Sugars + Carbohydrates Flashcards
What’s the energy source from carbs? (kcal)
1g carbs = 4kcal
What’s the key roles of carbs in the body?
- energy for physical + mental activities
- stimulate insulin production + satiety
- promote digestive health
What are the 2 types of dietary carbs?
Naturally occuring - in fruit etc
Added sugars - in sweet desserts etc
What 2 groups are carbs split into?
Simple - monosaccharides (glucose, fructose, galactose) and disaccharides (maltose, sucrose, lactose)
Complex - polysaccharides (starches, fibre)
Give examples of where each of monosaccharides are found
- Glucose = sweet confectionary, honey, sugar, fruit (main carb)
- Fructose = honey, fruit, some veg
- Galactose = milk sugar
Give examples of where each of disaccharides are found
- Maltose= plants, certain veg, cereal grains
- Sucrose= honey, fruit, some veg
- Lactose = milk sugar / dairy products
Give examples of where each of polysaccharides are found
- Starches = potatoes, bread, rice, pasta + cereals
- Fibres (non-starch) = wholegrains, beans, nuts, F+V
Fibres are indigestible chains of glucose molecules (cellulose, inulin)
What classifies a monosaccharide?
No more than 6 carbon atoms
After absorption, where is fructose transported to?
The liver to be metabolised rapidly into products like glucose or glycogen or fat and that depends on metabolic state of individuals
e.g. if got excess glucose, it will be stored at adipose tissue in fat stores
What are the general steps of digestion + absorption of carbs?
- Mouth - mechanical + enzymatic digestion of starch
- Small intestine - enzymatic digestion of starch
- monosaccharide metabolism in liver
Digestion + Absorption
Describe what occurs in more detail at the mouth
Salivary amylase breaks down starch into shorter polysaccharides + maltose
- has to be broken down as too large to be absorbed into bloodstream
Digestion + Absorption
Describe what occurs in more detail at the small intestine
Pancreatic amylase + disaccharidases from small intestine brush border = disaccharides into monosaccharide constituents
- these pass through enterocytes and absorbed into blood stream to be taken to the liver
- any unabsorbed CHO is transported to the large intestine
Digestion + Absorption
Describe what occurs in more detail at the liver
Galactose + fructose are converted to glucose then…
- Glycogenesis - glucose are stored as liver glycogen + muscle glycogen
- Blood glucose regulation - if glucose enters blood stream, its used for regulation
- energy production - used in glycolysis for ATP
- Conversion to fat - converted + stored as body fat cells (lipogenesis) - only if excess glucose
What happens with the undigested carbohydrates?
(Mainly fibre)
In the large intestine, gut (colonic) bacteria ferments fibre for survival + growth
The fermentation process…
- provides an energy source for bacterial survival
- releases short-chain fatty acids to support gut health
- produces gas as a natural by-product
Why is dietary fibre important?
- relieve constipation
- reduce risk of CVD + T2D + cancers
- oral health
- mental health
- improve gut microbiome + health
- weight management
What is a lactose intolerance?
The body has an impaired ability to digest lactose adequately
What occurs to the lactose that different to normal?
Normal digestion - digested by lactase at intestinal brush border = glucose + galactose
Intolerance - lactose passes to large intestine (not enough lactase ) = GI symptoms
- abdominal pain, diarrhoea, nausea
- hereditary
How can a lactose intolerance be managed?
Use diary free products (nut-milk)
Lactase enzyme tablet
What do Eat-Lancet say is the healthy reference diet of carb sources?
- whole grains
- fruit + veg
- minimising intake of added sugars
Why is removing wholegrains (e.g. eating white rice, white bread etc) considered worse?
It leads to a loss of nutrients + fibre = a increased risk of metabolic diseases + cancer
Is there differences in intake of carbs in different continents?
Based on research, europe + central Asia are behind greatly on whole-grains
- the Mediterranean diet aligns well with recommendations (rich in whole-grains + fruit and veg)
How is carb quality measured?
2 traditional methods…
- Glycaemic index - rates how quickly carb foods raise blood sugar
- Low GI (0-55) - break down slowly during digestion, raising blood sugar slowly
- Medium GI (56-69) - break + raise moderately
- High GI (70+) - break + raise rapidly - Fibre content - amount of fibre as a basic indicator as quality
What are the limitations of these traditional methods of carb quality?
X - too simplistic + reductionist
X - don’t fully capture complexity of carb quality
Describe a more holistic approach that can be taken to assessing carb quality
It combines traditional indices with other indices (protein quality, environmental sustainability, degree of processing)
- aims to positively impact both health + environmental outcomes but needs further validation before its used more widespread
What are the current traditional indices?
