Search NASA⌕ Search

SEARCH · Search NASA

Results for “Diet”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Determinants Affecting Physical Activity Levels In Animal Models

Weight control is dependent on energy balance. Reduced energy expenditure (EE) associated with decreased physical activity is suggested to be a major underlying cause in the increasing prevalence of weight gain and obesity. Therefore, a better understanding of the biological determinants involved in the regulation of physical activity is essential. To facilitate interpretation in humans, it is helpful to consider the evidence from animal studies. This review focuses on animal studies examining the biological determinants influencing activity and potential implications to human. It appears that physical activity is influenced by a number of parameters. However, regardless of the parameter involved, body weight appears to play all underlying role in the regulation of activity. Furthermore, the regulation of activity associated with body weight appears to occur only after the animal achieves a critical weight. This suggests that activity levels are a consequence rather than a contributor to weight control. However, the existence of an inverse weight-activity relationship remains inconclusive. Confounding the results are the multi-factorial nature of physical activity and the lack of appropriate measuring devices. Furthermore, many determinants of body weight are closely interlocked making it difficult to determine whether a single, combination or interaction of factors is important for the regulation of activity. For example, diet-induced obesity, aging, lesions to tile ventral medial hypothalamus and genetics all produce hypoactivity. Providing a better understanding of the biological determinants involved in the regulation of activity has important implications for the development of strategies for the prevention of weight gain leading to obesity and subsequent morbidity and mortality in the human population.

Tou, Janet C. L.↗
NASA NTRS2002

Body Composition of Rats on NASA Rodent Foodbar Versus Purina Lab Chow

The objective of this study is to test the nutritional adequacy of the NASA Rodent Foodbar for long term use for rats. The Foodbar was tested on two rat strains, Sprague Dawley and Fischer 344. Rats were fed either Foodbar or the control diet, Purina Chow #5012. Body composition analysis was performed on a selected number of samples (n=6 for each gender and treatment group) as part of extensive testing of the Foodbar. Water, fat, ash, and protein (and their percentages) for both treatment groups were compared. Sprague Dawley Foodbar fed rats had a lower % protein than Chow fed rats (25.8% vs. 30.0%). In addition, Sprague Dawley females fed Foodbar had higher total fat (42.1g vs. 24.6g) and % fat (16.4% vs. 10.5%), but lower % water (51.3% vs. 54.8%) than Sprague Dawley females fed Chow. Fischer 344 Foodbar fed rats had a lower % water (47.4% vs. 49,3%) and total water (93.2g vs. 99.6g). In addition, Fischer 344 Foodbar males had higher % fat (17.0% vs. 13.8%) and total fat (43.0g vs. 34.7g). The data suggests that body composition of Foodbar fed rats tends to have lower water content but a higher fat content compared to controls, but not all results are the same for different strains and even different genders within the same strains. The data obtained here, in addition to other data, helps provide a better understanding of the nutritional adequacy of the Foodbar and whether the formula may need to be modified.

Yu, Diane Sau Mun↗
NASA NTRS2001

The Challenges in the Development of a Long Duration Space Mission Food System

The Advanced Food System at Johnson Space Center/NASA will be responsible for supplying food to the crew for long duration exploratory missions. These missions require development of both a Transit Food System and of a Planetary Food System. The Transit Food System will consist of pre-packaged food of extended shelf life. It will be supplemented with salad crops that will be consumed fresh. The challenge is to develop a food system with a shelf life of 3 - 5 years that will use minimal power and create minimal waste from the food packaging. The Planetary Food System will allow for food processing of crops grown on the planetary surface due to the presence of some gravitational force. Crops will be processed to final products to provide a nutritious and acceptable diet for the crew. The food system must be flexible due to crop variation, availability, and shelf life. Crew meals, based on thesc: crops, must be nutritious, high quality, safe, and contain variety. The Advanced Food System becomes a fulcrum creating the right connection from crops to crew meals while dealing with issues of integration within a closed self-regenerative system (e.g., safety, waste production, volumes, water usage, etc.).

