Parece ser que los beneficios anti-cancer no son los mismos cuando se consume Vit C que cuando se administra por via intravenosa/
Visto en BBC:
High-dose vitamin C can boost the cancer-killing effect of chemotherapy in the lab and mice, research suggests.
El problema es que no hay muchos estudios y como no es un sistema patentable, no hay mucho interes comercial en ello, por lo que si el estado no toma medidas no las tomara nadie, el estado deberia de ser el interesado para reducir costes, asi como los seguros medicos.
Vemos en: http://www.cancer.org/treatment/treatme ... /vitamin-c
Many studies have shown a link between eating foods rich in vitamin C, such as fruits and vegetables, and a reduced risk of cancer. On the other hand, the few studies in which vitamin C has been given as a supplement have not shown a reduced cancer risk. The recent NAS report set the upper limit from both food and supplements at 2,000 mg (2 grams) per day.
La vitamina C provica que la Helicobacter Pilory se "despegue" del estomago, y en grandes cantidades (5g) la elimina en un 30% de los casos. (www.buscandolalibertad.com/intolerancia ... t1223.html)
Prevencion de arterioesclerosis (250mg vit C)
British researchers studied the effects of vitamin C supplementation (250 mg/day) on this adhesion process in 40 healthy adults.7 Before the study, subjects with low pre-supplementation levels of vitamin C had 30% greater monocyte adhesion than normal, putting them at higher risk for atherosclerosis. Impressively, after six weeks of supplementation, the rate of this dangerous monocyte adhesion actually fell by 37%.
Obesidad y salud cardiovascular:
In 2000, British researchers reported a six-month, double-blind study of vitamin C 500 mg/day versus placebo in 40 men and women, aged 60-80 years.2 The study was a “crossover” design in which subjects took the assigned pills for three months, stopped them for one week, and then reversed their assignments for another three months; this is a particularly strong study design because it helps to eliminate individual differences. The results were impressive—daytime systolic blood pressure dropped by an average of 2 mm Hg, with the greatest drop seen in subjects who had the highest initial pressures. Women in the study also had a modest increase in their beneficial high-density lipoprotein (HDL) levels. The authors concluded that these effects might “contribute to the reported association between higher vitamin C intake and lower risk of cardiovascular disease and stroke.”
Researchers in South Carolina conducted a 2002 study of 31 patients with a mean age of 62 years, who were randomly assigned to take 500, 1,000, or 2,000 mg of vitamin C daily for eight months.10 This research group actually found a drop in both systolic (4.5 mm Hg) and diastolic (2.8 mm Hg) blood pressure over the course of supplementation, although there was no change in blood lipid levels. Interestingly, this study found no differences between the groups taking the various doses, though the number of subjects was small and a larger study might have demonstrated important dose-related differences.
Body mass index (BMI) and waist circumference correlate well with risk for cardiovascular diseases and diabetes.11 A landmark 2007 study from nutritionists at the University of Arizona explored the relationships between vitamin C levels, body mass index, and waist circumference.12 In 118 sedentary, non-smoking adults, 54% of whom were classified as obese and 24% overweight by BMI standards, lower vitamin C levels were significantly correlated with higher BMI, percentage of body fat, and waist circumference. Women with higher vitamin C levels also had higher levels of the fat-suppressing hormone, adiponectin. This remarkable study demonstrated a vital relationship between vitamin C levels and obesity-related risk factors for cardiovascular disease.
Medical researchers explored the impact of vitamin C supplements on both arterial stiffness and platelet aggregation (an important early step in clot formation).13 They provided vitamin C in a single 2,000 mg oral dose, or placebo, to healthy male volunteers. Just six hours after supplementation, measures of arterial stiffness decreased by 10% in the supplemented group, and platelet aggregation (as stimulated chemically) by 35%, with no changes at all seen in the placebo group. As the authors point out, this impressive impact of vitamin C even in healthy subjects may imply an even greater effect in patients with atherosclerosis or cardiovascular risk factors, and that “vitamin C supplementation might prove an effective therapy in cardiovascular disease.”
Finnish researchers studied 440 adults aged 45-69 years with elevated total serum cholesterol. Subjects took daily doses of just 500 mg slow-release vitamin C and 272 IU vitamin E and were followed for six years for evidence of progression of atherosclerotic changes in blood vessels. The chief study outcome was the intima-media thickness, or IMT (an indicator of stroke risk) of the carotid arteries, which supply blood to the brain. Supplementation with vitamins C and E significantly decreased the rate of IMT increase over the six-year period by 26%. Importantly, this effect was even larger in people with low baseline vitamin C levels and those with pre-existing plaques in their coronary arteries.
El deporte y la Vitamina C:
British researchers evaluated the effects of just two weeks of modest vitamin C supplementation (200 mg twice daily) on the recovery from an unaccustomed bout of exercise.18 Eight healthy men were given either a placebo or vitamin C supplementation each day, and after 14 days performed a 90-minute-long running test. The supplemented group had less muscle soreness, better muscle function, and lower blood levels of the oxidative stress-induced molecule malondialdehyde. And although both groups experienced post-exercise elevations in levels of the inflammatory cytokine interleukin-6, increases in the supplemented group were smaller than in the placebo recipients. The scientists concluded that “prolonged vitamin C supplementation has some modest beneficial effects on recovery from unaccustomed exercise.” Timing is critical, however. When the researchers repeated their study with subjects who took vitamin C only after exercise, no benefit was seen.
Oxidative stress during exercise induces significant changes in proteins, producing compounds known as protein carbonyls. Measuring levels of protein carbonyls is therefore a useful indicator of oxidation. Exercise scientists at the University of North Carolina studied the impact of vitamin C supplementation (500 or 1,000 mg/day for two weeks) compared with placebo on oxidative stress indicators in 12 healthy men. As expected, exercise acutely reduced total blood levels of antioxidants in both groups. Levels of protein carbonyls increased by nearly four-fold in the placebo group, while vitamin C recipients experienced little or no elevation. This vital study demonstrates that vitamin C can protect against exercise-induced protein oxidation in a dose-dependent fashion.
Muscle soreness after exercising can be a big disincentive to continue on a healthy fitness program. That’s why the subsequent findings of that UNC group are so important. The scientists gave vitamin C supplements (3,000 mg/day) or placebo to a group of 18 healthy men for two weeks before and four days after performing 70 repetitions of an elbow extension exercise. Not surprisingly, considerable muscle soreness ensued, but it was significantly reduced in the supplemented group. The release of creatine kinase, an indicator of muscle damage, was also attenuated with vitamin C, compared with the placebo group. Blood levels of natural antioxidants fell significantly in placebo subjects, while vitamin C supplementation completely prevented this change. Results such as these suggest that the supplemented group would be much more enthusiastic about exercising the next day!
Se convierte en oxalatos que se asocian con el calcio (perdemos absorcion del calcio) y crean piedras renales, esto puede ocurrir con dosis de 1 o 2 gramos: www.buscandolalibertad.com/alimentos-sa ... t1558.html
Incrementa la absorcion del hierro, lo cual puede ser una ventaja o desventaja dependiendo de los casos.
Por lo menos 16 estudios bien fundamentados, demuestran que las megadosis de Vit C no previenen los resfriados y como mucho mejoran ligeramente los sintomas.
La dosis adecuada?
Hay muchas fuentes contradictorias, se diria que entre 400 y 1000 mg al dia divididos en diferentes tomas es lo ideal, y ser precavido y no superar los 2000 mg de forma constante es aconsejable para evitar problemas de piedras en el riñon.