Digestion; The liver

Question 1

Liver:
Main function

Answer 1

The portal vein transport all nutrients and toxins from the GIT (Mouth, Oesophagus, stomach, small and large intestine and anus) to the liver.
* The liver filters 1.4 litres of blood every minute.
* The liver stores carbohydrates, fats, minerals such as iron and vitamins A, D, E, K and B12. These can be released into the blood to be made available to cells as required.
* The liver also performs detoxification and deactivate hormones

Question 2

Liver detoxification - general overview

Answer 2

Hepatocytes convert toxins into non-toxic metabolites which can then be excreted from the body by the bowels, kidneys, skin or lungs.
* A healthy liver deals with thousands of toxins each day, including airborne pollutants, those in food, tap-water, drugs, cigarettes, plastic, alcohol etc.
* If the liver lacks essential nutrients, or if it is exposed to lots of trans-fats, heavy metals, alcohol, caffeine and pesticides, liver detoxification becomes impaired
* This results in partially broken-down toxins, dead cells and other wastes being recirculated
Hepato = liver, cyte = cell

Question 3

Liver detoxification:
Toxins entry and exit

Answer 3

Toxins enter via:
* Airways
* Skin
* GIT
Toxins except via:
* Lungs
* Bowels
* Skin
* Kidneys

Question 4

Liver detoxification:
Phase I

Answer 4

Liver detoxification involves two main phases:
Phase 1:
* Most toxins that arrive inside hepatocytes undergo Phase I detoxification. It involves converting volatile toxins into smaller substances that are also more water-soluble. This is important for excretion
* CYP450 enzymes create an active binding site on the toxin or hormone, so that it can be conjugated (in phase II)
* When Phase I is complete the toxin is oxidized. Free radicals are being formed and must be neutralized by anti-oxidants such as vitamin A, C and E to protect against oxidative damage.
* To support this process, digestion should be optimized to ensure that the co-factors and anti-oxidants needed are liberated from food

Question 5

Liver detoxification:
Phase II

Answer 5

Phase II:
* Involves ‘conjugation’: Chemical reactions which modify reactive toxins to make them safe and excretable by binding a chemical group to them. The bound toxins are then pumped into the blood or bile for excretion mostly via the kidneys or bowels
* Nutrients including sulphur (e.g. garlic and onions), magnesium, B vitamins are required for phase II. Whilst herbs such as dandelion, milk thistle and licorice root support liver detoxification.
* The key antioxidant for neutralizing free radicals in the liver is glutathione, which is the tripeptide formed from cysteine, glysine and glutamine
* The body and eliminates wastes by the bowels, urine, sweat and exhalation
* Melatonin (from the pineal gland) is a more potent antioxidant and glutathione, vitamins C and E. It is released in response to darkness
Conjugation = to link, di = two, tri = three, peptide = protein