Prof Margreet Vissers, Research Professor at University of Otago, New Zealand: http://www.kiwifruitsymposium.org/presentations/overview-of-the-many-health-benefits-of-vitamin-c/ Presented at 1st International Symposium on Kiwifruit and Health. Vitamin C is essential for life, and humans obtain this nutrient exclusively through the diet. It functions inside the cells in our bodies, where it plays an important role in supporting many essential processes. One kiwifruit a day gives the daily requirement of vitamin C.

1. The Health Benefits of Vitamin C
Prof. Margreet Vissers
University of Otago, New Zealand

2. The Health Benefits of vitamin C
Margreet Vissers
Centre for Free Radical Research
University of Otago, Christchurch
New Zealand

3. The University of Otago,
Dunedin, Christchurch and Wellington
University of Otago, Dunedin, NZ

4. The Centre for Free Radical Research, Christchurch

5. The Good News – we are living far longer than ever

6. Increased lifespan comes at a price
Exposure to chronic disease and loss of function
How to ensure maximum healthspan?
Cardiovascular
disease
Cancer Diabetes Cognitive decline Frailty

7. Increasing healthspan with diet and lifestyle choices
Willett WC, Science 296, 695-698 (2002)
Genetics
Life-
style
Diet
A large percentage of chronic
disease is potentially reduced by
diet and lifestyle changes.

8. J Epidemiology and Community Health, March 31, 2014 as 10.1136/jech-2013-203500
METHOD: 65,226 participants aged 35+ years in the 2001–2008 Health Surveys for England.

9. Multivariate-adjusted odds ratios for features of the metabolic syndrome across quintiles of fruit intake.
Am J Clin Nutr 2006;84:1489–97.

10. The importance of study design and method for epidemiological
evidence of dietary - health benefits
Study design
• Number and grouping of participants
• Intervention or correlation?
• Frequency of measures
• Duration of follow-up
• Participation rate
• Blinding ?
Method
• Use of validated assessment tools
• Use of validated outcome measures
• Adjustments for age, race, gender?

11. Quirk et al. BMC Psychiatry 2013, 13:175
Method: A computer-aided literature search was conducted using Medline, CINAHL, and PsycINFO, January 1965 to
October 2011, and a best-evidence analysis performed.
Results: Twenty-five studies from nine countries met eligibility criteria. Our best-evidence analyses found limited
evidence to support an association between traditional diets (Mediterranean or Norwegian diets) and depression.
We also observed a conflicting level of evidence for associations between (i) a traditional Japanese diet and
depression, (ii) a “healthy” diet and depression, (iii) a Western diet and depression, and (iv) individuals with
depression and the likelihood of eating a less healthy diet.
Conclusion: To our knowledge, this is the first review to synthesize and critically analyze evidence regarding diet
quality, dietary patterns and depression. Further studies are urgently required to elucidate whether a true causal
association exists.

12. Conclusion from fruit and vegetable intake studies?
(To date)
Higher fruit and vegetable intake is associated with decreased risk of
chronic diseases, with decreased all-cause mortality, increased lifespan
and with improved health status (both mental and physical health).

13. Dietary Recommendations vs Reality in the Western World

14. Micronutrients:
13 Vitamins and 14 Minerals
Essential Nutrients – Essential for Health
Micronutrients have many functions in the body
• Support hundreds of enzymes
• Cell and tissue function
• Energy production, growth and development
• Heart health
• Immune function
• Bone health
• etc
Vitamins A, B1, B2, B3, B5,
B6, B7, B9, B12, C, D, E, K
Macro minerals Calcium,
Magnesium, Phosphorus,
Potassium, Sodium
Trace minerals Chromium,
Copper, Fluoride, Iodine,
Manganese, Molybdenum,
Selenium, Zinc

15. From: Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary
Prevention: Systematic Review and Meta-analysis
JAMA. 2007;297(8):842-857. doi:10.1001/jama.297.8.842
What can we conclude?

