Evidence of rebound effect with ascorbic acid

Abrupt termination of vitamin C from ICU patients may increase mortality: secondary analysis of the LOVIT trial

BACKGROUND

The LOVIT trial examined the effect of vitamin C on sepsis patients, and concluded that in adults with sepsis receiving vasopressor therapy in the ICU, those who received 4-day intravenous vitamin C had a higher risk of death or persistent organ dysfunction at 28 days than those who received placebo. The aim of this study was to determine whether the abrupt termination of vitamin C administration could explain the increased mortality in the vitamin C group.

METHODS

We used Cox regression with two time periods to model the distribution of deaths over the first 11 days in the LOVIT trial.

RESULTS

Compared with a uniform difference between vitamin C and placebo groups over the 11-day follow-up period, addition of a separate vitamin C effect starting from day 5 improved the fit of the Cox model (p = 0.026). There was no difference in mortality between the groups during the 4-day vitamin C administration with RR = 0.97 (95% CI: 0.65-1.44). During the week after the sudden termination of vitamin C, there were 57 deaths in the vitamin C group, but only 32 deaths in the placebo group, with RR = 1.9 (95% CI: 1.2-2.9; p = 0.004).

CONCLUSION

The increased mortality in the vitamin C group in the LOVIT trial is not explained by ongoing vitamin C administration, but by the abrupt termination of vitamin C. The LOVIT trial findings should not be interpreted as evidence against vitamin C therapy for critically ill patients.

Weekly ascorbic acid infusion in castration-resistant prostate cancer patients: a single-arm phase II trial

BACKGROUND

Ascorbic acid (AA) has in vivo cytotoxic properties at concentrations that can only be achieved through intravenous (IV) administration in humans. Treatment with intravenous AA is widely and increasingly used in complementary medicine despite a lack of clinical evidence for the efficacy of this treatment.

METHODS

This non-comparative, single-center, phase II trial included patients with chemotherapy-naïve, metastatic castration-resistant prostate cancer (mCRPC) from an outpatient clinic to evaluate the efficacy and safety of IV AA therapy. Patients received weekly infusions of AA (week 1, 5 g; week 2, 30 g; and weeks 3-12, 60 g) followed by efficacy evaluation at 12 weeks. The primary endpoint for efficacy was a 50% reduction in the prostate-specific antigen (PSA) level. The secondary endpoints included changes in health-related quality of life (HRQoL), biomarkers of bone metabolism, inflammation and bone scans. Clinicaltrials.gov identifier: NCT01080352.

RESULTS

Twenty-three patients were enrolled in this study, and 20 completed the efficacy evaluation at 12 weeks. The mean baseline PSA level was 43 µg/L. No patient achieved a 50% PSA reduction; instead, a median increase in PSA of 17 µg/L was recorded at week 12. Among the secondary endpoints, no signs of disease remission were observed. In total, 53 adverse events (AEs) were recorded. Eleven were graded as "serious". Three AEs were directly related to AA, and all of which were related to fluid load.

CONCLUSIONS

Infusion with 60 g of AA did not result in disease remission. This study does not support the use of intravenous AA outside clinical trials.

Vitamin C in Alternative Cancer Treatment: Historical Background

Ascorbic acid is the single-nutrient supplement most commonly used by cancer patients, although in most cases this takes place without the physician's knowledge or supervision. A comprehensive review of the literature is presented on the impact of ascorbic acid on cancer survival. Findings from 6 uncontrolled studies suggest that ascorbic acid may increase survival, whereas 2 controlled trials have yielded null results. The relative strengths and limitations of these studies are discussed. A turning point occurred with the release of the 2 controlled (null) studies, which influenced many physicians to turn away from nutrition in the care of cancer patients. Controversy about these trials still persists, however, in the alternative cancer community.

Elimination of ascorbic acid after high-dose infusion in prostate cancer patients: a pharmacokinetic evaluation

Treatment with high-dose intravenous (IV) ascorbic acid (AA) is used in complementary and alternative medicine for various conditions including cancer. Cytotoxicity to cancer cell lines has been observed with millimolar concentrations of AA. Little is known about the pharmacokinetics of high-dose IV AA. The purpose of this study was to assess the basic kinetic variables in human beings over a relevant AA dosing interval for proper design of future clinical trials. Ten patients with metastatic prostate cancer were treated for 4 weeks with fixed AA doses of 5, 30 and 60 g. AA was measured consecutively in plasma and indicated first-order elimination kinetics throughout the dosing range with supra-physiological concentrations. The target dose of 60 g AA IV produced a peak plasma AA concentration of 20.3 mM. Elimination half-life was 1.87 hr (mean, S.D. ± 0.40), volume of distribution 0.19 L/kg (S.D. ±0.05) and clearance rate 6.02 L/hr (100 mL/min). No differences in pharmacokinetic parameters were observed between weeks/doses. A relatively fast first-order elimination with half-life of about 2 hr makes it impossible to maintain AA concentrations in the potential cytotoxic range after infusion stop in prostate cancer patients with normal kidney function. We propose a regimen with a bolus loading followed by a maintenance infusion based on the calculated clearance.

