Doctors used to tell everyone having their lipids checked to fast for 10 to 12 hours before having their blood drawn. Lipids include your cholesterol and triglyceride levels. If you're having only your total cholesterol level checked, you don't need to fast at all, according to the Harvard Health Letter. But if you're having your triglycerides or low-density lipoprotein level checked, you do need to fast, because what you eat or drink can affect triglycerides.
Total Cholesterol Levels
Doctors often test a lipid panel, which includes not only total cholesterol levels but also high-density lipoprotein, or HDL, the so-called "good" cholesterol, and low-density lipoprotein, or LDL, the so-called "bad" cholesterol, as well as triglycerides. Testing all four gives your doctor a much more complete picture of your lipid health. While total cholesterol is helpful, it tells just a small part of the overall picture. You could have low total cholesterol but high triglycerides and high LDL, which would make for an unhealthy lipid profile.
What you eat or drink within the 12 hours before a triglyceride test can raise your levels by as much as fivefold to tenfold, according to Lab Tests Online. While fatty foods such as cream might seem like the biggest culprit in raising triglyceride levels, sugar also raises your triglycerides. Plain tea without cream and sugar might not have the same effect, but don't drink it without asking your doctor first; MayoClinic.com recommends not drinking tea or coffee before checking your lipids.
The reason why LDL is affected by what you eat or drink is because doctors use your triglyceride levels to figure your LDL levels. Low-density lipoprotein is difficult to measure directly, so doctors use a formula called the Friedewald equation. To figure LDL by this method, use this equation: LDL = (Total cholesterol) - (HDL) - (Triglycerides ÷ 5). For example, if your total cholesterol is 200, your HDL is 50 and your triglycerides are 150, your LDL would be: 200 - 50 - (150 ÷ 5) = 120. So if your triglycerides were artificially high from what you ate or drank, it would affect your LDL levels.
Tea, particularly green tea, might help lower lipid levels when you drink it on a regular basis. A Chinese review of 14 studies published in the August 2011 "American Journal of Clinical Nutrition" found that drinking green tea significantly lowered total cholesterol and LDL levels but didn't affect HDL.
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