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Nutrition: Vitamin C

Notes from Lecture by Gerber


For midterm he recommends knowing these things about each nutrient:
function, sx of deficiency/insuffiency, requirements, food sources, prevention and tx roles, supplement issues

VITAMIN C

GENERAL INFO
can by synthesized from glucose in many animals, not humans
commercially synthesized from corn syrup but exact same as what's in food
natural is same as synthetic
buy the cheapest you can find when buying a supplement
difference: food has other stuff too

FUNCTIONS AND DEFICIENCY
fx: water soluble antioxidant and coenzyme
fx: collage, carnitine, norepinephrine synthesis
deficiency-->scurvy, petechial hemorrhages, corkscrew hairs, bleeding gums, loose teeth
bone deformities, extreme fatigue (carnitine can't get fatty acids into mitochondria)
deficiency-->high cholesterol and gallstones (can't convert chol to bile)
vit C supps lower cholesterol in those who are deficient
fx: facilitate iron absorption, mild antihistamine effect
anti-inflam effect possible from whole food sources
deficiency may be more common than known in developed world

RECOMMENDED DAILY ALLOWANCE
RDA designed to prevent even mild def, not to promote optimal health or prevent age-related dz
RDA: adult RDA 90mg female, 75mg male
RDA: smokers require 35 mg more due to higher oxidative stress
400 mg/day saturates body's vit c pool
amounts above this could influence blood chem or intestinal/urinary health
average intakes are not below RDA but nowhere near saturation
sources: sweet red peppers, strawberries, oranges, grapefruit, broccoli, tomato, potato
french fries have less than 50% of vitamin C in regular potato

SCIENCE
observational studies in will-nourished pops don't always find chronic dz protection
from C intakes higher than RDA
some studies show best protection at 300mg/day
dietary and circulating C may reflect higher fruit/veggie intake thus many good nutrients
modest supplementation (125-250mg/day) has some support for chronic dz prevention
Linus Pauling Inst says 400/day
Harvard School of Public Health says 200-300mg/day
studies on prevention are mostly negative
vit C doesn't prevent the cold in most people
exceptions: those with low intake under heavy physical demands/stress incl military

TREATMENT
slight reduction in duration of colds
studies using larger doses have better results (2g/day)

WHY ARE THERE SO MANY KINDS OF VIT C ON THE SUPPLEMENT SHELF?
lots of things added
rutin
bioflavinoids, rose hips, acerola cherry
bioflavinoids better in hundreds of mgs from diet than in little bits in pills
mineral ascorbates (eg calcium ascorbate) maybe good for some people, some minerals
less irritating to sensitive stomachs, ascorbates remove proton, decrease adicity
"enhanced" vit c (eg Ester-C) no evidence of superiority except for decr gastric senstivity

SAFETY
probably no issues with too much
widely publicized in vitro effects unreliable
tolerable upper level of intake 2000 mg/day based on preventing soft stools/GI upset
caution with anticoagulants

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