Avodah Zarah 3b ~ Heliotherapy

The first few pages of the new tractate we are learning, Avodah Zarah addresses the punishment that awaits those wicked nations that persecuted the Jewish people.  Then comes this parable:

עבודה זרה  ג,ב–ד,א 

דאמר רבי שמעון בן לקיש אין גיהנם לעתיד לבא אלא הקדוש ברוך הוא מוציא חמה מנרתיקה  ומקדיר. רשעים נידונין בה וצדיקים מתרפאין בה. רשעים נידונין בה... צדיקים מתרפאין בה  דכתיב וזרחה לכם יראי שמי שמש צדקה ומרפא בכנפיה אלא שמתעדנין בה שנאמר ויצאתם ופשתם כעגלי מרבק

As Rabbi Shimon ben Lakish says: There is no Gehenna in the World-to-Come. Rather, the Holy One, Blessed be He, will remove the sun from its sheath [minnarteikah], and heats [umakdir]that world with it. The wicked will be punished by it and consumed by the heat, but the righteous will be healed by it....moreover, not only will they be healed by it, but they will even be rejuvenated by it, as it is stated in the continuation of that verse (Malachi 3:20) “And you shall go forth and leap as calves of the stall.”

Other mentions of the sun as medicine

We met the same homily in the name of Resh Lakish when we studied Nedarim 8b. Elsewhere (Bava Basra 16b) we read a teaching of Abaye that also addresses the healing power of the sun:

בבא בתרא טז, ב

רבי שמעון בן יוחי אומר אבן טובה היתה תלויה בצוארו של אברהם אבינו שכל חולה הרואה אותו מיד מתרפא ובשעה שנפטר אברהם אבינו מן העולם תלאה הקדוש ברוך הוא בגלגל חמה אמר אביי היינו דאמרי אינשי אידלי יומא אידלי קצירא

Rabbi Shimon ben Yochai said: there was a precious stone that hung from the neck of Abraham our forefather. Any sick person who looked at it was instantly cured.  When Abraham our forefather died, the Holy One, Blessed be He, hung this stone in the orb of the sun. Abaye said, this is what is meant by the popular saying "when the sun is lifted, sickness is lifted"

We know not to take homilies literally, but it turns out that Resh Lakish (c.200 CE) and Abaye (d~339 CE) were on to something when they taught that the sun heals.   

A History of Heliotherapy

In 1903, the Nobel prize for Medicine was awarded to a Dane named Niels Finsen. Finsen had invented a focusable carbon-arc torch to treat – and cure – patients with lupus vulgaris, a painful skin infection caused by tuberculosis.  While this was the start of the modern medical use of phototherapy, using the sun as a source of healing is much, much older. Older even than the Talmud, which mentions it in today’s daf. 

“The Nobel Prize in Physiology or Medicine 1903 was awarded to Niels Ryberg Finsen “in recognition of his contribution to the treatment of diseases...with concentrated light radiation, whereby he has opened a new avenue for medical science”.”

Perhaps the earliest reference to heliotherapy – that is, using sunlight to heal - is found in Egyptian papyrus records from over 3,500 years ago, which record using the sun, together with ingesting a local weed, to treat skin conditions. The active ingredients of that weed, Ammi majus, were isolated in 1947. These ingredients, together with heliotherapy, were used in the first clinical trials to treat vitiligo, which were conducted, rather fittingly, in Egypt.  Further work determined that it was only a narrow part of the sun’s spectrum that was needed to treat vitiligo, psoriasis, and other skin conditions, and so lamps were developed that produced only narrow band ultraviolet light (UVB). These UVB lamps are now a mainstay of treatment for psoriasis. 

Sunlight for Healthy Bones

“For most white people, a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU (1.25 mg) vitamin D into the circulation within 24 hours of exposure”

— Environmental Health Perspectives 2008:116;4. A162

But ultraviolet light – UVB – can also be extremely dangerous. Too much exposure to sunlight will cause skin cancer, as the light produces molecules that directly damage DNA. Here is the great paradox of sunlight – too much of it will burn and can kill – but get the dose right and it is not only curative, but essential for healthy living. Sunlight is needed to produce vitamin D in the skin, and vitamin D is needed to produce healthy bones. Without it, you will develop rickets, a skeletal deformity that is characterized by bowed legs. 