16. From: Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary
Prevention: Systematic Review and Meta-analysis
JAMA. 2007;297(8):842-857. doi:10.1001/jama.297.8.842
Included all primary and secondary prevention trials in adults randomized to receive beta
carotene, vitamin A, vitamin C, vitamin E, or selenium vs placebo or no intervention.
Trials including general or healthy populations, or participants with specific diseases.
Dosing regimes: All antioxidant supplements were administered orally. The dose and
regimen of the antioxidant supplements were: beta carotene 1.2 to 50.0 mg , vitamin A
1333 to 200 000 IU, vitamin C 60 to 2000 mg, vitamin E 10 to 5000 IU, and selenium 20 to
200 μg daily or on alternate days for 28 days to 12 years (mean 2.7 years). In one
trial antioxidants were applied in a single dose and participants were followed up for 3
months thereafter. The mean duration of follow-up in all trials was 3.3 years (range, 28
days-14.1 years).

17. Conclusion from dietary antioxidant supplement studies?
(To date)
Supplementation of the healthy population has beneficial effect on
overall health status, on all-cause mortality, on susceptibility to
chronic diseases.
Some vitamin supplementation (Vit E, Vit A) may be harmful.

18. Vitamin C in plasma is inversely related to blood pressure and change in blood
pressure during the previous year in young Black and White women
Block et al, 2008. Nutrition Journal 7:35
Relation of Serum Ascorbic Acid to Mortality Among US Adults
Simon et al, Journal of the American College of Nutrition, 2001. 3, 255–263
Plasma vitamin C levels and health outcomes
Plasma and dietary vitamin C levels and risk of gastric cancer in the European
Prospective Investigation into Cancer and Nutrition (EPIC-EURGAST).
Jenab et al, 2006. Carcinogenesis 27, 2250–2257
No association observed for dietary vitamin C, whereas an inverse GC risk was observed in the
highest versus lowest quartile of plasma vitamin C [OR = 0.55].

19. In the early stages, the patients do not look very sick… But in a few days develop universal
lassitiude, stiffness, and feebleness of knees, difficulty breathing… Haemorrhages… the
gums bleed readily then become putrid and rotten… ulcers appear, coated with blood and
gore… Patients have abdominal pain, breathe with pain and labor and may die suddenly.
James Lind, 1753
Vitamin C – an essential nutrient
Discovery attributed to Albert Szent-Gyorgi in 1932,
after a long search for the cause of scurvy

20. Vitamin C uptake
Plasma
(10 – 100 µM)
High – 100x
Brain, spleen, wbcs,
pancreas, liver, lymph
Medium – 10x
Skeletal, heart muscle
Very high – 200x
Adrenals, pituitary,
retina

21. Variable tissue accumulation of ascorbate
- reflects functional requirement?
Harrison and May (2009) Free Radic Biol Med, 46(6):719-730.

22. How do variable plasma vitamin C levels affect with tissue levels?
Transport experiments using HT29
multicellular layers (MCL).
Modelling vitamin C transport into tissue
Kuiper et al 2014, Free Radical Biol Med 77:340–352

23. Modelling physiological plasma and tissue vitamin C levels
O2
Heat map modelling
Kuiper et al 2014, Free Radical Biol Med 77:340–352

24. How much vitamin C do we need? The RDA…
EAR = estimated average requirement; RDA = recommended daily allowance; UL = upper limit

25. How much vitamin C do we need? The RDA…
Prevention of scurvy
Another health benefit
Vitamin C: working on the x-axis.
Levine and Eck. Am J Clin Nutr 90:1121–3 (2009)

26. How much vitamin C do we need?
Levine et al, PNAS 93:3704-3709 (1996)
Optimal
levels

27. Vitamin C and health:
What is the vitamin C status for people today?
0
10
20
30
40
50
60
70
80
90
100
10 20 30 40 50 60 70 80 90 100
Frequency
Plasma vitamin C (µM)
Vitamin C status of 400+ normal healthy NZ adults (50 year olds), 2010

