Editing Reference range (section)

==Optimal health range==
''Optimal (health) range'' or ''therapeutic target'' (not to be confused with [[biological target]]) is a reference range or limit that is based on concentrations or levels that are associated with optimal health or minimal risk of related complications and diseases, rather than the standard range based on normal distribution in the population.

It may be more appropriate to use for e.g. [[folate]], since approximately 90 percent of North Americans may actually suffer more or less from [[folate deficiency]],<ref>[http://www.yourhealthbase.com/folic_acid.htm Folic Acid: Don't Be Without It!] by Hans R. Larsen, MSc ChE, retrieved on July 7, 2009. In turn citing: 
*{{cite journal | author = Boushey Carol J. | year = 1995 | title = A quantitative assessment of plasma homocysteine as a risk factor for vascular disease | journal = Journal of the American Medical Association | volume = 274 | issue = 13| pages = 1049–57 | doi=10.1001/jama.274.13.1049|display-authors=etal}}
*{{cite journal | author = Morrison Howard I. | year = 1996 | title = Serum folate and risk of fatal coronary heart disease | journal = Journal of the American Medical Association | volume = 275 | issue = 24| pages = 1893–96 | doi=10.1001/jama.1996.03530480035037| pmid = 8648869 |display-authors=etal}}
</ref> but only the 2.5 percent that have the lowest levels will fall below the standard reference range. In this case, the actual folate ranges for optimal health are substantially higher than the standard reference ranges. [[Vitamin D]] has a similar tendency. In contrast, for e.g. [[uric acid]], having a level not exceeding the standard reference range still does not exclude the risk of getting gout or kidney stones. Furthermore, for most [[toxin]]s, the standard reference range is generally lower than the level of toxic effect.

A problem with optimal health range is a lack of a standard method of estimating the ranges. The limits may be defined as those where the health risks exceed a certain threshold, but with various risk profiles between different measurements (such as folate and vitamin D), and even different risk aspects for one and the same measurement (such as both [[Vitamin A deficiency|deficiency]] and [[Hypervitaminosis A|toxicity of vitamin A]]) it is difficult to standardize. Subsequently, optimal health ranges, when given by various sources, have an additional [[Statistical variability|variability]] caused by various definitions of the parameter. Also, as with standard reference ranges, there should be specific ranges for different determinants that affects the values, such as sex, age etc. Ideally, there should rather be an estimation of what is the optimal value for every individual, when taking all significant factors of that individual into account - a task that may be hard to achieve by studies, but long clinical experience by a physician may make this method preferable to using reference ranges.
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