Carbohydrate Flashcards
Types of carbohydrate: MONOSACCHARIDES?
Pentoses
(5 carbon atoms):
Ribose
Deoxyribose
Hexoses (6 carbon atoms): Fructose Glucose Galactose
Types of carbohydrate: DISACCHARIDES?
Maltose:
Glucose
Glucose
Sucrose:
Glucose
Fructose
Lactose:
Glucose
Galactose
Types of carbohydrate: OLIGOSACCHARIDES?
Maltodextrin
Types of carbohydrate: POLYSACCHARIDES?
Amylose (starch)
Amylopectin (starch)
Dietary Carbohydrate Intake
• All sugars (mono, disaccharides) and starches
Starches:
• Typically associated in food items containing other nutrients. For example: – Vitamins – Minerals – Protein – Fibre
Free Sugars:
• Include mono and disaccharides added to food and drink by the manufacturer, cook or consumer AND sugars naturally present in honey, syrups and fruit juices.
– This does not include 1) lactose in milk and milk products and sugars contained within the cellular structure of food.
Carbohydrate Digestion:
Dietary Starch–>
(Salivary α-amylase- Stomach pH
Pancreatic α-amylase + Bicarbonate)
α-Dextrins–>(Isomaltase/Glucoamylase) Lactose, Maltose, Sucrose–>
Galactose, Glucose, Fructose–>
(SGL T1, 2Na+, Water + GLUT5) Galactose/Glucose + Fructose–>
(GLUT2+Na+, -K+, ATPase) Glucose, Galactose, Fructose–>
Liver
Total Carbohydrate Intake & Health: Total Carbohydrate & CVD?
• RR = 1.00 (0.89 to 1.12) per 8% EI ↑
Total Carbohydrate Intake & Health: Total Carbohydrate & CHD (per 8% EI ↑)
• No association (limited evidence)
Total Carbohydrate Intake & Health: Total Carbohydrate & BP?
- SBP = 0.71mmHg (-0.71 to 2.14)
* DBP = 0.02mmHg (-0.81 to 0.86)
Total Carbohydrate Intake & Health: Total Carbohydrate & Blood Lipids *
- [Total-C]= -0.16mmol/L (-0.28 to -0.04)
- [LDL-C] = No effect (adequate evidence)
- [HDL-C] = 0.03mmol/L (-0.06 to 0.01)
- Total-C:HDL-C = -0.03 (-0.12 to 0.05)
- LDL:HDL = 0.04 (-0.36 to 0.44)
Total Carbohydrate Intake & Health: Total Carbohydrate & Type II Diabetes?
• RR=0.96 (0.86 to 1.08) per 70g/d ↑
Total Carbohydrate Intake & Health: Total Carbohydrate & Blood Glucose?
- [Glucose] = -0.01mmol/L (-0.06 to 0.04)
* [Insulin] = No effect (adequate evidence)
Total Carbohydrate Intake & Health: Total Carbohydrate & Fat-Free Mass?
- FFM = 0.03kg (-0.77 to 0.83)
- Fat Mass = 0.30kg (-0.01 to 0.62)
- BM = -0.93kg (-1.87 to 0.01)
• BMI = Energy restricted HCHO-LFAT
may be better
• Waist Circumference = 0.04 (-1.26 to 1.34)
Total Carbohydrate Intake & Health: Total Carbohydrate & Colorectal Cancer?
- RR = 1.00 (0.87 to 1.14) per 70g/d ↑
- RR (colon) = 0.99 (0.89 to 1.08) per 70g/d ↑
- RR (rectal) = 0.99 (0.86, 1.14) per 70g/d ↑
Total Carbohydrate Intake & Health Summary?
Total carbohydrate intake appears to be neither detrimental nor beneficial to cardio-metabolic health, colo-rectal health or oral health.
Total Carbohydrate Intake: DRV
DRV drivers: • No association between total CHO Intake and.. – CVD – Type 2 diabetes – Colo-rectal cancer
DRV:
• Men = ~50% of total EI
• Women = ~50% of total EI
Current Intake:
• M (19-64y) = 251g/d (47.8%)
• W (19-64y) = 197g/d (48.2%)
Total Sugar Intake - Oral Health?
Carbohydrate–> (Bacteria)
Lactic acid/acetic acid–>
↓ Dental Plaque pH–>
Dental Enamel Dissolves–>
Dental Caries
• A 1% increase in % energy intake from “total sugar” is
associated with a 1.2%, 0.9% and 0.9% increase in the probability of DMFS, approximal DMFS, and pit and fissures.
Confectionary Intake - Oral Health?
• A child who consumes sweets daily/couple of times a week is 5.5 times more likely to have poor dental
health than those who eat sweets < once/wk
Sugar Sweetened soft drinks – BMI?
