Dietary Hazards - Fats and Disease

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Fats have been positively linked to numerous degenerative diseases such as

cancer and cardiovascular disease, but a number of common ailments can also be

attributed to a high-fat consumption.

 

It is, however, not only the quantity of fat that is implicated in disease, but

also the type of fat.

 

In countries where fat consumption is low, the incidence of degenerative

diseases is far lower than in Western countries with their high-fat consumption.

 

The Japanese have a fat intake of only 10%-20% of their food intake and they do

not seem to suffer from the diseases prevalent in Western society, and also seem

to enjoy greater longevity of life.

 

This phenomenon is definitely linked to their lifestyle, because Japanese

communities that have adopted Western lifestyles suffer from the same diseases

that are prevalent in these societies.

 

Different fatty acids exert different effects, and though research into the role

of fatty acids in disease causation is still in its infancy, some information is

available.

 

Precisely how fatty acid imbalances cause disease, is unknown, but because they

are incorporated into cell membranes, changes in dietary intake of fatty acids

can cause changes in membrane fluidity, responses to outside signals such s

hormones, binding of ligands (ie, lipoproteins) to their membranes, lipid

mediators of the intracellular signalling cascade (ie, inositol triphosphate,

prostaglandin, and leukotrine production).

 

Moreover, the oxidation products of fatty acids can cause damage and even cell

death.

Fats and Cancer

The role of fats in cancer promotion has received much attention of late, as

there is a strong correlation between various forms of cancer and total fat

intake.

Carcinogenic processes have two distinct stages: Initiation and Promotion.

Initiation involves an irreversible interaction between a carcinogen and the

genetic material of its target tissue. Not much is known about initiators, but

asbestos (lung cancer), viruses (lymphatic cancers and cervical cancer) as well

as tobacco smoke (lung cancer) are known to initiate cancer.

Initiation does not generally lead to observable tumours unless promoters are

present.

These promoters can cause the transformed cells to form tumours.

As the consumption of excess fats and certain types of fat can promote cancer,

it is important to plan dietary strategies accordingly. In table 3.3 the

association between fat and certain other parameters is presented.

The Association Between Selected Dietary Components and Cancer

World Health Organization. 1990. Diet Nutrition and the Prevention of Chronic

Diseases. Technical Report Series 797, Geneva: WHO, 1990

The Association Between Selected Dietary Components and Cancer.

Site of cancer

Fat

Body weight

Fruits and vegetables

Alcohol

Smoked, salted and pickled food

World Health Organization. 1990. Diet Nutrition and the Prevention of Chronic

Diseases. Technical Report Series 797, Geneva: WHO, 1990.

Clearly, fat is a strong promoter of colon and prostate cancer, and fruits and

vegetables act as anti-promoters.

Cancer of the breast, colon and prostate is common in countries with Western

lifestyles such as Switzerland, the US and South Africa, but is rare in Japan.

Japanese migrating to the US soon develop the same incidence of US prevalent

cancers in view of a change in diet.

In developing countries as much as 80% of total calories come from cereals and

grains, but in industrialized countries there is a calorie intake shift towards

animal fat, vegetable oil and refined sugar.

This latter diet reduces the incidence of gastric cancer but increases the

incidence of gastric cancer but increases the incidence of colon, ovarian,

prostate and breast cancer.

The drop in gastric cancer has been attributed to refrigeration, which has

replaced salting, pickling and smoking as a means of food preservation.

Countries such as Austria where smoked foods are used extensively also have high

incidences of gastric cancer.[ii]

International correlation studies have shown that a high-fat intake increases

the incidence of prostatic, breast and colon cancer.

Prostate cancer has been correlated with diets high in animal fats such as fatty

meats, cheeses, and cream.

The US, Britain, the Netherlands, Denmark and South Africa have some of the

world’s richest diets, and also have the highest incidence of breast cancer.2

Diabetes and pancreas cancer are also positively correlated with a high-fat

diet.[iii]

Saturated fatty acids in particular are associated with breast cancer,

particularly in post-menopausal women,[iv] colorectal adenomas[v], and ovarian

cancer, where a 20% increase in risk was observed for every 10 g of saturated

fatty acids consumed.[vi]

The association between polyunsaturated fats and cancer is even more profound.

Animal studies have shown that high linoleic acid consumption in particular

promotes mammary tumours to a greater extent than saturated fatty acids.

Safflower oil, soybean oil and corn oil, all rich sources of linoleic acid, were

more likely to induce tumours than were olive oil or even coconut oil because

these oils are poor in linoleic acid.1

Fibre, vitamin A, C and E, the trace element selenium, and some phytochemicals

in certain vegetables, beans, seeds and herbs have been identified as

anti-promoters which offer protection against cancer.

The food types that offer this protection contain sulfides, phytates,

flavonoids, glucerates, carotenoids, coumarins, mono- and triterpenes, lignans,

phenolic acids, indoles, isothiocyanates, phthalides, and polyacetylenes which

interfere with the processes of cancer initiation or promotion, and in this way

block the formation of tumours.

