Do you feel a bit tired, depressed, and have difficulty concentrating? Lost that loving feeling? You may be one of the men who have low testosterone levels.

Testosterone levels are highest when a man is young, and fall steadily beginning around age 30. In addition to being responsible for sexual function, adequate testosterone is also important for maintaining strong muscles and bones, and keeping fat evenly distributed.

Besides changes in sexual function and a decrease in muscle mass and bone density, low levels of testosterone can be responsible for a laundry list of problems including increasing «bad» cholesterol.

Testosterone supplements have been around for years, but doubts continue as to their long-term safety. And some men should never take them. Fortunately, there are natural, safe ways to boost your testosterone levels, Newsmax Health reports. They include:

Lose excess pounds. Extra body fat lowers testosterone levels, especially if extra weight is in the form of belly fat.

Cheer on your favorite team. Researchers found that rooting for the winning team caused a 20 percent increase in testosterone.

Enjoy a cup of coffee. In addition to providing a jolt of energy, caffeine boosts testosterone.

Take vitamin D . Scientists believe that vitamin D keeps the body from changing testosterone into estrogen while, at the same time, making the receptors on adrenal glands (which release testosterone) more sensitive.

Reduce stress. If you're stressed, your body releases large amounts of the stress hormone cortisol, which blocks the effects of testosterone. Common techniques to reduce stress include meditation and yoga.

Get enough sleep. The longer you sleep, the more testosterone circulates in your blood. 

Exercise. Exercise of all kinds appears to boost testosterone levels.

Snack on nuts. Almonds, Brazil nuts, walnuts, and peanuts increase the production of testosterone.