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
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.