• Sugar-containing drinks result in weight gain, fat accumulation and increases in BMI in normal-weight children.
Free Sugar Intake?
DRV drivers:
• Insufficient evidence for individual sugars
• Sugar intake/sugar sweetened products related to.. – ↑Dental caries (children, adolescents) – ↑ Energy Intake (obesity) – ↑Type 2 diabetes
DRV (adult):
• M&W = ≤5% of EI from free sugar
• M&W = Sugar sweetened beverages should
be minimised.
Current Intake:
Intrinsic Sugar
• M = 37.2g/d
• W = 35.3g/d
Non-Milk Extrinsic Sugar
• M = 68.4g (11.9%)
• W = 49.2g/d (11.1%)
Guidance on design suitable advice:
In individuals who are a healthy BMI and in energy balance, free sugar intake should be replaced by:
- Starches, sugars contained within the cellular structure of foods and
- lactose naturally present in milk and milk products (for those who consume dairy products)
In individuals who are overweight, the reduction of free sugars would be part of a strategy to decrease energy intake.
Glycaemic Index:
• The GI of a single food item is calculated by comparing the blood glucose response over the 2h period following food ingestion to that of a reference food (usually glucose).
• Foods are categorised as low GI (<55), moderate GI (55-70) and high GI (>70)
DRV Considerations:
• High GI/GL associated with ↑
– Type 2 diabetes
– CVD
• BUT, confounded by other variables:
2 hour blood glucose AUC in response to test food (50g CHO)
divided by:
2 hour blood glucose AUC in response to 50g glucose
Factors Influencing the GI?
• Particle size/Mastication (chewing)
• Cell wall structure (intact, ripening)
– Ripe = ↑GI
• Lipid/Protein/Fibre content
• Amylose: Amylopectin Content
– AP more rapidly digested
• Monosaccharide composition
– Fructose = ↓GI
• Molecular CHO composition
– Alternative bonds to α(1-4)and α(1-6) = ↓GI
• Gastric emptying
Dietary Fibre Intake: Old definition vs New definition?
Old Definition:
• Non starch polysaccharides (NSP) where this refers to non alpha-glucans
• Englyst Method
New Definition:
• All carbohydrates that are neither digested nor absorbed in the small intestine and have a degree of polymerisation of three or more monomeric units, plus lignin.
• AOAC method
Dietary Fibre Intake: Non-starch polysaccharides?
• Contain (β1-4 glycosidic bonds) and is not digestible.
• Physiological effects of dietary fibre are determined by the structure of fibre (laxation, blood glucose, blood cholesterol)
– Insoluble Fibre
– Soluble Fibre
Dietary Fibre Intake: Resistant Starch?
Resistant Starch:
• Naturally occurring and via
food processing
• 5 Types: – Barriers (eg plant cell wall) prevent breakdown – Crystalline structure prevents breakdown – Formed when cooking/cooling prevents breakdown – Chemically modified starch prevents breakdown – Amylose-lipid complex formation prevents breakdown
Dietary Fibre Intake: Lignin and Oligosaccharides?
Lignin • Branched polymer (not a carbohydrate), but located in close proximity to fibrous polysaccharides.
Oligosaccharides:
• Raffinose, Stachyose,
Verbascose, Inulin,
Fructo-oligosaccharides
• Chemical bonds are not α1- 4 or α1-6 and therefore cannot be broken down by pancreatic amylase or disaccharidases.
Dietary Fibre Intake & Health: results?
Total Fibre & CVD:
• RR=0.91 (0.88 to 0.94) per 7g/d ↑
Total Fibre & CHD:
• RR=0.91 (0.87 to 0.94) per 7g/d ↑
Total Fibre & Stroke:
• RR= 0.93 (0.88 to 0.98) per 7g/d ↑
Total Fibre & Type 2 Diabetes (per 7g/d↑)
• Risk Ratio = 0.94 (0.90 to 0.97)
Total Fibre & Faecal weight/transit time
• Positive association (1g=4g faecal weight)
Total Fibre & Colorectal Cancer
• RR = 0.92 (0.87 to 0.97) per 7g/d ↑
Total Fibre & Colon Cancer
• RR = 0.93 (0.89 to 0.98) per 7g/d ↑
Total Fibre & Rectal Cancer
• RR = 0.91 (0.86 to 0.97) per 7g/d ↑
Dietary Fibre Intake: DRV?
DRV drivers: • Based upon reduced risk of – Type II diabetes – CVD risk, – Colo-rectal cancer
• AOAC method
(methodological issues)
DRV (adult):
• M&W = 30g/d
• (note: equivalent to 24g/d using old
method)
Current Intake:
• Men = 15g/d
- Women = 13g/d
- (old method DRV = 18g/d)
