Amounts of available O2 and nitrogen (N2) per unit volume of air decrease with altitude. So, at 3500 m, there's 12 per cent of O2 whereas, at 5800 m, there's only 10 per cent. These changes have various metabolic effects in the body that may help patients with diabetes.
In its free state, nitric oxide (NO) is highly reactive (readily becoming damaging free radicals) but, in blood and tissues, NO is bound into complexes that make it easier to transport and store. Now, it appears that NO stores formed by nitrites can sequester excess free NO after its overproduction and, yet, serve as an additional NO source should it be deficient.
As mammals adapt to intermittent hypoxia by storing NO, the buildup and breakdown of NO stores might help prevent vascular disorders associated with either too much or too little NO. Indeed, there's growing evidence-albeit in animal studies so far-that NO is pivotal in the adaptation to intermittent hypoxia and its protective effects (Exp Biol Med, 2006; 231: 343-65; Adv Exp Med Biol, 2006; 578: 35-40).
This may help to protect against the all-too-common vascular complications of diabetes, especially in the feet. Similarly, IHT could also help to avoid diabetic retinopathy, which often leads to blindness in poorly controlled diabetes, and diabetes-related kidney disease.
These are chemical compounds that modify or transmit nerve impulses, but their production is rationed by specific rate-limiting enzymes. Chronic uncontrolled intermittent hypoxia (CUIH), such as apnoea, causes neurotrans-mitter changes by impacting on rate-limiting enzymes (Biochim Biophys Acta, 1987; 928: 56-62; Respir Physiol, 1995; 101: 219-30). This may help to protect against diabetic polyneuritis and other sensory and/or motor disturbances in the peripheral nervous system. IHT at the correct strength, dose, frequency and treatment intervals, as deter-mined by a trained IHT practitioner, may be able to beneficially modulate the hypoxic effect on the neurotransmitters associated with sensory and motor nerves.
Overweight and obesity
Just as high-altitude training improves performance in elite athletes (Med Sci Sports Exerc, 2007; 39: 1610-24), so can IHT coupled with exercise help to regulate glucose metabolism (Annu Rev Cell Dev Biol, 1999; 15: 551-78; FASEB J, 2005; 19: 1009-11). In obese subjects, exercise training together with IHT can improve levels of physical fitness, metabolic risk markers and body composition-and at substantially lower work-loads, as the obese often cannot cope with the same workload as can healthy, non-obese individuals. Also, the reduced mechanical stress on the joints is particularly welcome in obese patients with orthopaedic conditions (Obesity, 2009, 18: 116-20; J Appl Physiol, 2001; 91: 173-82; Eur J Appl Physiol Occup Physiol, 1988; 57: 203-9).
IHT with exercise may even reduce patients' appetite. This is because IHT targets the genes involved in oxygen transport, glycolysis, glucose transport and satiety, hence its appetite-suppressing effect (FASEB J, 2002; 16: 1151-62). Nevertheless, these effects of IHT require further study.
'Living low, training high' is the motto of many London athletes, who train at places with an altitude of around 1800 m above sea level because they know that this leads to moderate hypoxia that can improve their endurance and performance (Eur J Appl Physiol Occup Physiol, 1988; 57: 203-9; Exp Physiol, 2003; 88: 109-19). Indeed, the Haldane-Bohr effect refers to the fact that O2 and CO2 destabilize each other's capacity to bind haemoglobin. When O2 pressure is high, as at sea level, the blood releases its O2 more readily. In contrast, at high altitudes, the lower O2 pressure allows the body to retain more CO2.
CO2, produced in cells, releases O2 into tissues, relaxes blood vessels, prevents oedema (reverses fluid retention), eliminates ammonia and increases the efficiency of O2-based energy production. This means that IHT could also reduce the lassitude and fatigue that's often seen in type 2 diabetic patients (Nat Genet, 2003; 34: 267-73; N Engl J Med, 2004; 350: 664-71).
Other reported benefits of IHT include fewer headaches, less breathlessness, less insomnia and fatigue, fewer unpleasant sensations and improved mood (Kononenko TA et al. 'Hypoxytherapy in conditions of above Arctic Circle', in Intermittent Normobaric Hypoxytherapy. Moscow, 1997: 145-53).
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