[Food as Medicine] Food and the gut

At the end of this week you will be able to:

• identify foods/components of food that have an effect on different body systems including the gastrointestinal system, the brain and appetite, inflammatory processes

• discuss concepts impacting on over/under nutrition and how this can affect growth and body weight

• discuss and explain internal factors impacting on food choices and body weight

• recognise the relationship/interaction between genes, nutrition and health

• explore components of food that affect fertility and pregnancy.

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Fibre, prebiotics and the gut

Dietary fibre and prebiotics are both members of the large and diverse carbohydrate family. Dietary carbohydrates have received a lot of ‘bad press’ over the years which has left many people in our community believing that ‘carbs’ are something to be avoided.

Digestible carbohydrates (sugars and starches) are important to the body as a source of energy. The more indigestible carbohydrates (oligosaccharides, dietary fibre and resistant starch) provide little energy but they still have important effects on our health.

Firstly, they help waste products to be eliminated from the gut in our bowel movements (laxation). 소화가 잘되는 탄수화물은 장의 움직임에 방해되는 필요없는 생산물을 떼어내준다. (소화에 도움)

 Secondly, their presence in foods can slow down the digestion and absorption of glucose. 그런 후 음식물 속의 탄수화물들은 소화의 속도를 늦추며 포도당을 흡수한다. 

And last-the breakdown products formed when they are fermented by bacteria in the large intestine can help to reduce blood cholesterol. 음식물을 분해시켜 장내에서 박테리아를 통해 발효시켜 혈관내의 콜레스테롤을 낮추는 역할을 한다. 

The different kinds of indigestible carbohydrate all differ in their ability to promote these health effects. Some are better at one thing, some are better at another.

So it is very important to eat a range of types – which means including many different types of plant foods in your diet.

What are carbohydrates and where does fibre fit in?

Dietary carbohydrates generally include the term ‘saccharide(당류)’ in their name. They range greatly in size from simple sugars, or monosaccharides (consisting only of single sugar units), to very large complex polysaccharides (consisting of many thousands of sugar units joined together).

As well as differences in size, carbohydrates can also differ in their chemical structure. Such differences are important because they dictate how, and where and even whether specific carbohydrates can be digested and absorbed by humans.

The three major groups of dietary carbohydrates

Simple sugars (단당류, 이당류) 

Simple sugars or monosaccharides(단당류) and disaccharides(이당류). Monosaccharides consist of just a single sugar unit. The sugars glucose and fructose are two examples of monosaccharides. Disaccharides consist of two sugar units joined together. Examples of disaccharides include; sucrose (made up of one unit of glucose plus one unit of fructose) and lactose (which is made up of one unit of glucose plus one unit of galactose). 단당류는 가장 작은 단위의 탄수화물이다. 이당류는 두개의 단당류가 합쳐진것이다. (수크로오스, 락토오스)

Most monosaccharides and disaccharides in human diets are broken down very easily in the human gut and absorbed very quickly into the body. 단당류와 이당류는 가장 쉽고 빠르게 장안에서 흡수되고 분해된다. 

Oligosaccharides(올리고당)

These occur in a limited number of plant foods such as beans and lentils, onions, garlic and artichokes. Oligosaccharides form when three to nine sugar units become tightly joined together.

This tight bonding between the component sugars is difficult for the body to break down so that these types of carbohydrates cannot be digested and absorbed in the human small intestine. Instead they continue to move on into the large intestine. Here the resident bacteria are able to break them down as bacteria contain the enzymes necessary to do this. 소장에서 소화되지않고 대장에서 소화되며, 대장내에서 박테리아의 효소역할을 한다. 

These indigestible carbohydrates are examples of ‘prebiotics’.

Polysaccharides (다당류)

These carbohydrates have more than nine sugar units and often up to several thousands of sugar units joined together. The two major groups of polysaccharides are starch and dietary fibre. 9개 이상의 단당류가 결합된 다당류는 대표적으로 전분과 식이섬유이다. 

