Using Ketones as a Novel Strategy to Protect Astronauts and Pilots from Radiation

Apr 10, 2025

Aviation takes many safety precautions, but the dangers of radiation exposure are seldom considered. Invisible, radiation is not felt, poses no immediate risk, and spreads out its harmful effects. While exposure to pilots and flight attendants is less than the maximum recommended radiation levels, it is one risk factor that has been speculated.

In aviation, ionizing radiation from natural sources is considered an "occupational exposure" because of the high levels of galactic ionizing radiation at commercial cruise altitudes, according to US Federal Aviation Administration (FAA) Advisory Circular (AC) 120-61B, In-Flight Radiation Exposure. Flight crew members' exposure to ionizing radiation has increased scrutiny in recent years because it presents potential physiological challenges. The International Civil Aviation Organization (ICAO) addresses the risk of ionizing radiation exposure in its Manual of Civil Aviation Medicine (Doc 8984). In the manual, ICAO says: "In view of the fact that ionizing radiation is now assumed to play a role in the mutagenic or carcinogenic activity, any procedure involving radiation exposure is considered to entail some degree of risk." However, the radiation-induced risks associated with flying are small compared to other risks encountered in daily life.

How Much Radiation do Pilots and Passengers get, anyway?

According to the National Council on Radiation Protection and Measurements, airline employees face more radiation exposure than radiology workers or nuclear power plant engineers. Radiation exposure is measured using the Sievert, and a dose of 4 Sieverts or more at once is often fatal. A CT scan of your head is about 2 millisievert (mSv), or two-thousandths of a Sievert. For comparison with other sources, having a chest CT scan provides you with a 7 mSv dose over a period of a few minutes. The exposure for every extra-long trip across the globe is roughly equivalent to one X-ray (0.5 mSv). A pilot or flight attendant receives an annual exposure of 3 to 5 mSv — which beats out the annual doses received by other high-radiation jobs, such as X-ray technicians and nuclear power workers. Only astronauts are more exposed; ten days in space delivers about 4.3 mSv to the skin alone, which is about 4.3 years' worth of cosmic radiation on earth's surface. In one year, the maximum permitted dose for a radiation worker under US Federal law is 50 mSv.

For more comparisons of radiation doses, see https://xkcd.com/radiation/

They will receive less radiation on a lower-altitude flight because of the greater radiation shielding provided by the earth's magnetic field. This shielding is most significant near the equator and gradually decreases to zero as one goes north or south. Galactic cosmic radiation levels over the polar regions are about twice those over the geomagnetic equator at the same altitudes.

Ultraviolet (UV) Rays

The farther you ascend into the earth's atmosphere, the more exposure to the sun's UV rays. One study measuring UV radiation in a turboprop airplane pilot seat found that flying for under an hour at 30,000 feet had the same UV-A carcinogenic radiation exposure as a 20-minute tanning bed session. Other potential skin cancer risk factors include frequent disruption of one's circadian rhythm, which is the human body's 24-hour internal clock. This disruption can occur because of jet lag, crossing time zones, and irregular work schedules.

Pilots are also exposed to UV radiation. Although UV radiation is non-ionizing, UV radiation causes sunburns and skin cancer. In Australia, skin cancer is common, with data showing almost a million cases of skin cancer in 2015. Skin cancer is primarily caused by excessive exposure to ultraviolet (UV) radiation from the sun, causing DNA damage to skin cells. Failure to correct this damage by the body's internal DNA repair machinery can cause faulty cell replication, triggering the abnormal growth of cells, which eventually become cancers. People with pale skin types are more vulnerable to skin cancer. The greater the sun exposure, the greater the intensity of the UV radiation and the higher their risk.

