BP and Lipid Elevations: Can You Blame Them on Yesterday's Chips and Dip?

Some of my patients who are being treated for hypertension, hyperlipidemia, or both claim that an elevated blood pressure reading or lipid level measurement resulted from a sodium- or fat-laden meal that they had eaten 1 or 2 days before their office visit. They swear that they have been compliant with their drug regimen. Can a single meal that contains excessive salt or fat really cause either blood pressure or lipid levels to rise?

---- Percy D. Kepfer, MD
Fort Pierce, Fla

The simple answer to both parts of your question is no. With lipid measurements, the value that is most affected by recent food ingestion is the triglyceride level; high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol levels change relatively little. However, the LDL cholesterol level is often calculated by subtracting the HDL cholesterol level and one fifth of the triglyceride level from the total cholesterol level. Thus, if a patient has had a fatty meal within 12 hours of the test, it could throw the numbers off.

Acute salt loading does not have much effect on blood pressure; this has been shown in studies in which intravenous saline is given. In one such study, an infusion of 2 liters of normal saline over 4 hours raised systolic blood pressure by 4 mm Hg on average. Sensitivity to salt varies greatly from person to person, but even in those who are salt-sensitive, it generally takes several days of a high-salt diet to produce a significant increase in blood pressure.

---- Thomas G. Pickering, MD
Professor of Medicine
Columbia College of Physicians & Surgeons
New York