1.3.2Unit 1: Lifestyle, Transport, Genes and Health
Dietary Antioxidants and CVD — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 4 parts Lesson 20 of 29 Unit quiz
Part 1 of 4Antioxidants and Free Radicals
Free radicals
- Free radicals These are highly reactive molecules or atoms produced in normal metabolism that can damage lipids, proteins and DNA.
Oxidative damage
- Oxidative damage Damage to the artery lining and oxidised LDL are thought to help atheroma formation.
Antioxidants
- Antioxidants These substances, including vitamins C and E and β-carotene, can neutralise free radicals before they cause damage.
Sources
- Sources Fruit, vegetables, nuts and seeds are rich in antioxidants, and diets containing them are linked to lower disease risk.
Part 2 of 4Evaluating the Evidence
1
Observational studies found that people with high intakes of fruit and vegetables had lower rates of CVD, suggesting a protective effect.
2
Some studies reported that people with low blood vitamin C levels had more heart attacks than those with normal levels.
3
These studies show correlation only, because people who eat more fruit and vegetables also tend to exercise and smoke less.
4
Large controlled trials that gave supplements to volunteers often found no reduction in CVD, and some found possible harm.
5
Combining many studies in a meta-analysis reduces the effect of chance and helps to judge whether the overall evidence supports a link.
Part 3 of 4Drawing Conclusions
Drawing Conclusions
Confounding variables
- Confounding variables Other aspects of diet and lifestyle may account for apparent benefits so they must be controlled in a valid study.
Natural foods versus tablets
- Natural foods versus tablets Benefits may arise from the combination of nutrients in whole foods, not from isolated vitamin supplements.
Sample and bias
- Sample and bias A large, random sample and independent funding make a study more reliable and less likely to be biased.
Current view
- Current view The evidence that antioxidant supplements prevent CVD is inconclusive, though a balanced diet with plenty of plant foods is still advised.
Part 4 of 4Exam Checklist & Tips
1.3.2 – Key Points for the Exam
- Antioxidant A substance that prevents oxidation by neutralising free radicals.
- Free radical A reactive particle with an unpaired electron that can damage cells.
- Meta-analysis A study that combines the results of many separate studies.
- Confounding variable A variable other than the one being tested that may affect the result.
Common Mistakes
- Stating that antioxidants have been proven to prevent heart disease; the evidence is conflicting.
- Assuming that a correlation in an observational study shows that the vitamin caused the benefit.
- Writing that all free radicals are harmful and have no role in the body.
- Ignoring sample size and control of variables when evaluating a study.
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