vitamin C

Introduction

also known as ascorbic acid (from “anti-scorbutic agent”)
a water soluble vitamin found especially in various fruits and vegetables
citrus fruits were used on ships in the late 15th C to combat scurvy
discovered in 1912 and was the first vitamin to be chemically produced
apes (including humans) and monkeys (but not all primates), most bats, most fish, some rodents, and certain other animals must acquire it from dietary sources because a gene for a synthesis enzyme which is functional in most other animals has mutations that render it dysfunctional

cooking destroys vitamin C - hence very little is obtained from meats and cooked vegetables lose about 60% (via enzymatic activity and by losses from decanting the cooking water)
breast milk contains 5mg/100g which will be sufficient if the mother has an adequate intake
pasteurisation of milk destroys vitamin C
many fruits are good sources when eaten raw such as (in descending order): guava, capsicum, kiwi fruit, strawberry, papaya, citrus, pineapple, cantaloupe, mango, blackberry, honeydew melon, tomato, cranberry, blueberry,

essential in the formation of collagen
- ascorbic acid is required as a cofactor for prolyl hydroxylase and lysyl hydroxylase which are responsible for the hydroxylation of the proline and lysine amino acids in collagen. Hydroxyproline and hydroxylysine are important for stabilizing collagen by cross-linking the propeptides in collagen.
essential in the enzymatic production of certain neurotransmitters
antioxidant
carnitine production
helps TET1 epigenetic regulation
- vitamin C helps maintain TET activity by donating electrons to regenerate Fe²⁺ from Fe³⁺ and supplementation may thicken the skin epidermal layer which has become thinned during ageing ¹⁾

oral intakes of 100 to 200 mg/day result in saturation of plasma levels at about 65 μmol/L - higher intakes are less well absorbed in GIT and mostly just excreted in urine
recommended daily intake is 45-110mg/d depending on the authority
hypovitaminosis of vitamin C is defined as less than 23 μmol/L, and deficiency as less than 11.4 μmol/L
vitamin C deficiency is common in low and middle-income countries, and not uncommon in high income countries
scurvy occurs most commonly in people with mental disorders, unusual eating habits, alcoholism, and older people who live alone
4-45% of refugees have some degree of scurvy
other risk factors include intestinal malabsorption and dialysis
during the Age of Sail, it was assumed that 50 percent of the sailors would die of scurvy on a major trip

early symptoms:
- weakness and lethargy
after 1-3 months of deficiency:
- SOB
- bone pain
- general aches and pains (myalgias may be due to reduced carnitine production)
- weight loss
- rough skin
- emotional changes (which may appear before any physical changes)
scurvy
- gingivitis
- loosening of teeth
- scorbutic tongue
- petechiae
- easy bruising
- dry mouth and dry eyes
- bone fractures more readily
- scorbutic rosaries of chest wall in children
late stages
- jaundice
- generalised oedema
- oliguria
- neuropathy
- fever
- convulsions
- eventual death

supplementation with vitamin C 100mg/d will usually result in full recovery in most within 2 weeks (although only 10mg/d will improve symptoms)

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