Phenol-rich diet improves ailing immune system
An ailing immune system will work better as the amount of phenols in the diet increases. This is apparent from an animal study that Spanish biologists published 15 years ago in Nutrition. Phenols are found in coffee, tea, vegetables, fruits and herbs.

The researchers, affiliated with the Complutense University of Madrid, experimented with mice. In a first step, they determined how easily the mice could adapt to a situation in which they had to absorb new information. If the animals were no longer able to do that, they regarded the mice as prematurely aging [PAM]. If the mice were no longer able to adapt properly, the researchers considered the mice to be non-prematurely aging [N-PAM.]

The researchers then experimented with their test animals for 5 weeks. They gave the N-PAM mice standard food [NPAMc], and did the same with a group of PAM mice [PAMc]. Another group of PAM mice was given food consisting of 20 percent wheat bran [PAMb], and yet another group of PAM mice was given food consisting of 20 percent buckwheat [PAMc].
Both wheat bran [B] and buckwheat [C] contain relatively many phenols, the table below shows. HF = hydrosoluble fraction; LF = liposoluble fraction.

The researchers removed immune cells from the mice and exposed them to a substance that simulates the presence of pathogens [LPS]. The researchers then determined the production of interleukin-2 by the immune cells. More interleukin-2 means a stronger immune response.

You can see in the bottom right that the immune cells of the prematurely aging mice produced less interleukin-2 than the cells of the non-prematurely aging mice.
LPS stimulated the immune cells to develop, but the stimulus was lower in the prematurely aging mice. However, phenol supplementation normalized the immune response.
Click on the figure below for a larger version.

In another experiment, the researchers extracted Natural Killer Cells from the mice and placed them in a test tube together with cancer cells. They then determined how many cancer cells were turned off by the Natural Killer Cells.The table above shows that phenol supplementation also improved that aspect of the immune system in the prematurely aging mice.
"The present work has demonstrated that dietary supplementation with cereals naturally rich in polyphenols is a nutritional strategy targeted at restoring immune function in prematurely aging mice, thus leading to better health and increasing the probability of aging successfully," the researchers write.

"Moreover, the health benefits of these cereal fractions go far beyond slowing down the aging process; their intake is of considerable interest because they are effective, able to be included in different cereal products, and are completely safe because all of them are naturally present in cereal."
Nutrition. 2006 Sep;22(9):913-21.