Typical presentation of 2 children with rickets. The child in the middle is normal; the children on both sides have severe muscle weakness and bone deformities, including bowed legs (right) and knock knees (left). From Holick M. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr 2004;80(suppl):1678S–88S.

Sunlight for a Healthy Immune System

The sun’s light has been shown to have effect the immune system, although many of these effects are only poorly understood. 

When some nerve fibres are exposed to sunlight, they release a chemical called neuropeptide substance P. This chemical seems to produce local immune suppression.  Exposure to the ultraviolet wavelengths in sunlight can change the regulation of T cells in the body which can also modulate autoimmune diseases.

Sunlight to Treat Melanoma?

While sunlight can cause skin cancer, it has been shown to release a hormone called alpha melanocyte-stimulating hormone. This hormone appears to limit the damage to DNA damage from sunlight and so may actually reduce the risk of melanoma (but don't try this as a treatment yet. It's certainly not ready for prime time.)

Sunlight for Your Mood

Then there’s sunlight for your mood. Seasonal affective disorder – SAD – is caused by a lack of exposure to sunlight, which most affects those living in the northern latitudes in the winter.  SAD was first described in 1984 by Norman Rosenthal working at the National Institute of Mental Health but why it happens is still something of a mystery.  Rosenthal went on to write several best selling books on SAD and how to beat it. The answer appears to be something to do with sitting in front of a lamp that mimics sunlight (but the evidence that this works is still controversial).

 Sunlight for Babies with Jaundice

Sunlight is also a great treatment for babies with neonatal jaundice. This condition is very common and is caused when the baby breaks down the fetal hemoglobin with which it was born. A product of that breakdown is bilirubin, and if this is allowed to build up in the tissues it can cause lethargy, difficultly feeding, and in rare and extreme cases, brain damage. However, sunlight (or more precisely, the blue band of the spectrum at 459nm)  breaks down this dangerous bilirubin molecule into a harmless one called biliverdin.  So the best treatment for a newborn baby with mild jaundice is to put them out in the sun.  (Failing that, or if the degree of jaundice is not mild, you can consider phototherapy in the hospital.) 

The absorbance spectrum of bilirubin bound to human serum albumin (white line) is shown superimposed on the spectrum of visible light. Clearly, blue light is most effective for phototherapy, but because the transmittance of skin increases with increasing wavelength, the best wavelengths to use are probably in the range of 460 to 490 nm. Term and near-term infants should be treated in a bassinet, not an incubator, to allow the light source to be brought to within 10 to 15 cm of the infant (except when halogen or tungsten lights are used), increasing irradiance and efficacy. For intensive phototherapy, an auxiliary light source (fiber-optic pad, light-emitting diode [LED] mattress, or special blue fluorescent tubes) can be placed below the infant or bassinet. If the infant is in an incubator, the light rays should be perpendicular to the surface of the incubator in order to minimize loss of efficacy due to reflectance. From Maisels and McDonagh. Phototherapy for Neonatal Jaundice. New England Journal of Medicine 2008.358;920-928.

Sunlight for Infectious Diseases

 We don't treat infectious diseases with sunlight any more. But it wasn't always that way. Less than eighty years ago sunlight was recommended as a therapy for some patients with tuberculosis. The authors, writing in the journal Diseases of the Chest were cautious:

Even in those cases where the sun can be of great value, it is in no sense a specific cure for any manifestation of tuberculosis. Rest, good food, and fresh air, are still the fundamentals in treating all forms of the disease; and the sun, where it should be used, is only a valuable adjutant...Heliotherapy is not indicated in all cases of tuberculosis. The majority of patients with this disease should never use it...It is not a sure cure for any type of tuberculosis, but is often, especially in some of the extrapulmonary cases, a very valuable—or even necessary—aid.

In today's daf, Resh Lakish taught that sun can both reward and punish. His insight was more correct than he could ever have imagined.  

“Bright light therapy and the broader realm of chronotherapy remain underappreciated and underutilized, despite their empirical support. Efficacy extends beyond seasonal affective disorder and includes nonseasonal depression and sleep disorders, with emerging evidence for a role in treating attention-deficit/hyperactivity disorder, delirium, and dementia.”

