MadSci Network: Biochemistry

Re: Can fruit cause high LDL?

Date: Thu Oct 20 14:03:08 2005
Posted By: Gabriel Harris, Post-doc/Fellow, Diet and Human Performance Lab, USDA
Area of science: Biochemistry
ID: 1128932141.Bc

Thanks for your question. I've broken it down into several different parts to make it easier to answer.

How can the level of FFA in the blood increase the release of VLDL from the heart and thus cause the release of TAG and cholestrol become higher?

High levels of fatty acids in the blood may cause the liver to try to package those fatty acids into triacylglycerides (TAGs). High levels of triglycerides can then cause the formation of VLDL. (VLDL contains both triglycerides and cholesterol).

How can FFA be high in the plasma?

There are several ways that FFA can be high in the plasma. One way is an increase in enzymes that degrade TAGs to FFAs. This occurs during pregnancy as well as during exercise (FFA levels go back down after exercise). People who are overweight may have constantly elevated blood levels of FFAs. This constant elevation, but not the temporary elevations caused by exercise, appear to be related to atherosclerosis.

Does it mean that eating the lipid from the fruits, such as TAG can increase the tendency to get atherosclerosis?

Fruits (with the exception of fruits like avacados) are generally low in TAGs, so I do not think that they are likely to increase the tendency to get atherosclerosis.

Some animal studies have indicated that very high intake of fructose (the sugar contained in many fruits) causes increased formation of TAGs and VLDL. Humans, even those that consume fruit regularly, do not consume huge amounts of fructose, unless they drink a lot of soft drinks that use high-fructose corn syrup as a sweetener.

Fruits also contain many beneficial substances, such as vitamin C and flavonoids, so don't stop eating fruit whatever you do!

Thanks again for your question

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