Lately a great deal of medical research has been looking at inflammation as a possible cause of cardiovascular disease. Doctors and researchers use CRP (C reactive protein) to determine the amount of inflammation a person is experiencing. C reactive protein is a compound made in the liver and released into the blood stream in response to an inflammatory stimulus. The CRP test has been shown to correlate with inflammation. And it is been found to correlate with the severity of coronary artery disease. A recent study (1) sought to determine if a diet could lower C reactive protein.
This is still relatively early research since no studies have shown that reducing C reactive protein will reduce coronary artery disease. Also there were no studies prior to this one showing that cholesterol lowering diets, such as the NCEP (National Cholesterol Education Program), could reduce inflammation.
The NCEP diet is a low fat diet many doctors use to lower blood cholesterol. The researchers in this recent study wanted to find out if the NCEP diet could lower C reactive protein as much as a medication. A medication that has been shown to reduce C reactive protein is lovastatin.
In this particular study a variation of the NCEP diet was compared to lovastatin for its ability to reduce C reactive protein. The participants in the study were all on a low saturated fat diet for a month prior to the study.
They were then randomly chosen to be on the control diet only, or the control diet and lovastatin, or on the experimental diet. The control diet was the usual NCEP diet. The experimental diet was designed to provide more plant sterol, fiber, soy protein, and almonds.
The remainder of the experimental diet was fairly similar to the control diet. The experimental diet had the same amount of protein, slightly less carbohydrates, and slightly more fat and cholesterol than the control diet.
Differences In Diets
But the experimental diet probably differed in unintended ways as well as the intended ways. The intended ways the experimental diet differed was that it had 4 times the amount of vegetable protein and 40% more fiber.
Since it was not measured, the difference in the type of fiber in each diet was probably unintended. The experimental diet included oats and barley, whereas the control diet included whole wheat. Thus the experimental diet had more beta-glucan, a soluble fiber, and the control diet had more insoluble fiber. These types of fiber have different known effects in the body.
Another important difference not measured was the potassium and sodium in each diet. The potassium sodium ratio has been shown to affect the amount of inflammation in the heart in heart failure. A previous post discussed how inflammation can be reduced with a diet that has a high potassium to sodium ratio. This was shown directly in animals in the study cited in that post. Among other findings, the researchers directly saw the inflammation by looking at heart samples under the microscope.
These differences in the experimental diet rather than the designed differences may have been responsible for the results. Because of the increased amount of vegetables and nuts in the diet, it is highly likely that the people put on the experimental diet had a better potassium to sodium ratio. The blood pressure in the experimental group was also reduced more than in either the lovastatin or the control group. This is another indication of a better potassium to sodium ratio in the experimental group.
C Reactive Protein Lowered By Diet
So the researchers did find that the experimental diet reduced C reactive protein just as much as lovastatin did. And the increased intake of vegetables and nuts were likely the difference. But whether it was the vegetable protein, vegetable sterols and vegetable fiber (no matter what type) that made the difference is not clear.
The researchers did not measure the types of fiber. And they did not study potassium or sodium. The different types of fiber, and the difference in potassium and sodium, in the diets may have been the critical difference. Further studies that include these variables may help determine how much of the improvement in C reactive protein was due to potassium and sodium.
Links to tables of the potassium and sodium content of various foods can be found by clicking the “Links to Food Potassium Tables” tab at the top of the page.
1. Direct comparison of dietary portfolio vs statin on C-reactive protein. Jenkins DJ, Kendall CW, Marchie A, Faulkner DA, Josse AR, Wong JM, de Souza R, Emam A, Parker TL, Li TJ, Josse RG, Leiter LA, Singer W, Connelly PW. Eur J Clin Nutr. 2005 Jul;59(7):851-60.