Now studies show that beta carotene does not prevent heart disease. Just because the product is sold doesn't mean that it is safe. Cigarette smokers, for example, may actually increase their risk of lung cancer from taking beta carotene. We only know this after the product has been consumed by millions of people. Natural doesn't mean safe.
Some Chinese herbs are natural, such as ma huang , an amphetamine-like stimulant.
And this intense stimulation of the central nervous system has been known to cause heart palpitations, stroke, and even psychosis in some people. And it's all natural. Combinations of supplements with other medications can be deadly or at least create other health problems. For example, combinations of garlic with anticoagulants can cause internal bleeding. Check with your doctor if you are taking a prescription drug and ask if there are any side effects he or she knows about from combining your medication with food supplements.