Our food is 20-50% less nutritious than it was 100 years ago. It is extremely difficult to obtain all necessary nutrients in food. In fact, in some cases, it could be detrimental if food is the only source to correct a deficiency. For example, to obtain the recommended daily allowance of Vitamin D a person would have to drink 32 ounces of milk a day. To correct a deficiency it would take 5-10 times that amount. It is more practical and effective to use supplementation.