MRC/BHF Heart Protection Study
2002; Elsevier BV; Volume: 360; Issue: 9347 Linguagem: Inglês
10.1016/s0140-6736(02)11689-8
ISSN1474-547X
Autores Tópico(s)Vitamin C and Antioxidants Research
ResumoOne of the conclusions of the HPS Collaborative Group (July 6, p 23),1Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Summary Full Text Full Text PDF PubMed Scopus (1362) Google Scholar namely that “the lower risks of vascular disease and cancer found in observational studies among people with higher intake of [these] antioxidant vitamins must have been largely or wholly artefactual”, seems to go beyond the data.All the participants, including those subsequently randomised to the placebo group, received a 10-week supply of vitamins in the prerandomisation “run-in” phase.1Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Summary Full Text Full Text PDF PubMed Scopus (1362) Google Scholar This amount was equivalent to about an 8-month supply of vitamin C, 140 months of vitamin E, and 24 months of carotene, at median UK intakes.2Finch S Doyle W Lowe C et al.National Diet and Nutrition Survey: people aged 65 years and over. Volume 1: report of the Diet and Nutrition Survey. Stationery Office, London1998Google Scholar There was no wash-out period before the main trial. Nutrients, especially fat-soluble ones, are usually retained within the body for longer periods than most drugs, and wash-out periods are typically much longer. I also suspect that many of the non-vitamin group may have taken over-the-counter vitamins. Benefits from the correction of marginal vitamin deficiencies are not ruled out if all participants received vitamin supplements.In table 2,1Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Summary Full Text Full Text PDF PubMed Scopus (1362) Google Scholar the daily 250 mg supplement of vitamin C produced only a 30% increase in plasma vitamin C. However, calculations from a National Diet and Nutrition Survey (NDNS)2Finch S Doyle W Lowe C et al.National Diet and Nutrition Survey: people aged 65 years and over. Volume 1: report of the Diet and Nutrition Survey. Stationery Office, London1998Google Scholar and a meta-analysis of plasma vitamin C concentration versus vitamin C intake,3Brubacher D Moser U Jordan P Vitamin C concentrations in plasma as a function of intake: a meta-analysis.Int J Vitam Nutr Res. 2000; 70: 226-237Crossref PubMed Scopus (72) Google Scholar indicate that the increase in plasma vitamin C after an increase in intake from 70 mg per day to 320 mg per day should be at least 60%. The increase, however, would be smaller if both groups had taken vitamin C supplements.In the NDNS,2Finch S Doyle W Lowe C et al.National Diet and Nutrition Survey: people aged 65 years and over. Volume 1: report of the Diet and Nutrition Survey. Stationery Office, London1998Google Scholar at least 6% of participants aged 65–80 years, and possibly more,4Bates CJ Prentice A van der Pols JC et al.Estimation of the use of dietary supplements in the National Diet and Nutrition Survey: people aged 65 years and over—an observed paradox and a recommendation.Eur J Clin Nutr. 1998; 52: 917-923Crossref PubMed Scopus (32) Google Scholar were regularly taking over-the-counter supplements containing vitamin C. Unlike those in the NDNS, those in the HPS all had known medical risk factors. Since a prescription-only medication (simvastatin) was being compared with a vitamin supplement, participants wishing to minimise their own risk might have decided to take over-the-counter supplements.I would be interested to know whether the HPS Group monitored voluntary over-the-counter supplement use? It is important to determine whether correction of marginal micronutrient deficiencies has health benefits. This is a different question from pharmacological benefits of high doses, and the evidence must be assessed separately. One of the conclusions of the HPS Collaborative Group (July 6, p 23),1Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Summary Full Text Full Text PDF PubMed Scopus (1362) Google Scholar namely that “the lower risks of vascular disease and cancer found in observational studies among people with higher intake of [these] antioxidant vitamins must have been largely or wholly artefactual”, seems to go beyond the data. All the participants, including those subsequently randomised to the placebo group, received a 10-week supply of vitamins in the prerandomisation “run-in” phase.1Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Summary Full Text Full Text PDF PubMed Scopus (1362) Google Scholar This amount was equivalent to about an 8-month supply of vitamin C, 140 months of vitamin E, and 24 months of carotene, at median UK intakes.2Finch S Doyle W Lowe C et al.National Diet and Nutrition Survey: people aged 65 years and over. Volume 1: report of the Diet and Nutrition Survey. Stationery Office, London1998Google Scholar There was no wash-out period before the main trial. Nutrients, especially fat-soluble ones, are usually retained within the body for longer periods than most drugs, and wash-out periods are typically much longer. I also suspect that many of the non-vitamin group may have taken over-the-counter vitamins. Benefits from the correction of marginal vitamin deficiencies are not ruled out if all participants received vitamin supplements. In table 2,1Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20 536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Summary Full Text Full Text PDF PubMed Scopus (1362) Google Scholar the daily 250 mg supplement of vitamin C produced only a 30% increase in plasma vitamin C. However, calculations from a National Diet and Nutrition Survey (NDNS)2Finch S Doyle W Lowe C et al.National Diet and Nutrition Survey: people aged 65 years and over. Volume 1: report of the Diet and Nutrition Survey. Stationery Office, London1998Google Scholar and a meta-analysis of plasma vitamin C concentration versus vitamin C intake,3Brubacher D Moser U Jordan P Vitamin C concentrations in plasma as a function of intake: a meta-analysis.Int J Vitam Nutr Res. 2000; 70: 226-237Crossref PubMed Scopus (72) Google Scholar indicate that the increase in plasma vitamin C after an increase in intake from 70 mg per day to 320 mg per day should be at least 60%. The increase, however, would be smaller if both groups had taken vitamin C supplements. In the NDNS,2Finch S Doyle W Lowe C et al.National Diet and Nutrition Survey: people aged 65 years and over. Volume 1: report of the Diet and Nutrition Survey. Stationery Office, London1998Google Scholar at least 6% of participants aged 65–80 years, and possibly more,4Bates CJ Prentice A van der Pols JC et al.Estimation of the use of dietary supplements in the National Diet and Nutrition Survey: people aged 65 years and over—an observed paradox and a recommendation.Eur J Clin Nutr. 1998; 52: 917-923Crossref PubMed Scopus (32) Google Scholar were regularly taking over-the-counter supplements containing vitamin C. Unlike those in the NDNS, those in the HPS all had known medical risk factors. Since a prescription-only medication (simvastatin) was being compared with a vitamin supplement, participants wishing to minimise their own risk might have decided to take over-the-counter supplements. I would be interested to know whether the HPS Group monitored voluntary over-the-counter supplement use? It is important to determine whether correction of marginal micronutrient deficiencies has health benefits. This is a different question from pharmacological benefits of high doses, and the evidence must be assessed separately. MRC/BHF Heart Protection StudyAuthors' reply Full-Text PDF
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