This proposal will explore muscle function (strength and endurance) in men and women suffering from statin-induced muscle symptoms. The mechanisms responsible for these muscle symptoms will be explored. Also, the investigators will assess the potential usefulness of vitamin D supplementation in a randomized control trial.

Statins are a class of drugs that are widely prescribed to lower blood cholesterol levels. Although they have few side effects, many patients report muscle pain, cramps, and weakness when using these drugs. We know very little on the real impact of these muscle symptoms on patient quality of life, especially in relation to muscle strength and endurance.

Patients under statin therapy will stop medication for 2 months. Results from blood sample, muscle function and muscle biopsy (in some participants) will be compared with baseline. Participants will then take vitamin D supplementation or placebo for one month. Thereafter, statin will be reintroduced for two months while continuing vitamin D or placebo supplementation. At the end of that time, measures from blood sample, muscle function and muscle biopsy will be compared with other visits.

Inclusion Criteria:

• statin therapy
• healthy and sedentary or moderately physical active

Exclusion Criteria:

• Current treatment with other lipid-lowering drugs
• Natural medicine affecting lipid metabolism
• CK levels above the normal range
• Clinical vitamin D deficiency
• Impaired liver or kidney function
• Untreated hypo- or hyperthyroidism
• Treatment with other medications known to increase risk of myopathy
• Existing infection requiring antibiotic therapy
• Consumption of greater than 60 ml of grapefruit juice per day
• Inherited muscle disorders or myopathy
• Polymyositis or inflammatory myopathy
• Use of corticosteroids
• Comorbidities resulting in muscle or bone pain
• History of elevated CK
• Unexplained cramps
• Known sickle cell trait
• Cancer within the 5 years prior to study entry
• Diabetes
• Stroke, coronary artery or peripheral vascular disease
• Physical disability or previous injury interfering with exercise testing
• Pregnant or breastfeeding
• Depression (in last 3 years) or treatment with antidepressants
• Use of anti-psychotic drugs
• Alcohol abuse