APPLICATIONS OF EFA ADDITION TO FOODS

V. APPLICATIONS OF EFA ADDITION TO FOODS

A. Food Additives, Foods, or Dietary Supplements

Given that the essential fatty acids or, more precisely, their metabolic products, are require- ments for the body’s optimal function (i.e., they are essential), they don’t fit the general description of a food additive. They are not added to food to convey some new or better functionality to the food product; they are foods themselves. However, certain LC-PUFAs are unusual in that they are only needed in a small quantity relative to all dietary calories in order to generate the required function. Furthermore, the two classes of EFAs—the omega-3 family and the omega-6 family—may be presented in the diet in different propor- tions to one another. The consequences of this unbalancing of the diets of many Western cultures is thought to be the cause of the increase in incidence of many chronic diseases (Simopoulos, 1991).

Our diet has changed drastically in the last 100 years. With the advent of modern agricultural processes, the production of seed oils (corn, soybean, palm, etc.) has become so inexpensive that they now make up a major part of our diet. In the United States, the Our diet has changed drastically in the last 100 years. With the advent of modern agricultural processes, the production of seed oils (corn, soybean, palm, etc.) has become so inexpensive that they now make up a major part of our diet. In the United States, the

5 million years of evolution (Broadhurst et al., 1998). In other words, a dramatic change in the dietary ratio of omega-6 to omega-3 EFAs away from the ratio to which our species evolved has occurred in the last 100 years (Simopoulos, 1998). It is for this reason that it is important to return to a much lower ratio of omega-6 to omega-3 EFAs in our diet. This can be done by increasing the levels of omega-3 EFAs in our diet, or decreasing the level of omega-6 EFAs in our diet. Since the latter requires a radical change in our food consumption habits, we should consider improving the omega-3 content of our diet by supplementing our dietary calories with small amounts of omega-3 LC-PUFAs.

B. Not All Omega-3 EFAs Are Created Equal

When we consider supplementing foods with omega-3 fatty acids, the first question that arises is what omega-3 fatty acids do we use? Many of the chronic diseases thought to

be associated with the increase in the omega-6 to omega-3 ratio are believed to have their effect by an alteration of the ratios of the omega-6 versus omega-3 eicosanoids. However, they may also result from a deficiency of DHA—the important structural component of neural membranes. Although supplementing with the parent omega-3 EFA—ALA— should result in the elevation of EPA and DHA (the key fatty acids in poising the n-6/ n-3 ratio), supplementation with the preformed EPA and DHA themselves is much more effective. Much of the dietary ALA is oxidized for energy, and several groups have shown that it takes about 20 ALA molecules to make (or be equivalent to) one EPA molecule. Likewise, it takes about 10 EPA molecules to make a single DHA. This phenomenon has been referred to as biomagnification.

A biomagnification index is shown in Table 6, which can be used to approximate how much of a particular supplement would be required to get a certain effect. From this data we can see that if one wants to improve the dietary DHA levels by about 100 mg DHA per day, this would require either 100 mg DHA directly, 1000 mg of EPA, or about 20,000 mg of ALA per day. Since the richest, commercially available source of ALA is flaxseed (linseed) oil (ca. 67% ALA), it would require about 30 g of flaxseed oil per day

Table 6 Biomagnification of Parent Essential Fatty Acids into Their Metabolites

Biomagnification Fatty acid

factor

Omega-6 LA

Omega-3 ALA

EPA

DHA

(about 2 tablespoons) to provide the equivalent of about 100 mg DHA/day. This amount of oil would represent nearly 300 kCal per day, or about 15% of our daily caloric intake as this one fat. Clearly, if we want to amend the functional n-6/n-3 ratio and reduce our dietary fat intake at the same time, it would be more effective to use preformed EPA and DHA than the parent ALA.

C. Technological Hurdles

The principal technological hurdle in amending the diet with EFAs is a consequence of their high degree of unsaturation. Unsaturated fatty acids pose problems in food prepara- tion and processing as they are prone to oxidation, and the oxidation products are organo- leptically unacceptable. This becomes more of a problem with the higher degree of unsatu- ration in the very long chain PUFAs like EPA and DHA. Fish oil, for example, is very rich in highly unsaturated fatty acids and oxidises very quickly to give an unacceptable fishy odor and taste to a product. Even flaxseed (linseed) oil was used as an industrial oil historically because of the sensitivity of ALA to oxidation and the formation of polymers (varnish). As a result, if we want to supplement food with highly unsaturated EFAs, then food process technology must be modified to account for the oxidative sensitivity. Further- more, such products fortified with these EFAs may not have the same shelf-life as products prepared with saturated fatty acids.

One option recently employed by several manufacturers is to microencapsulate the highly unsaturated oil so that there is a greater oxygen barrier around the oil to prevent oxidation. Typical microencapsulated oils have an oil content of 20–30% by weight, and the microencapsulation matrix can have casein or gelatin as protein components and poly- dextrose as a carbohydrate component. Microencapsulated oils have a much greater stabil- ity than the neat oils, and this should translate into a greater shelf-life for the food product itself.

