Ask Dr. Gourmet

Can you eat too much fish?

I wondered if there's too much of a good thing: can salmon more than 4 times per week raise cholesterol levels or otherwise pose risks? Is there an upper limit? I'm referring to canned Pacific salmon, mackerel, or sardines.

I'm a lacto vegetarian, am likely deficient in omega-3 and omega-6 fatty acids, and don't have qualms incorporating fish into my diet - just wondered about an upper limit.

Dr. Gourmet Says...

Salmon is a safer choice as are mackerel and sardines. All three are higher in Omega-3 fatty acids, and there's less risk of contamination with mercury or other industrial pollutants than some other fish. A 3 1/2 ounce serving of each of these choices comes in at about 1,000 mg of Omega-3 fats but ≤ 0.5 parts per million of mercury.

You might want to take care of eating "too much of a good thing" as you say. I love all three of these fish, and although they are convenient because they come canned, you do have a lot of alternatives. Here's an article that discusses the amounts of good fats in fish along with the amounts of mercury: Dr. Tim Says... One fish, Two fish, Mercury in Your Fish

That said, you can get a lot of great quality fats from other sources. One of the best are nuts and oils. Here's a table to help you with some choices:

Oils

Olive oil	1 Tbsp.	0.1
Soybean oil	1 Tbsp.	0.9
Canola oil	1 Tbsp.	1.3
Walnut oil	1 Tbsp.	1.4
Cod liver oil	1 Tbsp.	2.8
Sardine oil	1 Tbsp.	3.7
Flax seed oil	1 Tbsp.	6.9

Nuts and Seeds

Almonds, dry roasted	1 oz.	0
Pistachios, roasted	1 oz.	0.1
Poppy seeds	1 oz.	0.1
Pumpkin seeds, shelled	1 oz.	0.1
Sesame seeds	1 oz.	0.1
Pecans, dry roasted	1 oz.	0.3
Flax seeds	1 oz.	1.8
Walnuts	1 oz.	2.6

Vegetable sources

Tofu, regular	4 oz.	0.3
Soybeans, dried, cooked	1/2 cup	0.5

* Values are rounded to the nearest tenth, with values less than 0.05 g given as "trace"

Source: Minnesota Nutrient Data Base 4.04, Tufts University School of Medicine, Boston, MA

Adding in nuts and choosing the right oils will help. There's some good (but not definitive) research to support taking supplements such as fish oil or flax seed oil if you are not getting enough essential fatty acids in your diet.

Thanks for writing,

Timothy S. Harlan, MD, FACP, CCMS
Dr. Gourmet