— Schwartz and Olds. The Psychiatry of Light. Harvard Review of Psychiatry 2015. 23 (3); 188.

[Mostly a repost from Bava Basra 16 and Nedarim 8.]

Bava Basra 84a ~ What Color is the Sun?

We are studying the tractate Bava Basrsa (The Last Gate), which is currently dealing with the circumstances under which the sale of goods may be voided.  The Mishnah (83b) ruled that if there is agreement to sell red wheat (שחמתית) and it was found to be white (לבנה), both the seller and the buyer have legal grounds to retract. The Talmud then discusses the names for these colors: what we call red and white are called "like the sun" and "like the moon." Rav Pappa (the Babylonian sage who died in 375CE) took this a step further:

בבא בתרא פד, א

שחמתית ונמצאת לבנה כו': אמר רב פפא מדקתני לבנה ש"מ האי שמשא סומקתי היא תדע  דקא סמקא צפרא ופניא והאי דלא קא חזינן כוליה יומא נהורין הוא דלא ברי

Rav Pappa said: From the fact that the Mishnah refers to one type of wheat as white, we should conclude from this that the sun is red, not white. We know that this is the case, because the sun is red in the morning and in the evening. The reason that we do not see the red color all day is because our eyesight is not strong and we cannot discern the redness of the sun.

Shmuel ben Meir, known as Rashbam (d. ~1158) explained that "our eyes are not able to discern the colors very well because in the middle of the day the light is blinding. But in the morning and the evening, when the sun is less bright, we can see the redness of the sun."

 מאור עינינו אינו ברור כל כך מתוך אור היום שמכהה עינינו אבל צפרא ופניא שהיום חשוך ניכר אדמומית החמה ורב פפא לפרש משנתנו בא אמאי מקרי שחמתית

According to Rav Pappa, the true color of the sun is red - but this true color can be seen only when the sun is at its least intense - in the evening and the morning. We have all experienced Rav Pappa's description: who cannot be moved by the sight of a blazing red sunrise or sunset? But what is the scientific explanation of these colors?

The Color of the Sun in Space, and on Earth

According to NASA experts (who really are rocket scientists, among other things), the sun emits all colors of the visible light spectrum. And when you mix all these colors together you get...white. If you were to look at the sun from high in space, (perhaps aboard the International Space Station), it would indeed appear to be a pure white.  Like this:

Courtesy of NASA.

It was in the seventeenth century that Isaac Newton used a prism to split the sun's light into its constituent colors. Before then it was raindrops that did the same thing, forming a rainbow as a result.

Isaac Newton divided  a ray of sunlight with a prism in a series of experiements published in 1672.  Lego recreation is from here.

The white light of the sun changes as it passes through our atmosphere, which absorbs and scatters much of the shorter wavelength blue light. (That is why the sky is blue, whatever else your dad may have told you.) However the longer wavelength red light is not absorbed, and passes pretty much unchanged.  So we see the sun as more red than blue.  This effect is especially apparent at sunrise and sunset, when in order to reach our eyes, the sunlight has to pass through more of our atmosphere. More of the shorter wavelength blue light is then absorbed, leaving even more of that longer wavelength red light. And as a result, we see those glorious red sunsets (and for those who can get up early enough, red sunrises too).

“Here on Earth, the atmosphere plays a role in the color of the sun. Since shorter wavelength blue light is scattered more efficiently than longer wavelength red light, we lose some of the blue tint of the sun as sunlight passes through the atmosphere. In addition, all wavelengths of visible light passing through our atmosphere are attenuated so that the light that reaches our eyes does not immediately saturate the cone receptors. This allows the brain to perceive color from the image with a little less blue – yellow. ”

— NASA

The Cultural determinants of the Sun's Color

On their website, the NASA scientists claim that "sometimes the display color of the Sun is culturally determined. If a kindergartener in the USA colors a picture of the Sun, they will usually make it yellow. However, a kindergartener in Japan would normally color it red!"  The rabbis of the Talmud had their own cultural explanation of the colors of the sun.  After later suggesting that the color of the sun may actually be white (because that is the color of a patch of skin with zora'at, usually identified as a kind of leprosy), the Talmud then explains the cause of the red sunrises and sunsets:  

ולמאי דסליק דעתין מעיקרא הא קא סמקא צפרא ופניא בצפרא דחלפא אבי וורדי דגן עדן בפניא דחלפא אפתחא דגיהנם

In the morning it becomes red as it passes over the site of the roses of the Garden of Eden, whose reflections give the light a red hue. In the evening the sun turns red because it passes over the entrance of Gehenna, whose fires redden the light...

