SOURCES , NUTRITIONAL AND HEALTH VALUES OF ω-3 AND ω-6 FATTY ACIDS

Because of the importance of functional food factors for the nutrition of humans and animals, an increasing scientific interest has emerged in health related effects occurring as a consequence of their content in diet. Therefore, in this paper we tried to present the state of the art concerning nutritional aspects as well as health benefits of the most important and widespread ω -3 and ω -6 fatty acids. Furthermore, we reviewed nonfish alternative sources of ω -3 and ω -6 fatty acids as well as their occurrence in domestic oil seeds, rare and medicinal herbs. Recent attempts to incorporate higher levels of ω -3 fatty acids into food and feed are also presented.

Fats are often cited as one cause of heart-related problem, but certain fatty acids are necessary for proper functioning of the body.Some nutritionists believe that more dietary polyunsaturated fats (PUF) are needed to prevent heart disease.They also agree that saturated fatty acids (SFA) should be consumed sparingly.Experts disagree, however, on whether dietary saturated fats are best replaced by carbohydrates, fat and oils containing monounsaturated fatty acids (MUFA) or polyunsaturated fatty acids (PUFA), or even if they need to be replaced at all.»One meal is not going to kill you or cure you.Heart disease and cancer are lifestyle diseases.There is no test to predict who will get heart disease or cancer.We talk about risks.Through diet we can lower out risks.« points out professor David Kritchevski, Medical Research Center in Philadelphia.
Good sources for ω -3 (n-3) fatty acids are some types of fish such as sardines, salmon and tuna, as well as soybeans, flaxseed oils, and some nuts, especially walnuts and butternuts.Eggs enriched with ω -3 fatty acids are also on the market.Researchers at Purdue University (West Lafayette, Indiana) are looking at ways to enrich cattle feed so that meat and dairy products will contain more ω -3 fatty acids.It is also known that the good sources of -6 fatty acids are corn, soybean, and sunflower oils (J e w e t t, 2002).

The balance of EFAs and their metabolites
The major roles of EFAs (Essential Fatty Acids) and their metabolites in living organisms are structural as integral part of cell membrane and communicational being involved in cell signaling.The membranes that are built out of inflexible, saturated or trans fatty acids are stiffer structured.Incorporation of more spacious long chain polyunsaturated fatty acids into membranes enhances their fluidity and makes it easier for chemical messengers to reach and bind to receptors.Difficulties in signaling may lead to an entire cascade of misinforma-tion at cellular level affecting everything from immune function to the electrical activity of ion transport across the cell membrane.
LA is more than sufficiently present in nutrition as it is widespread in food products from both animal and plant origin.Although plant sources of -3 fatty acids are beneficial in the diet, scientists are quick to point out that the biological effects of consuming ALA are more modest than those from consuming already performed long-chain ω -3 fatty acids, such as EPA (20:5 ω -3) and DHA (22:6 ω -3).This is because the performed long-chain -3 fatty acids are directly incorporated into body tissues.ALA however, must be converted into the long-chain forms before it exerts similar biological effects.ALA can be converted through desaturation and elongation in the body to the long-chain ω -3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).This elongation and desaturation process is influenced by many factors.This conversion is not always predictable (H a u m a n n, 1998).
However, over the years the intake of ALA and ω -3 family in developed countries has permanently declined.There are many reasons for that.Fish consumption has decreased while refined cereal product consumption has increased.The use of hydrogenation to ensure longer shelf-life has lead to the increase in trans fatty acids intake which interferes with the synthesis of unsaturated fatty acids.Also, it is the consumption of food animals that are themselves deficient in ω -3 fatty acids because they are no longer fed on ω -3-rich grass.In addition, LA and ALA compete metabolically for same enzymes.If LA dominates in diet more of its metabolites are synthesized.Signaling messengers generated from ω -6 family are considered pro-inflammatory whereas messengers generated from ω -3 family are considered anti-inflammatory.When balance of messengers is disturbed it means that self-regulation of ω -3 and ω -6 series is affected (W a t k I n s, 2004).This raises the question of the importance of the ratio between ω -6 and ω -3 fatty acids in diet.As the result, various governmental agencies and committees have sat dietary recommendations on ω -3 fatty acids as well as the ratio between ω -6 and ω -3 fatty acids in diet (Table 1) (H a u m a n n, 1998).

