Your Grandparents' Nighttime Ritual Might Kill You

You've probably taken a spoonful of this "cure all"...

In the 1850s, a few chemists started producing cod liver oil as a medicine. It had been a popular remedy for decades, but it took a Norwegian man named Peter Moller to figure out how to extract the oil in large quantities.

Generations afterward grew up taking spoonfuls of the stuff, often before bedtime. But recently, research has shown that not only is cod liver oil packed with toxins, but it also damages your bones.

According to a study from the American Journal of Epidemiology, women who took cod liver oil as children had a significantly lower bone mineral density as they aged. The more oil they took, the weaker their bones.

Researchers are still looking for the mechanism of action (or cause and effect), but they think the high levels of vitamin A could be the biggest risk factor. Also noted is that livers filter out toxins, so eating oil from a fish liver means higher exposure to those toxins.

And the same danger lurks in other fish-oil supplements...

I've talked before about why fresh fish is so good for you. If you remember, I'm a fan of fresh, cold-water fish.

We've seen several studies over the years explaining how eating two servings of fish a week lowers your risk of death from heart disease. What's more, fish makes up a big part of the Mediterranean diet... a lifestyle rich in vegetables, fruit, fish, and olive oil. Following the Mediterranean diet keeps your brain healthy, lowers your risk of some cancers, and boosts your immune system.

As a food, fish is low in carbohydrates, high in protein, and moderately high in fat. The fat composition of fish is the important issue.

Some fats are beneficial for you. Fish contains low levels of saturated fat, but because it's a naturally occurring form, it's generally not bad for you. What's more important are the unsaturated fats. Fish are loaded with monounsaturated fat and polyunsaturated fat.

Monounsaturated fat is what makes up olive oil and is well-known to aid heart health. It is also a strong anti-inflammatory. Polyunsaturated fats are necessary for our brain health, but too many of them can cause problems. They include the omega fatty acids.

Omega-3 fats reduce inflammation. Inflammation increases your risk of heart disease and diabetes, and accelerates aging.

Omega-6 fats also help promote brain health and, along with omega-3s, help keep your bones healthy and your metabolism on track.

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Now, there's a bit of a controversy over how much of each one you need. Omega-3s are great for your health and are a fatty acid I've advocated for in my write-ups on fish.

However, too many omega-6 fatty acids can trigger inflammation – they're almost the opposite of omega-3s. People ideally should be eating omega-6s and omega-3s in a ratio no greater than 4:1.

The problem is that omega-6s are also in heavily processed vegetable oils. The American obsession with these oils means we're getting about 16 omega 6s for every 1 omega 3. (The whole topic of omega fatty-acid ratios is fascinating. You can see a comprehensive list from Tufts University right here.)

Fish are great sources of omega fatty acids. But a lot of folks don't like seafood. That's why the dietary supplement industry came up with fish-oil pills.

Manufacturers market fish-oil supplements as miracle pills packed with healthy omega-3 fatty acids. Some research suggests the supplements can ease depression, high blood pressure, and even arthritis. However, despite the miracle-cure claims of fish oil, there are serious health concerns in taking fish oil, especially in such large amounts.

The biggest problem I've discovered is that some of these pills can be tainted with chemical killers like PCBs, mercury, and dioxin. Just like the liver from cod contains higher concentrations of these toxins, so too do these pills.

Yet supplement makers are stuffing pills, baby foods, and even milk with these omega-3 acids based on health claims that are equivocal at best. At worst, we're discovering that supplements lack the natural balance of oils and micronutrients that exist in the "whole" food – i.e. actual fish meat. Seafood likely contains other healthy chemicals and molecules not yet measured.

Plus, most of the good research showing clear benefits of fish involved whole fish, not fish oil.

In addition, I don't like fat-soluble, oil-filled vitamins. Fat-based chemicals can build up in human tissues. I avoid taking too many fat-soluble vitamins like A, D, E, and K. You should, too.

Finally, fish oil can alter your bleeding and coagulation functions. Too much and you could induce strokes from bleeding into your brain. Until high doses of fish oils are studied and the mechanism of action better understood by hematologists (blood doctors), I wouldn't take more than one or two pills a week, or 1,000 milligrams (mg) of oil. Anything more is just dangerous.

So what do I do? I prefer eating real fish. I eat salmon or light tuna (it has the lowest amount of mercury among tunas) three to four times a month and take an occasional fish-oil pill of 300 mg from GNC.

With moderation, a mix of whole food, and minimal pills, I get nearly all of the health benefits without having to worry about the risks. The important part is to consume fish and pills that are low in mercury. You can view a list of fish and the mercury in them here.

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