1: Alcohol & Nutrition Flashcards
What is the formula for calculating nutrient requirement?
Metabolic demand/efficiency of utilisation
Define EAR
Estimated Average Requirement
- Assumes a normal distribution of nutrient requirements across the whole population
- Will meet needs of 50% of whole population
Define LRNI
Lower Reference Nutrient Intake
- 2SD below EAR
- Minimum requirements
- Meets needs of 2.5% of pop. (those with low needs)
Define RNI
Reference Nutrient Intake
- 2SD above EAR
- Meets needs of 97.5% of pop.
- Equivalent to old RDA
What are RNI, LRNI & EAR all examples of?
DRV’s (dietary reference values), which reflect nutritional needs of a particular population, but the amount of each nutrient needed to maintain optimal health varies between individuals and life stages
Which health problems increase with regular heavy drinking?
-Cancers of the mouth, throat and breast. Upper GI tract : oral, pharyngeal, laryngeal & oesophageal cancers. Also liver & colon cancer
-Alcohol related liver disease: fatty liver disease; cirrhosis; lactic acidosis; metabolic tolerance
-Mental health problems
What is the energy content of fat, alcohol, carbohydrate and protein?
Fat: 9.0kcal/g
Alcohol: 7.0kcal/g
Carbohydrate: 4.0kcal/g
Protein: 4.0kcal/g
What % does the UK DRV for energy assume as alcohol?
5%. However moderate drinkers may take in 10% as alcohol, and alcoholics may take in 50%
What are the UK’s recommendations for upper limits of consumption for alcohol?
14 units a week (maximum), spread evenly over 3 or more days.
Having 2 or more heavy drinking episodes per week increases risk of death from long term illness and from accidents & injuries
What is 1 unit in ml of alcohol?
1 unit = 10ml (8g) alcohol in UK
What are the % of alcohol per volume in spirits, white wine, red wine, and beer?
Spirits = around 40% abv
White wine = 11-14% abv
Red wine = 12-15% abv
Beer = 4-8% abv
What are the units of alcohol in spirits, white wine, red wine and beer?
Spirits = measure (25ml) = 1 unit
White wine =
125ml glass = 1.4-1.8 units
250ml glass = 2.8-3.5 units
750ml bottle = 8.3-10.5 units
Red wine =
125ml glass = 1.5-1.9 units
250ml glass = 3.0-3.8 units
750ml bottle = 9.0-11.2 units
Beer =
Pint (568ml) = 2.3-5-4 units
How is alcohol absorbed?
Along the entire GI tract. Transported in blood unaltered.
Metabolised in the liver
How and where is alcohol metabolised?
In the liver via 2 main pathways:
1. alcohol dehydrogenase pathway
2. Cytochrome p450 system
Describe the alcohol dehydrogenase (ADH) pathway
Ethanol is converted into acetaldehyde/ethanal (by the enzyme alcohol dehydrogenase, which uses NAD as a cofactor, reducing NAD to NADH).
Acetaldehyde (ethanal) is potentially damaging to human tissue, and is further oxidised by enzyme (aldehyde dehydrogenase) to produce ethanoic acid (acetic acid). This is then converted into a key metabolite (bound to coenzyme A to form acetyl coenzyme A)
This can be used in the TCA cycle (to generate energy), or fatty acid synthesis (converted to fat & is stored)
Describe the cytochrome p450 pathway/MEOS pathway
Converts ethanol into acetaldehyde in the same way as ADH pathway but uses a different enzyme, as chronic alcohol consumption causes enzymes in ADH pathway to become depleted
How does chronic excessive alcohol consumption lead to fatty liver disease?
High NADH:NAD ratio, as when there’s high alcohol consumption, liver metabolises alcohol = NAD supplies are depleted as gets converted to NADH. High levels of NADH signal liver to synthesise fat (as acetyl CoA is converted into fatty acids & stored in the liver)
How does the body’s biochemical pathways try to correct the imbalance between NADH and NAD?
Pyruvic acid is converted into lactic acid, and simultaneously converts NADH back into NAD.
However lactic acid is also produced, causing lactic acidosis = nausea, vomiting, abdominal pain
Explain acetaldehyde toxicity
Acetaldehyde is very reactive and binds covalently to proteins, damaging them (as impairs their function). Build up in liver (as a result of heavy drinking regularly) impedes formation of microtubules in the liver leading to cirrhosis. = increased risk of liver cancer
Explain metabolic tolerance of alcohol, and give an example of how this might be a potential problem
Heavy drinkers are “tolerant” of acute effects due to metabolic adaptation (up regulation of MEOS pathway).
- ADH is not specific just for alcohol. Is responsible tor oxidation of other metabolites, e.g. conversion of retinol (vit A) to retinal (essential for vision).
Chronic consumption of ethanol competes with retinol for ADH, depleting retinal.
- Chronic alcohol consumption induces MEOS pathway (also not specific for alcohol metabolism). Excess retinol is oxidised by MEOS but to an inactive metabolite. Causes hepatic retinol depletion and elevated dietary requirements. Exacerbates vitamin deficiencies common in alcoholics.
What are the possible benefits of drinking alcohol?
- Important social factor
- Moderate ethanol consumption linked to :
- Increased blood HDL
- Decreased blood LDL
- Decreased CVD risk
- Decreased type 2 diabetes risk
What are the possible explanations for health benefits of drinking alcohol?
- (Direct effect of ethanol): ‘Hormesis’ = low levels of physiological challenges such as toxins, can promote health through adaptive responses
- (Other components of alcoholic beverages): phenolic compounds in wine, especially red; might explain French Paradox (low CVD when sat. fats high)
What cells are needed in the production of alcohol?
Yeast cells (Saccharomyces cerevisiae)
Describe the basic process to make alcohol in fruits/honey/sugar cane & cereals/tubers/root crops
- Fruits/honey, etc. (soluble sugars) -> juice extraction = hexose sugar
- Cereals/tubers, etc. (starch containing) -> saccharification - via malt, mould or salivary enzymes = hexose sugars
Hexose sugar -(Saccharomyces cerevisiae)-> 2 Ethanol + 2 C02
