Nutrition and Health in Space
As we approach the year 2001, many more people will be traveling in space. Does this pose a threat to their health? The biggest concern is that relatively little information has been gathered on the subject because there has not be large enough numbers of space travelers for a long enough time. In many ways, today's astronauts are part of the experiment of space travel. One thing we do know: travelling to Mars and back is not something a human can survive due to the stress of space, with the lack of gravity being the main factor. A 1994 edition of Nutrition Reviews (Volume 50 Number 1) examines some of the common nutritional problems encountered with space travel.
One of the most common problems with space travel is the gross loss of body mass. This despite proper intake of food and water. Fluid loss as high as 13%, which is quite significant loss, is not uncommon. Another problem is loss of bone mass. This problem is directly related to duration of the flight, with longer trips producing as much as 20% bone loss. In addition to bone, weight loss is augmented by muscle atrophy. The deterioration of muscles in the legs is most common, but that loss is mirrored throughout the body. This problem exists despite sufficient protein intake and exercise, with some flights providing for several hours of daily work outs. Although there is a shift to utilizing more carbohydrates (over fats) for energy in space, there is relatively little change in fat mass during flights.
In general, the stress of space travel creates metabolic problems on the human (and animal) body. Among the changes seen are an increase in blood sugar and lactic acid levels. Also, there is a continual decrease in red blood cell mass. In addition to the above problems encountered in space travel, the sealed space craft exposes the human body to potentially toxic gases. By far, the primary problem in space travel is radiation. The main type encountered is cosmic (or galactic) radiation.
Many problems encountered in space are improved corrected once the astronaut is back on earth. However some problems persist, especially when changes take place in the delicate brain and nervous system. These areas, when damaged, tend to be irreversible.