28. Level of Micronutrient intake insufficiency in Western Diets
(data from the USA, 2011)

29. • A strong reducing agent, oxidised in one-electron steps.
• Forms complexes with many metal ions, including Fe and Cu.
• Synthesised in plants and animals - but some mammals
lack the necessary enzyme, L-gulono--lactone oxidase.
• Acts as a co-factor for Fe- or Cu-containing enzymes.
Vitamin C: What do we know?
Ascorbic acid

30. Primary intracellular oxidation, reduction, and
degradation pathways for vitamin C
Bohndiek et al 2011. J Am Chem Soc 133, 11795–11801

31. Antioxidant activity of vitamin C
• Antioxidant activity is readily demonstrated in vitro.
• Vitamin C is an excellent radical scavenger, forming the benign
ascorbyl radical.
• Oxidation of biological molecules (lipids, proteins, DNA) can be
prevented in vitro by adding vitamin C.

32. Proposed antioxidant activity of vitamin C in vivo
Example. Roles of ascorbic acid during synaptic
activity and astrocyte-mediated recycling.
Covarrubias-Pinto et al, 2015 Int J Mol Sci ;16:28194-217

34. British Journal of Surgery 86: 1296-1301 (1999)

35. Hypovitaminosis C is common in hospitalised patients
Fain et al, Eur J Internal Medicine 14:419-425 (2003)

36. What can we conclude from in vivo evidence
of vitamin C turnover?
• Ascorbate turnover is accelerated in illness.
• The rate of turnover is associated with disease severity and
inflammatory illness.
• Supplementation is associated with improved outcome for sick
patients (e.g. the common cold and pneumonia).
However:
does oxidative damage imply antioxidant activity?

37. Fe and 2-oxoglutarate-dependent dioxygenases
An extended family of enzymes found in plants and animals, with a
multitude of functions.
• Commonly known:
Plant cell wall synthesis
Collagen modification
• Less commonly known:
Morphine synthesis
Antibiotic catabolism e.g. Penicillin
C Schofield

38. The co-factor activity of vitamin C:
2-oxoglutarate-dependent dioxygenases

39. The co-factor activity of Vitamin C – what’s new?
Hormone
synthesis
Protein 3o
structure
HIF hydroxylases
DNA & Histone
demethylases
EGF Asp/Asn
hydroxylases
Metabolic
control
Epigenetics
Signalling
Collagen hydroxylase

40. The co-factor activity of Vitamin C – what’s new?
Tissue formation
and
Wound healing
Mood
and
energyCancer,
immune system,
appetite
Gene
Function
(everything)
Stress
responses

41. Vitamin C co-factor activity
Mood and energy example: Vitamin C is a cofactor in the biosynthesis of carnitine.
Strijbis et al 2010, IUBMB Life 62(5): 357–362

42. Carnitine transports long-chain fatty acids into the mitochondria,
where they are used for energy generation.
Carnitine function

43. Week 4 Week 8 Week 4 Week 8Week 4 Week 8
Individual subject data for plasma vitamin C concentration (A) and for fat energy (B) and protein energy (C) expended
during submaximal exercise in vitamin C depleted (placebo capsule daily; n = 3) and vitamin C repleted (500 mg vitamin C
capsule daily; n = 5) subjects at week 4 (pre-intervention) and week 8 (post-intervention).
Nutrition & Metabolism 2006, 3:35

44. Cell response to lack of oxygen - hypoxia
Vitamin C is a cofactor for the enzymes that regulate
Hypoxia-inducible factor - HIF



