Fish Oil and Cholesterol: What to Do When Lowering Triglycerides Appears to Raise LDL

If you're diabetic and you've been taking fish oil to lower your triglycerides, you may have noticed a nasty (but misleading) relationship between fish oil and LDL cholesterol: When your triglycerides go down, your LDL goes up.

Or at least it appears to. This is what is really happening:

It's relatively expensive to measure LDL cholesterol directly. The cost of a true LDL test could run more than all the other tests your doctor orders at your diabetic checkup, well into the hundreds of dollars.

Labs typically estimate LDL levels by:

1. Measuring total cholesterol.
2. Measuring the denser, easy to separate, HDL or "good" cholesterol, and
3. Then assuming any cholesterol you happen to have in your blood that isn't HDL or LDL is 1/5 as much as your triglycerides.

Most people don't know that there is yet another major class of cholesterol, VLDL or very low-density lipoprotein. The typical rule of thumb is that you'd have 1/5 as much VLDL as triglycerides (from which it is formed).

So the equation is:

1. Take total cholesterol.
2. Subtract HDL.
3. Subtract triglycerides x 1/5.
4. And the answer is supposedly your LDL.

But what happens if you have been taking fish oil to lower your triglycerides? And it's been working?

Your triglycerides go down, so your LDL appears to go up.

Suppose before you started taking fish oil, you had:

Triglycerides: 400 mg/dl
Total cholesterol: 180 mg/dl
HDL: 45 mg/dl

Then your estimated LDL would be 180 - 45 - (1/5 of 400) or 55.

But then you work really hard at getting your triglycerides down. You take fish oil. You're really careful with your carbohydrate. You keep your blood sugars down. And you get your triglycerides all the way down to 100 mg/dl. Your total cholesterol stays at 180 and your HDL stays at 45.

And let's suppose your LDL didn't really go up--but the estimate will be off:

180 - 45 - (1/5 of 100)= 115.

So you're reward for getting your triglycerides down will be your doctor will want to put you on a statin for high LDL, even if your actual LDL stayed same, even if your actual LDL went down.

If your insurance does not cover your lab work, it probably won't pay for Lipitor, either. If you don't want to pay $500 for an Apo-B test ("bad LDL" is apo-B, LDL can also be apo-A, which doesn't require a statin) to keep you from paying $100 a month for a cholesterol-lowering drug, consider this:

1. Ask your doctor is there isn't a little room for interpretation of the lab results. Your doctor should know how LDL is estimated, and if they don't, well, consider finding another doctor.
2. You can lower both triglycerides and LDL safely and inexpensively by using both fish oil and red yeast rice. If LDL goes up, try red yeast rice for 3 months before submitting to either an expensive lab test or an expensive medication.