Starch (전분)

Starch consists of long chains of the simple sugar glucose joined together. Generally, these long glucose chains are very easy for the body to break down. This means that most starches are readily digested in the small intestine, and their glucose subunits are quickly be absorbed into the bloodstream. 길게 늘어진 당당류로 이루어진 전분은 쉽게 몸안에서 분해가된다 - 즉슨, 전분은 대부분 소장에서 분해되고 혈류사이에 흡수된다.

One particular group of starches, collectively known as resistant starch(저항성 전분), are contained within seeds or grains, or have been changed by cooking or have a particular structure that makes them much harder to digest. These starches behave like dietary fibre and pass down into the large intestine.저항성전분은 (씨류와 곡류에 많이들거나 조리과정에서 생김) 전분보다 소화의속도가 느리다. 그래서 식이섬유처럼 대장에서 분해된다.  

Dietary fibre (식이섬유)

The sugars in some types of polysaccharides are bound together in unusual ways and humans do not have the enzymes to break them down. These types of polysaccharides escape digestion in the small intestine and continue to move down into the large intestine. Here they can be broken down by bacteria living in this part of the gut (that produce a wider range of enzymes). 특이하게 집합된 단당류의 집합으로 생긴 다당류 (식이섬유)는 효소에 의해 분해가 되지않고 장내의 박테리아의 이해 분해된다.

So while you will see dietary fibre listed separately from digestible carbohydrate on food labels, dietary fibre is in fact a type of carbohydrate. Not all dietary fibre is exactly the same. The dietary fibre in some foods can be broken down by the bacteria in the lower intestine relatively quickly. This type of fibre has been called soluble or rapidly fermentable fibre and it is digested in the upper part of the large intestine. 식이섬유는 보통탄수화물과 다르고, 종류도 많이있다. 어떤 식이섬유는 박테리의 인해 빠르게 분회도된다. 유화/빠른발효 식이섬유?

Other dietary fibres are very difficult indeed to break down which means that they travel much further down the large intestine before bacteria can act on them. These fibres are known as insoluble or poorly fermentable fibre.어떤 식이섬유는 소장과 대장을 건너 먼곳에서 소회되는 것도있다 = . 용해안되는/발효하기 어려운 식이섬유 ?

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The importance of dietary fibre for health

Between 4% to 20% of people in Western countries suffer from constipation(변비). At the other extreme, going to the toilet too often is associated with watery and very soft-stools.

This condition is called diarrhoea and is an indication that waste products are moving much too rapidly through the lower intestine. Good bowel habit falls somewhere in the middle of these two extremes. If you think of your gut as a river then you do not want it to flow too quickly (raging river = diarrhoea) or too slowly (cracked dry river= constipation).

Promotion of good bowel(창자) habit

One of the important tasks of dietary fibre involves promoting a good bowel habit or bowel movement. This means that there is no straining or difficulty in using your bowels when going to the toilet. Straining and difficulty often occurs when stools (poo) become more solid and dense.

When stools become very hard this is called constipation, a condition that develops when waste products take an excessively long time to move through the lower intestine to be expelled.

What does a normal stool look like?

It may sound disagreeable, but it is important to know what your stool looks like, because it is a good indicator of your gut health. How do you know if you have good bowel movement? What does a normal stool look like?

A useful chart called the ‘Bristol Stool chart’* helps us understand how the appearance of stools changes depending on the time it takes for food to transit through your digestive system. You can use this chart to help understand more about your own bowel health.

Bristol stool chart · Faecal · Continence Foundation of Australia

So how best to control or change the type of stool you have? The answer is - through your diet!

Some types of dietary fibre are much better at increasing the volume of the stool than other types of fibre.

Increasing stool volume is important because a large bulky stool passes through the large intestine more quickly. There will be less time for the body to absorb water back from the stool, so the stool will be softer and easier to pass.

Dietary fibre from legumes and lentils produces fairly small stool volumes (although it has other good effects).

Dietary fibre from oats produces a larger stool; fibre from fruit and vegetables is even better, while the highest stool volume is found with dietary fibre from wheat bran.