Alternative sources of -3 fatty acids
General : Although fatty fish and fish oil are often the first source to come to mind for ω -3 PUFA, there are numerous other dietary sources, including vegetable oils, nuts, microalgae, and fungi (H a u m a n n, 1998).From the health point of view, ω -3 fatty acids are of interest because they are important constituents in the membranes of brain cells, heart muscle cells, and the rods and cones of the retina.Consuming fish or marine microalgae, on the other hand, directly provides performed long-chain ω -3 PUFAs, primarily EPA and DHA to the body.Some consumers, for various reasons, do not or can not eat fish rich in ω -3 fatty acids.Thus, nonfish sources of ω -3 acids can help provide dietary ω -3 PUFAs.In addition, because fish can be high in cholesterol, plant and micro algal sources provide a way to obtain ω -3 fatty acids without increasing dietary cholesterol intake.Meanwhile, vegetarians, who generally do not appear to suffer from -3 deficiency, get their dietary ω -3 acids by consuming ALA from plant sources.
The following provides a closer look to the nonofish sources of ω -3 PUFA, listed in the Table 2 (O f f i c i a l M e t h o d s of AOAC, 1997).

Tab. 2 -Selected sources of ALA
*Grams per 100 grams Plant sources .Soybean has been a valuable resource for humankind by providing both high quality protein (40%) and oil (20%) (B l a n u ã a et al, 1997, and 2000).The majority of soybeans produced are extracted as soybean meal for use as high protein animal feed and as soy oil.Traditionally, Asians use soybeans directly for soyfood productions, whereas new technologies introduce processed soybeans into soy protein products that are incorporated or further processed in wide arrays of other food items (V u c e l i ñ-R a d o v i ñ et al, 1999 and P e ã i ñ, et al 2005).Because it is widespread as a cooking and salad dressing and in food products, soybean oil is clearly the primary source of -3 acids in diet.Nonhydrogenated soybean oil contains 5.5-9.5% of ALA, but partial hydrogenation provides 3% of the acid.In addition, canola oil has been available to consumers since 1985 when the US Food and Drug Administration (FDA) approved its use in food products.Of potential concern, however, is a trend by the oilseed industry to genetically engineer low-ALA vegetable oils in order to increase oil stability.Oils that have some of the highest levels of ALA are not generally available for consumption, such as perilla (from mint plant species) and chia (wild growing herb) oil, i.e. nearly 60%.Meanwhile, traditional flaxseed oil contains more than 50% ALA.Owing to its tendency to oxidize, because of this high content of ALA, it must be stored under cold, oxygen and light free special conditions.So, flaxseed oil is not practical dietary source for widespread, regular consumption of ALA, but it tends to be treated as a medicinal or pharmaceutical product.In order to prevent the rapid oxidation flaxseed oil must be cold-press expelled and have special handing, including refrigeration.Recently, several publications appeared which describe the convenient cold-press expelling using specific mixture of enzymes (P i ñ u r i ñ-J o v a n o v i ñ, et al, 1999).
Domestic plant sources , Gooseberry oils, such as Rubus ideaus and Ribes nigrum seed oils were found to contain significant amount of ALA.Rubus idaeus (cultivar named Malling promise), family Rosaceae seed oil contains 26.4 % ALA (Table 3)(P i ñ u r i ñ-J o v a n o v i ñ, et al, 2000).This oil probably has tendency to oxidize because of the high PUFA content, thus it must be stored under cold oxygen-free and light-free conditions.However R. idaeus can not be used as commodity seed in the production of edible oil, but can be useful as medicinal or pharmaceutical product in consideration that this oil is a rich, relatively pure source of ALA.Oleic acid accounted for 9.9% of the total fatty acid content.R. ideaus seed oil was characterized by high content of polyunsaturated essential fatty acids: linoleic acid 18:2 ω-6, (LA, 59.2%) and linolenic acid 18:3 ω-3, (ALA, 26.4%).
Tab. 3 Ribes nigrum L., family Grossulariaceae, seed oil is similar to oils rich in linolenic acid, such as: linseed and hempseed oils (S o n n t a g, 1979).The major fatty acids in Ribes nigrum seed oil were linoleic and αand γ-linolenic acid (Table 3) (P i ñ u r i ñ-J o v a n o v i ñ, et al, 2002)].Among the Ribes nigrum seed oil, the Evening primrose oil species (EPO, Oenothera bienis, 24.8% of GLA) and the Borage oil (BO, Borago officinalis, 9.3% of GLA) are plant species known to be good sources of γ-linolenic acid (H u d s o n, 1984).The EPO and BO are the most frequently used for studying the nutritional and clinical beneficial effects of GLA (Y u n g-S h e n g, et al, 1995).Stearidonic acid (18:4ω3) accounted for 1.6% of the total fatty acid content.Stearidonic acid, which is reported to be of rare occurrence in the plant kingdom and which is of considerable dietary and pharmaceutical interest has been also found in three closely related Primula species (A i t z e t m u l l e r, 1991).
The fatty acid composition and characteristics of the melon seed oil, (Citrullus colocyntis L. family Cucurbitaceae) were in general agreement with the results obtained in earlier studies, however, the levels of the linoleic acid reported ranged from 52-65%, but there was no trace of the presence of ω-3 fatty acids (M i l o v a n o v i ñ, et al, 2005).

