Clinical Nutrition Assessment of ISS Astronauts, SMO-016E (Clinical Nutrition Assessment) - 05.13.15

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Nutritional assessments of astronauts before, during, and after spaceflight ensure adequate intake of energy, protein, and vitamins during missions. Scientists use the information to understand the connections between nutrition and human health during space flight, and to develop effective dietary strategies to reduce adverse health impacts.
Science Results for Everyone
Astronauts are what they eat, too. To better understand connections between nutrition and health, researchers measured astronauts’ dietary intake, body composition, and more than 60 vitamins and minerals before, during and after spaceflight. Results showed decreases in their intake of energy, body weight, bone mineral content and density, antioxidant capacity and Vitamin D concentration. Scientists are further analyzing the data to identify and address specific effects of microgravity on nutrition and health. The data also will contribute to studies of bone loss during spaceflight and on the nutrition and bone connection, which will help those suffering bone loss on Earth.

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Experiment Details


Principal Investigator(s)

Information Pending

Information Pending

Information Pending

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits
Information Pending

ISS Expedition Duration
November 2000 - April 2007

Expeditions Assigned

Previous ISS Missions
Similar studies were completed during NASA/Mir.

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Experiment Description

Research Overview

  • The Clinical Nutritional Status Assessment measures dietary intake, body composition, protein, bone, iron, mineral, vitamin, and antioxidant status. Currently, it is a medical requirement for U.S. crewmembers on-board the ISS.

  • Blood and urine samples are collected pre and postflight from the astronauts and analyzed for over 60 diagnostic compounds, vitamins, and minerals. Weekly dietary intake and body mass are measured in-flight; these measurements are used by the crew flight surgeon to adjust the astronauts' food intake.

  • The results of data analysis are used both to understand the connections between nutrition and human health during space flight, and to develop effective dietary strategies to reduce adverse health impacts (including bone loss, loss of important vitamins and minerals, and increased genetic damage from radiation).

To provide nutritional recommendations to crew members for long-duration space travel, we need to better understand how nutritional status and general physiology are affected by the microgravity environment. Dietary intake during space flight has often been inadequate, and this can greatly compromise nutritional status. Data from both short- and long-duration space flights provide evidence that energy intake is typically 30-40% below World Health Organization recommendations, but energy expenditure is typically unchanged or even increased. This imbalance may explain some of the observed negative changes in overall nutritional status during flight. However, blood concentrations of some nutrients, such as vitamin D, continue to be low even when astronauts receive supplements during flight. The space environment itself results in physiologic changes that can alter nutritional status. For example, changes in iron metabolism are closely associated with blood chemistry alterations during space flight. Similarly, increased levels of radiation and oxidative stress during flight likely contribute to decreased antioxidant status and genetic damage during or after space flight.

There are six components to the research program.

  • The food system provides a six to ten-day menu cycle; before each mission, crew members participate in food-tasting sessions, and dietitians plan menus that will use crew choices and best fulfill the defined nutritional requirements for space flight.

  • During flight, crew members are asked to record their dietary intake once per week using a Food Frequency Questionnaire (FFQ) designed for use with the space flight food system. The FFQ is designed to obtain a near real-time estimate of intakes of energy, protein, water, sodium, calcium, and iron, as well as to collect information about vitamin supplement use and any crew comments. The questionnaire inputs from the astronauts are transmitted to the ground and results are calculated and reported to the flight surgeon within 24 to 48 hours.

  • Body mass is determined pre, post, and inflight, while body composition is determined pre and postflight using laboratory measurements.

  • Blood and urine samples are collected pre and postflight for analysis of whole blood, plasma, serum, and various analytes; blood pH and ionized calcium levels are measured inflight using finger sticks.

  • Biochemical analysis of the blood and urine samples are performed at Johnson Space Center using standard laboratory methods.

  • Statistical analysis of the analytical results is performed to detect differences in nutritional status from preflight to postflight.
Body mass and body composition analyses were performed using an X-ray absorptiometer that was equipped with a fan beam densitometer. In-flight body mass measurements require two astronauts, one to take measurements and the other to record the data. The measurements were obtained using a body-mass measuring device; this device exerts a known force on the body and measures body acceleration. Body mass was then calculated. Standard medical finger sticks and capillary tubes were used to obtain blood samples for input into an analyzer unit onboard. A single astronaut performed the blood collection and analysis procedure. The FFQ program, which was loaded on station computers, was used to input food consumption information on a weekly basis.

