Gentlemen, if you want to keep your sperm swimming — and who doesn’t? — head on over to the nearest fish market and load up on tuna and salmon.

The fattier the fish, the better — because the same fatty acids that make these fish such healthy choices for everything from your heart to your eyes to your brain are also positively critical to your fertility.

The omega-3 fatty acid docosahexaenoic acid (DHA) is one of the essential building blocks of sperm — and a new study on mice shows how it’s also a key part of the acrosome, which is what enables the sperm to penetrate the egg.

You might say it’s the most important part of all. The mice would agree: When they were denied DHA, they produced fewer sperm — and the ones they did create were misshapen, rendering them infertile.

But once DHA was put back into their diets, they began to produce again like, well, mice. (Side note: There has to be a pest-control angle in here somewhere).

This is, of course, just one study on mice. But human studies have also shown how high levels of these essential fatty acids can boost your fertility.

One study from just a couple of years back found that fertile men tended to have higher blood levels of omega-3 fatty acids, while infertile men had higher levels of omega-6 fatty acids.

And these days, with diets heavy in grain fed animals from factory farms, most of us get less of the desirable omega-3s and far more of the undesirable omega-6 fatty acids.

Call it one more reason to switch to fresh all-natural grass-fed meats.

Naturally, omega-3 fatty acids aren’t the only answers for sperm health. A lot goes into male fertility — and studies over the years have shown that high levels of vitamin D can boost the speed and forward motion of sperm, an essential trait called motility.

Other studies have also shown that junk food, soda and the BPA used to line canned goods (including soda cans) can slash sperm levels and turn the ones that are left into the microscopic equivalent of couch potatoes: slow, lazy and uninterested in the quest for the egg.

That would explain the recent rise in male infertility.

Inflammation has gone from a condition you should worry about to a marketing buzzword used to sell everything from drugs to juice to cereal.

Well, at least they got it half right: You should worry about inflammation, and do what you can to bring your own levels down.

But forget the drugs, juice and cereal — because none of those things will ever beat the anti-inflammatory powers of plain old fish oil, and the latest research proves it again.

A new look at data on 702 patients who took part in one of 11 clinical trials finds that people who take fish oil supplements have lower blood levels of homocysteine, an inflammation marker linked to everything from heart risk to dementia to bone breaks, according to the study in Nutrition.

Other studies have also found that fish oil can put the hurtin’ on homocysteine.

One published in 2009 found that omega-3 supplements reduced levels of the inflammation marker by 22 percent in diabetics — versus just one percent among those who took a placebo.

And that’s really only the beginning of the benefits.

Studies have found that healthy omega-3 fatty acids can help protect your heart, eyes, and gums while raising levels of HDL (“good”) cholesterol and lowering levels of deadly triglycerides.

Fish oil can also help boost the mood and beat depression — especially among seniors.

The best sources of these omega-3s are fatty fish such as salmon, tuna, trout and herring — and the highest concentrations are often in the one part of the fish you’re probably not eating: the liver.

Researchers looked at a dozen fish commonly eaten in Spain and found all had livers rich in the long-chain polyunsaturated fatty acids you need for good health.

And if you like anchovies, good news: The livers of these famously oily little fish had some of the highest omega-3 levels of all.

But why stick to the liver when you can eat anchovies whole?

OK, I know that’s not for everyone — but if you don’t like anchovies, fish livers or even fish itself, there’s a simple solution: a high-quality fish oil supplement from a company you trust.

Some can leave a fishy aftertaste or, even worse, a case of the “fish burps,” but don’t give up — refrigerate your capsules instead.

And if that doesn’t work, try a different brand until you find one that leaves you with all the benefits… but none of the burps.

Depressed? Skip the doc and head straight to the docks–as in your favorite dockside seafood restaurant.

If the maritime atmosphere doesn’t lift your spirits, the menu sure will–because the omega-3s found in fatty fish like salmon and tuna are the ultimate blues busters.

And a new study finds that seniors in particular could have the most to gain.

Iranian researchers recruited 66 seniors and gave them either a placebo or an omega-3 fatty acid supplement that contained 300mg of both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Six months later, and the catch of the day was a genuine mood boost: The Seniors who took the supplement did significantly better on a 15-question depression assessment, according to the study in the European Archives of Psychiatry & Clinical Neuroscience.

This wasn’t a fluke, either–in fact, we’ve seen these results before.

Back in 2008, researchers put 1,000 mg of fish oil a day up against a standard 20 mg dose of fluoxetine, better known as Prozac.

And if more depression patients knew about the results of this one, maybe they’d finally cut the line on Prozac for good–because the researchers found the fish oil to be every bit as effective, with none of the drug’s notorious side effects.

But you don’t have to be depressed to start taking fish oil –other studies have found that a daily omega-3 supplement now will lower your risk of even coming down with the condition later.

Daily fish oil can also help your heart, brain, eyes, and gums, raise levels of HDL cholesterol, lower triglycerides and prevent blood clots.

Don’t be left adrift on this one: If you’re not getting enough omega-3 fatty acids from a diet rich in salmon, tuna, trout, herring and anchovies, make sure you add some fish oil capsules to your regimen.

You won’t be alone–fish oil was the number one supplement last year.

It even beat out multivitamins, although it probably got a big assist from the fact that Big Pharma fish oil, Lovaza, did about $1 billion in business.

I’ve got mixed feelings on that: It shows Big Pharma that you can make money and help people by selling a natural supplement instead of risky drugs, and that can’t be all bad… right?

On the other hand, it’s badly overpriced–so unless you’ve got the world’s best prescription drug plan, skip the Lovaza and stick to a high-quality fish oil supplement from a trusted brand.

You’ll get all the benefits for a fraction of the price.

I’m not done with senior health yet–keep reading for some fun and easy ways to avoid physical and mental decline.

Do you want to keep your mind in top shape and lower your risk for dementia?

The answer is simple: Eat more fish.

It’s easier said than done, I know – but a study published in August in the American Journal of Clinical Nutrition finds that the more fish people eat, the lower the risk of dementia.

Although the study didn’t take it to the next level and find out what specifically was providing this great benefit, the smart money is on the omega-3 fatty acids found in so many fish.

And that’s not the only great news about omega-3 fatty acids this week. Another new study confirms what most of us have been seeing in practice for a while now: Fish oil helps support a healthy heart.

The study, published in the Journal of the American College of Cardiology, recommends that healthy men get 500 mg of omega-3 fatty acids per day, and that men facing heart disease get 1,000 mg per day.

You’ll get that in just a couple of ounces of good, fresh salmon.

When I need to collect my thoughts, or if I’m just looking to unwind for an afternoon, I like to head up into Glacier National Park and hike the great trails there.

Some of the area’s lakes are filled with Kokanee salmon. Most tourists think we’ve always had salmon here, but the locals will tell you the fish were introduced nearly a century ago – but that’s another story.

Why am I telling you this? You’re probably thinking this is just a red herring – but it’s not (even if herring are another great source of fish oil).

Each of these salmon – and there are so many of them – are loaded with omega-3 fatty acids. A six-ounce serving of salmon can have up to 3 grams of omega-3 fatty acids.

And while the salmon are more noticeable, the lakes here also have freshwater trout, another great source of omega-3 fatty acids. In fact, the trout can have even more omega- 3 fatty acids than the salmon. The secret is the source: Stick to freshwater trout, like the ones we have out here, because sea trout can be high in mercury.

While nothing beats a natural source of omega-3 fatty acids, I always encourage my patients to add a supplement. It’s the only way to make sure you’ll get all the great benefits of omega-3 fish oils, unless you really love your salmon.