Micronutrients: Minerals

11 important questions on Micronutrients: Minerals

Risk factors for marginal nutrition/deficiencies and its corresponding sport:


What are the different shapes of iron in the body?

  • Erythrocytes
  • plasma
  • body stores (liver/spleen)
  • myoglobin and spiratory enzymes (mitochondria)

What are the stages of iron deficiency? And are deficiencies in iron common?

  • Early stage: ferritin decreases
  • intermediate stage: transferrin decreases
  • late stage: haemoglobin decreases, altered RBC volume parameters

  • not different to general population
    • female athletes, endurance athletes
  • depletion iron stores
    • female and adolescent athletes (reduced stores)
    • male lower risk > 16% female; 4% male
  • iron deficiency anemia
    • quite low - not different for athletes
    • adolescent girls, young men
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Iron - effects on performance/symptoms deficiency:

Energy metabolism:
  • oxygen transport
  • oxidative enzymes and respiratory chain proteins
  • erythropoiesis, thyroid hormone, neural and immune function
  • excess: free oxygen radicals

symptoms deficiency:
- weakness, breathlessness, impaired aerobic capacity
- non-specific symptoms
- may also be indicative of over-training, immune deficiency, psycosocial stress

Effect on aerobic capacity/performance:
  • iron depletion: no effect on aerobic capacity (VO2max)
  • iron deficiency, no anemia: probably effect
  • iron deficiency, anemia: clear impairment

Causes of iron deficiencies in exercise are:

  • Training (strenous endurance exercise)
  • Growth and pregnancy

  • Infection/inflammation (hepcidin)
  • Other medical / physiological reasons

  • Inadequate intake (vegetarians)
  • Low dietary iron availability
    • enhancers (Vit C, fermented food)
    • inhibitors (phytate, polyphenols, calcium)

Iron intake recommendations for athletes:

  • No specific recommendations
  • iron-loss in endurance runners: ~1.6 mg/day(men) and ~2.2 mg/day(women) (0.8-0.9 non athletes)
  • intake ~ 20 mg/day (10% absorption)
  • EAR 1.3-1.7 times higher for athletes: 1.8 times higher for vegetarians
    • female vegetarian athletes: 3 times higher

  • foods rich in heme iron 4/week
  • iron-fortified foods
  • nonheme iron food sources
  • combine nonheme iron foods with meat or foods rich in vit C
  • avoid drinking tea/coffee/milk at meals

exercise and bone health?

  • Present in bones
  • bone health:
    • osteoporosis, osteopenia (especially in women that exercise a lot)
      • Bone Mineral Density (BMD) is decreased

> exercise and bone health:
  • active lifestyle: greater bone mass
  • type of exercise:
    • weight bearing vs non weight bearing
  • site specific
  • paradox: athletic premenopausal women
    • femal athlete triad = combi of disorder eating, osteoporosis and amenorrhoea

How is the calcium status in athletes?

  • Calcium excretion may be increased during exercise (via sweat and urine)
    • protein, sodium, alcohol, caffein
  • reduced intake:
    • young femal athletes
    • weight-classes
    • vegans
  • vitamin D is needed as well!!

Calcium intake recommendations for athletes:
especially when on energy-restricted diet:

  • Adults men and women: 1000 mg/day
  • children and elderly: 1300 mg/day
  • postmenopausal women: 1500 mg/day

  • amenorrhoeic athletes (due to low estrogen): 1500 mg/day

When on energy-restricted diet:
- include three servings per day low-fat dairy
- include these dairy foods in high CHO meals
- eat fish with bones
- include Ca-enriched soy products
- eat leafy green vegetables

Symptoms of magnesium deficiency:

  • Muscle spasms
  • CVD
  • osteoporosis
  • caused by poor intake, disturbed digestion r excessive excretion (kidney disease)

Magnesium intake recommendations for athletes:

  • No specific recommendations for exercise: 300-350 mg/day
  • good dietary sources: leafy vegetables, nuts, grain
  • supplements: make sure not to exceed safe upper level!
    • GI complications e.g. cramps, diarrhea

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