Vitamin A probably acts as an anti-promoter for lung, colon, stomach, bladder,

esophagus and oral cavity cancers. Vitamin C and E are associated with reduced

incidence of breast and colon cancer.2

Fibre on the other hand protects against cancer by decreasing the length of time

that faecal matter stays in the digestive tract, thus limiting the build up of

potential carcinogens.[viii]

Finns for example have a high consumption of whole grains and the associated

high faecel mass has been cited as a contributing factor to the low incidence of

colon cancer in this nation.

The vegetarian lifestyle thus offers considerable protection against cancer, and

a vegan diet seems to be more effective than other vegetarian diets.

In studies conducted on vegetarians it was found that ovo-lacto vegetarians

(vegetarians that include dairy products in their diet) have a higher incidence

of prostate and ovarian cancer than do their vegan (vegetarians that do not use

any animal products) counterparts.[ix]

Cardiovascular Disease

Coronary heart disease has become one of the biggest killers in modern

societies, and the consumption of animal fats has been positively associated

with this phenomenon.

Arteriosclerosis does not only lead to heart disease, but can also be

responsible for strokes and kidney diseases.

Arteriosclerosis is a slow insidious disease which progresses slowly as a result

of the deposition of fat and cholesterol in the walls of the arteries.

These fatty deposits become hardened, making the blood vessels less elastic, and

eventually clogging them with plaque (a mass of fat and cholesterol).

It sometimes happens that blood platelets become caught on the rough edges of

plaque, thus initiating clot formation. In this way blood flow to the tissues

can be further diminished or stopped.

If a clot stays in place it is called a thrombus but if it becomes dislodged and

travels around it is called an embolus.

Clogged blood vessels in turn lead to a host of secondary effects such as

ischaemia (lack of blood supply and oxygen in the area supplied by the blood

vessel) or coronary or cerebral infarct where the supply of oxygen is completely

cut off as in the case of a heart attack or stroke.

Angina attacks are an indication that the coronary arteries are clogged to the

extent that only a quarter of the normal blood supply is being sent to the heart

muscle.

It has been clearly established that high cholesterol levels can pose a serious

risk of contracting cardiovascular diseases. Besides cholesterol, there are

other compounding factors which increase the risk of getting a heart attack,

such as high blood pressure and smoking.

What is more, the risk is more than additive, as being exposed to more than one

of these factors will more than double the risk of having a heart attack.

Cholesterol levels per se are however not necessarily a good indication of the

overall risk, but it seems as if the relationship between HDL- and

LDL-cholesterol is a better criterion to use when determining the risk factor.

HDL-cholesterol has been firmly established as a predictor of protection from

atherosclerotic disease.

People with low HDL cholesterol levels have the highest heart attack rates, even

if their cholesterol levels are in the supposedly safe range of 116 to 192 mg/dl

for men and 124 to 211 mg/dl for women.

LDL-cholesterol, on the other hand, appears to remain a risk factor throughout

life.[x]

An elevated serum triglyceride level is also a risk factor for arteriosclerosis.

This could be because high triglyceride levels are associated with low

HDL-cholesterol levels.

When triglyceride metabolism is efficient, the triglyceride is high. When

triglyceride is sluggish, the triglyceride concentration is high and the HDL

concentration is low.[xi]

Elevated triglyceride levels will also lead to obesity which has also been

established as a leading cause of disease. The incidence of obesity also

increases with age, as to the risks of contracting cardiovascular disease.

The ration of saturated to unsaturated fats in the diet is also of significance

when determining the risk of contracting cardiovascular disease.

Saturated fat is highly correlated with the incidence of coronary heart

disease.1 A high intake of total fat, cholesterol and saturated fatty acids can

also lead to thrombosis.

Clinical studies have shown, that stearic acid (found in animal products) is the

most thrombogenic fatty acid,1 and diets high in animal products will thus

increase the risk of thrombosis.

Research has focused for many years on the benefits of polyunsaturated fatty

acids in the diet, and these fats have become the desirable replacement for

saturated fats to lower cholesterol levels.

However, this practice has raised some concern, as studies showed that

polyunsaturated fats lowered the levels of the desirable HDL-cholesterol, which

was not the case if foods rich in monounsaturated fatty acids were

consumed.[xii]

Moreover, it was found that diets high in polyunsaturated fats increased cancer

risk[xiii] and had a negative influence on the immune system.[xiv]

Trans fatty acids in the diet have been positively associated with

cardiovascular disease.

Clinical studies have also shown, that hydrogenated vegetable fats (corn, soy,

canola, cottonseed, peanut, or safflower) consistently increased blood

cholesterol levels compared to the natural unhydrogenated oils.1

Mediterranean diets rich in monounsaturated fats, on the other hand, seem to

afford protection against heart disease and cancer.

