From the article: "It often takes many months for high Vitamin D levels to drop, and it took six months for Shannon’s level to fall into the 50s."

I don't think a journal will help in these circumstances, the time lapse between cause and effect is just too long. Getting tested is cheap and easy (and here I'm thinking of people who are deficient in vitamin D, if the results are too low then it seems that taking a supplement would be a good idea).