Antioxidants: Vitamins

11 important questions on Antioxidants: Vitamins

What is the relation between vitamn intake and vitamin status?

Generally a moderate but (often) significant correlation exists between intake and blood concentrations. But there are inter individual responses to intake!

Folate status assessment:

  • Plasma/serum folate = most widely used marker, short term (7-40 nmol/L)
  • whole blood/red blood cell folate = best mid term indicator, but laborious and prone to error (depends on Ht measrement)
  • total folate test most common in routine labs:
    • gold standard microbial assay, but sensitive to antibiotic treatment
    • total folate binding test
  • total folate (routine labs) vs folate profile (research labs)

B12 status assessment:

  • Direct plasma/serum B12 analysis (~200/300-600 pmol/L)
  • functional markers better than B12
  • lack of standardisation between different B12 tests..!
  • hydroxocobalamin is used as a treatment for cyanide poisoning
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Are vitamin deficiencies prevalent in athletes? Maybe because they have higher turnover?

Physical exercise had no impact on folate and B12 status.
Whereas sex, age, energy intake per day did have an impact.

Recommendations for B-vitamin intake in athletes:

  • No evidence to suggest better performance at higher intakes, so general recommendatinos apply:
    • B6: ~1.5-1.8 mg/day
    • folate: 300 yg/day
    • B12: 2.8 ug/day
  • with a balanced diet, no immediate concern for B-vitamin deficiency
  • risk groups for deficiency are:
    • dietary restrictions
    • vegans (B12)
    • use of certain medication (protein pump inhibitors, metformin)
  • supplements use only after clinical assessment and evidence for vitamin deficiency
  • not all supplements are safe! Excessive does and/or misleaing labelling, not all B vitamins are excreted!

Health effects of vit D:

  • Necessary for optimal bone health (interaction with Ca and Mg)
  • deficiency increases risk of autoimmune diseases and can have profound effect on human immunty, inflammation and muscle function
  • compromised vit D status can affect an athletes overall health and ability to train
    • i.e. By affecting bone healt, innate immunity and exercise-related immunity and inflammation

Vit D status assessment:

  • 25(OH)D = accepted status marker
  • optimal range 75-100 nmol/L
  • insufficiency < 50 nmol/L
  • deficiency < 30 nmol/L

Vit D deficiencies in athletes:

  • 70% of all athletes showed an insufficient or deficient 25(OH)D level at baseline (the end of winter season)
  • it is common, but not different from general population
    • inadequate sun exposure, lattitude, skin type
    • restrained eating
    • low body fat % ?

picture is indoor vs outdoor sport
There is more 25(OH)D in outdoor athltes in all seasons.
At low 25(OH)D, there is high illness.
> outdoor exercise elevates vit D levels!! And therefore also the performance

Vit D recommendations:

Various expert groups recommend a target blood concentration of 75-100nmol/L

  • stimulate outdoor exercise! But consider skin cancer risk
  • screen athletes:
    • at least 2x per year: late summer/winter
    • history bone injury, frequent illness, restrained eating/vegetarians and indoors 
  • correct deficiencies (< 75 nmol/L)
  • D3 slightly more effective than D2
  • dose:
    • sun exposure
    • 100 IU increases serum 25(OH)D with ~2.5 nmol/L
    • > 10.000 IU/day is toxic

Safety of vit D supplements:

  • Hypercalcaemia, hypercalciuria at high doses (> 100 ug/day for extended periods
  • 25(OH)D > 375 nmol/L = risk for toxicity
  • UVB feedback mechanism
  • 10.00 IU/day ; UL: 4000 IU
  • intoxication from exess supplementation is rare

Antioxidant vitamins - A and E:

  • exercise leads to VO2 goes up to 10-20x -> incomplete reduction of oxygen > ROS formation
    • ROS sources: skeletal muscle/mitochondria, immune cells
  • two classes of ROS:
    • radicals: O2-, OH-
    • non-radicals: H2O2, O3

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