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.
Actually my internist told me that some seniors hate difficulty with VIT D synthesis from the sun. I find this quote at Parentgiving.com:
Why Are Seniors at Risk?
People over age 50 have an increased risk of vitamin D deficiency and the risk increases with age. As people age they lose some of their ability to synthesize vitamin D from sunlight. Vitamin D also needs to be activated in the kidney before it can be used by the body and this function also decreases with age. Finally, elderly people who are homebound are less likely to get outdoor exercise and activity. Researchers have suggested that it takes up to 30 minutes of sun exposure twice a week to make a sufficient amount of vitamin D from sunlight.