Perchonok, Michele H.↗
NASA NTRS2001

Bioregenerative Life Support Systems Test Complex (Bio-Plex) Food Processing System: A Dual System

A Bioregenerative Life Support Test Complex, BIO-Plex, is currently being constructed at the Johnson Space Center (JSC) in Houston, TX. This facility will attempt to answer the questions involved in developing a lunar or planetary base. The Food Processing System (FPS) of the BIO-Plex is responsible for supplying food to the crew in coordination with the chosen mission scenario. Long duration space missions require development of both a Transit Food System and of a Lunar or Planetary Food System. These two systems are intrinsically different since the first one will be utilized in the transit vehicle in microgravity conditions with mostly resupplied foods, while the second will be used in conditions of partial gravity (hypogravity) to process foods from crops grown in the facility. The Transit Food System will consist of prepackaged food of extended shelf life. It will be supplemented with salad crops that will be consumed fresh. Microgravity imposes significant limitation on the ability to handle food and allows only for minimal processing. The challenge is to develop food systems similar to the International Space Station or Shuttle Food Systems but with a shelf life of 3 - 5 years. The Lunar or Planetary Food System will allow for food processing of crops due to the presence of some gravitational force (1/6 to 1/3 that of Earth). Crops such as wheat, soybean, rice, potato, peanut, and salad crops, will be processed to final products to provide a nutritious and acceptable diet for the crew. Not only are constraints imposed on the FPS from the crops (e.g., crop variation, availability, storage and shelf-life) but also significant requirements are present for the crew meals (e.g., RDA, high quality, safety, variety). The FPS becomes a fulcrum creating the right connection from crops to crew meals while dealing with issues of integration within a closed self-regenerative system (e.g., safe processing, waste production, volumes, air contaminations, water usage, etc.). Options for the first test, for duration of 120 days, currently scheduled for late 2003 are outlined.

Perchonok, Michele↗
NASA NTRS2002

Building Muscles, Keeping Muscles: Protein Turnover During Space Flight

As we age we lose muscle mass and strength. The problem is a matter of use it or lose it and more - a fact to which any active senior can attest. An imbalance in the natural cycle of protein turnover may be a contributing factor to decreased muscle mass. But the answer is not so simple, since aging is associated with changes in hormones, activity levels, nutrition, and often, disease. The human body constantly uses amino acids to build muscle protein, which then breaks down and must be replaced. When protein turnover gets out of balance, so that more protein breaks down than the body can replace, the result is muscle loss. This is not just the bane of aging, however. Severely burned people may have difficulty building new muscle long after the burned skin has been repaired. Answers to why we lose muscle mass and strength - and how doctors can fix it - may come from space. Astronauts usually eat a well-balanced diet and maintain an exercise routine to stay in top health. During long-duration flight, they exercise regularly to reduce the muscle loss that results from being in a near-weightless environment. Despite these precautions, astronauts lose muscle mass and strength during most missions. They quickly recover after returning to Earth - this is a temporary condition in an otherwise healthy population. Members of the STS-107 crew are participating in a study of the effects of space flight, hormone levels, and stress on protein turnover. When we are under stress, the body responds with a change in hormone levels. Researchers hypothesize that this stress-induced change in hormones along with the near-weightlessness might result in the body synthesizing less muscle protein, causing muscles to lose their strength and size. Astronauts, who must perform numerous duties in a confined and unusual environment, experience some stress during their flight, making them excellent candidates for testing the researchers' hypothesis.

Arny Ferrando↗
NASA NTRS2003

Recovery After Prolonged Bed-Rest Deconditioning

Recovery data were analyzed from normal healthy test subjects maintained in the horizontal or head-down body position in well-controlled bed rest (BR) studies in which adherence to the well-designed protocol was monitored. Because recovery data were almost always of secondary importance to the data collected during the BR period, there was little consistency in the recovery experimental designs regarding control factors (e.g., diet or exercise), duration, or timing of data collection. Thus, only about half of the BR studies that provided appropriate data were analyzed here. These recovery data were sorted into two groups: those from BR protocols of less than 37 days, and those from protocols greater than 36 days. There was great disparity in the unchanged responses at the end of BR in these two groups. Likewise with the variables that required more than 40 days for recovery; for example, some immune variables required more than 180 days. Knowledge of the recovery process after BR in healthy people should assist rehabilitation workers in differentiating "healthy" BR recovery responses from those of the infirmity of sick or injured patients; this should result in more appropriate and efficient health care.

