First of all, I am extremely alarmed to see 50,000 I.U. (or 1.25mg) of Vitamin D, being prescribed to patients, by doctors! THIS prescribed AMOUNT OF Vitamin D, IS WAY TOO MUCH! By the way, the majority of doctors have the equivalent of a one half hour course, in nutritional education, IF THAT, included in their schooling. Food is medicine. Having said this, I will proceed with my personal experience, and knowledge, about Vit.D. I take Vit.D because, it is SO IMPORTANT for our overall health.... I am 53 years old, and take a heart medicine, (called Atenolol,) which does not allow me to go out in the Sun. So, I have to take a Vit.D supplement. I take 400 I.U. (or 10mcg) of D3, everyday. (600 I.U. is the RDA, or the Recommended Daily Allowance, for people over the age of 70.) Vit.D is EXTREMELY IMPORTANT to the normal functioning of our bodies, and plays a large part in keeping us Cancer-free, as well. Our bodies, continuously, scan through EVERY CELL in our entire body. When this scanning mechanism encounters a cell with a "bite out of it," (due to exposure to radiation, through x-rays, etc.,) or other mutation, it replicates this abnormal cell, and this is one of the ways Cancer occurs. Vit.D keeps this from happening. That's why it is SO important. When we have healthy Vit.D levels, the mechanism that scans each and every cell, can recognize the mutated cell, or the cell with "the bite out of it's DNA," that is faulty, and NOT replicate it. It, instead, discards the cell from our body, and we stay healthy. 15 minutes of DAILY sunshine is, generally, enough for Caucasians to get the amount of needed Vit.D. African Americans, and those with more pigment in their skin, need a few more minutes, (if sunlight is allowed.) In addition to this, scientists have recently learned that, Vit.D (in larger doses, and over an extended period of time,) is extremely beneficial, in fighting the COVID-19 coronavirus, in it's early stages. Vit.D is essential for normal growth and development. It promotes the use of calcium and phosphorus in the formation of our bones and teeth. It is especially needed for infants, children, and women, during pregnancy, and lactation. In mild cases, results of lack or deficiency of Vit.D, are the interference with utilization of calcium and phosphorus in bone and teeth formation. Irritability, and weakness are also results of a lack, or deficiency, of Vit.D. Severe deficiency leads to rickets. Valuable sources of Vit.D, are Sunlight and Fish-liver oil. Low concentrations are found in egg yolk, cream and butter. Milk may be enriched with it, (but, 1 quart of whole milk, fortified with V.itamin D, only equals 400 I.U.) Ultraviolet rays from special lamps, acting on the skin, are another way to get Vit.D. Lesser, or trace, amounts can be found in (fortified) yeast and sea vegetables (Nori, Dulse, etc.) Natural food sources of Vitamin D are meager. If one chooses to use Fish Oil, keep it under refrigeration, as that is where it is stable. We store Vit.D. in our liver. Again, the Recommended Daily Allowance is 400 I.U. until the age of 70 years old. Then, the (RDA) Recommended Daily Allowance, goes up to 600 I.U. I am a Vegetarian. So, additionally, I take B12, along with my Vit.D, DAILY. I, also, eat Iron, DAILY, as well, through Natural, Organic, Whole Food Sources, like: Egg Yolk, Beans, Oatmeal, Raisins, Apricots, Peaches, Prunes, Molasses, Peas, Green Leafy Vegetables, Almonds and Soy Beans. ~Note: If you take a Calcium - Magnesium Complex: Calcium (1,000mg.) - Magnesium (500mg.) *We can ONLY absorb 600mg. of Calcium, at a time. So, eat your supplement (of 600mg. Calcium) in the morning, AND at night. Read More Read Less