Supplementation of vitamin D is effective in preventing overall mortality in a long-term. It is not significantly effective in a treatment duration shorter than 3 years.
Vitamin D therapy significantly decreased all-cause mortality with a duration of follow-up longer than 3 years. No benefit was seen in a shorter follow-up periods.
The following subgroups of long-term follow-up had significantly fewer deaths:
- female only,
- participants with a mean age younger than 80,
- daily dose of 800 IU or less,
- participants with vitamin D insufficiency and cholecalciferol therapy.
The combination of vitamin D and calcium significantly reduced mortality and vitamin D alone also had a trend to decrease mortality in a longer time follow up.
A tree is a plant with an elongated stem, or trunk, supporting branches and leaves in most species. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years.
A variety of plant species have independently evolved a woody trunk and branches to compete for sunlight. In more general sense, tall palms, tree ferns, bananas and bamboos are also trees. The roots branch out under the ground to anchor the tree and to extract moisture and nutrients from the soil. Above ground, the branches usually bear leaves, which capture light.
Trees reduce erosion and moderate the climate. Trees and forests provide a habitat for many species of animals and plants. Some trees provide edible fruit.