The recent discovery of the skeleton of a three-foot tall adult female belonging to a new human-like species, Homo floresiensis, is exciting news to anthropologists. The new species, named after the island on which the skeleton was discovered, appears to be descended from populations of Homo erectus, the closest known relative of modern humans. The skeleton was estimated to be 18,000 years old. This means that populations of Homo floresiensis existed well after modern man appeared approximately 160,000 years ago. Thus, researchers are wondering if the two species interacted. 

The first descendents of Homo floresiensis to reach Flores Island may have been similar in size to Homo erectus. Researchers hypothesize that the small size of Homo floresiensis (only three feet tall) is due to a process known as "island dwarfing." This phenomenon  has been observed in other mammals, where local isolation, absence of predators, and small population sizes, combined with restricted resources, lead to reductions in body size and modifications in brain size. The smaller individuals with reduced energy requirements are favored by natural selection in environments where food is limited and there is no need for defense against predators. In a small population with a limited gene pool, these changes could occur quite rapidly.

This presentation provides background science and health information related to the “Food and Fitness” unit created by scientists and educators at Baylor College of Medicine’s Center for Educational Outreach. The unit covers concepts related to energy, Calories, metabolism, diet and nutrition, and is particularly appropriate for students in grades 5–8. Viewing this presentation also fulfills part of the requirements for the Virtual Workshop on Energy, Food and Nutrition (“Food and Fitness”) offered for professional development contact hours on BioEd Online.

Funding for development of the Food and Fitness unit and accompanying online professional development was provided by the National Space Biomedical Research Institute (NSBRI), a consortium of leading biomedical research centers funded by the National Aeronautics and Space Administration (NASA). Visit the following sites for more information about these organizations:

Center for Educational Outreach, Baylor College of Medicine  http://www.ccitonline.org/ceo
National Space Biomedical Research Institute  http://www.nsbri.org
National Aeronautics and Space Administration http://www.nasa.gov

PowerPoint slides were written by Nancy Moreno to compliment Roberta Andings’ presentation on Adolescent Nutrition to a Food and Fitness Teacher Education Workshop in March, 2004.

Diabetes is a disease in which levels of glucose in the blood are above normal. In type 2 diabetes, cells in the muscles, liver and fat do not use insulin (a hormone used by cells to process glucose for energy) properly. Over time, levels of glucose in the blood become higher, while cells in the body become starved for energy. Type 2 diabetes can damage nerves and blood vessels, and may lead to complications, such as heart disease, stroke, blindness, kidney disease, nerve problems, gum infections, and amputation (NIDDKD, 2004).

Risk factors for type 2 diabetes include: overweight; lack of exercise; parent, brother or sister with type 2 diabetes; African American, American Indian, Asian American, Pacific Islander, or Hispanic American/Latino family background; or blood pressure of 140/90 or higher. While more common in older adults, type 2 diabetes can develop at any age, even childhood. Weight carried in the abdomen (“apple-shaped” figure) appears to be related to a predisposition to develop type 2 diabetes. Similarly, a dark rash or ring of pigmentation on the neck or other skin creases indicates that a predisposition to type 2 diabetes may exist.

A molecule carries no net electric charge when there are as many negatively charged orbiting electrons as there are positively charged protons in its atomic nuclei. Different parts (poles) of an electrically neutral molecule can nevertheless carry a partial positive or negative charge that can attract or repel other charged structures. Such molecules are called polar molecules.

A water molecule consists of two hydrogen atoms and one oxygen atom and is electrically neutral. Water molecules are highly polar, however. Oxygen has a greater affinity for electrons than does hydrogen, so on average, the outer electrons are closer to the oxygen atom than to either of the two hydrogen atoms. The result is that the oxygen atom carries a partial negative charge and the hydrogen atoms each carry a partial positive charge.

Because opposite charges attract each other, the hydrogen atoms of a water molecule tend to "stick" to oxygen atoms on nearby water molecules. This property is called hydrogen bonding. Hydrogen bonding keeps water from spreading out when it is placed on a surface, that is, it gives water the property of surface tension. This structure of water is so stable that when something else is tossed into water it tends to separate out (that is, the water molecules separate themselves from the intruding molecules) unless the new substance contributes something "special" to the structure of water. In scientific terms, it takes free energy to disrupt the molecular structure of water or of any solvent. Therefore, if a substance is to go into solution spontaneously, it must make the structure of water even more stable.

