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The Human Effect Matrix looks at human studies (excluding animal/petri-dish studies) to tell you what effect Vitamin C has in your body, and how strong these effects are.
|Grade||Level of Evidence|
|A||Robust research conducted with repeated double blind clinical trials|
|B||Multiple studies where at least two are double-blind and placebo controlled|
|C||Single double blind study or multiple cohort studies|
|D||Uncontrolled or observational studies only|
|Level of Evidence ||Effect||Change||Magnitude of Effect Size ||Scientific Consensus||Comments|
Surprisingly mixed influences on biomarkers of oxidation, with either a decrease or no significant influence the majority of the time (with limited evidence to hint at... show
An increase in blood flow is seen in instances of impaired blood flow (smoking, obesity, etc.) which may be due to preservation of nitric oxide function (via reducing oxidation... show
No significant alterations seen in inflammatory cytokines associated with Vitamin C supplementation
Although not acute, a possible reduction in biomarkers of muscle damage is sometimes noted with antioxidative supplementation which applies to Vitamin C; results are unreliable
1g of Vitamin C taken prior to exercise is associated with unreliable reductions in the cortisol spike seen during exercise
|B||Exercise-induced Immune Suppression|
More evidence suggests no significant effect than a possible protective effect, although the latter is possible
|B||Protection from Smoking|
There do not appear to be any inherent protective effects of Vitamin C against the oxidative and inflammatory changes associated with cigarette smoking, although the reduction... show
No significant influence on glycemic control in diabetics with Vitamin C supplementation
No significant influence on fasting or postprandial triglycerides seems apparent with Vitamin C
Mixed and weak influences on lipid peroxidation, but a possible reduction exists
No significant influence on heart palpitations
|C||Symptoms of Bacterial Vaginosis|
Vaginal bacterial infections are somewhat treatable with directly applied (via silicon coated tablets), as Vitamin C exerts some antioxidant effects against those bacterial strains
An increase in microcirculation has been noted secondary to increased blood flow, thought to be a general property of antioxidants
Does not appear to significantly influence fat mass
Vitamin C does not appear to have a weight reducing effect
|C||Adaptations to Exercise|
It is thought that, secondary to reducing the rate of muscular damage, that adaptations gained from exercise are attenuated; there is mixed evidence to support this, but... show
Does not appear to have a role in altering VO2 max
No significant influence on aerobic exercise performance
No significant influence on total cholesterol seems apparent with vitamin C supplementation
|C||Symptoms of Charcot-Marie-Tooth Disease|
Insufficient evidence to support a role
No significant influence on insulin sensitivity
No significant influence on pre-eclampsia risk
|C||Risk of Cataracts|
No significant influence on the risk of cataracts
|C||Spontaneous Birth Risk|
No significant influence on spontaneous birthing
|C||Upper Respiratory Tract Infection Risk|
No significant influence on the rate of acquiring sickness
|C||Length of Sickness|
Mixed influences on the length one is sick for, with possibly no effect
An improvement in mood has been noted in hospitalized persons
|C||Bone Mineral Density|
The rate of bone mineral density loss over time in elder women appears to be reduced with dietary antioxidants, and as such applies to Vitamin C supplementation. The protective... show
|C||Anti-oxidant Enzyme Profile|
An increase in antioxidant enzymes have been noted in elderly persons
A possible reduction in C-Reactive Protein exists with Vitamin C supplementation
No significant influences on DNA damage
Highly mixed interactions with the exercise:oxidation axis with Vitamin C, with both increases and decreases being noted. Unlikely to have a reliable role
A possible reduction in muscle soreness the day after exercise may result when preloading exercise with Vitamin C
No significant influence of Vitamin C supplementation on HbA1c levels
|C||Oxidation of LDL|
No significant influence on the oxidation rates of LDL cholesterol
No significant influence on HDL cholesterol
No significant alterations in LDL cholesterol seen with Vitamin C supplementation
A decrease in heart rate has been noted in exercising obese adults, a per se effect of Vitamin C on heart rate (rather than secondary to the rate of percieved exertion)... show
|C||Rate of Percieved Exertion|
The rate of percieved exertion in obese adults appears to be attenuated with Vitamin C supplementation
A decrease in fatigue has been noted in obese adults given Vitamin C in conjunction with exercise
No significant influence on fat oxidation
|D||Symptoms of Osteoarthritis|
No significant influence on the symptoms of osteoarthritis
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European regulation state that any supplement with the label 'Vitamin C' may be one of five compounds; L-Ascorbic Acid (actual vitamin C), Sodium-L-Ascorbate, Potassium-L-Ascorbate, Calcium-L-Ascorbate, and L-Ascorbyl-6-Palmitate. For vitamin-related purposes, they are equipotent. They differ on some parameters such as DNA oxidation where Sodium Ascorbate and Ascorbic Acid could exert pro-oxidative effects on DNA, Calcium Ascorbate acting neutral and Ascorbyl-6-Palmitate being protective.
