Vitamin C - Ascorbic Acid Flashcards
Vitamin C- Ascorbic Acid
- Vitamin C functions as a key antioxidant, and as an enzyme cofactor. In both of these functions vitamin C is a potent reducing agent, meaning that it readily donates electrons to recipient molecules.
- Most animals can synthesise vitamin C: ascorbic acid / ascorbate. Some scientists postulate this has made humans more susceptible to viral illnesses , raised cholesterol, cardiovascular disease and cancer, and less resistant to stress.
- Vitamin C does not need to be modified by the body to function.
- Until the ‘cure’ for the vitamin C deficiency disease ‘Scurvy’ was found, more sailors died of scurvy than of any other cause (estimated 2 million sailors or 50% of any major voyage
Vitamin C: Food Sources
- All fresh raw fruit and vegetables, particularly peppers, kiwi fruit, papaya, currants, berries, citrus, crucifers, mangoes and tomatoes.
- Very significant losses occur as vegetables wilt, or when they are cut as a result of the release of ascorbate oxidase from the plant tissue.
- Ascorbate oxidase is why lemon or lime juice can prevent the browning (oxidising) of other foods (e.g. sliced apple) the vitamin C creates an antioxidant barrier from oxygen until it is all used up.
Vitamin C: Absorption
- Absorbed in the mouth and in the small intestine (by active and passive means). Up to 100% absorption per 200mg serving.
- Transported into cells by glucose transporters; so high blood glucose levels can inhibit vitamin C uptake significantly. Think about diabetics and clients with sugar laden diets. High doses of vitamin C can also skew blood glucose test results.
- Vitamin C concentrates in the adrenal glands, white blood cells, thymus and pituitary although there is no specific storage site .
- Factors that increase breakdown or excretion of vitamin C include: Stress: psychological, chemical, emotional or physiological, and fever and viral illnesses. Alcohol, smoking, heavy metals, aspirin, OCP.
Vitamin C: Roles
Anti-Oxidant (immune boosting) Cholesterol Lowering Iron Absorption Endocrine Functions Collagen Synthesis Neurotransmitter Synthesis Energy Production
Vitamin C: Anti-oxidant - Functions
- Primary water soluble antioxidant in blood and tissues protecting proteins, lipids, carbohydrates, RNA & DNA from damage from free radicals.
- Recycles other antioxidants such as vitamin E and glutathione making them usable again as antioxidants.
- Up regulates interferons, natural killer cells and T cells
Vitamin C: Anti-oxidant - Therapeutic Uses
- Cancer
- Cardiovascular disease
- Alzheimer’s
- Asthma/COPD
- Cataracts
- Immune support e.g. cold sores (2g per day can halve healing time)
Vitamin C: Cholesterol lowering - Function
• Conversion of cholesterol to bile acids (lowering blood LDL levels)
Vitamin C: Cholesterol lowering - Therapeutic use
Cardiovascular disease
Vitamin C: Iron Absorption - Function
• Enhances iron absorption by protecting iron from oxidation. It keeps it in Fe2+ form, not allowing it to become Fe3+,
which is not a bioavailable form.
• A dose of 25mg of vitamin C taken together with a meal increases iron absorption by 65%. Optimum iron absorption may require more than 100mg/day.
Vitamin C: Iron Absorption - Therapeutic uses
Anaemia
Vitamin C: Endocrine Functions - Function
• Synthesis of thyroxine and adrenal steroid hormones.
Vitamin C: Endocrine Functions - Therapeutic uses
- Adrenal fatigue
* Hypothyroidism
Vitamin C: Collagen Synthesis - Functions
- Vitamin C is a co factor required for collagen synthesis.
* Important for forming strong tendons, ligaments and bones, repairing wounds, improving gum health.
Vitamin C: Collagen Synthesis - Therapeutic uses
- Osteoarthritis
- Cartilage injuries
- Ligament injuries
- Gum diseases
- Bruising
- Fracture repair
- Blood vessels
Vitamin C: Neurotransmitter synthesis - Functions
A co-factor for the production of serotonin.
Vitamin C: Neurotransmitter synthesis - Therapeutic uses
Weak digestion
Vitamin C: Energy Production - Functions
• Transport of long chain fatty acids into the mitochondria for ATP production
Vitamin C: Energy Production - Therapeutic use
- Fatigue
* Chronic fatigue
Vitamin C: Deficiency Signs and Symptoms
• The two most notable signs of vitamin C deficiency reflect its role maintaining blood vessel integrity:
- The gums bleed easily around the teeth.
- Capillaries under the skin break spontaneously producing pinpoint haemorrhages
• When intake falls to about 1/5 of its optimal store size (approx. 1 month on a vitamin C depleted diet), Scurvy symptoms appear:
- Further haemorrhaging from inadequate collagen synthesis.
- Muscle degeneration and rough, brown scaly skin
- Wounds do not heal . Bone rebuilding falters fractures develop.
Vitamin C: Deficiency States
- During stress, the adrenals release vitamin C with other hormones into the blood. The exact role of vitamin C in stress is unknown, but it is known that stress raises vitamin C needs likely due to additional free radical damage.
- Burns, infections, toxic metal intakes, chronic use of medications and cigarette smoking are among the stresses that increase vitamin C demand.
- Smokers have lower levels of serum vitamin C 25mg of vitamin C is lost with every cigarette smoked.
- Subclinical deficiency is common: susceptibility to infections, poor wound healing, fatigue, skin and gum degeneration, petechiae.
Vitamin C: Dosage and Tolerance
• 500mg/day+ vitamin C is a sound general dose. • A high dietary intake of vitamin C is cancer protective, and can be mega dosed (e.g. 25-75g intravenously) for cancer support. • 250mg - 1g of vitamin C prophylactically can reduce the incidence of colds by 50% in those who undertake strenuous exercise - potential support in sports nutrition . • Unabsorbed ascorbate from very high doses (3g/day plus) is a substrate for intestinal bacterial metabolism causing gastrointestinal discomfort and diarrhoea ( bowel tolerance) • No high doses in third trimester of pregnancy. The baby becomes accustomed to high doses that are unsustainable when born.
Vitamin C - Toxicity
- Vitamin C is non toxic , even at extremely high doses. No reliable scientific evidence of toxicity in adult doses up to 10g per day. No credible scientific evidence that supplemental vitamin C promotes oxidative damage in humans.
- People with kidney disease and those with a tendency toward gout are prone to forming kidney stones if they take large doses of Ascorbic Acid beyond a few months
- Be mindful of high dose vitamin C with haemochromatosis.
Vitamin C: Drug interactions
• May reduce effectiveness of warfarin, statins, some cancer drugs.
Increases oestrogen therapy effects. Skews diabetes test results.