Airplane windshields allow ultraviolet (UV) radiation to enter the cockpit, giving pilots a dose similar to dangerous levels found in tanning beds. The greater UV-A radiation exposure in the cockpit results from the design of the airplane's windshield. Tests have shown that plastic and glass windshields can block most UV-B radiation but only 50 percent of UV-A radiation. This puts the crew at risk of developing melanoma, the most severe form of skin cancer. According to a study in JAMA Dermatology, published by the American Medical Association, flight crews have twice the incidence of melanoma compared with the general population. But much is still unknown about why.

Polar Routes

Pilots flying polar routes receive more cosmic radiation. The planet's magnetic field helps to minimize radiation for most latitudes, but that shield dissipates at the extreme north and south poles. In the most extreme examples, planes caught over the poles in a solar storm could see radiation levels spike up to 10 mSv for a single flight, like exposure in outer space. The nature of the hazard is invisible, so it's easy to forget about. The US has far fewer regulations than Europe for protecting flight crews from radiation. Pilots need more training to help them consider radiation in their flight planning and altitude choices.

Polar routes aren't new, of course. The Swedish airline SAS AB completed the first trans-Arctic commercial flight in 1952, followed by a regularly scheduled "Polar shortcut" route two years later, linking Copenhagen and Los Angeles. United Airlines inaugurated a Chicago-Hong Kong nonstop polar route in 2001, but only during summer months when winds were more favorable. Air France Supersonic jets routinely measured radiation levels on their flights. Forecasting a higher radiation risk for these routes would allow commercial airlines to warn pilots to reroute planes to lower altitudes to decrease the risk of long-term exposure to radiation for their crews, who fly the same route repeatedly. An NOAA weather satellite launched on March 1, GOES-17, is expected to increase the fidelity of space weather forecasts. A sensor developed at the University of New Hampshire monitors the level of energetic ions, the primary radiation source.

Understanding how radiation causes damage to cells

A double-edged sword is the best description for the status of ionizing radiation. It is harmful to health from its role as a carcinogen. However, it is beneficial for use in both diagnostic and therapeutic medical applications. Radiation has long damaged biological tissues and cells. In the cells, radiation deposits energy as ionized and excited atoms or molecules distributed at random throughout the cells. The ionizations cause chemical changes in the exposed area, producing highly unstable charged or "ionized" molecules. These rapidly undergo chemical changes, producing free radicals that react with cellular components such as DNA and lead to permanent damage. An immediate consequence of DNA damage from radiation is triggering programmed cell death or apoptosis. A sufficiently high dose of radiation will inhibit cell division, which is how radiation kills cells.

Tissue damage from radiation results from the interaction between high energy radiation with water in single electron oxidation of water to form oxygen radicals, or superoxide (O2 −). The terminal destructor of oxygen radicals (antioxidants) is glutathione, which is present in most cells at concentrations of 5 mM and handles the maintenance of the intracellular sulfhydryl groups in the reduced — SH form. Glutathione is maintained in the reduced state by a near-equilibrium reaction with the cytosolic └NADP+┘/└NADPH┘ couple, the most reduced redox pair in the cell with a very negative redox potential of 0.42V.

Besides ionizing radiation, it can form free radicals in the mitochondria via the non-enzymatic reaction of the free radical co-enzyme Q semiquinone. The amount of Q semiquinone is decreased by the metabolism of ketone bodies, thus decreasing the formation of free radicals. The metabolism of ketones also reduces the free cytosolic └NADP+┘/└NADPH┘ ratio's redox potential, thus reducing the GSH couple's potential, facilitating the terminal destruction of oxygen free radicals.

Radiation Poisoning: Also called radiation sickness or acute radiation syndrome, radiation poisoning involves damage to biological tissue because of excessive exposure to ionizing radiation. The term refers to acute problems caused by a large dosage of radiation in a short period, though this also has occurred with long-term exposure to low-level radiation. Many of the symptoms of radiation poisoning result from ionizing radiation interference with cell division. Beneficially, this same interference enables the treatment of cancer cells; such cells are among the fastest dividing in the body.

