Guys whose sex life isn't exactly red-hot may want to examine their diet as a possible culprit. Individuals who don't consume enough protein actually risk having a low testosterone level, according to recent research. And low levels of this important hormone can cause not just poor sexual function, but muscle loss, damage to bones, and reduced red blood cells, according to the research, reported by the BBC.

Vegetarians and vegans in particular may be at risk, since animal products like meat are excellent sources of high-quality protein. It's not just vegetarians and vegans who may not eat meat. Older people typically consume less meat due to a reduced appetite as well as difficulty with chewing. Older men, too, can be at risk for having a low-protein diet affect their sex life.

The research linking low sex drive with low meat consumption, from the University of Massachusetts Medical School, was led by Christopher Longcope, MD. He and his colleagues focused their research on 1,552 men between the ages of 40 and 70. They learned that both fiber and protein levels helped to determine sex hormone levels, acccording to the research that was published in The Journal of Clinical Endocrinology and Metabolism.

Longcope, according to the BBC News article, noted that "the decrease in bioavailable testosterone can then result in declines in sexual function and red cell mass, and contribute to the loss of bone density."

Spyros Mezitis, MD, an endocrinologist at Lenox Hill Hospital in New York City, called the research "an important study because it shows us that there is a good association between animal protein consumption and testosterone."

"People need to be eating enough animal protein," Mezitis says. "If they are not, they may have low testosterone, which has other consequences as well. It can cause low muscle tone as well as depression." In older men, low testosterone levels have been linked to bone fractures as well. "Getting enough protein can help this," Mezitis says.

So does this mean that older men who want to rev up their sex life should start eating a daily steak? Not exactly. Protein is important, but you can also get it from other sources. And zinc increases the libido as well, Tanya Zuckerbrot, MS, RD, told Fox News.

"Protein is essential for producing sperm in men," she said.  "If your guy isn't into oysters there are other sources of protein that are going to be high in zinc."  Turkey, beef, and beans all increase male fertility and sperm production, she told Fox News. Pine nuts, too, are a good source of protein and they're loaded with healthful monounsaturated fats.

"Pine nuts, out of all the nuts, have the most amount of protein," Zuckerbrot told Fox News. "So we're back to the sexual drive and increasing fertility, but pine nuts are also seen in elegant dishes. It's a lot sexier than the average peanut."

Sources:

Browne, Melissa. "The best foods to jump start your sex drive." 13 September 2007. FoxNews.com

http://www.foxnews.com/story/0,2933,296685,00.html

"Sex drive warning to vegetarians and elderly." 21 January 2000. BBCNews.

http://news.bbc.co.uk/2/hi/health/613396.stm