Mediterranean diets include primarily olive oil as the main fat, and they

contain lower levels of polyunsaturated and saturated fats.

Mediterranean diets are also rich in grain products such as all kinds of breads,

baked goods and pastas.

They also include many legumes, seeds, nuts, fruits and vegetables.

Populations on this type of diet have low cholesterol levels and a low incidence

of coronary heart disease compared to counterparts in other regions of the same

country.13

Olives, monounsaturated sunflower oils, and almonds are rich in oleic acid which

is a monounsaturated fatty acid.

In figure 3.7 the relationship between the various fatty acids in foods commonly

used in Mediterranean countries is presented.

Vegan vegetarians consume very similar foods to those prevalent in Mediterranean

diets. It has also been established that a vegan vegetarian diet can afford

protection against cardiovascular disease.

Vegan vegetarians have lower LDL-cholesterol and triglyceride levels than are

prevalent in the general population, but HDL-cholesterol levels are not

depressed.[xv]

Thus the ideal relationship between these components can be maintained by a

vegan diet and this lifestyle can help both adults and children to maintain or

achieve desirable blood lipid levels.

In view of the increase in the prevalence of cardiovascular diseases with age, a

vegan vegetarian diet can contribute substantially to the quality of life during

old age.

There is also quite a body of evidence, that coronary lesions can even be

reversed by extremely stringent diets combined with other lifestyle

changes.[xvi]

Having said this, it is essential to note, that stringent lifestyles changes may

be acceptable for adults who want to reduce fat intake to present cardiovascular

disease, but care should be taken not to enforce similar changes on children,

who require higher fat intakes than adults.[xvii]

--

References:

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.

[ii] Cohen, L.A. 1987. Diet and Cancer. Sci. Amer. 257:42-49.

[iii] Dwyer, J.T. 1988. Health aspects of vegetarian diets. Am. J. Clin.

Nutr.48:712-38.

[iv] Howe, G.R., Hirohata, T., Hislop, T.G., Isovich, J.M., Yuan, J.M.

Hatsouyanni, K., Lubin, F. Marubini, E., Modan, B., Rohan, T., Toniolo, P.,

Shunzhang, Y. 1990. Dietary factors and risk of breast cancer: Combined analysis

of 12 case-control studies. J.Natl Cancer Inst. 82:561-9.

[v] Giovannucci, E., Stampfer, M.J., Colditz, G., Renim, E.B., Willett, W.C.

1992. J. Natl Cancer Inst. 84:91-8.

[vi] Rish, H.A., Jain, M., Marret, L.D., Howe, G.R. 1994. Dietary fat intake and

risk of epithelial ovarian cancer. A pooled analysis. J.Natl Cancer Inst.

86:1409-12.

[vii] Caragay, A.B. 1992. Cancer-preventive foods and ingredients. Food Tech.

April 1992.

[viii] Anderson, J.W.A. and Gustafson, N.J. 1988. Hypocholesterolemic effects of

oat and bean products. Am. J. Clin. Nutr.48:749-53.

[ix] Snowdon, D.A. 1998. Animal products consumption and mortality because of

all causes combined, coronary heart disease, stroke, diabetes and cancer in

Seventh-day Adventists. Am. J. Clin. Nutr. 48:749-53.

[x] Abbott, R.D., Wilson, P.W.F., Kannel, W.B., Castelli, W.P. 1988. High

density lipoprotein cholesterol, total cholesterol screening, and myocardial

infarction. The Framington sutdy. Arteriosclerosis. 8:207-11.

[xi] Albrink, M.J. 1991. Age-related dietary guideance and cardiovascular risk

assessment. Nutrition Today. July/August 1991

[xii] Mattson, F.H., Grundy, S.M. 1985. Comparison of effects of dietary

saturated, monounsaturated, and polyunsaturated fatty acids on plasma lipids and

lipoproteins in man. J. Lipid.Res. 26:194.

Grundy, S.M. 1989. Monounsaturated fatty acids and cholesterol metabolism:

Implications for dietary recommendations. J.Nutr. 119:529.

[xiii] Broitman, S.A., Vitale, J.J., Jakuba, E.V., Gottlieb, L.S. 1977.

Polyunsaturated fat, cholesterol and bowel tumorigenesis. Cancer. 40:2455

[xiv] Bennet, M., Uauy, R., Grundy, S.M. 1987. Dietary fatty acid effects on T

cell-mediated immunity in mice infected with mycoplasma pulmonis or injected

with carcinogens. Am.j.Pathol. 1236:103.

[xv] Resnicow, K., Barone, J., Engle, A., Miller, 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.

[xvi] Scrimshaw, N.S. 1996. Nutritrion and Health from Womb to Tomb. Nutrition

Today.31 (2), march/April 1996. pp.55-67

[xvii] Olson, R.E. 1995. The folly of restricting fat in the diet of children.

Nutrition Today. 30 (6), November/December, 1995. pp.234-244.

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

J. Veith available through our webstore.

Page updated 02/19/2005

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