Diet, Cooking, and Exercise: fatty acids

Top 10 Fish to Eat for Health

Rank	Species	Mercury (ppm)	Omega-2 (g)	M-O
1.	JACKSMELT	0.108	5.6	5.49
2.	PERCH (Freshwater)	0.14	3.5	3.36
3.	AMERICAN SHAD	0.065	2.65	2.59
4.	ATLANTIC MACKEREL (N. Atlantic)	0.05	2.6	2.55
5.	COD	0.095	2.5	2.41
6.	MACKEREL CHUB (Pacific)	0.088	2.2	2.11
7.	SARDINE	0.016	1.58	1.56
8.	HERRING	0.044	1.6	1.56
9.	TUNA (CANNED, LIGHT)	0.118	1.6	1.48
10.	WHITEFISH	0.069	1.5	1.43

The Next 10

Rank	Species	Mercury (ppm)	Omega-3 (g)	M-O
11.	ANCHOVIES	0.043	1.4	1.35
12.	MACKEREL SPANISH (S. Atlantic)	0.182	1.48	1.29
13.	SALMON (FRESH/FROZEN)	0.014	1.26	1.24
14.	SALMON (CANNED)	0	1.176	1.17
15.	BUTTERFISH	0.058	0.7	0.64
16.	MULLET	0.046	0.6	0.55
17.	TROUT (FRESHWATER)	0.072	0.6	0.53
18.	CARP	0.14	0.6	0.46
19.	POLLOCK	0.041	0.5	0.46
20.	CATFISH	0.049	0.5	0.45

About Fish and Health

We know that the American Heart Association and the United States Department of Agriculture recommend that we limit our consumption of fat to less than 20-35% of our total calories. And, most of our dietary fats should come from polyunsaturated and monounsaturated fatty acids. We may also know that the recommended ratio of omega-6 polyunsaturated fatty acids to omega-3 should be six to one and that the typical American diet contains a ratio of twenty to one.

Sources of Good Fats

Sources of omega-6 polyunsaturated fatty acids are liquid vegetable oils, such as soybean oil, corn oil, and safflower oil. Omega-3 polyunsaturated fatty acids come from both plant sources, and from fish and shellfish. Plants contain omega-3 in the α-linolenic acid form (ALA) and soybean oil, canola oil, walnuts, and flaxseed, are among the better sources. Fish and shellfish contain the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Fish that naturally have more fat, like salmon, trout, and herring, have more EPA and DHA than less fatty fish like cod, haddock, and catfish. There are suggestions in the literature that consuming omega-3 fatty acids from a fish source can improve heart health and reduce the chance of mortality from heart disease.

Caveats

The problem with eating large amounts of fish is that these fish live in water that has been polluted by mercury, polychlorinated biphenyls PCBs, dioxins, and other environmental contaminants. These substances, many of which are potent carcinogens, can cause nerve damage and are implicated in a number of diseases. These toxins are found in the flesh and fat of fish to varying degrees, generally higher in larger, older, fish at the top of the food chain.

The worst offenders are:

Tilefish (golden bass or golden snapper) 1.45 ppm
Shark with 0.99 parts per million (ppm) of mercury
Swordfish 0.97 ppm
And, King mackerel at 0.73 ppm

The United States Food and Drug Administration (FDA) recommends that nursing or pregnant women, women who are about to become pregnant, and small children should not eat any of these fish. For everyone else, the guidelines allow for up to 7 oz. per week. Why anyone would eat these fish when there are better alternatives is beyond me.

Also according to the FDA, people in this group should limit their consumption of fish that carry about .5 ppm to 12 ounces per week, and all others to 14 oz. per week. Clearly we should be eating more fish, but it’s hard to know what is safe.

Methodology

I prepared a spreadsheet putting the fish on the FDA mercury monitoring list in the first column, the sampled mercury levels in the second column, and the combined omega-w (EPA+DHA) in the third column. I filtered the list for high and moderate levels of mercury and then subtracted the omega-3 levels from the mercury levels. What remains are low mercury fish with high levels of healthy omega-3 fatty acids.

Here is my recap from yesterday.