Have you checked your spam filter lately? If you have, then you've probably noticed one or two email messages about herbal sex pills. While constant bombardment with dodgy marketing campaigns might make you assume that herbal sex pills are totally bogus, there are some products out there that are based on real scientific research. So lets take a look at a few herbal supplements and the science behind them.

Low Libido Vs. Poor Health

Before we get into pills, let's talk health. Who doesn't want a better love life? That, in a nutshell, pretty much explains why there are so many products out there that claim to improve libido. But when taking a product for symptoms of low libido, it's important to first ask yourself why your libido is low in the first place. For men and women alike, reduced libido can be a symptom of relationship problems, hormonal changes, and cardiovascular problems, as well as a side effect of stress, insomnia and nutritional deficiency. It might be tempting to take a pill to solve the problem, but in terms of your long-term health, it pays to treat the cause.

Libido Enhancers

The Contender: Panax ginseng

Does it work?

Paola Sandroni, a neurologist from the Mayo Clinic, published a study in Clinical Autonomic Research in 2001 clarifying the research around several natural aphrodisiacs used around the world. In addition to bufo toad skins and live beetles (which let's face, are unlikely to land on your shopping list), the roots of the panax ginseng have shown marked libido enhancing properties. Ginseng contains chemicals, known as ginsenosides, which increase nitric oxide levels in the corpus cavernosum tissues of the penis. They also affect libido through various hormonal and chemical pathways. If you see panax ginseng as an ingredient, it may actually do you some good. Ginseng is known to boost energy and mood. Best of all, it appears to help women too. Beware though: ginsenosides are known to increase blood pressure. (Want to learn more about penis? Read 10 Things You Don't Know About Penises.)

Mood Elevators

The Contenders: Rhodiola, lavender, saffron, echium

Do they work?
When the world is feeling gray and dull, it can be hard to be in the mood for fun. Some herbal sex pills claim to improve energy and mood levels, thereby supporting libido. First thing's first: If you're on antidepressants or anti-anxiety medication, don't buy herbal pills intended for improving your mood. They may interact with your medication and mess with your neurochemical balance.

Naturopathic physician Anna V. Dwyer and her colleagues published a review of research in Alternative Medicine Review in 2011, revealing several plant medicines that are effective in supporting mood, as well as mild to moderate depression. Rhodiola, lavender, saffron, and echium were all shown to be effective in improving mood in clinical human trials, with saffron and rhodiola also showing promise for libido and sexual dysfunction in other studies. (Another way to spice up your sex life? Try something new! Read Beyond Plain Vanilla: 8 New Things to Learn in the Bedroom.)

Nitric Oxide Regulators

The Contenders: L-arginine, yohimbine, panax ginseng, ginkgo biloba, maca root, horny goat weed

Do they work?
For guys, nitric oxide (NO) is an important subject. NO is an enzyme that is present in the tissues of smooth muscles and blood vessels throughout the body, including the corpus cavernosum in the penis. When NO is released, penile blood vessels dilate and allow blood to flow into the penis, causing erection. (Have you seen "Fast & Furious?" It's like that for your johnson rod.) While drugs, including Cialis and Viagra, work (in part) by enhancing nitric oxide signaling in the body, a number of natural ingredients have proved to do the same.

Naturopathic doctor Douglas MacKay from Thorne Research published a review of the natural botanical and nutritional substances known to enhance NO production in the body. L-arginine (the primary ingredient for making NO), yohimbine, panax ginseng, ginkgo biloba, and maca root were all mentioned as effective treatments for erectile dysfunction, mostly by working through NO pathways.

Another Chinese study in The Journal of Ethnopharmacology found that the aptly named herb horny goat weed as effective in improving NO production, as well as testosterone production, and was nearly as effective as Viagra in one double-blind, clinical trial.

Circulatory Stimulants

The Contenders: ginkgo biloba, hawthorn berries, ginseng, oak bark, gotu kola, chili ginger and black pepper

Do they work?

For getting blood pumping to the nether regions, circulatory stimulants are the go-to. These are not going to solve impotence or low libido on their own, no matter what the label claims, but they may help to carry nutrients and other chemicals throughout the body. Those who suffer from poor circulation, cardiovascular disease, diabetes and high cholesterol may find this group of herbal supporters the most useful. Circulatory stimulants used in herbal sex pills range from household spices, like chili , ginger and black pepper, to the rather exotic, such as ginkgo biloba, hawthorn berries, oak bark and gotu kola.

There is currently not enough research on this area of herbal sex pills. Ginkgo has shown in studies to support erectile dysfunction, but this is theorized to have more to do with changes in NO production than circulation. In a study funded by Petra University in Jordan, researchers found that gotu kola, in addition to four other herbal extracts (including ginseng), was similar in effectiveness to Viagra in the treatment of erectile dysfunction in animals. All the same, considering the lack of evidence, it may be just as beneficial to have a curry at home, or a bit of extra black pepper with your dinner.

Dodgy Ingredients

Here is where things get dangerous. Occasionally when herbal products work really well, it's because they actually contain something other than what's on the label. James Neal-Kababick, director of Oregon-based Flora Research Laboratories, told NBC News in 2007 that 90 percent of the herbal sex enhancers he samples he examined contained patented drugs, such as Cialis, Levitra or Viagra. Because herbal supplements aren't as thoroughly regulated as drugs, consumers might think they are getting something "natural", when really, there is no guarantee that is actually the case.

Herbal sex pills can work, but you can't trust the hype. Do your research, seek out a qualified naturopath or herbalist and be sure to ask your doctor about possible interactions.