Lack of effect of foods enriched with plant- or marine-derived n-3 fatty acids on human immune function.
BACKGROUND
Greatly increasing dietary flaxseed oil [rich in the n-3 polyunsaturated fatty acid (PUFA) alpha-linolenic acid (ALA)] or fish oil [rich in the long-chain n-3 PUFAs eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids] can reduce markers of immune cell function. The effects of more modest doses are unclear, and it is not known whether ALA has the same effects as its long-chain derivatives.


OBJECTIVE
The objective was to determine the effects of enriching the diet with ALA or EPA+DHA on immune outcomes representing key functions of human neutrophils, monocytes, and lymphocytes.


METHODS
In a placebo-controlled, double-blind, parallel study, 150 healthy men and women aged 25-72 y were randomly assigned to 1 of 5 interventions: placebo (no additional n-3 PUFAs), 4.5 or 9.5 g ALA/d, and 0.77 or 1.7 g EPA+DHA/d for 6 mo. The n-3 PUFAs were provided in 25 g fat spread plus 3 oil capsules. Blood samples were taken at 0, 3, and 6 mo.


RESULTS
The fatty acid composition of peripheral blood mononuclear cell phospholipids was significantly different in the groups with higher intakes of ALA or EPA+DHA. The interventions did not alter the percentages of neutrophils or monocytes engaged in phagocytosis of Escherichia coli or in phagocytic activity, the percentages of neutrophils or monocytes undergoing oxidative burst in response to E. coli or phorbol ester, the proliferation of lymphocytes in response to a T cell mitogen, the production of numerous cytokines by monocytes and lymphocytes, or the in vivo delayed-type hypersensitivity response.


CONCLUSIONS
An intake of <or= 9.5 g ALA/d or <or= 1.7 g EPA+DHA/d does not alter the functional activity of neutrophils, monocytes, or lymphocytes, but it changes the fatty acid composition of mononuclear cells.
Kew
Samantha
S
Institute of Human Nutrition, University of Southampton, Southampton, United Kingdom.
Banerjee
Tapati
T
Minihane
Anne M
AM
Finnegan
Yvonne E
YE
Muggli
Reto
R
Albers
Ruud
R
Williams
Christine M
CM
Calder
Philip C
PC
D000328:Adult; D000368:Aged; D016207:Cytokines / Q000096:biosynthesis; D004281:Docosahexaenoic Acids / Q000008:administration & dosage*; D004311:Double-Blind Method; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage*; D005260:Female; D005395:Fish Oils / Q000737:chemistry; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000187:drug effects / Q000276:immunology*; D008043:Linseed Oil / Q000737:chemistry; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000737:chemistry / Q000276:immunology*; D010587:Phagocytosis; D010743:Phospholipids / Q000097:blood* / Q000737:chemistry; D016897:Respiratory Burst; D017962:alpha-Linolenic Acid / Q000008:administration & dosage*
D016207:Cytokines; D005395:Fish Oils; D010743:Phospholipids; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids; D008043:Linseed Oil; D015118:Eicosapentaenoic Acid