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Space Applications
Nutritional monitoring is vital to ensuring crew health during long-duration space flight. The results are being used to identify specific effects of microgravity on nutrient-depended processes such as vitamin uptake, antioxidant production, and metabolism of iron. Alterations to nutrient assimilation in microgravity are also important for studies of bone loss while in microgravity.

Earth Applications
Increased understanding of the connections between nutrition and bone loss has potential value for patients suffering bone loss on Earth.

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Operational Requirements
Data collection is completed on every ISS expedition as it is a requirement for medical monitoring during the flight. Body mass, FFQ, and blood sample data is downlinked on a weekly basis for review by the flight surgeon.

Operational Protocols
Astronauts use the FFQ program to record their menu choices during the week as other operational duties and tasks allow. Astronauts also include vitamin supplements (such as Vitamin D) with their daily food intake. Body mass measurements are taken each week by each US astronaut using the body-mass measuring device. Blood samples are analyzed using finger sticks and the onboard analyzer to monitor blood pH and ionized calcium levels on a weekly basis. This information is recorded and downlinked each week to the flight surgeon, who uses the information to track the nutritional status of each astronaut. If decreases in body mass or nutritional balance are noted, the flight surgeon may advise the astronaut on measures to compensate.

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Results/More Information

Results have been compiled and analyzed for International Space Station (ISS) crew members. Intake of energy (relative to World Health Organization standards) was observed to generally decrease over time during missions. However, when dietary counseling was provided to a single astronaut during flight, adequate energy intake was maintained throughout the mission. Body weight, total bone mineral content, and bone mineral density decreased during flight. Antioxidant capacity decreased during flight, leading to increased susceptibility to genetic damage from radiation. Vitamin D concentration in crew bone was decreased, and bone resorption increased, by long exposure to microgravity. The relative concentrations of other blood and urine analytes preflight and postflight were variable and subject to several confounding factors that limit conclusions as to particular effects of spaceflight (Smith, 2005, 2008). The results of this study formed the basis for the nutrition and repository experiments, currently being operated on the ISS. 

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Results Publications

    Smith SM, Zwart SR, Heer MA, Hudson EK, Shackelford LC, Morgan JL.  Men and women in space: Bone loss and kidney stone risk after long-duration spaceflight. Journal of Bone and Mineral Research. 2014 January 28; epub. DOI: 10.1002/jbmr.2185. PMID: 24470067.

    Smith SM, Heer MA, Shackelford LC, Sibonga JD, Ploutz-Snyder LL, Zwart SR.  Benefits for bone from resistance exercise and nutrition in long-duration spaceflight: Evidence from biochemistry and densitometry. Journal of Bone and Mineral Research. 2012 Sep; 27(9): 1896-1906. DOI: 10.1002/jbmr.1647.

    Smith SM, Zwart SR, Block G, Rice BL, Davis-Street JE.  The nutritional status of astronauts is altered after long-term space flight aboard the International Space Station. Journal of Nutrition. 2005; 135(3): 437-443.

    Smith SM, Zwart SR.  Nutrition issues for space exploration. Acta Astronautica. 2008; ;63: 609 - 613.: 609-613. DOI: 10.1016/j.actaastro.2008.04.010.

    Hall PS.  Past and Current Practice in Space Nutrition. Cleveland, OH: Bone Loss During Spaceflight: Etiology, Countermeasures, and Implications for Bone Health on Earth; 2007.

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Ground Based Results Publications

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ISS Patents

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Related Publications

    Smith SM, Davis-Street JE, Rice BL, Nillen JL, Gillman PL, Block G.  Nutritional status assessment in semiclosed environments: ground-based and space flight studies in humans. Journal of Nutrition. 2001; 131: 2053-2061.

    Morgan JL, Heer MA, Hargens AR, Macias BR, Hudson EK, Shackelford LC, Zwart SR, Smith SM.  Sex-specific responses of bone metabolism and renal stone risk during bed rest. Physiological Reports. 2014 August 7; 2(8): e12119-e12119. DOI: 10.14814/phy2.12119.

    Smith SM, Lane HW.  Gravity and space flight: effects on nutritional status. Current Opinions in Clinical Nutrition and Metabolic Care. 1999; 2: 335-338.

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Related Websites

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image NASA Image: ISS012E12635 - ISS Science Officer Bill McArthur during expedition 12, during check out of the SLAMMD hardware of HRF-2. Measuring the mass of a crewmember in space is difficult because mass does not equal weight in the absence of gravity.
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