pastafreak, there is no evidence that we absorb vitamins less in advanced age. There is also no evidence that soil is not as enriched as it was. The latter statement addressed to a scientist would elicit a response enquiring exactly when was "was". When does "was" begin?
Not to put too fine a point on it, the links you provided are largely opinion and have no foundation. The NCBI article has been written for those with more than a basic knowledge of biochemistry and biotechnology and involve methods and conclusions that are readily misinterpreted by the public.
Be aware that NCBI relies on peer review of published papers and one cannot cite the information within one article and conclude that the article is correct. In fact, I've read the entire article through and I'm sorry to say that it's quite simplistic and doesn't provide a reliable insight into either nutrition in the elderly or vitamin utilisation. Furthermore, there are some pretty fundamental errors in the article.
I earned a few bob for around 18 years reviewing a NCBI articles. This article would have fallen within my remit and it fails to overly impress.