Noticeable muscle weakness, such as trouble climbing stairs or decreased performance in the gym, can be a sign of a vitamin D deficiency. Without enough vitamin D in the diet, muscles don't get the fuel that they need to function at optimal levels.
In young adults and elderly, there have been numerous cases of extended vitamin D deficiency causing extreme muscle weakness, sometimes to a disabling extent. In these cases, the addition of vitamin D into the patient's diet improved the condition after a short time. This is especially evident in the elderly as their demand for vitamin D increases. If you are experiencing noticeable muscle weakness, adding a suitable supplement might be a good avenue to explore.

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