Greenleaf, John E.↗
NASA NTRS2003

Measurement of nutritional status in simulated microgravity by bioelectrical impedance spectroscopy

The potential of bioelectrical impedance spectroscopy (BIS) for assessing nutritional status in spaceflight was tested in two head-down-tilt bed-rest studies. BIS-predicted extracellular water (ECW), intracellular water (ICW), and total body water (TBW) measured using knee-elbow electrode placement were compared with deuterium and bromide dilution (DIL) volumes in healthy, 19- to 45-yr-old subjects. BIS was accurate during 44 h of head-down tilt with mean differences (BIS - DIL) of 0-0.1 kg for ECW, 0.3-0.5 for ICW, and 0.4-0.6 kg for TBW (n = 28). At 44 h, BIS followed the within-individual change in body water compartments with a relative prediction error (standard error of the estimate/baseline volume) of 2.0-3.6% of water space. In the second study, BIS did not detect an acute decrease (-1.41 +/- 0.91 kg) in ICW secondary to 48 h of a protein-free, 800 kcal/day diet (n = 18). BIS's insensitivity to ICW losses may be because they were predominantly (65%) localized to the trunk and/or because there was a general failure of BIS to measure ICW independently of ECW and TBW. BIS may have potential for measuring nutritional status during spaceflight, but its limitations in precision and insensitivity to acute ICW changes warrant further validation studies.

Non-NASA Center↗
NASA NTRS2003

Effect of dietary sodium on fluid/electrolyte regulation during bed rest

BACKGROUND: A negative fluid balance during bed rest (BR) is accompanied by decreased plasma volume (PV) which contributes to cardiovascular deconditioning. HYPOTHESIS: We hypothesized that increasing dietary sodium while controlling fluid intake would increase plasma osmolality (POSM), stimulate fluid conserving hormones, and reduce fluid/electrolyte (F/E) losses during BR; conversely, decreasing dietary sodium would decrease POSM, suppress fluid conserving hormones, and increase F/E losses. METHODS: We controlled fluid intake (30 ml x kg(-1) x d(-1)) in 17 men who consumed either a 4.0 +/- 0.06 g x d(-1) (174 mmol x d(-1)) (CONT; n = 6), 1.0 +/- 0.02 g x d(-1) (43 mmol x d(-1)) (LS; n = 6), or 10.0 +/- 0.04 g x d(-1) (430 mmol x d(-1)) (HS; n = 5) sodium diet before, during, and after 21 d of 6 degrees head-down BR. PV, total body water, urine volume and osmolality, POSM, and F/E controlling hormone concentrations were measured. RESULTS: In HS subjects, plasma renin activity (-92%), plasma/urinary aldosterone (-59%; -64%), and PV (-15.0%; 6.0 ml x kg(-1); p < 0.05) decreased while plasma atrial natriuretic peptide (+34%) and urine antidiuretic hormone (+24%) increased during BR (p < 0.05) compared with CONT. In LS, plasma renin activity (+166%), plasma aldosterone (+167%), plasma antidiuretic hormone (+19%), and urinary aldosterone (+335%) increased with no change in PV compared with CONT (p < 0.05). Total body water did not change in any of the subjects. CONCLUSIONS: Contrary to our hypothesis, increasing dietary sodium while controlling fluid intake during BR resulted in a greater loss of PV compared with the CONT subjects. Reducing dietary sodium while controlling fluid intake did not alter the PV response during BR compared with CONT subjects.