Without the scientific understanding we have today, the Talmud claimed that the red color of sunrise and sunset was due to the light filtering though the red roses of the Garden of Eden, and fires of Hell.

is the Garden of Eden real or metaphorical?

It would seem that the Talmud's description of the locations of the Garden of Eden and the Gates of Hell is to be taken literally, for it is given as an explanation for physical phenomena.  But here is where things can get tricky. The famous rabbi Joseph Hayyim of Baghdad (1834–1909) wrote a work that is widely read by Sephardic Jews to this day called Ben Ish Hai. He also  published three volumes of responsa between 1901 and 1905 called Rav Pe’alim. (A fourth volume was posthumously published in 1912.) In an undated question, R. Hayyim was asked about the location of the Garden of Eden. In one tradition, the garden was located “on the other side of the world,” somewhere below the equator in the southern hemisphere. However, the questioner continued, the world has been circumnavigated, and the Garden of Eden has not been identified. Where then is it located?

In his answer, R. Hayyim digressed into the truth claims of science, and then returned to the location of the Garden of Eden. He noted that although it may be located on the Earth itself, it existed on a different spiritual plane and would therefore not be perceived by the human senses. I suppose many moderns would agree with the suggestion that the Garden of Eden is not to be found in a geographic location. But today's page of Talmud reminds us that at least in talmudic Babylon, the Garden of Eden was not just a metaphor.  It determined the very colors of the sun.

Bava Basra 16b ~ Here Comes the Sun

בבא בתרא טז, ב 

רבי שמעון בן יוחי אומר אבן טובה היתה תלויה בצוארו של אברהם אבינו שכל חולה הרואה אותו מיד מתרפא ובשעה שנפטר אברהם אבינו מן העולם תלאה הקדוש ברוך הוא בגלגל חמה אמר אביי היינו דאמרי אינשי אידלי יומא אידלי קצירא

Rabbi Shimon ben Yochai said: there was a precious stone that hung from the neck of Abraham our forefather. Any sick person who looked at it was instantly cured.  When Abraham our forefather died, the Holy One, Blessed be He, hung this stone in the orb of the sun. Abaye said, this is what is meant by the popular saying "when the sun is lifted, sickness is lifted"

Abaye, the great Babylonian sage of the fourth century, commented on a statement made Rabbi Shimon ben Yochai about two centuries earlier, and suggested that sunlight helps heal.  This was not the only time Abaye opined about the health benefits of sunlight. We came across another example when we studied Nedarim: 

נדרים  ח, ב

שמש צדקה ומרפא אמר אביי ש"מ חרגא דיומא מסי ופליגא דר"ש בן לקיש דאמר אין גיהנם לעולם הבא אלא הקב"ה מוציא חמה מנרתיקה צדיקים מתרפאין בה ורשעים נידונין בה

“The sun of righteousness, with healing in its rays” (Malachi 3:20)...Abaye said: “We learn from here that the dust of the sun heals”…Rabbi Shimon ben Gamliel said, “there is no hell in the world to come. Rather God takes the sun out of its canopy; the righteous are healed by it and the wicked are punished by it” (Nedarim 8b.)

A HISTORY OF HELIOTHERAPY

In 1903, the Nobel prize for Medicine was awarded to a Dane named Niels Finsen. Finsen had invented a focusable carbon-arc torch to treat – and cure – patients with lupus vulgaris, a painful skin infection caused by tuberculosis.  While this was the start of the modern medical use of phototherapy, using the sun as a source of healing is much, much older. Older even than the Talmud, which mentions it in today’s daf. 