- Glycaemic index
- Wholegrain content
- Fibre content
- % added sugars
Why is it a government focus to improve UK pop. dietary intakes?
There is a significant role of diet in the burden of disease
- this impacts health services
- also contributes to health inequalities (least deprived has better health etc)
Unhealthy diet is one of largest contributors to overall disease burden
How are guidelines formed?
A hierarchy of evidence is considered (ranging from non-human studies to systematic reviews)
Non-human studies -> observational studies -> intervention studies -> meta-analyses + systematic reviews
Broad classification of non-human studies
What are the 2 types?
- In-vitro studies - performed on isolated cells or tissue samples
- less expensive + time intensive
- cannot assume results will apply to whole living organism - Animal studies (in-vivo)
- can control food intake
- less expensive + time intensive than human
- only preliminary models of disease (different from human diseases)
Broad classification of human studies
What are the 2 groups?
- observational - exposure of participants occurs naturally without any intervention from researchers
- correlation does not prove causation however
- Interventions - experimental group is exposed to treatment while control group is not (exposure is assigned to participants)
What are the studies seen in observational research?
describe purpose, whether it’s strong or not and limitations
Longitudinal cohort studies
Purpose - follow a group of people over time + measure factors
Design strength - strong as can track changes + associations
Limitations: (1) cannot definitively prove that exposure to a specific diet directly prevents CVD and (2) potential for confounding variables to influence results
What are the studies seen in intervention research?
describe purpose, design + how to reduce bias
Randomised controlled trials
Purpose - provide evidence of cause + effect between treatment + outcomes
Design - experimental group is exposed to the treatment while control is not
Follow-up - both groups then followed for comparison to be made between respective outcomes
Minimising bias - ‘blinding’ participants + researchers to reduce bias
Based on the SACN report (2015), what is the dietary reference value for carbs? (as a % of total dietary EI)
Are carbs good or bad?
Roughly 50%
The evidence indicated that total carb intake appears neither detrimental nor beneficial to cardiometabolic health, colorectal or oral health
Based on the SACN report (2015), what is the recommended intake of fibre (2-5, 5-11 and 11-16 yrs + adults) that the pop. need to increase to and why?
2-5yrs = 15g/day
5-11 yrs = 20g/day
11-16 yrs = 25g/day
Adults = 30g/day
Diets rich in fibre (cereal fibre + wholegrains) are associated with lower incidence of CVD, T2D + colorectal cancer
- also decrease intestinal transit times + increase faecal mass
What’s the benefit of fibres such as oat bran and isolated beta-glucans?
They can lower cholesterol, LDL + triacylglycerol conc + lower BP
What are free sugars?
All sugars that are added to food and drinks by manufacturer, cook or consumer as well as sugars naturally present in honey, syrups + fruit juices
- these are sugars that are not contained within the cellular structures inside foods
Based on the SACN report (2015), what are SSBs and their effect to an individuals health?
SSBs are all ‘non-diet’ carbonated drinks, coffee/tea with sugar, squash, juice drinks + sports / energy drinks
- high consumptions of sugars within foods + drinks = increased risk of dental caries
- increased risk of T2D
- more free-sugars = more energy intake
- weight gain and higher BMI compared to non-calorically sweetened drinks
What is the recommendation of free sugars?
Average intake of free sugars should not exceed 5% of total EI from 2yrs+
Consumption of SSBs should be minimised in children + adults
- because one can of coke = 35g of free sugars! - more than max daily intake in one go
What policy actions have been introduced to reduce free sugars intake?
- Advice to limit foods + drinks high in free sugars as part of national dietary guidelines
- SSBs are a key focus - tax
- Soft drinks industry levy (2018) - tax rate based on sugar content = encouraging reformulation + decreased volume of sugar purchased via drinks
How has the sugar tax been beneficial?
2015-19 = reduction of over 47000 tonnes of sugar each year from soft drinks sold
£334m in revenue raised in 21-22 alone
Describe the Public Health England Voluntary Sugar Reduction Programme…
Objective + success
Objective - reduce sugar in 10 food categories by 20% in 2020
Actual reduction was only 3.5%!
- were larger reductions for yoghurts, breakfast cereals, ice cream + lollies
- smallest reduction for chocolate + puddings
As a result, additional strategies are required to lower free sugars in food + drinks
List 3 of these
- A widespread mandatory food industry reformulation approach to get consistent reductions in sugar content
- Stricter advertising restrictions - especially among young children
- Criteria for marketing claims needs to have more rigorous standards + eliminate use of child-friendly characters on packaging
If the SACN recommendations to reduce sugar intake to 5% of energy intake is achieved in next 10 years, this could….
Reduce the cost on the NHS by $500m per annum by year 10
