Light and life

Did you know that mums need more than ten hours of uninterrupted darkness a night or they wont bloom? And that older people need more sunlight than younger people? We have much yet to learn about sunlight.

Allan R. Magie, Ph.D., is chairman of the Department of Environmental and Tropical Health at the School of Health, Loma Linda University, Loma Linda, California.

The place: A greenhouse full of chrysanthemum plants—robust, but flowerless. The time: Late on a cool October evening.

Suddenly light bulbs flash in brilliance through the inky darkness and momentarily bounce off greenhouse windows. As rapidly as they appeared, the lights are turned off; darkness returns. The significance?

In contrast to their outdoor cousins, which have long since displayed colorful blossoms proclaiming the end of summer, these greenhouse chrysanthemums have continued sending their budless shoots upward. Foliage, but no flowers.

What made the difference? Light. The chrysanthemum needs at least ten and a half hours of uninterrupted darkness. With any less the plants won't flower. When the lights were turned on during the night it interrupted the plants' dark period, or "sleep," that is necessary for them to form buds and flowers. A chemical transformation necessary for their development was halted. By controlling the periods of darkness in which chrysanthemums and other similarly light-sensitive plants grow, nurserymen can cultivate lovely blooms for people to enjoy year-round.

"And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:... to give light upon the earth: and it was so" (Gen. 1:14, 15).

Light. Given for life—and seasons. Given to sustain life, to energize the chlorophyll, which drives the chemical factories of the plant kingdom and produces an abundant harvest for all creatures.

Upon creating the verdure that covered the dry land with colorful carpets of flowers and ripened grain, fruit trees of every description, and lofty giants pointing their leafy fingers to the sky, God placed in the heavens a ball of fire that directed its energy earthward as streamers of light. Thus our Creator completed this most efficient and orderly system for the transfer of energy, from the lowest plant to the most magnificent expression of His artistry—man. The sun's radiant energy, trapped by molecules in plants, is converted eventually into the chemical energy (calories) that makes up the food we eat by a process called photosynthesis. Thus, even before man stepped forward to have dominion over the earth, his Maker had provided a perfectly designed environment that contained all the ingredients necessary for continued life and radiant health.

But the sun .does more than just allow plants to manufacture food.

Sunlight tans skin, stimulates the formation of vitamin D, and synchronizes the rhythms that characterize our body's activities. Beyond these obvious effects the sun's many-colored rays send more subtle ripples through this planet's creatures. As in the chrysanthemum plants, light helps to initiate chemical processes that activate many human and animal biological functions—sleep, food consumption, physical activity, water intake, body temperature, and the rates at which many glands secrete hormones to direct body activity. These vary with periods that approximate twenty-four hours. Several essential bio chemical and hormonal rhythms within our bodies are synchronized, either directly or indirectly, by the daily pattern of light and dark.

For example, the concentration of cortisol, one of the principal hormones manufactured by the adrenal gland, reaches its highest levels in the morning before you awake and drops to a minimum in the evening. The increasing amounts of cortisol result in increased amounts of nutrients, particularly glucose, in the blood. Thus energy is available to begin the day's activities before additional nutrients are supplied by a meal.

In adults the period of wakefulness usually centers early in the afternoon, and most adults are most soundly asleep twelve hours later. When people reverse their daily sequence of activities by working nights and sleeping days, the body reverses its rhythms, adapting in five to ten days. Unsighted persons often have an irregular pattern of cortisol release, indicating that an absence of light-sensitive cells in the retina of their eyes upsets the rhythmic pattern.1

At present little is known about the intensity or quality (wavelength) of light needed to synchronize rhythmic patterns within man and animals. Poultry growers know that chickens raised under almost perpetual light lay more eggs than similar chickens in a natural cycle of day and night. Light received through the chicken's eyes stimulates its hormonal control, resulting in an increased capacity to lay eggs through an alteration in hormone production. If the pituitary gland, the master balance wheel of the body's entire glandular system, responds similarly in man as it does in chickens, then the entire glandular system can be affected by light received through our eyes. What, for example, happens when natural sunlight is filtered through different kinds of window glass? Could it be that polarized light might affect hormone production differently from unpolarized natural light? What about the effect of differing kinds of light and lighting conditions ranging from natural unfiltered sunlight to the various types of artificial light? Could it be that the light reflected from various hues of room walls also affects the physical health or well-being of a person?

