It’s more difficult for seniors to convert sunlight to Filament D so supplementation advised.
I just went through this myself. I’m 64.
There may be an age greater than this where what you are talking about is true. It may even be true for folks my age.
All I know is that I took my labs. Laid out in the sun. Took my labs. Perfect.
You should provide some more parameters. Perhaps that could help me or others.