What it's normally used for
Having Calcium and Vitamin D in a healthful diet is important for building strong bones and teeth and may reduce the risk of osteoporosis Calcium is the main mineral responsible for bone strength, while magnesium and vitamin D are needed for proper bone mineralization, and zinc is involved in the synthesis of collagen in bone tissue.
A steady supply of zinc aids in enzymatic actions. If you have a gastrointestinal disease affecting mineral absorption or retention, more zinc may be needed in your diet.
What it does for Lucid Dreaming
With Calcium/Magnesium/Zinc, you remember more of your dreams, and Zinc is known for generating vivid dreams.
My own results
I take Calcium/Magnesium/Zinc after six hours of sleep and I remember more of the dream, where it seems like it's a longer dream.