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Lecture 4b- 28 January 2015

Fibre

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Overview of lecture 4b

Fibre

Fibre structure and classification and effects

Idatme of fibres

Fibres in health and disease

How to get higher fibre in the diet

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Overview of lecture 4b continued

Recommendations for fibre intake too much fibre in the dietFibres as food additivesWhat is new in fibre research?Choosing carbohydrates wisely

Next lecture-5A

Lipids-structure -function -IDATME

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Fibre structure and classification and effects

InsolubleCellulose-bran,vegetablesHemicellulose-bran, whole grainsLignins-fruits, mature vegetables, flax

Generally-accelerate gi transit, -increase fecal weight(promotes bowel movements) -slow starch digestion, -delay glucose absorption

-but can be exceptions

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Fibre structure and classification and effects continued

Soluble

Pectins-apples, carrots, gums and mucilages- oats, legumes

Generally-delay gi transit, -delay glucose absorption, -lower blood cholesterol -but can be exceptions

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Other fibre functions (classifications)

- water holding capacity- viscosity- cation exchange capacity- bile binding capacity- fermentability

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Fibre ingestion, digestion, absorption and transport, metabolism, excretion

• mouth for ingestion• fibre not digested in mouth or stomach or by small intestine enzymes-why?• bacteria-make short chain fatty acids, water, gas• short chain fatty acids and water absorbed at large intestine

and transported by blood used for energy (fatty acid metabolismnext week – lecture 5A), water can split molecules to release energy•Excretion- gas exits anus, undigested fibre leaves in faeces, water excreted via faeces, urine, sweat, saliva?, and breathing)

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Fibre in health and disease

weight control

-bulk-less appetite-soluble and insoluble fibres

heart disease

-soluble fibres lower cholesterol (bile issue)-fibre may displace fat in diet

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Fibre in health and disease continued

Cancer

1)Lower colon cancer-fibre may help by diluting and binding and more rapid excretion of carcinogens- both soluble and insoluble fibre may help

2)Breast cancer-secoisolariciresinol diglucoside (SDG) is a mammalian lignan pre-cursor that is found in flaxseed-SDG is not a fibre but is found in the fibre region of flaxseed

-metabolites of SDG are mammalian lignans which are produced by bacteria in the large intestine- these mammalian lignans may reduce breast tumour growth in humans)

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Fibre in health and disease continued

Diabetes

control weight-diabetesslow glucose absorption-glucose surge

soluble fibres are key here

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How to get higher fibre in the dietFibre content

High Medium Low 5g 2 g 0.5 g

Breads cereal Rice Group

Breads Whole wheat white1 slice bread bread

Cereal All Shredded Rice ½ cup bran Wheat Krispies

Pasta whole macaroni½ cup wheat pasta

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How to get higher fibre in the diet continued

Fibre content

High Medium Low 4 g 2 g 1 g

Fruit group

1 MEDIUMOR ½ CUP berries apple melon

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How to get higher fibre in the diet continued

Fibre content High Medium Low 4 g 2 g 1 g

VegetableGroup

½ cup peas green asparagus beans

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Remember that: •fibre from natural sources rather than commerciallyprepared fibre is better because foods contain vitamins and minerals as well as the fibre

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DRI recommendation for fibre intake

follow DRI recommendations for carbohydrate intake and this will provide sufficient fibre

DRI - 14 grams fibre/1000 kcal (roughly 25-35 grams of fibre/day)(no distinction between soluble and insoluble but variety is the key to balance)

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Too much fibre in the diet gives:

•flatulence

•obstruct gi tract if greater than 50 g fibre /day

•top recommendation is 40 g/d for adults (who)

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Too much fibre in the diet continued

•insoluble fibre has phytates that can bind minerals- e.g. calcium, iron, zinc and magnesium

•prevents enzyme contact

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Too much fibre in the diet continued

• increases volume of food required to meet energy requirements

• satiety before adequate nutrition-generally only a problem if diet low in micronutrients or in small children (small stomachs)

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Too much fibre in the diet continued

-important to increase water intake with increases in dietary fibre

-otherwise constipation but if have enough water can get diarrhea (bacterial breakdown of fibre)

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Fibres as food additives

pectin -common in fruits and vegetables-forms gel when sugar and acid added-commercially from citrus peels and apples-thickening agent in jams, jellies and tomato paste

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Fibres as food additives continued

-carbohydrate gums- used and thickeners and stabilizers because they combine with water to keep solutions from separating

-used in gravies, pie fillings, jellies and puddings

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Fibres as food additives continued

gums derived from gum arabic, gum karaya, guar gum, locust bean gum, xanthan gum and gum tragacanth

gums extracted from shrubs, trees and seed pods

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Fibres as food additives continued

pectins and gums are used in reduced fat products to mimic the texture and viscosity of fat

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Fibres as food additives continued

other thickening agents and stabilizers are from seaweeds ( e.g. agar, carrageen and alginates)

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What’s new in fibre research?

Oligosaccharides now considered fibre (used to be that fibre was only in polysaccharide form)

Oligosaccharides (e.g. inulin which is found in chicory and Jerusalem artichoke for example, can promote growth of good (for health) bacteria in the large intestine (please note that inulin is a pre-biotic and the bacteria are called pro-biotics)

Slavin, J. Nutrients 5:1417-35 (2013)

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How to choose carbohydrates wisely

1)increase intakes of whole grains

2)use whole grain products such as oatmeal, brown rice and whole wheat bread

3)increase consumption of legumes such as kidney, black and pinto beans)if fresh fruits not available, choose frozen or canned fruits without added sugar

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How to choose carbohydrates wisely continued

4)use whole grain flour for ¼ to ½ the amount of flour in the recipe

5)use less sugar in baking

6)use less added sugars in foods

7)eat fewer high sugar foods

8)use food labels to guide one’s choices