How does dietary fibre promote stool bulk?

Different fibres do this in different ways. Some dietary fibre contains a lot of cellulose, a poorly digested fibre, found in cereal grains and in fruit and vegetables. Because of its chemical structure, cellulose is excellent at retaining water (like a sponge) and so this helps bulk up the volume of the stool.

Other fibres that break down more quickly can also increase stool volume more indirectly by promoting the growth of bacteria in the lower bowel. These bacteria add to the size of the stool and the bacteria themselves also retain a lot of water which again adds to the stool bulking.

This is why drinking water is so important for regular bowel habit and prevention of constipation.

Selectively stimulate the growth of beneficial bacteria

Dietary fibres that can selectively stimulate the growth and or activity of beneficial bacteria in our gut are called prebiotics.장안에서 좋은 박테리아를 키우고 움직임을 돕는 식이섬유를 우리는 프리바이오틱스 라고 한다.(유산균의 밥정도로 생각)  Not all dietary fibres can do this- it is a specialised role for certain types of fibres.

Many different kinds of bacteria can metabolise(신진대사시키다) or ferment carbohydrates. Two important groups that you may have heard of are Bifidobacteria, and Lactobacilli(젖산균). When bacteria ferment carbohydrates they produce gases and compounds called short chain fatty acids.

We now know that short chain fatty acids play many different roles in maintaining the health of the gut. For example, one type of short chain fatty acid called butyrate is the preferred energy source for the cells lining the large intestine. When plenty of butyrate is available the gut lining remains very healthy and is unlikely to become inflamed or to go on to develop colon cancer.

The best way to produce short chain fatty acids at the location that they are required (the large intestine) is through consuming foods that are good sources of poorly digested carbohydrates: dietary fibre, oligosaccharides and resistant starch. Resistant starch is a particularly good substrate for butyrate production by the bacteria in the lower intestine. So we can say that resistant starch is a good example of a prebiotic dietary fibre.

Prebiotic fibres used by the food industry often come from oligosaccharides. These include fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS).

These are easy to isolate from food sources (for example from chicory root) and are often added to foods such as yoghurts, dairy foods and infant formula by the food industry.

Here’s what we know, so far

Research on the effects of prebiotics has not as yet yielded very clear results. Prebiotics appear to be effective in changing the profile of gut microorganisms (particularly increasing the population of Bifidobacteria). They can improve intestinal function (contributing to stool bulking and improved stool consistency), and they may improve the absorption (e.g. of some minerals particularly calcium, which is important for bone health).

Less clearly established effects which still need further research include beneficial effects on the immune system, reducing the risk of gastrointestinal infections and possibly assistance with weight management through effects on energy metabolism and satiety.

Interestingly, prebiotic oligosaccharides are found naturally in human breast milk. Here they are useful in encouraging the growth of the Bifidobacteria and Lactobacillus in the gut of the young infant. It is important in early life to establish a good population of these types of bacteria in the infant(유아) gut - it helps in the development of the infant’s immune system and protects against infection.

Gas production

Gas production is the other major by-product of the bacterial fermentation of dietary fibre in the gut. Gas (or excessive wind) is one of the side-effects of a high fibre diet that concerns many people.

Include more fibre in your diet without excessive gas

Another way to look at ‘gas’ is that it is a sign that you are feeding your gut bacteria the carbohydrates they need to make some useful by products- such as butyrate. Take it as a good sign that your bugs are busy!

Allowing the bacteria in your gut time to adapt to an increase in dietary fibre is a good idea. To do this, don’t increase your intake of fibre quickly- do it gradually over a week. By slowly including foods that are higher in fibre over 7 days gives the population of bacteria in your gut that can process this carbohydrate time to expand to deal with the extra material.

Generally these symptoms will reduce as your gut bacteria adapt to the new dietary regime(관리). Many of the good bacteria – bifido, are not gas-producing and so encouraging the growth of this population means that often your symptoms will subside over time.

