One Mom in the Middle…
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Vitamin D level target

Published 10.24.2016
After publishing the previous piece, it was pointed out to me that I did not actually discuss how I chose my target serum vitamin D level of 46 ng/mg (nanograms per milliliter), which corresponds to 115 nmol/L (nanomole per liter). I chose that level based on the information presented in this Dr. Greger video. As I always do when I link to a Greger video or blog, I acknowledge that the doctor has a distinct bias towards veganism. The answer to just about every question for Greger amounts to, "Eat more plants," or "Eat only plants."

In the video, he discussed what the “natural” level of serum vitamin D levels for humans, using the values seen in hunter-gatherers in Africa. The human race began under the African sun, so the thinking is that the "natural" human level of vitamin D is found in people who have lifestyles that have them outside most of the day wearing very little.

Per Greger, the normal human serum vitamin D level is greater than 100 nmol/L. In this video, the effect of vitamin D levels are not represented as a U curve, which would mean that too much is as dangerous as too low, but rather a backwards J curve. A backwards J curve means too little is bad, but then once the body has enough, the benefit levels off. Harm does not occur until you go much higher in level.

As I noted in the previous writing on this topic, my specialist is not on board with this idea. She told me that I should keep my levels in the 30's (that's in ng/ml units.) A serum vitamin D level of 35 ng/ml (my level when I was taking the calcium/vitamin D combo vitamin) corresponds to 90 nmol/L.

The reality is that my vitamin D level was decent when I was taking 800 IUs (International Units) a day (the amount in the combo vitamin), so I probably could back off to 2000 IUs a day. On the other hand, I'm stuck on the fingernail thing. My nails have always been weak, and were so when my level was at 35 ng/ml. At 54 ng/ml, they are strong and all but unbreakable. The bottom line is that I will lower my intake as described previously. My average daily intake will be 3000 IUs for the time being. If I don't notice a difference in my nails, then I'll lower it again to 2000 IUs a day.

Nails tell the Tail?

People have looked into the question of whether fingernail health is related or can be correlated to bone health. In 2015, researchers looked to see if T-scores* be correlated with Raman spectral features of keratin from women’s nails? The answer in this study was no. This is the abstract to a 2012 paper that used laser induced breakdown spectroscopy to find very weak correlations between nail and bone health. A weak correlation was also found in this 2013 paper, so weak was the correlation that the authors say that the bone quality test (BQT) using fingernails should not be used to diagnose osteoporosis. The goal in all these papers is a low cost test to diagnose and then monitor the disease.

BQT provides information on the state of trabecular bone (bone structure) rather than cortical bone (bone mass). Raman spectroscopy allows the analysis of human fingernail for BQT by means of a laser beam which hits the fingernail for a few seconds. Reflected light provides information on the chemical structure of the disulphide bonds in the fingernail. By analyzing the wavelengths of the reflected light, information on the level and types of chemical bonds present can be obtained.BQT is still a new technology under early investigation for clinical applicability with limited data available. Some preliminary studies have shown significantly lower disulphide content in nails obtained from patients with a history of fracture (3) and in patients with osteoporosis (4). A weak association was observed between Raman measurement of disulphide content and bone mineral density as measured by DXA.


Bottom line, I haven't found any significant evidence that fingernail health and bone health are correlated. I will say that looking for information on the benefits of vitamin D requires a healthy dose of skepticism. Plenty of sites claim that vitamin D is a wonder substance that can cure all ails. On the other hand, there is some interesting and suggestive data about prostate cancer. Per the researcher, there were no adverse effects of Vitamin D up to 10,000 IUs per day. Certainly there was no issue taking 2000-4000 IUs a day. And taking it every day, rather than in a huge once a week bolus is what is necessary.

*T-scores are how osteoporosis is diagnosed. The T-score is how far the bone mineral density (BMD) is below the benchmark. The benchmark is based on the BMD of an average
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