Although microencapsulation may lend itself to certain food products, it is not ac- ceptable in others. In salad oils, spoonable dressings, and margarines, for example, a neat oil is necessary. In such cases we must look to ways of stabilizing the oil itself. Some oils appear to have an inherently higher degree of stability, which may have to do with the presence of pro-oxidants in the oil itself, the history of the oil processing (many oils carry a ‘‘memory’’ of oxidative insults imposed during processing), the total unsaturation index, or even the position of the unsaturated fatty acid on the triglyceride molecule itself. When fish oils are randomized (i.e., the fatty acid moieties are scrambled with respect to their position on the triglyceride), they become more oxidatively stable, whereas the oppo- site is true for the oils of marine mammals. The principal difference between the two oils is that the DHA molecule is primarily on the sn2 position of the triglyceride (the middle position) in the nonrandomized fish oil and on the sn1 and sn3 positions of the nonrandom- ized whale oil (Ackman, 1989). It may well be that when the DHA resides on the external positions of the triglyceride, there is a self-stabilization that takes place as a consequence of the overlap of adjacent π bonds of the DHA. This is supported by the fact that a DHA- rich oil produced by a microalgae which has DHA preferentially on positions sn1 and sn3 appears to have about a tenfold greater stability than a typical fish oil on a DHA for DHA basis (Kyle, 1996).

D. Sources of EFAs

Table 7 Commercialised Sources of Essential Fatty Acids Fatty acid

Levels Omega-6

Commercial sources

LA Vegetable oils: corn 1 59 soy 1 50 canola 1 30

GLA Specialty plant oils: primrose 1 9 borage 1 22 black current seed 1 17

Single cell oils: Mucor 2 18 Mortierella 2 8 ARA

Single cell oils: Mortierella 3 48 Animal:

4 a Omega-3

egg yolk

LNA Vegetable oils: soy 1 9 canola 1 7

flax (linseed) 1 58 EPA

Animal (fish): menhaden 4 10 salmon 4 12

tuna 4 6 DHA

Animal (fish): menhaden 4 13 salmon 4 4 tuna 4 17 Animal:

2 a Single cell oils:

egg yolk

Crypthecodinium 5 47 Schizochytrium 6 25 b

a Primarily in the form of phosphatidylcholine. b Also contains 13–15% omega-6 DPA.

Sources : 1 Murray, 1996; 2 Ratledge, 1992; 3 Koskelo et al., 1997a; 4 Perkins, 1993; 5 Behrens and Kyle, 1996; 6 Kendrick and Ratledge, 1992.

6 or omega-3 sources that can be used for enrichment. Some of the popular sources of omega-3 and omega-6 fatty acids are shown in Table 7. The choice of the source will be dictated by the sort of benefit the manufacturer wants to convey with that food. For exam- ple, if one wants to elevate an individual’s DHA status by about 50%, it would take about 200 mg of DHA per day. This could be provided in about 0.5 g DHA-rich algal oil per day, or 60 g flaxseed oil per day ( Table 6 ). Clearly the former provides a much lower caloric load than the latter (5 versus 600 kCal per day). Likewise, the elevation of GLA levels can be easily attained with the consumption of 1000 mg of evening primrose oil, but would require over 20 g of corn oil per day. It is, therefore, important for the manufac- turer to first determine what effect is desired before choosing the source of oil that will give that effect.

E. Foods with Supplemental EFAs

Various foods have been supplemented with omega-3 EFAs, particularly in Japan and Southeast Asia. At first, they were indicated as a specialty food, but are now in the main- stream market, including fast and convenience foods. Several companies are marketing

Table 8 Examples of Food Products Supplemented with Essential Fatty Acids Category

EFA supplementation Beverage

Product name

Manufacturer

Recovery

Fish oil/DHASCO (EPA/DHA) UltraCare

Great Circles (USA)

DHASCO (DHA) Bread

UltraBalance (USA)

Fish oil (EPA/DHA) Heartbeat

Live

Irish Pride (Ireland)

Fish oil (EPA/DHA) North’s Extra

British bakeries (UK)

Fish oil (EPA/DHA) Flax bread

Allied Foods (NZ)

Flax seed (ALA) Cereal

Natural Ovens (USA)

Flax seed (ALA) Flax Plus

Golden Flax

Health Valley (USA)

Flax seed (ALA) Bar

Lifestream (USA)

Recovery

Fish oil/DHASCO (EPA/DHA) Prozone

Great Circles (USA)

Borage oil (GLA) Spread

Nutribiotic (USA)

Fish oil (EPA/DHA) Essential Omega

Pact

MD Foods (DK)

Flax oil (ALA) Live

Spectrum Naturals (USA)

Golden Vale (Ireland)

Fish oil (EPA/DHA)

the fish oil which is the primary source of the EPA and DHA added to many of these foods. In all cases, there appears to be a strong advertising message in the Japanese DHA- containing products to claims of improving mental or visual function. Some products are even advertised as study aids.

In Europe and the United States, the EFA-enriched foods have been mainly restricted to dairy products (butters and margarines) or other spreads (Table 8). In most cases, such products are presented as having important cardiovascular benefits and may be labeled as fish oil products. One morning spread enriched with fish oil is even sold in a container shaped like a heart. Such claims were generally supported by a long list of clinical studies demonstrating the advantages of fish oil consumption on lowering triglycerides.

A common problem to all PUFA-enriched products, however, is shelf-life. Since PUFAs are highly susceptible to oxidation, care must be taken in processing, packaging, and storage of the foods. Since foods in the dairy case are generally refrigerated, these make the best candidates for supplementation. Packaging with low oxygen permeability materials with ‘‘flavor seals’’ that are removed by the customer at first use are common to avoid the oxidation and consequential off flavors and odors. An alternative to adding the active PUFAs themselves is to add the precursors—GLA and/or ALA. Although gen- erally less susceptible to oxidation than ARA, EPA, or DHA, these components must be added in a much higher level to provide the same level of effectiveness as the final prod- ucts, and the overall effect on the shelf-life of the finished product may be no better. This approach has been used in the United States, however, to market bread products enriched with whole flax seeds as a source of ALA. The advantage of this approach is that the flax seeds themselves are not only protected from oxidation by the barrier of the seed coat, but the seeds also contain a large amount of endogenous antioxidants.