Ester-C is a brand name product for Vitamin C that is non-acidic and consists of Vitamin C metabolites (the aldonic acids L-lyxonic, L-xylonic, and L-threonic acid) with Calcium; labelled as Calcium Ascorbate. Ester-C is more effective in preventing scurvy than basic L-Ascorbic Acid in a deficiency state. Ester-C is patented by Zila Nutraceuticals.
One pilot study noted that although L-Ascorbic Acid (basic form of vitamin C) and Ester-C were equally potent in increasing serum levels of Vitamin C up to 5 days, the group given L-Ascorbic Acid experienced a decline whereas Ester-C levels remained elevated.
This particular form of Vitamin C has been implicated in reducing both occurrence and duration of the common cold, but was not compared to L-ascorbic acid. Another study conducted on oxalate levels in vivo (most common substrate from which kidney stones are formed) found Ester-C more effective than an equal dose of L-Ascorbic Acid when both were dosed at 500mg; 25% more subjects experienced a significant decline in 24-hour oxalate with Ester-C relative to L-ascorbate.
One study suggests that when consuming 1g of Vitamin C, Ester-C is tolerated better due to being non-acidic; this study was conducted in persons with self-reported sensitivity to acid containing foods. 53.6% of the Vitamin C group experienced gastric upset compared to 14.3% of the Ester-C group, the latter was rated as more tolerable during follow-up.
Studies conducted using Ester-C that have been funded by Zila Nutraceuticals are cited following this sentence.
Serum levels of Vitamin C appear to be inversely related with risk of Dementia, with an Odds Ratio (OR) of 0.29 after controlling for school education, intake of dietary supplements, smoking habits, body mass index, and alcohol consumption.
Vitamin C (400mg), in conjunction with Vitamin E (286mg) as a mixed anti-oxidant supplement for 6 weeks in otherwise healthy men, is not significantly better than placebo at attenuating an exercise-induced reduction of power output seen during the recovery phase of exercise.
It is generally accepted that the state of obesity, relative to a non-obese state, makes the same amount of exercise more tiring to the body (perception) and uses more caloric reserves for the same amount of work. Ingestion of 500mg Vitamin C via supplementation when paired with both an exercise regimen and a caloric restriction diet was able to significantly reduce heart rate during exercise and the rate of perceived exertion, although it didn't affect success on the diet.
DOMS is a soreness and tenderness of the muscle tissue that arises after exercise, usually with a delay where it does not suface immediately but usually the next day or 48 hours afterwards.
One study using Vitamin C at 400mg (with Vitamin E at 264mg) failed to notice any benefit to soreness with treatment relative to placebo.
At least one rat study notes that supplementation with Vitamin C (5mg) is associated with an attenuation of bone loss due to ovariectomy, an animal model of menopause. After 8 weeks of supplementation, the control ovariectomy group experienced bone loss while the ovariectomy group with Vitamin C was not significantly different than control.
An attenuation of exercise-induced cortisol release has been noted in response to mixed Vitamin C/Vitamin E supplementation at 400mg/286mg when measured one hour after exercise, with values pre-exercise and a day later not differing between groups. This reduction of exercise-induced cortisol elevations have been noted in heat-subjected marathon runners at 1,500mg daily for 12 days prior to exercise.
At least one study at 60% VO2 max cycling for 2.5 hours in trained athletes found that this attenuation of cortisol to not be statistically significant.
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