The two key areas for countermeasures covered in this presentation are radiation-enhanced cancer and muscle wasting. Let’s start with countermeasures against muscle wasting.

To maintain muscle mass on Earth, muscle protein synthesis must equal muscle protein breakdown. This is not true in space, where protein breakdown exceeds protein synthesis, due to a number of factors, including inactivity (caused in large part by the microgravity environment), which does not place stress on the muscles. In addition, a depression in energy intake in space contributes to suboptimal nutrition and an increase in catabolic hormones, such as cortisol, as a reaction to stress. To counteract these negative effects on muscle mass and strength, it is necessary to develop countermeasures that supply optimal nutrition and appropriate exercise, and perhaps include anabolic agents.

This slide shows the protocol for the Wolfe bed rest study. Days 1-5 were the diet stabilization period in which initial measurements were made: lean leg mass (by DEXA* – Dual Energy X-Ray Absorptiometry); calf volume (by MRI); and a series of strength tests. On Day 6, the first tracer study** was done with a stable isotope to measure muscle protein synthesis. During days 7-33, subjects were in bed rest (with other samples collected and food intake controlled). Day 34 was a repeat of the tracer study done on Day 6, and Days 35-38 provided time for re-ambulation and repeats of measurements made on days 1-5. There were two groups, a placebo group and the group receiving the essential amino acid supplement.

* DEXA: a precise instrument that uses energy in the form of very small doses of X-rays to determine bone mineral density.
** Tracer studies: harmless radio isotopes are attached to specific amino acids that travel through the bloodstream. Blood samples are taken to determine the amount of amino acids that enter and leave the muscle.

There were three groups in the study. One group received amino acids only; one group received an amino acid supplement plus resistance training; and one group combined the amino acid supplement with resistance training and the optimal timing between ingestion of the supplement and initiation of the exercise. It is important to note that all subjects received only 85% of their energy requirements, in order to mimic the usual depressed energy intake of astronauts.

The exercise component consisted of one-hour sessions which used all of the major muscle groups, six days per week. Sessions focused on upper body one day and lower body the next. The exercise intensity was at an active moderate/high level.

Some of the important study outcome measures were analyses of body composition, resting energy expenditure, mid-thigh composition, and muscle strength and function. The following two slides illustrate some of our findings.

The graph on this slide illustrates the reduction in lower body strength after 28 days of bed rest. As on the previous slide, the green bar represents the group that received the amino acid suupplement only. The group represented by the yellow bar received the amino acid supplement plus resistance training; and group represented by the orange bar had a combination of the amino acid supplement, resistance training and timing. Lower body strength was reduced by 24% in the amino acid only group. Resistance training mitigated the reduction of strength, and timing further enhanced the protective effect. An important difference between this bed rest study (Tufts) and the Wolfe bed rest study was that all subjects in the Tufts study received only 85% of their daily energy requirement. The effectiveness of the amino acid supplement alone was much less in this study than was observed in the Wolfe study.

Nutrients are delivered through foods. When foods are digested, nutrients are disbursed and absorbed into all parts of the body not just our site of interest, such as muscle or the colon. Thus, we must be concerned with the effect of any single countermeasure on ALL systems, not just our system of interest. For example, some preliminary data suggest that an amino acid supplement provided to enhance muscle protein synthesis may exacerbate bone loss. Certain amino acids produce a lower metabolic pH in the body, which, in turn, can cause reabsorption of calcium from bone. This issue must be considered. In contrast, fish oil, which we have shown to protect against radiation—enhanced colon cancer, also may enhance muscle mass through an effect on decreasing protein breakdown.

The single most important overall effect of suboptimal nutrition is inadequate energy intake—not eating enough food—which is characteristic of individuals in space. Inadequate food intake results in inadequate nutrition. We saw this in the Tufts bed rest study, where energy intake was intentionally kept 15% lower than required (to mimic the intake observed in spaceflight). As we saw, under these conditions, the amino acid supplement was not effective in protecting against loss of muscle mass. The amino acids probably were being used for energy instead of protein synthesis. Finding a solution to promote adequate energy intake is an important goal of our team.