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Foods and fibre

JANEANE DART : video transcript

Dietary fibre occurs naturally in plants and all the foods that are derived from plants. And as we know, foods such as whole grains, cereals, fruits and vegetables are most of the plant foods that are in our diet. Why is dietary fibre good for us? Just to recap-- it's really good for our bowel health, so both in terms of creating stools or helping us develop bowel motions. It's also helpful in terms of modifying the texture of our bowel motions. So fibre has a really big role to play in terms of fecal bulk, but also in terms of the consistency and texture of stools. And that can have a big impact on people's health and well-being.

So where is it found?Dietary fibre is found in, as you can see here, an array of the foods that are within our diet, so breads and cereals, whole grains, fruits and vegetables, legumes, nuts and seeds.It's present in lots of different foods in our diet.

How much do we need to eat? We need to be eating-- certainly in Australia the recommendation is around 30 grams a day. How much are we eating? Most recent surveys indicate that adults are only consuming about 20 grams a day, so we're falling about sort of 1/3 short of what we need to be consuming. And then certainly for children they don't need to be having certainly quite that amount of fibre, but certainly they need to have good amounts of fibre as well.

So where abouts do we get fibre? So as you can see here we've got an array of different foods here. So the vegetable group-- and generally if we think back to that 30 gram recommendation-- for vegetables per half a cup of vegetable there's about two to three grams of fibre. So if we're eating our recommended five serves a day that's somewhere around sort of 10 to 15 grams of fibre, so you're about halfway there just if you eat your vegetables. With fruit-- about two serves of fruit a day you'll get around, again, another five to eight grams of fibre. If we then look at the legume group, so chickpeas, there's some black-eyed beans here, some lentils, and of course some of the Asian countries have a really high or regular intake of legumes. They're a really rich source of fibre at about five grams of fibre per half a cup. Then things such as seeds and nuts are another really good source of fibre. Per serve, which is around sort of a small handful, there's around three to four grams of fibre. So again, you can see that through a diverse intake you can notch up your fibre intake through the day.

What I'd like to share with you is a sample of what a daily intake of fibre might look like, so over here we've got some examples of say some breakfast options. So something like a wheat-based cereal and some fruit or whether it's an oat-based cereal with some nuts, some seeds, or coconut. You could potentially put some fruit on that. A couple of slices of whole grain bread and some crunchy peanut butter-- that would give you somewhere between around five to nine grams of fibre a day.(breakfast) So again, already you've started the day off well. A couple of serves of fruit a day-- again, another five to six grams. And then lunch-- something like this lunch, which is vegetable soup, carrot and pumpkin soup, and a slice of bread there's nearly 10 grams of fibre in that lunch. And similarly here, there's actually about 12 to 13 grams of fibre, and that's just half a cup of baked beans and a jacket potato. Or similarly, something like a salad wrap or a salad sandwich, and of course culturally this is going to really vary whether it's a dal-based lunch or whether it's another grain, so I think keeping that in mind that as long the foods are fairly predominately plant-based then you're going to have a really good chance of getting a fibre intake where it needs to be. Snacking on some nuts, again, about four grams of fibre in that serve of nuts, and then something like a whole meal pasta in a vegetable sauce-- a tomato-based sauce-- or three serves of vegetables with maybe some kind of protein with it, again, is your way of getting 30 grams in each day.

So the benefits are many in terms of fibre intake, so from lowering cholesterol, from helping with slowing down blood glucose absorption, from helping with appetite and feeling satisfied, helping softening stools, and helping people if they're quite constipated or have very poor stool volume fibre can be beneficial. So we can really, as dieticians-- certainly in my experience-- modify the different types of fibre in someone's diet. And just to recap so the different types of fibre-- so the soluble fibres are really present in oats and oat bran, in legumes, in things like apple and citrus. And soluble fibre will dissolve in water. It forms like a thick gel, and the soluble fibre is really good at helping soften stools. And then insoluble fibre is not soluble or doesn't dissolve in water or as its digested, and the insoluble fibre really can help give fecal bulk. It can help us feel satisfied of full when we're eating. And a really good source is something like wheat bran or wheat germ. Even something like a tablespoon of that-- weather its sprinkled over a salad or through a dal or on a breakfast cereal can add about 4 grams of fibre really quickly, so a simple strategy like that can be really beneficial.