Obviously, what we don't know about the effect of light on our health far outweighs what we do know at the present time. That light does, in fact, have an influence on our health is emphasized by Mrs. Ellen G. White when she lists sunlight as one of the true natural remedies that God has provided for man's needs and counsels that attention should be given to it. She says further, "In building, many make careful provision for their plants and flowers. The greenhouse or window devoted to their use is warm and sunny; for without warmth, air, and sunshine, plants would not live and flourish. If these conditions are necessary to the life of plants, how much more necessary are they for our own health and that of our families and guests!" 2

Apparently the older a person becomes, the more important it is to meet one's need for sunshine. "Vigor declines as years advance, leaving less vitality with which to resist unhealthful influences; hence the greater necessity for the aged to have plenty of sunlight." 3 This may indicate that light plays some regenerating role along the lines of the so-called Fountain of Youth.

Light also has the important role of blocking the production of melatonin, the major pineal-body hormone. Located in the brain of humans and other mammals, the pineal body has a function that we do not yet precisely understand. However, introducing its hormone into the body experimentally produces some interesting effects on the brain: it causes sleepiness, modifies brain-wave activity, and affects the level of 'serotonin, an important chemical in mental activity. 4

In addition, in some animals melatonin represses, or inhibits, ovulation and alters the secretion of hormones from such organs as the adrenals, pituitary, and sex glands. This inhibition may result from melatonin acting on brain centers that control the release of these hormones.

In reference to sex hormones, a question immediately comes to mind: Has the advent of electricity, with extended exposure of humans to light, especially from powerful sources such as television, resulted in the lowering of one's resistance to evil and temptation? It has been discovered that laboratory rats kept in total darkness prefer alcohol to plain water. 5 During normal day-night cycles the rats favored water, but when several days of continuous darkness ensued, they switched to alcohol. In rats the pineal body produces more melatonin in the dark than in the light. Also, continued darkness is a stress to rats, and stressed rats are known to consume more alcohol. But when melatonin is administered to rats exposed to a normal day-night cycle, they too show a preference for alcohol. If these findings of a "darkness-induced drinking phenomenon" in rats is ultimately found to apply to humans, it may offer more understanding of the problem of addiction. Certainly further research is needed.

Sunlight is not an unmixed blessing. Prolonged exposure of the body to sunlight can have a number of known undesirable effects on our health. Most of us are acquainted with the temporary discomfort of sunburn, but too much sun can cause premature aging of the skin and also cancer. Certain drugs and other chemicals cause skin to be more sensitive to sunlight, resulting in blemishes and rashes from overexposure. Furthermore, chemical changes alter body function deep within our tissues, and we become more susceptible to infections (mainly viruses) because of too much sunshine.

On the positive side, exposure to sun light results in the production of vitamin D in the skin, increased resistance to disease, and a faster recovery from illness.

"Life in the open air is good for body and mind. It is God's medicine for the restoration of health. . . . Sunshine ... [is one of His means for restoring the sick to health in natural ways. To the sick it is worth more than silver or gold to lie in the sunshine." 6

God said, "Let there be light." Are we listening?

Notes:

1 Nathaniel Kleitman, Sleep and Wakefulness (Chicago and London, The University of Chicago Press, 1963), p. 367.

2 The Ministry of Healing, p. 275.

3 Ibid.

4 R. J. Wurtman, "The Effects of Light on the Human Body," Scientific American 233(1):66, 77, July, 1975.

5 John N. Ott, Health and Light (Old Greenwich, Conn.: The Devin-AdairCompany, 1973), pp. 145, 156, 157.

6 Ellen G. White, Counsels on Health, p. 166.


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Allan R. Magie, Ph.D., is chairman of the Department of Environmental and Tropical Health at the School of Health, Loma Linda University, Loma Linda, California.

June 1981

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