According to the Medical Dictionary for the Health Professions and Nursing, Recommended Daily Allowance or RDA is “the average daily intake of a nutrient judged sufficient to meet the requirements of most healthy people, categorized by gender and age.”
Soil quality is often poor, thanks to extensive use of fertilizers and chemicals. This means crops no longer have the minerals and vitamins at the levels they once did. Our increased consumption of highly processed foods, our sedentary lifestyle choices, side effects of prescription medications and high concentrations of stress – all work against us.
Beyond all the above, RDA standards were created with the aim of preventing deficiencies that would lead to certain serious health conditions. For example, Vitamin D deficiency is determined when a vitamin D metabolite falls below 12 ng/mL in a blood sample. A person may show symptoms of the disease called Rickets in children or osteomalacia in adults. The latter involves serious softening of bones and severe joint pains.
So the RDA was determined by asking the question: “How much vitamin D should a person receive daily to prevent the development of Rickets and Osteomalacia?” In this case, the level determined was 12 ng/mL. If an individual had a vitamin D level of say, 16 ng/mL, they would not be diagnosed as “deficient in vitamin D” by a practitioner, and therefore, not prescribed a vitamin D supplement or asked to bask in the sun.
Experts, however, believe that optimal levels of this key vitamin run a lot higher, say between 30 and 50 ng/mL. They say that Vitamin D levels below 30 ng/mL are insufficient because, at these levels, the vitamin is unable to do its job of promoting health and preventing several chronic diseases from developing.
This is often not a fixed number but an evolving target, based on what ongoing fresh research reveals.
Changes to RDA include new levels for iron and protein as referred to in 2001. A more recent change is the recommended daily value for vitamin D, changed in 2010. The new adequate blood level for vitamin D has been raised to 20 ng/mL from 12 ng/mL. Revisions do not happen quickly as substantial research and agreement must occur first within the medical establishment to form an acceptable new level for RDAs.
So you need to be your own best health advocate and work with your healthcare provider to determine what will work best for you.