Article by Ruth McKean, Sports Nutritionist

5. Micronutrient Requirements at High Altitude


Vitamins (A,B,C,D,E,K)

No convincing evidence suggests that supplementation of vitamins provides an advantage to individuals participating in prolonged treks at high altitude, provided that energy intake is adequate. However, antioxidants especially vitamin E and the energy releasing B vitamins have received some attention.

Vitamins required to release energy from food include some of the B vitamins; thiamine, riboflavin and niacin. Therefore, if basal energy needs are increased the need for these vitamins is increased. It is often assumed that the increased food intake automatically supplies the increased levels of B vitamins required for energy released. However, the theoretic increased requirements for these nutrients at high altitude nor the assumed adequacy of these B vitamins have been established.


Antioxidants

From scientific journals to fashion magazines the words "free radicals" and "antioxidants" (antioxidants quench these free radicals) are commonly cited in health scares or in improving your health. Factors that play a role in oxidative stress (increased production of free radicals) are cigarette smoking, alcohol and high altitude. High altitude exposure is thought to be associated with an increase in oxidative stress caused by increased ultra violet light, added stress of reduced oxygen particle pressure, and increased metabolic rate. Vitamin E is an antioxidant which is known to suppress oxidative damage.

In science there are tests which can be carried out to indicate the level of oxidative attacks our DNA gets per day. Such tests have been used to assess the damage caused by oxidative stress during exercise. There are many studies suggesting that strenuous physical activity cause DNA damage. In support of such findings these studies have also shown that oxidative stress leads to lowering of antioxidants in our bodies, indicating that more antioxidants are being used to overcome the increased damage caused by oxidative stress. However, if you are endurance trained it is shown that you actually increase antioxidant enzyme activity. In contrast, habitual inactivity reduces such protection and as a result it appears that frequent physical activity is necessary to maintain and promote our natural capacity to protect against the damage of oxygen stress.

Most studies have reported no beneficial effect on performance with vitamin E supplementation above what is already recommended by the Food and Nutrition Board. However, vitamin E supplementation at high altitude has shown positive effects in mountain climbers working at 5000m, there were lower levels of oxidative damage as well as a higher performance capacity. It was suggested that this positive effect may be to do with the antioxidant properties of vitamin E which may counteract the effect of increased lipid peroxidation. However there are confounding factors in this study and other studies have not conclusively proven that vitamin E intake exceeding the recommended daily level would have any beneficial effects on athletic performance.


Rich sources of vitamin E

  • Vegetable oils are the richest source natural source e.g. sunflower, olive oil
  • Unprocessed cereal & nuts are also good sources
  • Animal sources include meat

Foods rich in Antioxidant include:

  • Fruit & Vegetables
  • Tea- green and black
  • Red wine
  • Red grape juice (sorry, you can have the benefits without the alcohol!)


Minerals (calcium, copper, iron, selenium, zinc)

Except iron, there is no data to support the need for concern about other minerals at altitude.

Iron

At altitude the atmospheric pressure is lower and there is less oxygen in each breath. In response to this the body adapts by increasing the number of red blood cells from bone marrow, so the capacity of the blood to carry oxygen increases. It is for this reason that a variety elite endurance athlete's train at altitude - it improves their aerobic capacity. Repeatedly supported by the prevalence of some athletes illegal use of blood doping to increase red blood cells.

However, the availability of iron is crucial for this oxygen carrying as one function of iron is to deliver oxygen to cells and facilitate the use of oxygen by cells. The importance of adequate nutrition in the maintenance of this function at high altitude is well documented. The general consensus is that iron stores are of critical importance before prolonged exposure to altitude greater than 2500m therefore attention to iron in the diet before and during altitude exposure is important. It has even been shown that athletes with low iron stores do not benefit from training at moderate altitude.

If you think you have a low iron intake the best way to increase your iron is through food (although if you have iron deficiency or have frank anaemia, under medical advice a dose of iron through supplements is normal). Iron at large doses is toxic as it is stored in the body and supplements taken in large doses without a medial reason can be seriously detrimental to your health. Athletes often take a multivitamins with iron at the recommended nutrient intake dose set by the Food and Nutrition Board, which under normal circumstances is harmless.

Meats are an excellent source of iron which is well absorbed (haem iron). In contrast, cereals, legumes, whole grain, deep green leafy vegetables contain iron (non- haem) but are not absorbed well. The best way to increase iron is to consume red meat about 80g of lean beef three to four times a week. Poultry and fish also contain haem iron but less than red meat. Meat, poultry, fish and vitamin C enhance the absorption of plant iron sources so it is a good idea to eat a mixed meal containing both plant iron sources (non-heme) and animal (heme) food and have a small amount of fresh orange juice with your meals.

 

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