“The Nobel Prize in Physiology or Medicine 1903 was awarded to Niels Ryberg Finsen “in recognition of his contribution to the treatment of diseases...with concentrated light radiation, whereby he has opened a new avenue for medical science”

Perhaps the earliest reference to heliotherapy – that is, using sunlight to heal - is found in Egyptian papyrus records from over 3,500 years ago, which record using the sun, together with ingesting a local weed, to treat skin conditions. The active ingredients of that weed, Ammi majus, were isolated in 1947. These ingredients, together with heliotherapy, were used in the first clinical trials to treat vitiligo, which were conducted, rather fittingly, in Egypt.  Further work determined that it was only a narrow part of the sun’s spectrum that was needed to treat vitiligo, psoriasis, and other skin conditions, and so lamps were developed that produced only narrow band ultraviolet light (UVB). These UVB lamps are now a mainstay of treatment for psoriasis.

“For most white people, a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU (1.25 mg) vitamin D into the circulation within 24 hours of exposure”

— — Environmental Health Perspectives 2008:116;4. A162

SUNLIGHT FOR HEALTHY BONES

But ultraviolet light – UVB – can also be extremely dangerous. Too much exposure to sunlight will cause skin cancer, as the light produces molecules that directly damage DNA. Here is the great paradox of sunlight – too much of it will burn and can kill – but get the dose right and it is not only curative, but essential for healthy living. Sunlight is needed to produce vitamin D in the skin, and vitamin D is needed to produce healthy bones. Without it, you will develop rickets, a skeletal deformity that is characterized by bowed legs. 

Typical presentation of 2 children with rickets. The child in the middle is normal; the children on both sides have severe muscle weakness and bone deformities, including bowed legs (right) and knock knees (left). From Holick M. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr 2004;80(suppl):1678S–88S.

SUNLIGHT FOR A HEALTHY IMMUNE SYSTEM

The sun’s light has been shown to have effect the immune system, although many of these effects are only poorly understood. 

When some nerve fibres are exposed to sunlight, they release a chemical called neuropeptide substance P. This chemical seems to produce local immune suppression.  Exposure to the ultraviolet wavelengths in sunlight can change the regulation of T cells in the body which can also modulate autoimmune diseases.

SUNLIGHT TO TREAT MELANOMA?

While sunlight can cause skin cancer, it has been shown to release a hormone called alpha melanocyte-stimulating hormone. This hormone appears to limit the damage to DNA damage from sunlight and so may actually reduce the risk of melanoma (but don't try this as a treatment yet. It's certainly not ready for prime time.)

SUNLIGHT FOR YOUR MOOD

Then there’s sunlight for your mood. Seasonal affective disorder – SAD – is caused by a lack of exposure to sunlight, which most affects those living in the northern latitudes in the winter.  SAD was first described in 1984 by Norman Rosenthal working at the National Institute of Mental Health but why it happens is still something of a mystery.  Rosenthal went on to write several best selling books on SAD and how to beat it. The answer appears to be something to do with sitting in front of a lamp that mimics sunlight (but the evidence that this works is still controversial).

 SUNLIGHT FOR BABIES WITH JAUNDICE

Sunlight is also a great treatment for babies with neonatal jaundice. This condition is very common and is caused when the baby breaks down the fetal hemoglobin with which it was born. A product of that breakdown is bilirubin, and if this is allowed to build up in the tissues it can cause lethargy, difficultly feeding, and in rare and extreme cases, brain damage. However, sunlight (or more precisely, the blue band of the spectrum at 459nm)  breaks down this dangerous bilirubin molecule into a harmless one called biliverdin.  So the best treatment for a newborn baby with mild jaundice is to put them out in the sun.  (Failing that, or if the degree of jaundice is not mild, you can consider phototherapy in the hospital.) 

The absorbance spectrum of bilirubin bound to human serum albumin (white line) is shown superimposed on the spectrum of visible light. Clearly, blue light is most effective for phototherapy, but because the transmittance of skin increases with increasing wavelength, the best wavelengths to use are probably in the range of 460 to 490 nm. Term and near-term infants should be treated in a bassinet, not an incubator, to allow the light source to be brought to within 10 to 15 cm of the infant (except when halogen or tungsten lights are used), increasing irradiance and efficacy. For intensive phototherapy, an auxiliary light source (fiber-optic pad, light-emitting diode [LED] mattress, or special blue fluorescent tubes) can be placed below the infant or bassinet. If the infant is in an incubator, the light rays should be perpendicular to the surface of the incubator in order to minimize loss of efficacy due to reflectance. From Maisels and McDonagh. Phototherapy for Neonatal Jaundice. New England Journal of Medicine 2008.358;920-928.

