|Figure 1. People in the Sun. Edward Hopper.
1960. Smithsonian American Art Museum.
In his paintings, Edward Hopper shows us a reality that is the result of a rational contrast between lights and shadows. The summer sun illuminates the natural landscapes but cannot penetrate through the large windows of the buildings, which inside look like dark boxes. The characters are often light seekers, but they do not need the artificial light that, on the contrary, makes them look like ghosts with no eyes, but rather the sunlight. Not surprisingly, the protagonists of Hopper’s paintings are often placed in border areas, the door or near a window, in a limbo between a source of well-being and an unhealthy environment (see the paintings by the same author: Morning Sun, Summertime). This representation of the human condition is scientifically made explicit in the painting People in the Sun (1960, Fig. 1), where you can see adults curing themselves with sunlight, and who seem—abnormally for a work of Hopper—happy. This work allows us, fifty years after it was painted, to make some observations about the history of sun exposure in medicine.
Light therapy or phototherapy emerged as a medical practice before the relationship between ultraviolet (UV) radiation and vitamin D status was appreciated. In the early decades of the past century, evidence of the production of vitamin D in the skin by UV rays was achieved, first by McCollum with the use of the lamps, and then by Mellanby through sunlight exposure. This provided the scientific foundations of heliotherapy and also definitively solved the medical puzzle about the underlying cause of rickets, an enigma arising in England about three centuries earlier.1 Yet articles reporting the positive effect of sunlight exposure on different skin diseases were already present in the scientific literature of the eighteenth century. The best-known and widespread use of heliotherapy was in sanatoriums established between the nineteenth and twentieth century all over the world. Here, the main therapeutic indication of heliotherapy was the treatment or the secondary prevention of tuberculosis and other infectious diseases. Rest, fresh air and sunlight exposure represented the paradigm of tuberculosis care at that time.
|Figure 2. Charles William Andrews (far left) and other patients sitting outside in lawn chairs.
1960. With permission from Elaine Andrews.
The treatment of tuberculosis with light therapy was adopted around the world as a result of the studies conducted in the late nineteenth century by Niels Ryberg Finsen (Nobel Prize in Physiology or Medicine in 1903), who demonstrated the effectiveness of the light emitted by a carbon arc lamps in treating lupus vulgaris, the cutaneous manifestation of tuberculosis.2 The photo shown in Figure 2 was taken at Clare Hall Sanatorium (1746–1975) in London in May 1960, the same year in which Hopper created his People in the Sun, and it presents significant similarities with this painting. But also in the 1960s the use of heliotherapy began to decline with the advent of effective chemotherapy, together with a growing feeling that being in a sanatorium was tantamount to being imprisoned. This led to the treatment of tuberculosis being abandoned in such institutions especially after the 1960 publication of the results of the famous experiment conducted in Madras (India) where the chemotherapy method was compared with “sanatorium practice.”3 At the same time, since the early twentieth century several scientists have fueled the debate about the harmful effects of using lamps for therapeutic purposes, which culminated in the mid-70s with the experimental evidence of the carcinogen effect of ultraviolet radiations.4 The association between skin cancer and solar ultraviolet radiation has led the major health agencies to launch worldwide campaigns, still active today, and emphasizing only the potential harmful effects of sun exposure, thus sweeping away in one fell swoop all the history, and benefits, of heliotherapy.5
The growing number of studies finding low vitamin D blood levels in many people may require us to reflect on our history and on our approach to sun exposure.6 We now know that vitamin D not only helps to maintain strong bones, but also counteracts sarcopenia, protects blood vessels, and supports the action of the immune system.7 Recent studies have also suggested that the once empiric therapeutic approach in sanatoria may have been based on the ability of vitamin D to boost immune cells against Mycobacterium tuberculosis.8 Is it time to look again at sun exposure, in the right doses, as therapy? Perhaps it would be a way to bring peace to the ghosts trapped between lights and shadows in Hopper’s masterpieces.
- Keegan RJ, Lu Z, Bogusz JM, Williams JE, Holick MF. Photobiology of vitamin D in mushrooms and its bioavailability in humans. Dermato-endocrinology. Jan 1 2013;5(1):165-176.
- Bloch H. Solartheology, heliotherapy, phototherapy, and biologic effects: a historical overview. Journal of the National Medical Association. Jul 1990;82(7):517-518, 520-511.
- Andrews RH, Devadatta S, Fox W, Radhakrishna S, Ramakrishnan CV, Velu S. Prevalence of tuberculosis among close family contacts of tuberculous patients in South India, and influence of segregation of the patient on early attack rate. Bulletin of the World Health Organization. 1960;23:463-510.
- Hockberger PE. A history of ultraviolet photobiology for humans, animals and microorganisms. Photochemistry and photobiology. Dec 2002;76(6):561-579.
- (Intersun program, http://www.who.int/uv/intersunprogramme/en/).
- Hagenau T, Vest R, Gissel TN, et al. Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: an ecologic meta-regression analysis. Osteoporosis international: a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA. Jan 2009;20(1):133-140.
- Bouillon R, Carmeliet G, Verlinden L, et al. Vitamin D and human health: lessons from vitamin D receptor null mice. Endocrine reviews. Oct 2008;29(6):726-776.
- Coussens AK, Martineau AR, Wilkinson RJ. Anti-Inflammatory and Antimicrobial Actions of Vitamin D in Combating TB/HIV. Scientifica. 2014;2014:903680.
ADRIANO ANGELUCCI, born in Chieti, Italy, is assistant professor of General Pathology at Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, L’Aquila, Italy. He has a master’s degree in molecular biology and a doctoral degree in experimental medicine. He is chief of the laboratory of cell pathology at University of L’Aquila and he is co-author of numerous papers in the field of experimental oncology.