Foods and Nutrition 1021 Lecture Notes - Lecture 4: Dietary Fiber, Bran, Hypercholesterolemia
29 Aug 2016
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Chapter 4 – The Carbohydrates: Sugar, Starch, Glycogen, and Fibre
Carbohydrates (CHO)
• The ody’s first hoie for eergy eeds
o Used as glucose or stored as glycogen
• Dietary sources:
o Grains (eg. Breads/cereals/pasta/etc.), beans/legumes
o Milk and alternatives
o Fruits
o Starchy vegetables (eg. Potatoes/turnip/corn/carrots/etc)
Types of Carbohydrates
• Monosaccharides
• Disaccharides
• Oligosaccharides
• Polysaccharides
Simple Carbohydrates
• Sugars (1-2 polymers)
o Monosaccharides: glucose, galactose, fructose
o Disaccharides: sucrose, lactose, maltose
o Sugar alcohols: sorbitol, mannitol
• Monosaccharides (single sugars)
o Glucose
▪ Blood sugar (dextrose)
▪ Essential CHO – main source of energy for brain & nerves
▪ Excreted in the urine by diabetics
o Fructose
▪ Fruit sugar; sweeter than sugar
o Galactose
▪ Part of lactose (milk sugar); freed during digestion
• Disaccharides (double sugars)
o Sucrose (fructose-glucose)
▪ Table sugar (beet or cane)
o Lactose (galactose-glucose)
▪ Sugar in milk
▪ Poorly digested by some people
o Maltose (glucose-glucose)
▪ Malt in sugar
▪ In germinating seeds
▪ Important in brewing
When you eat food containing single sugars you can absorb it directly into the blood,
disaccharides must be digested first.
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Most become monosaccharides and disaccharides become glucose in the body.
Complex Carbohydrates
• Starch & Fibre (3 or more polymers)
o Oligosaccharides (3-9 polymers)
▪ Malto-oligosaccharides: maltodextrins
▪ Other oligo-saccharides: raffinose, stachyose, fructo-oligosaccharides
o Polysaccharides (>9 polymers)
▪ Starch: amylose, amylopectin, modified starches
▪ Non-starch polysaccharides: cellulose, hemicellulose, pectins,
hydrocolloids
• Polysaccharides
o Starch
▪ Excellent source of glucose
▪ Storage form of glucose in plants
o Fibre
▪ Indigestible parts of plant foods
▪ Cellulose; hemicellulose; pectins; gums; mucilages; nonpolysaccharide
lignin
o Glycogen
▪ Storage form of CHO in liver & muscles in humans & animals
Fibre
• Polysaccharides; sugar units held by bonds indigestible by human enzymes
• Whole grains, F&V, legumes
o Supply valuable vitamins, minerals, phytochemicals, & fibre, with little or no fat
• Two types:
o Soluble (viscous)
o Insoluble (non-viscous)
• Important to drink enough water for the fibre you eat
• Soluble Fibre (viscous fibre)
o Dissolve in water/viscous and form gummy gels
o Add thickness to foods (eg. Pectin)
o Inside of apples, barley, carrots, legumes, oats, psyllium
o Help stool formation
o Have significant cholesterol-lowering effect
o Help regulate blood glucose following a CHO-rich meal
o In the colon, bacterial fermentation of soluble fibres produces small fatlike
molecules such as butyrate
▪ Butyrate provides energy to colon cells
▪ Butyrate helps the colon resist chemical injury that could lead to cancer
▪ Higher fibre leads to the replacement of cells in the colon lining
• Cells are sloughed off before they can initiate the cancer process
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find more resources at oneclass.com
• Insoluble Fibre (non-viscous)
o Less readily fermented
o Cellulose & hemicellulose in bran, tough, stringy, gritty
o Some legumes, wheat bran, skin on fruits and vegetables, and hull of seeds
o Helps to move our stool through the large intestine
Recommendations for CHO
• Recommendations for total CHO
o Caada’s Food Guide CFG – grains, fruit, starchy vegetables, legumes, milk
o DRI
▪ Minimum 130 g/d (glucose for brain & nerves)
▪ 45-65% of total calories from CHO
• Recommendations for added sugar
o DRI – max 25% of total calories
• Excess sugar consumption is associated with:
o Heart disease, stroke, obesity, diabetes, high blood cholesterol, cancer, and
dental cavities
o Sugar-sweetened beverages are the single-largest contributor of sugar in the diet
• Recommendations for dietary fibre
o DRI
▪ Men, age 14-50: 38 g/day
▪ Men, age 51+: 30 g/day
▪ Women, age 19-50: 25 g/day
▪ Women, age 51+: 21 g/day
o Issues with too much fibre:
▪ Adding too much purified fibre and not enough water
▪ Binders in some fibres act as chelating agents
• Bind nutrient minerals and carry them out of the body
• For example, excess fibre may limit the absorption of iron, zinc,
and calcium
Carbohydrate Digestion
• Mouth
o Digestion initiated by salivary amylase; split starch to maltose (sweet taste)
• Stomach
o Salivary enzyme still acts on food stored in upper storage area
o Enzyme deactivated by stomach acid & other juices
o No further starch digestion in stomach
• Small intestine
o Pancreatic amylase: digestion of starch into disaccharides & small
polysaccharides
o Lactase, sucrose, maltase: disaccharides split to monosaccharides in intestinal
walls
o Absorption of glucose takes place in capillaries
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Chapter 4 the carbohydrates: sugar, starch, glycogen, and fibre. Carbohydrates (cho: the (cid:271)ody"s first (cid:272)hoi(cid:272)e for e(cid:374)ergy (cid:374)eeds, used as glucose or stored as glycogen, dietary sources, grains (eg. breads/cereals/pasta/etc. ), beans/legumes: milk and alternatives, fruits, starchy vegetables (eg. potatoes/turnip/corn/carrots/etc) Types of carbohydrates: monosaccharides, disaccharides, oligosaccharides, polysaccharides. When you eat food containing single sugars you can absorb it directly into the blood, disaccharides must be digested first. Most become monosaccharides and disaccharides become glucose in the body. Indigestible parts of plant foods lignin: glycogen, storage form of cho in liver & muscles in humans & animals. Fibre: polysaccharides; sugar units held by bonds indigestible by human enzymes, whole grains, f&v, legumes, supply valuable vitamins, minerals, phytochemicals, & fibre, with little or no fat, two types, soluble (viscous) Important to drink enough water for the fibre you eat: soluble fibre (viscous fibre, dissolve in water/viscous and form gummy gels, add thickness to foods (eg. pectin)
