I read that aging lowers the body's capacity to produce vitamin D. Even regular sun exposure will not suffice and one may have to take a vitamin D3 supplement during old age to meet our body's regular requirements. Please comment on this.
This is not entirely correct. Older people are certainly able to produce vitamin D from sun exposure and can produce adequate amounts, but, for a number of reasons, vitamin D levels tend to be lower in older people, making it important for many to increase sun exposure and/or increase vitamin D in the diet (which may include supplements). More details about this are found in the "What to Consider When Buying" section of the Vitamin D Supplements Review >>