Other sources, microalgae and fungi
While various plants contain ALA, microalgae are seen by some companies as a way of providing long-chain ω-3 fatty acids because EPA and DHA originate in phytoplankton.Microalgae can produce up to 40-50% of their biomass in extractable triglycerides (about 40% DHA), which are used in animal feeds and, as an ingredient of aquaculture feed.Fungi and related microbes present a viable potential source of long-chain ω-3 fatty acids.Only the higher fungi's produce ALA, EPA and DHA, but some lower fungi's produce EPA.

Animal sources
Egg concept: Eggs enriched with -3 fatty acids are also on the market.Concentrate egg yolk is an alternative to fish oil for supplementing infant formula.In this product the PUFA is bound to phospholipids (DHA attached to phospholipids may be better absorbed than DHA in the triglyceride form).Egg concept means that two to three eggs would provide the same amount of DHA, as serving a salmon, and at a lot lower price.Some researchers have altered the fatty acid composition of pork fat.It was found that significant changes in the ω-3 fatty acids content of pork can be achieved within a short period by feeding pigs a diet containing 5% flaxseed.Meanwhile, egg concept is feeding flax to increase the ω-3 fatty acid compositions in the pork, chicken and duck meat.Unlike fish oil, flaxseed as a part of the feed does not result in an oxidized odor or taste.Thus, this is the way to use any ω-3 fatty acid in animal feed to produce animal products higher in ω-3 composition and still have a good stability and taste (H a u m a n n, 1998).

