This was an experiment using controls?
Yes. When I first approached my friend, who owns a large-scale marijuana operation (he supplies weed for a number of medical dispensaries in the Denver area), with the idea of using colloidal gold as a plant supplement, he was very skeptical. I was actually not sure, myself, what would happen, as I had never used gold on plants, but I had read reports (including this from the US government in 1970: http://pubs.usgs.gov...314b/report.pdf ). Basically, he diluted 16oz (475ml) of colloidal gold (15nm/30ppm) into five gallons of water and added it to some plants he had in vegetation. To our surprise, the plants grew 6-9inches per day, after administration, and the lights above the plants had to be raised every day.
To get a better indication of what might be happening, he proceeded to take 12 cuttings (clones) from four different mother plants, of four different strains (48 plants total). These cuttings were rooted and grown to approx. 9 inches tall and, within the 12 of each strain, 8 were selected that were rather uniform in height and health. All of the cuttings were divided into four sections, each section of plants featuring 8 plants; 2 each of the four strains, all of identical genetics and of equal size and health..
Section 1 was given Miracle Grow.
Section 2 was given a very-popular-but-unnamed organic fertilizer. (Unnamed because this company markets their high-quality fertilizer for this industry, and I don't want to discredit anyone's business)
Section 3 was given a fertilizer "tea" that has been developed by a local grower (now in his 70's), that has been proven to be superior in every respect.
Section 4 was given colloidal gold, of the same particle size and measurements described above.
In less than 24 hours, colloidal-gold plants (hereafter referred to as CGP) were about 5 inches higher than all other plants. Within a week, the CGP looked so large and green compared to the others in the test group that they looked like they were 6 weeks older. Furthermore, the others (with the exception of the ones given the "tea") started to show signs of yellowing or curling, which is indicative of the need for nutrient augmentation, which is typical in an indoor grow operation. This was not the case with the CGP. They looked healthy and beautiful.
The next pleasant surprise came after flowering, when the CGP *all* finished flowering in less time than usual (an average of 10 days early, but one strain finished 16 days early!). Furthermore, the flowers had acheived a density and weight/light ratio that was previously unheard of. Needless to say, all of this grower's current operation is supplemented now with colloidal gold.
Next, I planted a vegetable garden in four raised beds, in a neighbor's front yard. I planted squash, beans, tomatoes, carrots, cabbage and peppers. I planted the exact same plants in all four beds, in the same spots within the beds, and used the same soil for each. I used the same fertilizers used in the marijuana experiment. Within one week, the difference was clear; the gold-plants experienced a much faster rate of growth and maturity than with the other fertilizers.
(Side note: the vegetables grown with the "tea" were absolutely delicious, and were some of the sweetest specimens I had ever tasted, of each of the varieties. In fact, the difference in taste was so striking that it was like they were completely different plants, and it was difficult to believe the plants had come from the same seed stock!)
Lastly, in an attempt to clean up a friend's dry, brown lawn for a house showing, I gave her a bottle of gold to put into her fertilizer attachment for her garden hose. She watered her lawn without high hopes.. In the morning her dry, brown lawn was lush and green! It was as if someone had shown up during the night and re-sodded her yard.
I am not sure how this relates to human consumption, but this is the extent of my experience.