The short wavelengths of natural light interact with serum bilirubin, converting it to a nontoxic substance. A study by the Council of Educational Facility Planners compared cool white to broad spectrum fluorescent lamps in a controlled scientific test in classrooms. Students had a 2.5 times better attendance record in rooms with broad spectrum lamps. That is they were sick much less frequently. Physiological studies have also conclusively shown that, under broad spectrum lamps versus cool white lamps, humans have increased oxygen intake, reduced heart rate, increased ability to absorb vitamin D and calcium and improved muscle utilization.
Natural sunlight makes people feel better than artificial light does.
The more natural the light the more comfort and better performance. Statistically significant differences are proven for subjects in rooms lit by cool white lamps versus broad spectrum lamps. Subjects brought from outdoors into cool white rooms tended to become less lively or lethargic. The subjects exhibited no change when brought from outdoors into broad spectrum rooms. Visual accuracy and alertness were measurably better in the broad spectrum rooms versus the cool white rooms.