Vitamins: Vitamin C – Ascorbic Acid Flashcards
1
Q
Vitamin C – Ascorbic acid
A
Vitamin C functions as a key antioxidant, and as an enzyme co-factor. 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 scientist 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 crew)
2
Q
Food sources
A
All fresh raw fruits and vegetables, particularly:
* Peppers
* Kiwifruit
* Papaya
* Currents
* Berries
* Citrus
* Crucifers
* Mangoes
* Tomatoes
3
Q
Food prep
A
- 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 (oxidizing) of other foods (e.g. sliced apple) – the vitamins C creates an antioxidant barrier from oxygen until it is all used up
4
Q
Absorption, transportation, storage and factors that increase breakdown
A
- Absorbed in the mouth and in the small intestine (by active and passive means).
- Up to 100% absorption per 200 mg 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
- Vitamins 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 vitamins C include:
o Stress – psychological, chemical, emotional or physiological, fever and viral illnesses
o Alcohol, smoking, heavy metals, aspirin, OCP
5
Q
Antioxidant and immune boosting: functions and therapeutic uses
A
- Functions:
o Primary water soluble antioxidant in blood and tissues – Protecting proteins, lipids, carbohydrates, RNA and DNA from damage from free radicals
o Recycles other antioxidants such as vitamins E and glutathione – making them usable again as antioxidants
o Up-regulates interferons, natural killer cells and T-cells - Therapeutic uses:
o Cancer
o Cardiovascular disease
o Alzheimer’s
o Asthma/COPD
o Cataracts
o Immune support e.g. cold sores– 2 g per day can halve healing time
6
Q
Cholesterol-lowering: functions and therapeutic uses
A
- Functions:
o Conversion of cholesterol to bile acids (Lowering blood LDL levels) - Therapeutic uses:
o Cardiovascular disease
7
Q
Iron absorption: functions and therapeutic uses
A
- Functions:
o Enhances iron absorption by protecting iron from oxidation. It keeps it in Fe2+ form, not allowing it to become Fe3+, which is not a bio-available form
o A dose of 25 mg of vitamin C taken together with a meal increases iron absorption by 65%. Optimal iron absorption may require more than 100 mg/day - Therapeutic uses:
o Anaemia
8
Q
Endocrine functions: functions and therapeutic uses
A
- Functions:
o Synthesis of thyroxine and adrenal steroid hormones - Therapeutic uses:
o Adrenal fatigue
o Hypothyroidism
9
Q
Collagen synthesis: functions and therapeutic uses
A
- Functions:
o Vitamin C is a co-factor required for collagen synthesis
o Important for forming strong tendons, ligaments and bones, repairing wounds, improving gum health - Therapeutic uses:
o Osteoarthritis
o Cartilage injuries
o Ligament injuries
o Gum diseases
o Bruising
o Fracture repair
o Blood vessels
10
Q
Neurotransmitter synthesis: functions and therapeutic uses
A
- Functions:
o A co-factor for the production of serotonin - Therapeutic uses:
o Weak digestion
11
Q
Energy production: functions and therapeutic uses
A
- Functions:
o Transport of long-chain fatty acids into the mitochondria for ATP production (Vitamins C synthesises the amino acid L-carnitine, which gets fatty acids into mitochondria) - Therapeutic uses:
o Fatigue
o Chronic fatigue
12
Q
Deficiency signs and symptoms
A
- The two most notable signs of vitamin C deficiency reflect its role maintaining blood vessel integrity:
o The gums bleed easily around the teeth
o Capillaries under the skin break spontaneously producing pinpoint haemorrhages - When intake falls to about 1/5 of its optimal store size (approximately 1 month on a vitamin C depleted diet), scurvy symptoms appear:
o Further haemorrhaging from inadequate collagen synthesis
o Muscle degeneration and rough, brown scaly skin
o Wounds do not heal. Bone rebuilding falters; fractious develop
13
Q
Deficiency states
A
- During stress, the adrenals release vitamin C with other hormones into the blood. The exact role of vitamins 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 – 25 mg of vitamin C is lost with every cigarette smoked
- Subclinical deficiency is common:
o Susceptibility to infections
o Poor wind healing
o Fatigue, skin and gum degeneration
o Petechiae
14
Q
Dosage and tolerance
A
- 500 mg/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 - 75 g intravenously for cancer support)
- 250 mg – 1 g 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 (3 g / 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
15
Q
Toxicity
A
- Vitamin C is non-toxic, even extremely high doses.
- No reliable scientific evidence of toxicity in adult doses up to 10 g per day.
- No credible scientific evidence that supplemental vitamin C promotes oxidative damage in humans
- People with kidney disease and those with a tendency towards 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
Haemochromatosis = iron overload
