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If you've considered taking supplements to tackle cholesterol levels, what should you know before jumping in?

Diet has an impact on cholesterol levels, and . Berberine and niacin may reduce the low-density lipoprotein (LDL) cholesterol and triglycerides that are linked to cardiovascular disease. Fish oil may reduce triglycerides. Ground flaxseed and green tea or green tea extract may reduce LDL cholesterol. Plant stanols and sterols may also cut LDL cholesterol, particularly in people with the genetic form of high cholesterol called familial hypercholesterolemia.

Red yeast rice products can contain a substance known as monacolin K, which is the active ingredient in a prescription cholesterol-lowering statin drug, lovastatin (Altoprev). But it's actually illegal to sell any supplement that contains more than trace amounts of monacolin K, which is a drug.

But because dietary supplements are not regulated or monitored the same way pharmaceutical drugs are, there is no way to be sure what dose you're actually getting. Investigations have shown that the from product to product without matching the labeled amount.

High-quality evidence from the most reliable type of health study -- a randomized clinical trial -- found that preventive low-dose statin therapy lowered LDL cholesterol to a degree that dietary supplements and placebo (a "fake" pill with no active ingredients) couldn't match. Fish oil, cinnamon, turmeric, plant sterols, and even red yeast rice all failed to measure up and do better than a placebo, while garlic pills actually worsened cholesterol levels.

"Natural" does not mean "safe."

Red yeast rice that contains monacolin K can also cause the same types of side effects as lovastatin but also carry the risk of being that harms the kidneys. Botanical ingredients like red yeast rice can also damage the liver when taken inappropriately.

Berberine, green tea components, and plant sterols and stanols when taken as supplements can all cause digestive problems. Fish oil and garlic pill supplements are also known for their breath and body odor issues. Niacin, when taken at the higher doses usually needed for any impact on cholesterol, can cause itching and flushing.

Read previous installments in this series:

For Your Patients: Hypercholesterolemia: Understanding Your Diagnosis

For Your Patients: Why Do High Cholesterol Levels Matter?

For Your Patients: Who Gets Hypercholesterolemia?

For Your Patients: Screening and Diagnosis of High Cholesterol

For Your Patients: Understanding Inherited Cholesterol Disorders

For Your Patients: Daily Choices That Help Tackle Hypercholesterolemia

"Medical Journeys" is a set of clinical resources reviewed by doctors, meant for physicians and other healthcare professionals as well as the patients they serve. Each episode of this journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.