9).

  1. Obesity and Type 2 Diabetes

The health benefits of unavailable carbohydrates with respect to obesity and diabetes are associated with the effect they have on the gastrointestinal tract, the digestion of all carbohydrates and their absorption. High-fibre diets usually require longer chewing time compared to low-fibre diets (1). This promotes the secretion of more saliva and gastric juices, decreases gastric emptying and increases gastric distension promoting satiety (4). With the decrease of gastric emptying, chyme enters the ileum at a slower rate decreasing the rate of nutrient absorption. This is useful regarding the management of type 2 diabetes. A high fibre diet slows the absorption of glucose and consequently reduces the release of insulin, lowering the glycaemic index of foods. Carbohydrate-rich diets with low-glycaemic index have been associated with lower risk of diabetes (12). High peaks of insulin levels have been linked to the aetiology of both diabetes and coronary heart diseases (4). Unavailable carbohydrates have a lower energy density, varying from 1.4 – 2.4 kcal/g, are less palatable and hence are associated with reduced food intake and satiety (6). This yield depends upon the degree of fermentation and the proportion of the short-chain fatty acids produced (3). A high-fibre diet would prove beneficial in the management of obesity as it is closely linked to both Type 2 diabetes and coronary heart diseases.

  1. Cardiovascular diseases (CVD)

High intakes of fibre have been associated with a reduced risk of CVD (1). A study on Japanese Men and Women with no previous predisposition of cancer, stroke or coronary heart disease, showed that dietary intakes of fibre, in particular fruits and cereal fibres, could have a reduction in the mortality of coronary heart diseases (13). High levels of blood cholesterol are closely linked to CVD (14). As cholesterol is a precursor of bile, an increase in bile synthesis would reduce the cholesterol level in the blood. Unavailable carbohydrates bind to bile acids, increasing their excretion in faeces while increasing the bile synthesis in the gallbladder (5).

As seen in Table 1, the SCFA produced from the fermentation of the unavailable carbohydrates have antagonistic effects in the hepatic synthesis of cholesterol. This will depend on the rate of production of acetate with respect to propionate, which will either stimulate or inhibit cholesterol synthesis respectively.  A meta-analysis looking at four types of primary sources of fibre, oat products, psyllium, pectin and guar gum showed they had a similar effect on lowering cholesterol levels (14).

The health benefits associated with the increase intake of dietary fibre are an active area of research. The concern still remains why people consume less fibre than is currently recommended and what can be done to change this?

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References

  1. Cummings J., Mann J. Chapter 3 Carbohydrates. In: Mann J. and Truswell A. S. (eds). Essential of Human Nutrition. 4th Oxford: Oxford University Press, 2012; pp. 21- 48.
  2. Widmaier E. P., Raff H, Strang K. T. Vander’s Human Physiology – The Mechanisms of Body Function, 13th edition, New York, McGraw-Hill, 2014. Chapter 15 – The digestion and absorption of food; pp. 533-571.
  3. Bender D. A. (ed) Chapter 6 – Carbohydrate metabolism. In: Geissler C., Powers H. (eds), Human Nutrition, 12th edition, London, Elsevier, 2011; pp. 111-132.
  4. Sanders T., Emery P., Molecular Basis of Human Nutrition, 1st edition, London, Taylor and Francis, 2003 Chapter 4 – Carbohydrates; pp. 44-57.
  5. Mathers J., Wolever T. Chapter 5 – Digestion and Metabolism of Carbohydrates. In: Gibney M. J. et al (eds), Introduction to Human Nutrition, 2nd edition, 2009; pp. 74-85
  6. Scientific Advisory Committee on Nutrition. Draft Carbohydrates and Health report – Scientific consultation: 26 June to 1 September 2014 p 270
  7. Cummings J. H., et al, Fecal Weight, Colon Cancer Risk, and Dietary Intake of Nonstarch Polysaccharides (Dietary Fiber). Gastroenterology 1992, 103: pp. 1783-1789.
  8. Bingham S. A. Mechanisms and experimental and epidemiological evidence relating dietary fibre (non-starch polysaccharides) and starch to protection against large bowel cancer. Proceedings of the Nutrition Society 1990, 49: pp. 153-171.
  9. Brownawell A. M., et al, Prebiotics and the Health Benefits of Fiber: Current Regulatory Status, Future Research, and Goals. Journal of Nutrition 2012, 142: pp. 962–974.
  10. Topping D. L., Clifton P. M. Short-Chain Fatty Acids and Human Colonic Function: Roles of Resistant Starch and Non-starch Polysaccharides. Physiological Reviews 2001, 81 (3): pp. 1032-1054.
  11. Gibson G. R., Roberfroid M. B. Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics. The Journal of Nutrition 1995, 125 (6): pp. 1401-1412.
  12. Ley S. H., et al Diabetes 1: Prevention and management of type 2 diabetes: dietary components and nutritional strategies. The Lancet 2014, 383: 1999-2007.
  13. Eshak E. S., et al Dietary Fiber Intake Is Associated with Reduced Risk of Mortality from Cardiovascular Disease among Japanese Men and Women. Journal of Nutrition 2010, 140: pp. 1445-1453.
  14. Brown L. et al, Cholesterol-lowering effects of dietary fiber: a meta-analysis. The American Journal of Clinical Nutrition 1999, 69: pp. 30-42.
  15. Scientific Advisory Committee on Nutrition, Report on Nutrition recommendations on carbohydrates, including sugars and fibre. London: TSO;2015.