The influence of fat on immune function

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The influence of fat on immune function

JoAnn Guest

Oct 16, 2005 20:35 PDT

 

 

 

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The influence of fat on the immune function has only recently come

under

serious study. It is known that polyunsaturated fatty acids,

particularly linoleic acid, are required for optimal functioning of

the

immune system, but there is an optimum level which should not be

exceeded. In recent years there has been a tremendous increase in

the

consumption of polyunsaturated fats to combat heart disease, but

this

has brought to the fore a host of problems not previously envisaged.

High level of fats, impact negatively on the immune system and

decrease

its ability to cope with cancer tumours, allergies, infections by

microbial organisms and both thymic-dependent and thymic-independent

antigens.

Immune responses can thus be enhanced or depressed, depending on the

concentration and extent of unsaturation of dietary lipids. It has

been

found that high-fat diets consistently depress resistance to malaria

and

tuberculosis in rats, and respiratory infections in chickens, but

the

same seems to be true for humans. Lower respiratory tract infections

in

infants, for example, are significantly more common in obese infants

than in non-obese infants, and in one third of obese infants,

adolescents and adults studied there was impairment of cell-mediated

immune responses.[ii]

The mechanism whereby fats interfere with the body's ability to

combat

the growth of cancerous tumours has also been investigated. A

subpopulation of T-lymphocytes, known as natural killer cells,

specifically react to destroy tumour cells before they can

proliferate.

Recently it has been found that diets high in polyunsaturates,

particularly those rich in n-6fatty acids (e.g. linolenic acid),

impact

negatively on the ability of these killer cells to seek out and

destroy

cancer cells.[iii]

Three types of blood cells are associated with the immune response

and

secrete substances that effect B- and T-cell activity in many ways.

Examples of lymphokines are interferon and interluekon 1, of which

interferon stimulates T-cell proliferation and interleukon 1

stimulates

a broad range of cells, including the natural killer cells,

neutrophils,

and B- and T-lymphocytes. T-cells do not produce antibodies which

combine with antigens, rendering them inactive and enabling

phagocytes

to engulf the invaders.

These substances, including prostaglandin, which are produced from

the

essential fatty acids, linolenic and linoleic acid. Those

prostaglandins

that have a relaxing, anti-flammatory and anti-clotting effect are

generally formed from alpha-linolenic acid whilst those with the

opposite effect are manufactured from linoleic acid and arachidonic

acid. More than one hundred different prostaglandins have been

identified, and they promote or inhibit basic bodily functions such

as

fever, blood clotting, vasodilation and constriction, stress,

allergy

responses, membrane permeability, eye pressure, inflammation,

steroid

production, appetite, fat metabolism and the functioning of the

immune

system.[iv] When prostaglandins occur in a balanced relationship

they

tend to relax arteries and reduce blood pressure as well as slow

down

tumour formation and decrease platelet aggregation, thus lowering

the

risk of thrombus formation. If the balance of prostaglandins is,

however, disturbed then the opposite effects are achieved. It is

interesting to note that tumour cells produce large amounts of the

prostaglandin PGE2 and cancer patients can produce four times the

normal

amount of this prostaglandin. It has an immunorepressive effect and

leucotriene B4 is a potent chemotactic and chemokinetic agent.[v]

A reduction in the amounts of polyunsaturated fats in the diet,

inclusive of the essential fatty acids, can provide a substantial

anticarcinogenic effect.[vi] A whole-food diet, which includies

grains,

legumes, seeds and nuts will provide the ideal blend of fatty acids

and

total fat composition to ensure the optimal fuctioning of the immune

system.

Fatty Acid Profiles of Foods High in Monounsaturated Fats

Source: Resnicow, K., Barone, J., Engle, A., Mliler, S., Haley,

N.C.,

Fleming, D., Wynder, E. 1991. Diet and serum lipids in vegan

vegetarians: A model for risk reduction. J. Am. Diet. Assoc. 91:447-

453

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References:

Maki, P.A., Newberne, P.M. 1992. Dietary lipids and immune

function.

J.Nutr. 122:610-614.

[ii] Chandra, R.K. 1981. Immune response in overnutrition. Cancer

Res.

41:3795-3796.

[iii] Byman, L.D. 1991. Dietary fat and natural killer cell

function.

Nutrition Today. Jan/Feb 1991, pp.31-36.

[iv] Lee, L.B. 1976. " Prostaglandins and blood pressure control "

(Combined clinical and basic science seminars) Am. J. of medicine

61:681.

[v] Jonnalagagadda, S.S., Mustad, V.A., Yu, S., Etherton, T.D.,

Kris-Etherton, P.M. 1996. Effects of individual fatty acids on

chronic

diseases. Nutrition Today. 31 (3) May/June 1996.

[vi] Barone, J., Hebert, J.R., Reddy, M.M. 1989. Dietary fat and

natural

killer cell activity. Am.J.Clin.Nutri. 50:103-106.

Hebert, J.R., Barone, J., Reddy, M.M., Backlund, J.Y. 1990. Natural

killer cell activity in a longitudinal dietary fat intervention

trial.

Clin.Immunol.Immunopathol. 54:103-16.

The above has been excerpted from the book Diet and Health by

Professor

Walter J. Veith available through our webstore.

www.amazingdiet.org

_________________

JoAnn Guest

mrsjo-

www.geocities.com/mrsjoguest/Diets