Clinical Trial↗
NASA NTRS2003

Disuse exaggerates the detrimental effects of alcohol on cortical bone

BACKGROUND: Alcohol abuse is associated with an increased risk for osteoporosis. However, comorbidity factors may play an important role in the pathogenesis of alcohol-related bone fractures. Suboptimal mechanical loading of the skeleton, an established risk factor for bone loss, may occur in some alcohol abusers due to reduced physical activity, muscle atrophy, or both. The effect of alcohol consumption and reduced physical activity on bone metabolism has not been well studied. The purpose of this study was to determine whether mechanical disuse alters bone metabolism in a rat model for chronic alcohol abuse. METHODS: Alcohol was administered in the diet (35% caloric intake) of 6-month-old male rats for 4 weeks. Rats were hindlimb-unloaded the final 2 weeks of the experiment to prevent dynamic weight bearing. Afterward, cortical bone histomorphometry was evaluated at the tibia-fibula synostosis. RESULTS: At the periosteal surface of the tibial diaphysis, alcohol and hindlimb unloading independently decreased the mineralizing perimeter, mineral apposition rate, and bone formation rate. In addition, alcohol, but not hindlimb unloading, increased endocortical bone resorption. The respective detrimental effects of alcohol and hindlimb unloading to inhibit bone formation were additive; there was no interaction between the two variables. CONCLUSIONS: Reduced weight bearing accentuates the detrimental effects of alcohol on cortical bone in adult male rats by further inhibiting bone formation. This finding suggests that reduced physical activity may be a comorbidity factor for osteoporosis in alcohol abusers.

NASA Discipline Cell Biology↗
NASA NTRS2002

Smart medical systems with application to nutrition and fitness in space

Smart medical systems are being developed to allow medical treatments to address alterations in chemical and physiologic status in real time. In a smart medical system, sensor arrays assess subject status, which is interpreted by computer processors that analyze multiple inputs and recommend treatment interventions. The response of the subject to the treatment is again assessed by the sensor arrays, thus closing the loop. An early form of "smart medicine" has been practiced in space to assess nutrition. Nutrient levels are assessed with food frequency questionnaires, which are interpreted by flight surgeons to recommend inflight alterations in diet. In the future, sensor arrays will directly probe body chemistry. Near-infrared spectroscopy can be used to non-invasively measure several blood and tissue parameters that are important in the assessment of nutrition and fitness. In particular, this technology can be used to measure blood hematocrit and interstitial fluid pH. The non-invasive measurement of interstitial pH is discussed as a surrogate for blood lactate measurement for the development and real-time assessment of exercise protocols in space. Earth-based application of these sensors is also described.

NASA Discipline Life Sciences Technologies↗
NASA NTRS2002

Opportunities for nutritional amelioration of radiation-induced cellular damage

The closed environment and limited evasive capabilities inherent in space flight cause astronauts to be exposed to many potential harmful agents (chemical contaminants in the environment and cosmic radiation exposure). Current power systems used to achieve space flight are prohibitively expensive for supporting the weight requirements to fully shield astronauts from cosmic radiation. Therefore, radiation poses a major, currently unresolvable risk for astronauts, especially for long-duration space flights. The major detrimental radiation effects that are of primary concern for long-duration space flights are damage to the lens of the eye, damage to the immune system, damage to the central nervous system, and cancer. In addition to the direct damage to biological molecules in cells, radiation exposure induces oxidative damage. Many natural antioxidants, whether consumed before or after radiation exposure, are able to confer some level of radioprotection. In addition to achieving beneficial effects from long-known antioxidants such as vitamins E and C and folic acid, some protection is conferred by several recently discovered antioxidant molecules, such as flavonoids, epigallocatechin, and other polyphenols. Somewhat counterintuitive is the protection provided by diets containing elevated levels of omega-3 polyunsaturated fatty acids, considering they are thought to be prone to peroxidation. Even with the information we have at our disposal, it will be difficult to predict the types of dietary modifications that can best reduce the risk of radiation exposure to astronauts, those living on Earth, or those enduring diagnostic or therapeutic radiation exposure. Much more work must be done in humans, whether on Earth or, preferably, in space, before we are able to make concrete recommendations.

Review↗
NASA NTRS2002

Water and Energy Dietary Requirements and Endocrinology of Human Space Flight

Fluid and energy metabolism and related endocrine changes have been studied nearly from the beginning of human space flight in association with short- and long-duration flights. Fluid and electrolyte nutrition status is affected by many factors including the microgravity environment, stress, changes in body composition, diet, exercise habits, sleep cycles, and ambient temperature and humidity conditions. Space flight exposes astronauts to all these factors and consequently poses significant challenges to establishing dietary water, sodium, potassium, and energy recommendations. The purpose of this article is to review the results of ground-based and space flight research studies that have led to current water, electrolyte, and energy dietary requirements for humans during space flight and to give an overview of related endocrinologic changes that have been observed in humans during short- and long-duration space flight.