Symptoms of radiation poisoning include a reduction of red and white blood cell count, decreased immune function (with increased susceptibility to infection), nausea and vomiting, fatigue, sterility, hair loss, tissue burns and necrosis, gastrointestinal damage accompanied by internal bleeding, and so forth.

Radioprotective agents

A radioprotective agent is anything that can decrease the harmful effects of radiation on the cells and tissue before or after exposure. Multitudes of substances have been used to mitigate the adverse effects of radiation. Most efforts at radioprotection have been centered on antioxidants such as thiols, glutathione and prevention of hypoxia.

Vitamins E and C, glutathione, even honeybee venom.

Ketones and radiation

A ketogenic diet can mitigate the damage from radiation exposure

Ketones are naturally produced in the body and act as radioprotective agents that can minimize or prevent the damage from solar radiation exposure experienced by astronauts, pilots, and other flight personnel. Scientists have discovered that ketones can protect cells and tissues from ionizing radiation. The development of effective radio protectant molecules is of great importance in reducing tissue damage following intentional or accidental radiation exposure. This discovery can also increase the therapeutic efficacy of radiation therapies by protecting non-target tissues from incidental radiation damage.

Humans can make ketone bodies (beta-hydroxy-butyrate or BHB) from the liver or consume them exogenously. The body produces ketones naturally while consuming a low-carbohydrate diet or fasting. For humans, plasma β-hydroxybutyrate levels range from 0.2 to 0.5 mmol/L but levels can reach 5 to 7 mmol/L during fasting. A level of 5.5 mmol/L can also be achieved by repeated KE ingestion (three daily doses of 714 mg/kg of body weight for 5 days) which has been described as well tolerated. Ketone levels from 10 to 20 mmol/L are observed in subjects suffering from diabetes and, they are considered pathological.

It is estimated that humans who practice a well-formulated ketogenic diet can produce between 100 and 150 grams of ketones per day. It takes weeks to months to maintain a ketogenic lifestyle to produce this level of ketones. Most people find that limiting carbohydrates to 20 o 50 grams a day will keep the body in a state of nutritional ketosis.

Exogenous ketones - Ketone Esters and salts

Ketones esters are produced synthetically as a fermentation process from two natural products via an enzymatic reaction of D-BHB free acid and R 1, 3 butanediol."

Ketone esters and salts are synthetically made BHB molecules that will pass enter the body through the gastrointestinal (GI) system and raise the level of BHB in the blood. Ketone salts are BHB molecules attached to sodium, magnesium, potassium, or calcium and raise blood BHB levels, especially with a low or ketogenic diet. However, ketone salts are sometimes poorly tolerated and can cause GI side effects.

Ketone esters are synthetically made oligomers of hydroxybutyrate that will cause a potent increase in blood BHB levels. Ketone esters are more potent than ketone salts in raising blood BHB levels. National Institutes of Health (NIH) scientists have discovered that ketone esters can reduce tissue damage if they are administered before or after radiation exposure. Ketone esters can minimize, reduce and prevent tissue damage following intentional and accidental radiation exposure, and increase the therapeutic efficacy of radiation therapies by protecting non-target tissue from incidental radiation damage.

The surprising finding that the metabolism of ketone bodies decreases radiation damage to living tissue is just beginning to be understood. The concept of radioprotection is in its infancy and is very important, especially as we live longer in outer space and travel to other planets such as Mars. We can achieve protecting tissue and cells from damage caused by radiation exposure through both natural and exogenous methods. The paper written by Bill Curtis and colleagues suggests that the concentration of blood BHB to protect cells from doses of radiation is in the 3 mM range. Achieving this concentration or state of ketosis is quickly done with fasting for most individuals. However, consuming food and other life events can make it challenging to maintain such a concentration of ketones in the blood. The best way to achieve an effective concentration is likely to combine a ketogenic diet, fasting, and exogenous ketones.

Johnathan Edwards MD Substack

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