Health benefits
Fats are often cited as one cause of heart-related problems, but certain fatty acids are necessary for proper functioning of the body.The following healthrelated effects are recommended as key topics for ISF (International Society for Fat Science).
Heart disease.Recent meta analyses studies seem to indicate that dietary -3 fatty acids have a positive impact on health and longevity of patients with preexisting coronary hearth disease.The effect that ω-3 fatty acids have on mortality does not seem to be related to their lipid-lowering effect in serum, but seems to be associated with their anti-thrombotic activity, their anti-inflamatory activity and their effects on arrhythmia (L i e p a, 2006).
On the other hand, epidemiological studies in a number of countries have found a positive association between trans fatty acid intake and coronary risk.They raise undesirable low-density lipoprotein, LDL cholesterol and lower desirable high-density lipoprotein, HDL cholesterol from the blood-stream.Trans PUFAs are formed during the high-temperature frying.Little is known of the effects of trans -linolenic acid.The role of oxidized dietary fats in heart disease is also observed (B e r g e r, 2001).
DHA-against Alzheimers disease.DHA rich diet may protect brain against Alzheimers (C o l e, 2004).This is the first proof of diets effect, which explained how our brain cells communicate with each other under the duress of Alzheimers disease.The diet rich in DHA dramatically reduced the impact of Alzheimers gene, in helping the brain against the memory loss.
Fatty acids and immune function.The fatty acid composition of inflammatory and immune cells is sensitive to dietary fatty acids, and the proportion of different types of PUFA is easily changed.For example, arachidonic acid (20:4-6) is the precursor of prostaglandins and leukotrienes, both of which have been associated with inflammatory action.Animal and human studies have shown that dietary fish oil, containing ω-3 PUFA suppress the production of two inflammatory substances (B e r g e r, 2001).
Cancer disease.Due to their anti-inflamatory activity ω-3 fatty acids are considered beneficial in preventing and treating cancer, which has been classified as chronic inflammatory disease.However, it is also known that the oils with substantial amounts of unsaturation, particularly 18:2 fatty acids, are susceptible to oxidation and may produce products that contribute to arteriosclerosis and carcinogenesis.Some studies on experimental animals indicate that excessive amounts of linoleic acid, LA (18:2 -6) promote carcinogenesis (K u b o w, 1990).
Other health benefits.There are some other health benefits of each type of fatty acids.For example, research conducted in the 1980-90 has shown that increased consumption of ω-3 fatty acids alleviates the symptoms of rheumatoid arthritis (the pain and progression).In addition, such fatty acids (as well as the balance of dietary of ω-3/-6 acids) are thought to be important in suppressing excessive inflammatory responses.The results of a number of studies were conflicting, but one conclusion is observed that a minimum intake of 0.8g/day of fish oil fatty acids was advisable.It was also found that high-MUFA intake appeared to protect against age-related cognitive decline.Limited evidence suggests that both MUFA and PUFA may prevent blood clots; limited evidence also suggests that very high MUFA intakes lower blood pressure.As the debate on MUFA or PUFA continues, the ratio of fats in the diet has emerged as the major research topic (B e r g e r, 2001).It was also reported that ω-3 fatty acids can improve the bone growth.It was found that bones of rats and chickens fed increased amounts of ω-3 acids had improved formation rates and were stronger when compared to the bones of the control animals (H a u m a n n, 1997).
ω-3 fatty acids in low-fat diets.For optimal health, a person needs to balance fat content of the diet with calorie control.For example, number of studies have shown that programs aimed at lowering fat consumption to 20% of calories in free-living subjects on self-selected diets actually results in fat intake of 20-23% of calories or even higher.Although there is evidence that some people can follow a very low-fat diet, it requires major lifestyle changes and significant commitment to following the diet.The American Heart Association (AHA) has long encouraged people with high cholesterol to follow the associations "step diets" which replace fat with carbohydrates.Total fat is limited to 30% or less of daily calories, carbohydrates are 55% or more.In the first step of the diet saturated fat is 7-10% but goes to less than 7% in the second step.
Although following these diets leads to a reduction in low-density lipoprotein (LDL) cholesterol, the "bad" cholesterol, the "step diets" often also lower high-density lipoprotein (HDL), named as "good" cholesterol, and may raise triglycerides.Because of this, researches have been exploring diets in which the saturated fats and some of carbohydrates are replaced with mono-or polyunsaturated fatty acids (K r I s-E t h e r t o n, et al, 1990).

C o n c l u s i o n
Some scientists believe that functional food is translation of scientific knowledge (or fiction) into a product.One of the ways to achieve that is raising quantity and changing proportion of different PUFAs in food products.A health claim is necessary for a functional food because its effect can not be perceived.The claim must be based on the scientific evidence obtained using the product on humans.From the consumers' aspect, on one hand they desire indications of the attributes to be sought for a functional food.On the other hand, technology and marketing considerations determine what is possible.From the agricultural commodity point of view, it means utilizing more crude plant oils of different origin than would normally be used in traditional products.Also, it prevents the net loss of vegetable oils, from the marketplace since other fat replaces often completely displace these oils.

Plant source Basil seed oil Perilla oil ( Perilla ocimoides ) Chia oil ( Salvia hispanica )
. -Fatty Acid Content and Summary of It's Important Parameters of Rubus idaeus and Ribes nigrum Seed Oils