short duration↗
NASA NTRS2002

Skeletal unloading and dietary copper depletion are detrimental to bone quality of mature rats

This study was designed to examine the skeletal response to copper depletion and mechanical unloading in mature animals. In a 2 x 2 experimental design, 5.5-mo-old male Sprague-Dawley rats (n = 36) consumed either the control (AIN-93M) or Cu-depletion ((-)Cu) diet beginning 21 d before suspension and throughout the remainder of the study. Half of the rats in each dietary treatment group were either tail-suspended (TS) or kept ambulatory (AMB) for 28 d. Lower bone mineral densities (BMD) of 5th lumbar vertebra (L5) (P < 0.05) and femur were observed with (-)Cu and TS, but no differences were noted in the BMD of the humerus. Mechanical strength in the femur and vertebra decreased in response to TS, but were unaffected by copper depletion. Urinary deoxypyridinoline, an index of bone resorption, was significantly greater in TS rats, but unaltered by (-)Cu. No changes in serum or bone alkaline phosphatase activity, an indicator of bone formation, were observed. Our findings suggest that TS and (-)Cu decreased BMD in unloaded femur and vertebra but had no effect on normally loaded humerus. Bone loss with TS appeared to be related to accelerated bone resorption. Alterations in bone metabolism and bone mechanical properties in the mature skeleton resulting from (-)Cu warrant further investigation.

NASA Discipline Musculoskeletal↗
NASA NTRS1998

Insight into mechanisms of reduced orthostatic performance after exposure to microgravity: comparison of ground-based and space flight data

Since the beginning of human spaceflight, the value of understanding mechanisms of physiological adaptation to microgravity became apparent to life scientists who were interested in maintining crew health and developing countermeasures agains adverse effects of the mission. However, several characteristics associated the the logistics of spaceflight presented significant limitations to the scientific study of human adaptation to microgravity. Because space missions are so infrequent and involve minimal numbers of crewmembers, meaninful statistical analysis of data are limited. Reproducibility of results from spaceflight experiments is difficult to assess since there are few repeated space missions involving the same crewmembers. Since the emphasis of space missions is placed on operations, experiments are compromised without adequate control over various factors (e.g., time, diet, physical activities, etc.) that can impact measured responses. With the mimimal opportunity to collect spaceflight data, there is a high risk of experiments that simultaneously interfere with other experiments by the increasing demand on the crewmembers to participate in mumerous experiments proposed by multiple investigators. The technology and ability to measure physiological functions necessary to test specific hypotheses can be severely limited by physical space and power constraints of the space enviroment. Finally, technical and logistical aspects of space missions such as launch delays, extended missions, and inflight operational emergencies can significantly compromise the timing and control of experiments. These limitations have stimulated scientists to develop ground-based analogs of microgravity in an effort to investigate the effects of spaceflight on physiological function in a controlled experimental setting. The purpose of this paper is to provide a selected comparison of data collected from ground-based experiments with those obtained from spaceflight in an effort to assess the adequacy of ground analogs of actual flight for the study of human physiological adaptation to microgravity. Specifically, results from ground and spaceflight will be used to provide insight into mechanisms underlying adaptations of blood pressure regulation and reduced orthostatic performance to the microgravity environment.

Non-NASA Center↗
NASA NTRS1998

Nutrition, endocrinology, and body composition during space flight

Space flight induces endocrine changes that perturb metabolism. This altered metabolism affects both the astronauts' body composition and the nutritional requirements necessary to maintain their health. During the last 25 years, a combination of studies conducted on Skylab (the first U.S. space laboratory), U.S. Shuttle flights, and Soviet and Russian flights provides a range of data from which general conclusions about energy and protein requirements can be drawn. We have reviewed the endocrine data from those studies and related it to changes in body composition. From these data it appears that protein and energy intake of astronauts are similar to those on Earth. However, a combination of measures, including exercise, appropriate diet, and, potentially, drugs, is required to provide the muscle health needed for long duration space flight.