The health effects of vitamin C supplementation: a review

A comprehensive review of the literature indicates that populations with long-term consumption of higher than RDA levels of vitamin C (> or = 60 mg/day) from foods and/or supplements have reduced risks of cancer at several sites, cardiovascular disease, and cataracts. The safety of higher than RDA intakes of vitamin C is confirmed in eight placebo-controlled, double-blind studies and six non-placebo clinical trials in which up to 10,000 mg of vitamin C was consumed daily for up to 3 years. There are no clinical data which suggest that vitamin C's enhancement of non-heme iron absorption in individuals with low iron status could be a critical factor in the possible increased risk of heterozygous hemochromatosis-related cardiovascular disease. In fact, the cumulative data do not confirm that iron status is related to risk of cardiovascular disease. Moreover, higher than RDA intakes of vitamin C have been associated with several indices of lowered cardiovascular disease risk including increases in HDL, and decreases in LDL oxidation, blood pressure and cardiovascular mortality.

Drug antioxidant effects. A basis for drug selection?

A free radical is any species capable of independent existence that contains one or more unpaired electrons. Free radical reactions have been implicated in the pathology of more than 50 human diseases. Radicals and other reactive oxygen species are formed constantly in the human body, both by deliberate synthesis (e.g. by activated phagocytes) and by chemical side-reactions. They are removed by enzymic and nonenzymic antioxidant defence systems. Oxidative stress, occurring when antioxidant defences are inadequate, can damage lipids, proteins, carbohydrates and DNA. A few clinical conditions are caused by oxidative stress, but more often the stress results from the disease. Sometimes it then makes a significant contribution to the disease pathology, and sometimes it does not. Several antioxidants are available for therapeutic use. They include molecules naturally present in the body [superoxide dismutase (SOD), alpha-tocopherol, glutathione and its precursors, ascorbic acid, adenosine, lactoferrin and carotenoids] as well as synthetic antioxidants [such as thiols, ebselen (PZ51), xanthine oxidase inhibitors, inhibitors of phagocyte function, iron ion chelators and probucol]. The therapeutic efficacy of SOD, alpha-tocopherol and ascorbic acid in the treatment of human disease is generally unimpressive to date although dietary deficiencies of the last two molecules should certainly be avoided. Xanthine oxidase inhibitors may be of limited relevance as antioxidants for human use. Exciting preliminary results with probucol (antiatherosclerosis), ebselen (anti-inflammatory), and iron ion chelators (in thalassaemia, leukaemia, malaria, stroke, traumatic brain injury and haemorrhagic shock) need to be confirmed by controlled clinical trials. Clinical testing of N-acetylcysteine in HIV-1-positive subjects may also be merited. A few drugs already in clinical use may have some antioxidant properties, but this ability is not widespread and drug-derived radicals may occasionally cause significant damage.

Growth, ascorbic acid and iron contents of tissues of young guinea-pigs whose dams received high or low levels of dietary ascorbic acid or Fe during pregnancy and suckling

1. Guinea-pig dams were fed on purified diets containing high (5 g/kg diet plus 1 g/l drinking water) or moderate (0.5 g/kg diet) levels of ascorbic acid, in combination with high (1 g/kg diet) or moderate (0.043 g/kg diet) levels of iron, during pregnancy and suckling. Their offsprings' diets contained 0.1 g ascorbic acid/kg and 0.04 g Fe/kg. 2. High ascorbic acid intake clearly enhanced both tissue ascorbate and Fe storage in the dams, and high Fe intake increased both the dams' and the pups' tissue Fe stores. 3. In the animals receiving high Fe intake, a co-existing high ascorbate intake by the dams reduced the growth rate of the offspring, but only during the early stages of development, not during the later stages of post-weaning growth. All the pups' tissue ascorbate levels fell after weaning, but those born of the dams receiving the high ascorbic acid diets did not fall to levels lower than those of the other pups. 4. Thus, although certain disadvantages to the offspring resulting from very-high ascorbic acid intake by pregnant guinea-pig dams were detected, these did not include permanently increased ascorbate requirements, and hence a progression to scurvy as the pups grew and matured.

A re-evaluation of nutritional goals--not just deficiency counts

There is considerable controversy about the soundness and relevance of so-called "megavitamin" therapy for various illnesses. In this article it is suggested that this disagreement is caused to a large extent by the use of two very different approaches to nutrition, which are referred to here as the "nutritional need" and "optimal intake" approaches. It is clear that a re-evaluation of the goals of nutrition is required, as nutritional recommendations deal mainly with the prevention of deficiency diseases and are not concerned with optimal levels of intake.