Most of us have heard of the omega-3 craze sweeping across the nation, but now some are concerned that the growing demand for this vitamin is depleting fish populations in our oceans.

Omega-3 fatty acids are polyunsaturated fatty acids essential to human health. According to WebMD, regular consumption of omega-3 acids can reduce blood pressure, triglycerides, and inflammation of the joints as well as reduce the risk of coronary heart disease and heart failure. On top of that, some research suggests that omega-3s may help protect against infant brain development, Alzheimer's disease and dementia.

There are several kinds of omega-3 fatty acids, but the main three are eicosapentaenic acid (EPA), docosahexanoic acid (DHA), and alpha-linolenic acid (ALA). While ALA is found in plant sources such as nuts and seeds, EPA and DHA are primarily found in certain fish, like salmon, sardines and tuna.

Experts say to that it's most beneficial to eat fish high in DHA and EPA omega-3 fatty acids two to three times a week, with a recommended daily intake of about 250 mg, One Green Planet reports.

But it's this large appetite for fish meat and omega-3 supplements (in the form of fish and fish liver oil) that's causing fish populations to plummet. According to Save Our Seas, 75 percent of the world's fish populations are removed faster than they can reproduce. About 80 percent are already in rapid decline, and 90 percent of all large predatory fish - including tuna, sharks, swordfish, cod and halibut - have been wiped out. Scientists now believe that fisheries will collapse by 2050 if current practices continue.

And with some species taking decades to mature, deep-sea dwellers like sharks are especially vulnerable to over-exploitation.

"The omega-3 tablets that we buy comes from lots of different sources but there are some that are shark liver oil," Marine wildlife scientist Allison Perry said, according to Mail Online.

"There are some vessels actively targeting deep-water sharks," she added.

And while such over-fishing is detrimental to fish populations like sharks, it also means bad news for fish eaters. One of five people on this planet depends on fish as the primary source of protein.

"Overfishing cannot continue," Nitin Desai, Secretary General of the 2002 World Summit on Sustainable Development in Johannesburg, warned in a United Nations news release. "The depletion of fisheries poses a major threat to the food supply of millions of people."

One solution to this growing problem is to get this beneficial vitamin via other sources, like walnuts, flax, chia or pumpkin seeds.