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Correspondence

 

Spaceflight Vol 47 July 2005; 274

 

Obesity or space flight - the heart can't see the difference

 

Sir,
    It is indeed remarkable that many of the complications of obesity on Earth [1] and those complications in space, including malabsorption [2], weight loss and anorexia [3]. predispose to several identical abnormalities of the cardiovascular system.

For example, both obesity and space flight have been shown to cause insulin resistance, increased blood vessel constrictors, clot formation, oxidative stress, and (in space animals) injury to the lining of blood vessels and heart muscle, and finally chronic inflammation [1,4,5].

   The latter has been shown in recent years to be the underlying factor responsible for atherosclerosis, which can be triggered by a magnesium deficit [5]. In the treatment of obesity, pharmaceuticals, up to now, have either not been successful or dangerous. But because our genes - probably having changed very little in the past 50, 000 years - demand it, if each individual attempted to simulate the life-style of today's primitives [6], in terms of diet restraint and sufficient exercise, obesity would be rare.

On the other hand, regarding space flight. various diets [3] and exercise countermeasures [4] have been only partially successful, and unfortunately pharmaceuticals appear to be contraindicated, except for emergencies and minor symptomatic treatment. There are at least a few reasons for this.

First. microgravity-induced malabsorption [2] can lead to unpredictable side effects and would require various parenteral medications, perhaps repeatedly throughout the day, requiring extensive laboratory guidance.

Second, there is potential impairment of liver and renal function, with inability to metabolize or excrete various drugs.

Finally there is the problem of deterioration of some pharmaceuticals in space, which may be related to excessive radiation [4],

These pharmaceutical problems in space, can potentially be offset to some extent by substituting. repeatedly during a mission, stable subcutaneous magnesium· which can now be accurately monitored - with delivery by a subcutaneous, reliable, and replenishable device. As of now, such a device has not been developed [4].

William J. Rowe MD
Virginia, USA

References

1.                               1. D.D. Christou, C.L. Gentile, CA De Souza, et al, Fatness is a better predictor of cardiovascular disease risk factor profile than aerobic fitness in healthy men, Circulation 2005: 111.

                   2. G.I. Amidon, G.A. De Brincat, N. Najib, Effects of gravity on gastric emptying, intestinal transit and drug absorption, J Clin Pharmacol 1991; 31: 968-73

3.                              3. M.S Da Silva, P,M. Zimmerman, M.M. Meguid et al, Anorexia in space and possible etiologies: an overview Nutrition 2002: 18:805-13,

4.                              4. W.J. Rowe, The case for a subcutaneous magnesium product and delivery device for space missions, J Am Coll Nutr 2004: 23:525S-528S.

5.                              5. J.A.M. Maier, C. Malpuech-Brugere, W. Zimowska, Low magnesium promotes endothelial cell dysfunction: implications for atherosclerosIs, inflammation and thrombosis Biochimica et Biophysica Acta 2004 ;1689 :13-21.

6.                              6. W.J. Rowe, Our ancestors had it right, Am J Cardiol 2000: 86:256.