Flight Experiment↗
NASA NTRS1995

Evidence for gammacerane as an indicator of water column stratification

A new route for the formation of gammacerane from tetrahymanol is proposed; in addition to dehydration and hydrogenation, sulphurisation and early C-S cleavage are shown to be important in the pathway of formation, especially in marine sediments. Evidence is twofold. First, relatively large amounts of the gammacerane skeleton are sequestered in S-rich macromolecular aggregates formed by natural sulphurisation of functionalised lipids. Selective cleavage of polysulphide linkages with MeLi/MeI led to formation of 3-methylthiogammacerane, indicating that the gammacerane skeleton is primarily bound via sulphur at position 3, consistent with the idea that tetrahymanol (or the corresponding ketone) is the precursor for gammacerane. Second, upon mild artificial maturation of two sediments using hydrous pyrolysis, gammacerane is released from S-rich macromolecular aggregates by cleavage of the relatively weak C-S bonds. The stable carbon isotopic compositions of gammacerane and lipids derived from primary producers and green sulphur bacteria in both the Miocene Gessoso-solfifera and Upper Jurassic Allgau Formations indicate that gammacerane is derived from bacterivorous ciliates which were partially feeding on green sulphur bacteria. This demonstrates that anaerobic ciliates living at or below the chemocline are important sources for gammacerane, consistent with the fact that ciliates only biosynthesize tetrahymanol if their diet is deprived of sterols. This leads to the conclusion that gammacerane is an indicator for water column stratification, which solves two current enigmas in gammacerane geochemistry. Firstly, it explains why gammacerane is often found in sediments deposited under hypersaline conditions but is not necessarily restricted to this type of deposits. Secondly, it explains why lacustrine deposits may contain abundant gammacerane since most lakes in the temperate climatic zones are stratified during summer.

NASA Discipline Exobiology↗
NASA NTRS1994

Conditions and constraints of food processing in space

Requirements and constraints of food processing in space include a balanced diet, food variety, stability for storage, hardware weight and volume, plant performance, build-up of microorganisms, and waste processing. Lunar, Martian, and space station environmental conditions include variations in atmosphere, day length, temperature, gravity, magnetic field, and radiation environment. Weightlessness affects fluid behavior, heat transfer, and mass transfer. Concerns about microbial behavior include survival on Martian and lunar surfaces and in enclosed environments. Many present technologies can be adapted to meet space conditions.

NASA Discipline Life Support Systems↗
NASA NTRS1988

Cultural systems for growing potatoes in space

Higher plants are being evaluated for life support to provide needed food, oxygen and water as well as removal of carbon dioxide from the atmosphere. The successful utilization of plants in space will require the development of not only highly productive growing systems but also highly efficient bioregenerative systems. It will be necessary to recycle all inedible plant parts and all human wastes so that the entire complement of elemental compounds can be reused. Potatoes have been proposed as one of the desirable crops because they are 1) extremely productive, yielding more than 100 metric tons per hectare from field plantings, 2) the edible tubers are high in digestible starch (70%) and protein (10%) on a dry weight basis, 3) up to 80% of the total plant production is in tubers and thus edible, 4) the plants are easily propagated either from tubers or from tissue culture plantlets, 5) the tubers can be utilized with a minimum of processing, and 6) potatoes can be prepared in a variety of different forms for the human diet (Tibbitts et al., 1982). However potatoes have a growth pattern that complicates the development of growing the plants in controlled systems. Tubers are borne on underground stems that are botanically termed 'rhizomes', but in common usage termed 'stolons'. The stolons must be maintained in a dark, moist area with sufficient provision for enlargement of tubers. Stems rapidly terminate in flowers forcing extensive branching and spreading of plants so that individual plants will cover 0.2 m2 or more area. Thus the growing system must be developed to provide an area that is darkened for tuber and root growth and of sufficient size for plant spread. A system developed for growing potatoes, or any plants, in space will have certain requirements that must be met to make them a useful part of a life support system. The system must 1) be constructed of materials, and involve media, that can be reused for many successive cycles of plant growth, 2) involve a minimum quantity of media, 3) contain media that is essentially inert and not oxidize or degrade with use, 4) utilize a recirculating nutrient solution to permit regulation of pH and nutrient concentrations, and 5) be capable of complete automation of all planting, maintenance and harvesting procedures.

NASA Discipline Number 61-10↗