SUNLIGHT FOR INFECTIOUS DISEASES

 We don't treat infectious diseases with sunlight any more. But it wasn't always that way. Less than eighty years ago sunlight was recommended as a therapy for some patients with tuberculosis. The authors, writing in the journal Diseases of the Chest were cautious:

Even in those cases where the sun can be of great value, it is in no sense a specific cure for any manifestation of tuberculosis. Rest, good food, and fresh air, are still the fundamentals in treating all forms of the disease; and the sun, where it should be used, is only a valuable adjutant...Heliotherapy is not indicated in all cases of tuberculosis. The majority of patients with this disease should never use it...It is not a sure cure for any type of tuberculosis, but is often, especially in some of the extrapulmonary cases, a very valuable—or even necessary—aid.

In today's daf, Abaye once again noted that the sun can heal. His insight were more correct than he could ever have guessed.  

“Bright light therapy and the broader realm of chronotherapy remain underappreciated and underutilized, despite their empirical support. Efficacy extends beyond seasonal affective disorder and includes nonseasonal depression and sleep disorders, with emerging evidence for a role in treating attention-deficit/hyperactivity disorder, delirium, and dementia.”

— — Schwartz and Olds. The Psychiatry of Light. Harvard Review of Psychiatry 2015. 23 (3); 188.S

[Repost from Nedarim 8.]

Nedarim 8b ~ Heliotherapy

נדרים  ח ב׳

שמש צדקה ומרפא אמר אביי ש"מ חרגא דיומא מסי ופליגא דר"ש בן לקיש דאמר אין גיהנם לעולם הבא אלא הקב"ה מוציא חמה מנרתיקה צדיקים מתרפאין בה ורשעים נידונין בה

“The sun of righteousness, with healing in its rays” (Malachi 3:20)...Abaye said: “We learn from here that the dust of the sun heals”…Rabbi Shimon ben Lakish said, “there is no hell in the world to come. Rather God takes the sun out of its canopy; the righteous are healed by it and the wicked are punished by it” (Nedarim 8b.)

A History of Heliotherapy

In 1903, the Nobel prize for Medicine was awarded to a Dane named Niels Finsen. Finsen had invented a focusable carbon-arc torch to treat – and cure – patients with lupus vulgaris, a painful skin infection caused by tuberculosis.  While this was the start of the modern medical use of phototherapy, using the sun as a source of healing is much, much older. Older even than the Talmud, which mentions it in today’s daf. 

“The Nobel Prize in Physiology or Medicine 1903 was awarded to Niels Ryberg Finsen “in recognition of his contribution to the treatment of diseases...with concentrated light radiation, whereby he has opened a new avenue for medical science”.”

Perhaps the earliest reference to heliotherapy – that is, using sunlight to heal - is found in Egyptian papyrus records from over 3,500 years ago, which record using the sun, together with ingesting a local weed, to treat skin conditions. The active ingredients of that weed, Ammi majus, were isolated in 1947. These ingredients, together with heliotherapy, were used in the first clinical trials to treat vitiligo, which were conducted, rather fittingly, in Egypt.  Further work determined that it was only a narrow part of the sun’s spectrum that was needed to treat vitiligo, psoriasis, and other skin conditions, and so lamps were developed that produced only narrow band ultraviolet light (UVB). These UVB lamps are now a mainstay of treatment for psoriasis. 

Sunlight for Healthy Bones

“For most white people, a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU (1.25 mg) vitamin D into the circulation within 24 hours of exposure”

— Environmental Health Perspectives 2008:116;4. A162

But ultraviolet light – UVB – can also be extremely dangerous. Too much exposure to sunlight will cause skin cancer, as the light produces molecules that directly damage DNA. Here is the great paradox of sunlight – too much of it will burn and can kill – but get the dose right and it is not only curative, but essential for healthy living. Sunlight is needed to produce vitamin D in the skin, and vitamin D is needed to produce healthy bones. Without it, you will develop rickets, a skeletal deformity that is characterized by bowed legs. 

Typical presentation of 2 children with rickets. The child in the middle is normal; the children on both sides have severe muscle weakness and bone deformities, including bowed legs (right) and knock knees (left). From Holick M. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr 2004;80(suppl):1678S–88S.

