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Summary of Lectures of Food components and Health
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A summary of all lectures of the course Food components and Health at the WUR. The MOOCs are not included
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Summary Food components & HealthLecture 1
- Study designs:
Cohort
Case-control
Observational
Cross sectional
Study designs Ecological
Intervention
Experimental
Cross-over
- Ecological study example: Less alcohol intake causes less car accidents in Germany. → This is less
likely to be true. It is probably because the infrastructure is better, the cars are of good quality and
people use seatbelts. The ecological (population) study design is a useless design for this study. On
individual level, the causation could be determined.
- Cross-sectional study = Exposure and outcome are present at the same time. You don’t know whether
exposure or outcome came first.
- Case-control study = Looking back to exposures in the past which could cause a rare or specific
disease. In this study you compare the dietary habits in a case (colon cancer) and a control group
(people with other illness).
- Cohort study = Population fills in a Food Frequency Questionnaire (FFQ) at the beginning. Then, the
population is followed over time and the FFQ is repeated every 5 years, for example. This study design
is not suitable for rare disease. The cohort study is the most used study design for nutritional studies.
- Intervention study = This design is based on a real intervention. It consists of a control group (placebo)
and intervention group (drug). For example: looking for a correlation between fish oil and blood
cholesterol. Intervention group gets fish oil pill, control group gets a placebo pill. The participants
and interviewers can be blinded. This design is not really suitable for nutrition studies, because a
change in the diet is easy to recognize. A cross-over study design would be better (both arms will get
the placebo and real drug).
Carbs & health
- Monosaccharides: Glucose, fructose, galactose.
- Disaccharides: Maltose (glucose + glucose), sucrose (glucose + fructose), lactose (glucose +
galactose).
- This is meant, when we talk about…
o Sugars: mono- and disaccharides
o Sugar: sucrose
o Blood sugar: blood glucose
o Invert sugar: glucose or fructose
o High fructose corn syrup (HFCS): mixture of glucose and fructose
- Added sugar = added sugar during processing of foods. These include: free mono- and disaccharides,
sugars from syrup and honey, sugars from fruits and vegetables (not: jams, jellies, 100% juices,
because these sugars are naturally present in the fruit).
- Polysaccharides:
o Glycogen
o Starch: amylose and amylopectin (branched molecule). They are broken down in glucose.
They are most common in the diet.
o Fibers: are digested by bacteria and are resistant to digestion.
▪ Soluble (viscous) fibers: pectins, hemicelluloses, fructans (inulin):
• Lower blood cholesterol
, • Slow glucose absorption
• Hold moisture in stools
▪ Insoluble (non-viscous) fibers: cellulose (can’t be digested by humans), lignins,
hemicelluloses and resistant starch (RS1: physically inaccessible starch, RS2: granular
starch (not opened up, raw vegetables for example), RS3: retrograded starch, RS4:
chemically modified starch):
• Increase fecal weight
• Speed up fecal passage
• Provide bulk and feelings of fullness
- Good sources of fibers: fruits, vegetables, nuts, seeds, legumes, whole grains. Poor sources: milk,
meat, processed foods and eggs.
- Fibers are lost during processing.
Lecture 2
- Carbohydrate digestion:
o Mouth: salivary amylase: digests starch into small polysaccharides and glucose.
o Stomach: nothing happens.
o Pancreas: pancreatic amylase: digests starch into maltose (2x glucose) and glucose.
o Small intestine: disaccharides are digested to monosaccharides, because these are available
for uptake by the villi in the small intestine and are distributed to the portal vein.
▪ Lactase: breaks lactose into glucose and galactose
▪ Sucrase: breaks sucrose into glucose and fructose
▪ Maltase: breaks maltose into glucose (2x)
o The portal vein is rich in nutrients and low in O2. The blood flows to the liver, where every
monosaccharide is converted to glucose.