The amount of fibre that we require on a daily basis can vary different times in our life, and at times when someone might have, say, an acute incident of diverticulitis or some kind of tummy trouble they might need to be on a low-fibre diet, but predominately across our lifespan we should be having a diet that's very much based around plants and plant-based foods, so therefore a diet that's high in fibre. And for most adults certainly they're only consuming about 2/3 of what they need, if that. If they're excluding grains then they really need to be paying attention to the fruits and vegetables, nuts and seeds and legumes.

Boosting your fibre intake is based around perhaps looking at what you're currently doing and then thinking about areas and ways you can maybe swap or increase in variety. If your meeting your two fruits and your five vegetables per day you're getting around 20 grams of fibre already, so you're about 2/3 of the why there. But it might be thinking about how often do you have legumes? Because about half a cup of baked beans or chickpeas is around 5 grams of fibre-- a small handful of nuts. Thinking about what you have for breakfast-- is there a way that you can increase the fibre intake, so that might be a good way to start think about your current intake of fibre, and certainly there are lots of resources online you can use to estimate your fibre and look at some ways to try and boost up to that total of 30 grams. You might already be there or you might be way off.

In conclusion, dietary fibre plays a major role in boosting our health and helping manage our gut health in particular. It can have a role to play in supporting diabetes and heart disease management, and overall it's just very good for general health.

Increasing the amount of fibre is a good goal for most people to be aiming for, and up to about 30 grams a day in Australia is what the recommendation is. It might be different in different countries. One of the key ways to do this is really having a diet that is predominately based around plant-based foods. And I guess, plant-based foods in particular, looking at grains and different cereals and foods made from them, using legumes and everything that's within that family-- chickpeas, kidney beans, black-eyed beans, baked beans, cannellini beans-- things like nuts and seeds, and also of course fruits and vegetables.

So having a diverse intake-- and we've got quite a few different foods here today to just represent sort of a very small range of what's available, of course-- but having a diverse intake of foods through the day will really support you to optimize your fibre intake. For those people that are Celiac or choosing to follow a diet that's low in grain then they will need to pay extra attention to look at grains that are gluten free or to use foods outside of the grain group that are high in fibre.

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In Australia it is recommended that you eat 25g to 30g of fibre each day to maintain general good health.

The following table lists food pairs and their associated dietary fibre levels. The levels for some foods have been omitted. Can you guess which food in each food pair has the highest level of dietary fibre?

Food 1	Fibre content per 100 g	Food 2	Fibre content per 100 g
Boiled potato	1.5	Boiled sweet potato
Green grapes	2.3	Dry figs
Corn kernels		Cucumber	1.4
Fried eggs	0.0	Baked beans
Lettuce		Carrots	4.0

 

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What is the difference between probiotics and prebiotics?

Probiotics are preparations of live micro-organisms which when administered in adequate amounts may confer health benefits.

They are mostly found in your supermarket or pharmacy (sold as a product such as capsules) and in some foods such as yoghurts.

When you consume probiotics, the major challenge is for their organisms to survive passage through the stomach (which has a very low pH of 2 and will kill most bacteria) and gut. They must also survive the enzymes and other secretions produced naturally in our gut.

Once there, it can be hard to take up residency as they can be crowded out by other micro-organisms that are already there and well established.

The most common species used as probiotics are Lactobacillus(젖산균) and Bifidobacterium. Before these preparations can be sold to consumers, of course they need to pass a number of testing and safety assessments (to show they are non-pathogenic). While the use of probiotics has attracted a great deal of research focus the results from these many studies have been rather mixed and often dependent on the type of probiotic culture used (as there are many different types available).

The types of benefits that have been explored range from treatment of Travellers Diarrhoea and other gastrointestinal(위장의) problems, to upper respiratory tract infections, allergies, various skin disorders, diabetes, weight loss to infantile colic.