OH
OH
VHL
OH
OH
Stress responses
EPO
VEGF
Apoptosis
Hydroxylases

45. HIF-1
ANGIOGENESIS
• Flt-1 (VEGF receptor)
• Vascular endothelial cell growth factor (VEGF)
• Plasminogen activator inhibitor-1
• Intestinal trefoil factor
• Leptin
RED CELL MATURATION
• Erythropoeitin
• Transferrin
• Ceruloplasmin
• Tyrosine hydroxylase
CELL GROWTH AND FATE
• Insulin-like growth factor-2
• IGF-binding protein 1,2&3
• Bcl-2/EIP interacting protein 3(BNIP3)
• p21
• NIP-3
GLYCOLYSIS
• Adenylate kinase-3
• Aldolase A&C
• Enolase 1
• Hexokinase 1
• GAPDH
•Carbonic anhydrase-9
• Phosphofructokinase L&C
• Pyruvate kinase
• 6-phosphofructo-2-kinase
• Fructose 2,6-bisphosphatase-3
• Lactate dehydrogenase
MISCELLANEOUS
• Cyclo-oxygenase-2
• Presinilin 1&2
• Collagen prolyl hydroxylase
•VL60
• p35srj
• ETS-1
• DEC 1&2
VASOMOTOR CONTROL
• Endothelin-1
• Nitric oxide synthase
• a-adrenergic receptor
• Adrenomedullin
• Heme oxygenase-1
GLUCOSE TRANSPORT
• Glucose transporters 1&3

46. Ide et al Am J Roentgenol. 1939;42:891-899
Hypoxia and HIF-1 in biology
Cancer Inflammation
Hypoxia in intestinal colitis
Karhausen J. et al. J. Clin. Invest. 114, 1098–1106 (2004).

47. Inflammation and the Neutrophil
In the circulation Movement into tissues Bacterial killing
Neutrophils have high vitamin C levels, suggesting an essential function.

48. Vitamin C and removal of neutrophils.
Regeneration of normal lung tissue homeostasis after inflammation.

49. Removal of dying neutrophils
Mature
neutrophil
Neutrophil removal
The same phenotype is seen in either hypoxia or with low
vitamin C levels and is centered on activation of HIF-1.

50. Epigenetics – our growing understanding of genes and inheritance
Is there a role for vitamin C?

51. Epigenetics and the co-factor activity of vitamin C
Fe and 2-oxoglutarate-dependent dioxygenases
• Histone demethylation
Jumonji histone demethylases (JHDMs). Up to 12 known enzymes
• DNA demethylation
Ten-eleven translocases (Tet) – 3 known

52. The Tet enzymes, vitamin C and epigenetics
Blaschke et al, Nature, vol 500, August 2013

53. Diet and the Fe-2-OGD dioxygenases
Ascorbate
Oxygen
Fe
Metabolic
Intermediates

54. Summary
• Plasma vitamin C levels are positively correlated with health and
survival benefits.
• Body stores and tissue saturation are dependent on
adequate/optimal plasma supply.
• Vitamin C is depleted by oxidative stress conditions – e.g. illness.
• Intracellular vitamin C influences the activity of many Fe and Cu-
containing enzymes.
• Many physiological benefits of vitamin C intake reflect the co-factor
activity.

55. CFRR
Caroline Kuiper, Stef Bozonet, Anitra Carr, Juliet Pullar,
Usha Pujary, Mary Morrison, Prachee Gokhalé, Amy Scott-Thomas, Rachel Wilkie,
Lewis Braithwaite, Mark Hampton.
McKenzie Cancer Research Group
Lizzie Campbell, Gabi Dachs, Sarah Gunningham, Margaret Currie
OBSTETRICS AND GYNAECOLOGY
Peter Sykes, John Evans
UOC
Arron Dyer, Ruth Owers, Katie Saunders John Pearson
FUNDING:
Health Research Council of NZ, Canterbury Medical Research Foundation, Zespri
International, University of Otago, Tertiary Education Commission, MBIE.
ACKNOWLEDGEMENTS