"It's like the RDA - "here's the level at which you don't have any known deficiency disease" as opposed to "here's what you should have". -- TheAnglican--quote used with permission
Let's think about this a little.
How do you find and define normal?
Do squirrels talk about normal? Do they talk about health? People use words and as my daughter says, "We make all of it up." All of the words. All of the definitions. What is health and what is illness? My daughter also says, "I can understand wanting to have a book that defines everything. Because science changes. It's scary."
So think about the science of health. Yes, first you define deficiency .... a disease? What does disease MEAN?
The word cretin is a medical term for a child that has grown up with inadequate thyroid hormone. They have mental retardation and distinctive physical problems. When I was in residency in 1993 we had a young teen who had grown up without enough thyroid hormone. It is rare in the US now because we do the newborn heelstick to test for "inborn errors of metabolism". The most common one is hypothyroidism. It is very rare. But it matters to THAT child, THAT family and we can PREVENT or do we say CURE cretinism by supplementing the newborn with the thyroid hormone.
Different states do different newborn tests. They all test for hypothyroidism. BUT we keep finding NEW disorders. Adding tests. If it's treatable, wouldn't you want your baby tested? Some are grim: if your child needs a lifetime special diet because they can't metabolize an amino acid and it will build up in their bodies and kill them....not fun.
Now, what about vitamins? I have never seen a case of pellagra. Look at the web pictures. Wonder Bread was initially a wonder because the flour was supplemented with niacin, a vitamin. Flour is supplemented. Pellagra is virtually gone in developed countries.
Goiter due to iodine deficiency is virtually unknown in the US because salt was supplemented with iodine. I keep wondering if I will see it again because now we have a lot of salt on the market that is not supplemented.
Ok, so the RDA, recommended daily allowance is to keep people from having problems due to deficiencies. Let's talk about the opposite: is there a dose that is too high?
How are you going to test it? Vitamin A...will you do a clinical trial where you give increasing doses until people have a "disease" or croak? Hmmm. Historically there have been some horrific clinical trials on prisoners and concentration camps. We don't consider that ethical. Even using squirrels is frowned on and makes me squeamish.
But there are case reports. Here: http://www.carrotjuice.com/did-basil-brown-really-die-from-too-much-carrot-juice.html. Dude. Died from hypervitaminosis A, carrot juice.
Vitamins A, D, E and K are fat soluble and can build up in your tissues. All can poison you. Wow, bummer.
The other vitamins are water soluble so your kidneys will clear them. But the kidneys are stressed in US culture. Kidney failure was NOT in the top ten causes of death in 1995 and is in the top ten now. The main cause is TOO MANY PILLS. Supplements, vitamins, prescription, over the counter. Any concentrated substance that is absorbed is metabolized by either the liver or kidneys.... and the kidneys are more vulnerable. The main nasties for the liver are alcohol and hepatitis, both viral and increasing liver inflammation from fatty liver disease. I suspect corn syrup as the culprit there because the liver turns out to store high fructose/glucose ratios as fat....quit drinking sodas and all sweetened drinks, ok? No mochas. Also high dose tylonol can kill the liver quite nicely. And don't get me started on mushroom pills. Holy cats.
Now, let's go back to testosterone. How do we define normal? We can't do a clinical trial on humans to give more and more...not ethical. So we test people and set definitions of normal. Labs have ranges.
But....how good are they? Growth charts for babies in the US used to be based on bottle fed caucasians. They were revised because breast fed babies grow differently and also the charts are now multiracial, which means that the guatemalan babies that I used to take care of in Colorado don't "fall off" the growth chart.....
The other thing to remember is that normal is a range. And the ranges set are never 100%. We are taught to think of the ranges as about from the 5th percentile to the 95th. So that means that 10% of people will have a lab result below the 5th or above the 95th and they are still normal.
Right now testosterone has lots of opinions. The MD mainstream currently says to consider supplementing testosterone if the person has symptoms AND the level is under 300. The naturopaths want a higher range. The anti-aging doctors appear to think that they can stop aging so my impression is that they are insane quacks and they use a really high range.
If the testosterone is too high, there is an increased risk of prostate cancer and also erythrocytosis or polycythemia. What the heck is that, you say? That is where you have too high a red blood cell count. This puts you at high risk for stroke, heart attack and/or kidney failure. Not good. And yes, I have seen a testosterone in a twice normal range with polycythemia. Then we bleed the person. Call the leeches*.
I am seeing more high vitamin B12 levels than low ones. Higher than the normal ranges. High folate, high vitamin D. We have not described all of the "diseases" due to high vitamin levels.... watch for the case reports....
....science is so much fun. Read your vitamin label. The manufacturer does NOT care about you. If it has 6667% of the RDA of vitamin A, do not take it. Hello. I don't like any vitamin with more than 200% because you do get some in your food. Well, not if you live on twinkies and coke but vitamins are not going to fix you if you do.
Eat food. Don't use methamphetamines. Quit smoking. Keep alcohol intake low or none. Exercise. Don't be a twitter addict......
inborn errors of metabolism: http://pedsinreview.aappublications.org/content/30/4/131?sso=1&sso_redirect_count=1&nfstatus=401&nftoken=00000000-0000-0000-0000-000000000000&nfstatusdescription=ERROR%3a+No+local+token
Dietary Reference Intakes:https://ods.od.nih.gov/Health_Information/Dietary_Reference_Intakes.aspx
1114 pages on calcium and vitamin D: https://www.nap.edu/read/13050/chapter/1#xv
*No, I don't use leeches. Physician humor. It would need too many leeches. We phlebotamize a pint of blood, run 1000cc iv fluid in to dilute and then take out another pint of blood. This is emergent with symptoms and the person is admitted and can spend a couple of days being diluted. Without symptoms a pint is removed weekly until the hematocrit is under 45%. Over 45 is erythrocytosis, over 55 is polycythemia.