This month, Americans will make New Year’s resolutions to eat healthy, exercise more, get more sleep, and maybe even find ways to manage stress. Those that do are also more likely to purchase dietary supplements, a market that reached $32.5 billion in sales in 2012.

Sixty eight percent of Americans take vitamin, mineral and herbal supplements, and 20 percent do so for heart health, according to a report by the Council for Responsible Nutrition.

Yet supplements are unregulated by the FDA— there’s no telling exactly what’s in them— and some can also be harmful to the heart, interact with medications and have serious side effects.

Here are seven supplements you should avoid, especially if you have heart disease or cardiovascular disease risk factors.

1. Calcium
Approximately 43 percent of Americans, including nearly 70 percent of older women, take a supplement that contains calcium for bone health.

Yet a recent study out of John Hopkins Medicine found that taking calcium supplements may increase the risk for plaque buildup in the arteries and heart damage.

Experts agree, however, that there likely isn’t a cause and effect relationship. Calcium is actually beneficial for the cardiovascular system, but only when both vitamins D and K2 are optimal because they help manage calcium status.

“Without a nice level of vitamin D or vitamin K2 in your body, calcium has a tendency to start to deposit in other tissues like your arterial system,” said Dr. Michael Smith, author of “The Supplement Pyramid,” and senior health scientist for Life Extension in Fort Lauderdale, Florida.

Nevertheless, you should talk to your doctor about a calcium supplement.

“Not everybody that is taking calcium needs to. The best way to get calcium is through food, not a supplement,” said Dr. Deepak Bhatt, executive director of interventional cardiovascular programs at Brigham and Women’s Hospital in Boston.

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2. Licorice root
Licorice root is an herb that is used to improve prostate health and digestive problems such as ulcers, acid reflux and gut discomfort. It is also used to ease symptoms of menopause and inflammation, including viral and bacterial infections and coughs.
Yet licorice root can cause high blood pressure and deplete potassium levels, so if you have a history of cardiovascular disease, you should avoid it, Smith said.

3. Yohimbe
Yohimbe is sold as a supplement for erectile dysfunction but it’s not clear if it’s even effective, Bhatt said.

It may also help to control appetite, aid weight loss and help depression, but you should avoid it if you have heart disease because it can have adverse cardiac effects.

4. Ephedra
Commonly used to aid weight loss and boost energy, ephedra raises the heart rate and blood pressure and can exacerbate heart arrhythmias.

“Somebody that has heart failure, even mild heart failure, can start having shortness of breath episodes,” Smith said.

Taking ephedra can lead to irregular heartbeat or heart attack, particularly in people who have heart disease, or those who have undiagnosed heart disease.

People who have risk factors for heart disease should avoid it, too.

5. Arginine
Arginine or l-Arginine, is an amino acid in the body. In supplement form, studies show it may have positive cardiovascular effects because it dilates and relaxes the arteries. It can also help those with angina, high blood pressure and heart failure.

Yet taking the supplement can be deadly, a study in the Journal of the American Medical Association found.

The bottom line? “It’s not clear that it hurts but it’s not clear that it helps either,” Bhatt said.

6. Bitter orange
Studies show bitter orange, a plant, is used to control appetite and aid weight loss, yet it can also be dangerous.

“Bitter orange is known to have some heart side effects mostly because it has a caffeine-like compound in it,” Smith said.

If you’re sensitive to caffeine or have risk factors for heart disease, it’s a good idea to avoid taking it.

7. St. John’s Wort
St. John’s Wort is well known as a therapy for mild to moderate depression without all the side effects of anti-depressant medications, but taking the supplement can also lead to blood pressure spikes, according to a study in the journal Clinical and Experimental Pharmacology and Physiology.