Sunlight for a Healthy Immune System

The sun’s light has been shown to have effect the immune system, although many of these effects are only poorly understood. 

When some nerve fibres are exposed to sunlight, they release a chemical called neuropeptide substance P. This chemical seems to produce local immune suppression.  Exposure to the ultraviolet wavelengths in sunlight can change the regulation of T cells in the body which can also modulate autoimmune diseases.

Sunlight to Treat Melanoma?

While sunlight can cause skin cancer, it has been shown to release a hormone called alpha melanocyte-stimulating hormone. This hormone appears to limit the damage to DNA damage from sunlight and so may actually reduce the risk of melanoma (but don't try this as a treatment yet. It's certainly not ready for prime time.)

Sunlight for Your Mood

Then there’s sunlight for your mood. Seasonal affective disorder – SAD – is caused by a lack of exposure to sunlight, which most affects those living in the northern latitudes in the winter.  SAD was first described in 1984 by Norman Rosenthal working at the National Institute of Mental Health but why it happens is still something of a mystery.  Rosenthal went on to write several best selling books on SAD and how to beat it. The answer appears to be something to do with sitting in front of a lamp that mimics sunlight (but the evidence that this works is still controversial).

 Sunlight for Babies with Jaundice

Sunlight is also a great treatment for babies with neonatal jaundice. This condition is very common and is caused when the baby breaks down the fetal hemoglobin with which it was born. A product of that breakdown is bilirubin, and if this is allowed to build up in the tissues it can cause lethargy, difficultly feeding, and in rare and extreme cases, brain damage. However, sunlight (or more precisely, the blue band of the spectrum at 459nm)  breaks down this dangerous bilirubin molecule into a harmless one called biliverdin.  So the best treatment for a newborn baby with mild jaundice is to put them out in the sun.  (Failing that, or if the degree of jaundice is not mild, you can consider phototherapy in the hospital.) 

The absorbance spectrum of bilirubin bound to human serum albumin (white line) is shown superimposed on the spectrum of visible light. Clearly, blue light is most effective for phototherapy, but because the transmittance of skin increases with increasing wavelength, the best wavelengths to use are probably in the range of 460 to 490 nm. Term and near-term infants should be treated in a bassinet, not an incubator, to allow the light source to be brought to within 10 to 15 cm of the infant (except when halogen or tungsten lights are used), increasing irradiance and efficacy. For intensive phototherapy, an auxiliary light source (fiber-optic pad, light-emitting diode [LED] mattress, or special blue fluorescent tubes) can be placed below the infant or bassinet. If the infant is in an incubator, the light rays should be perpendicular to the surface of the incubator in order to minimize loss of efficacy due to reflectance. From Maisels and McDonagh. Phototherapy for Neonatal Jaundice. New England Journal of Medicine 2008.358;920-928.

Sunlight for Infectious Diseases

 We don't treat infectious diseases with sunlight any more. But it wasn't always that way. Less than eighty years ago sunlight was recommended as a therapy for some patients with tuberculosis. The authors, writing in the journal Diseases of the Chest were cautious:

Even in those cases where the sun can be of great value, it is in no sense a specific cure for any manifestation of tuberculosis. Rest, good food, and fresh air, are still the fundamentals in treating all forms of the disease; and the sun, where it should be used, is only a valuable adjutant...Heliotherapy is not indicated in all cases of tuberculosis. The majority of patients with this disease should never use it...It is not a sure cure for any type of tuberculosis, but is often, especially in some of the extrapulmonary cases, a very valuable—or even necessary—aid.

In today's daf, Abaye noted that the sun can heal, and Rabbi Shimon ben Lakish (a.k.a Resh Lakish) taught that the sun can both reward and punish. Their insights were more correct than they could ever have guessed.  

“Bright light therapy and the broader realm of chronotherapy remain underappreciated and underutilized, despite their empirical support. Efficacy extends beyond seasonal affective disorder and includes nonseasonal depression and sleep disorders, with emerging evidence for a role in treating attention-deficit/hyperactivity disorder, delirium, and dementia.”

— Schwartz and Olds. The Psychiatry of Light. Harvard Review of Psychiatry 2015. 23 (3); 188.