In summary, with probiotics you are consuming the live micro-organisms directly. In contrast prebiotics are fibres that stimulate the growth of beneficial bacteria that are already present in your gut. The best way to improve our microbiota is a very active area of research worldwide and over the next 10 years great advances in our understanding will be made.

It is possible that a combination of both probiotics and prebiotics (called a symbiotic(공생)) may be best.

While the role of prebiotics and probiotics are still being explored – it is clear that increasing dietary fibre in the diet can have a very important protective role against a range of common diseases that affect our community including prevention and treatment of cardiovascular disease and Type 2 diabetes as well as various gastrointestinal disorders.

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Diet and gut symptoms – The low FODMAP diet for IBS

FODMAP stands for Fermentable Oligo- Di- and Mono-saccharides And Polyols.(발효가능한 탄수화물) FODMAPs are found in a wide variety of foods and include lactose (in milk), free fructose (in pears, apples), fructans and fructo-oligosaccharides (FOS, found in wheat, rye, artichokes, garlic and onions), galacto-oligosaccharides (GOS, in legumes and nuts), and sugar polyols (sorbitol and mannitol in stone fruits and artificial sweeteners).

The team in the Department of Gastroenterology at Monash University have developed a special diet - the Low FODMAP diet to help patients with a common gut disorder called irritable bowel syndrome (IBS). IBS is a chronic and re-lapsing problem that affects 1 in 7 adults.

Low FODMAP Diet | IBS Research at Monash University - Monash Fodmap

Translational Nutritional

Symptoms of IBS are lower abdominal pain and discomfort, bloating, excessive passing of wind and altered bowel habit (can range from diarrhoea to constipation).

The strategy

The Low FODMAP dietary strategy is based on the knowledge that the malabsorption of certain carbohydrates (such as lactose, fructose, GOS, fructans) can trigger gastrointestinal symptoms. This occurs because FODMAPs can be poorly absorbed in the small intestine and therefore reach the large intestine where they are fermented by the bacteria to produce gases.

Some FODMAPs are small in size and so can have an osmotic effect which draws water into the bowel that can contribute to diarrhea in some people. The production of gas and the movement of water all act to stretch the wall of the intestine, which in turn, triggers the symptoms of pain and discomfort experienced by people with IBS.

People with IBS are very sensitive to the distension of their intestines.

The low FODMAP diet is effective for 3 out of 4 patients with diagnosed IBS and is quickly becoming the first line of medical therapy for managing IBS.

The key principle of the Low FODMAP diet is to restrict all dietary short-chain carbohydrates that are poorly or slowly absorbed in the small intestine (FODMAPs) and replace them with similar foods low in FODMAPs. The team at Monash have established the techniques to quantify FODMAPs in a wide range of foods.

It is very important to note, however, that the low FODMAP diet is a special therapeutic diet for controlling gastrointestinal symptoms associated with IBS. A medical practitioner should rule out all other possible causes of symptoms and make the diagnosis of IBS before this diet is considered.

Implementing the diet

If diagnosed with IBS, the implementation of the diet requires being managed by a dietitian with knowledge in this area. This is not a life-long diet (unlike a strict gluten-free diet required to manage coeliac disease). This diet is  not recommended to be followed for any more than 2 to 6 weeks, after which re-introduction of foods under the guidance of a qualified dietitian should begin.

A gentle reintroduction under the guidance of your dietitian will help you to identify your tolerance level of food.

One of the major reasons for why we encourage this re-introductory phase is that a low FODMAP diet can be low in dietary fibre including prebiotic fibre, which may affect gut bacteria and good bowel function.

Find out more

In the See also section of this step, you can access links to online resources related to FODMAPS, IBS and diet.

https://www.youtube.com/watch?v=Z_1Hzl9o5ic

 

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• Reference 

Food as Medicine from Future Learn. free courses https://www.futurelearn.com/courses/food-as-medicine

Food As Medicine Online Nutrition Course - FutureLearn

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