supplements
7 interactions related to supplements
rosuvastatin + berberine
Rosuvastatin is carried into liver cells by the OATP1B1 transporter. In a laboratory study using human liver-cell cultures, berberine increased OATP1B1 activity and pushed more rosuvastatin into the cells. This is an early, test-tube signal only: there is no human or animal data showing it changes blood levels, cholesterol response, or side-effect risk in real life.
caffeine + ashwagandha
Caffeine is a stimulant that raises alertness and cortisol; ashwagandha is an adaptogenic herb that, taken on its own, modestly lowers cortisol and perceived stress in human trials. People combine them hoping ashwagandha will take the edge off caffeine's jitters. That pairing is plausible but has not been tested directly in humans, so the 'calm focus' benefit remains theoretical rather than proven. The combination is generally well tolerated in healthy adults.
atorvastatin + vitamin d
Vitamin D's active metabolite (calcitriol) can mildly induce CYP3A4, the liver enzyme that breaks down atorvastatin, which can lower atorvastatin blood levels. Despite this, the cholesterol-lowering effect appears largely preserved, so the combination is generally fine. Strip precise dose targets and review high-dose vitamin D regimens with your doctor or pharmacist.
simvastatin + berberine
Simvastatin is activated and cleared by the CYP3A4 enzyme. A human study found that repeated berberine inhibits CYP3A4, which could raise simvastatin levels and increase the risk of muscle-related side effects. Some animal data suggest berberine can also induce CYP3A4 over time, so the net effect on statin exposure is hard to predict. There are no published human case reports of myopathy from this specific combination, so the concern is mechanistic and moderate.
caffeine + creatine
Daily high-dose caffeine taken throughout a creatine loading week may modestly blunt creatine's strength benefit, but ordinary pre-workout caffeine in someone already taking creatine daily is at worst neutral and often additive. There is no safety concern at normal intakes.
caffeine + vitamin d
Higher caffeine intake is weakly associated with lower vitamin D status. In cell studies caffeine reduces vitamin D receptor (VDR) expression in bone-forming cells, and a large NHANES cross-sectional analysis links higher caffeine intake to a modestly greater chance of low serum 25-hydroxyvitamin D. The effect is small and matters most for people who already have low vitamin D, low calcium intake, and high bone-loss risk (for example, postmenopausal women). It is not an absorption-level interaction, so there is no need to separate the timing of a vitamin D supplement from coffee.
atorvastatin + berberine
In human trials, adding berberine to a statin did not raise muscle or liver side effects, and the two are sometimes studied together for cholesterol. The earlier claim that berberine meaningfully raises atorvastatin levels and risk is not supported by human evidence.