- Dietary fiber digestion:
o Mouth, stomach, small intestine, colon: no digestion.
o Only soluble fibers will be broken down by some bacteria into short chain fatty acids and gas
in the colon.
- Density of bacteria increases from upper to lower GI tract. The colon contains ~10 12 bacteria.
- The gut microbiome is influenced by the diet, DNA, lifestyle, age, weight, medicine intake (antibiotics)
and hygiene.
- During the fermentation of fibers, some gasses are released, like acetate, propionate, butyrate, lactic
acid, methane, hydrogen, ethanol, hydrogen sulfide and carbon dioxide.
- Low blood glucose: glucagon (made by the pancreas) converts glycogen (from liver or muscles,
especially liver, muscle glycogen is used for local use) into glucose → glucose into blood.
- High blood glucose: insulin (made by the pancreas) converts glucose into glycogen (stored in liver or
muscles) → less blood glucose.
- Glucose from muscles will be used for local use (physical activity) and glucose from the liver will be
released into the blood.
- The brain and red blood cells work on carbohydrates.
The kidney, muscles, heart and liver work on fat and
carbohydrates.
- Uptake in the brain is independent of plasma
concentration over physical range. Uptake in liver and
pancreas (beta-cells) is proportional to plasma
concentration.
- A diabetic person has in fasting state a blood glucose
level of >7 mmol/L.
- When glycogen is depleted, amino acids from muscles
are used → these are available up to weeks, but there
will be muscle loss.
, - Pancreas has exocrine (excretion) and endocrine cells and produces enzymes like protease, lipase
and amylase for small intestine. The islets of Langerhans (1% of the pancreas) are clustered endocrine
cells. -cells produce glucagon, -cells produce insulin.
- Incretins = hormones, like GIP and GLP-1 (glucagon like peptide 1) activates the pancreas to make
insulin. Other functions:
o Delays gastric emptying
o Suppresses glucagon secretion
o Enhances glucose-dependent insulin secretion
o Enhances -cell proliferation
o Possibly improves insulin sensitivity
- Glycemic index = reflection of the increase in blood sugar level after consumption of fixed amount of
carbohydrates.
- Carbohydrates can be converted to fat, NOT the other way around!!
- Negative health effects of sugar:
o Contains calories
o ‘Empty’ calories → doesn’t provide vitamins and minerals
o Liquid calories → soft drinks
o Fructose → causes fatty liver in animals
- There is no difference between fructose and glucose in the end (liver).
- Saturated fats are the most unfavorable.
- Strategy of sugar industry: denial, creating doubts, disseminating false information.
- Sucrose and HFCS (High fructose corn syrup) consist both 50% of glucose and fructose.
- Strategy to reduce sugar intake:
o Remove vending machines at school
o Schools forbid sugar-rich snacks and drinks
o Extra tax on soft drinks
o Major of NYC tried to ban soda in cups larger than 0.5 L
- Non-nutritive sweeteners (= high intensity sweeteners): stevia, aspartame, sucralose, saccharin.
These sweeteners do NOT influence blood glucose level.
- Nutritive sweeteners (= sugar alcohols or bulk sweetener): sorbitol, maltitol, xylitol, mannitol and
lactitol. These sweeteners are caloric, provide fewer calories than sugar. They don’t promote tooth
decay, they can have a laxative effect and don’t cause sudden increases in blood glucose levels (for
diabetics).
- Type 1 diabetes = absolute insulin deficiency, autoimmune disorder. Seen in childhood (due to
inheritance/DNA). Recommendations: insulin injections and strict regimen of food intake.
- Type 2 diabetes = relative insulin deficiency, insulin resistance. More often seen in older people (due
to lifestyle). Recommendations: weight loss, drugs and healthier foods.
- Two types of insulin resistance:
o Ectopic fat model = fat cells get bigger and storage of fat in muscles and liver.
o Inflammation model = fat tissues get inflamed. Chronic low-grade inflammation reduces
responsiveness to insulin.
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