When evaluating studies, we must remember that all findings reveal another gateway of investigation. While many studies may support benefits and attributes, some may arise contraindicating previous findings. Recognizing differences in study evaluations is always important. Even though findings from similar studies do not concur, it would be a display of extreme hubris to conclude a complete understanding of all the mechanisms through which any nutrient, condition, or disease interfaces.
Science has long recognized the important role of long-chain polyunsaturated acids, and continued studies have further established and categorized unsaturated fatty acids attributing their benefits, functions, and mechanisms of action. However, it seems to be a popular consensus to solely consume vegetable oils or vegetable products that are high in concentrations of omega-6 fatty acids. Unfortunately, such a strategy can backfire. There is an obvious need to balance the ratio of certain fatty acids. The typical American diet is inundated with omega-6 fatty acids. Other beneficial fatty acids termed as omega-3’s are often left ignored or forgotten.
The omega-3 fatty acid alpha-linolenic acid (ALA) is termed essential, meaning it can solely be obtained from our diets. However, there are important omega-3 fatty acids that are termed non-essential, meaning that they can be synthesized within the body. Omega-3 fatty acids have a variety of critical functions and the many benefits are attributed to the structure of these oil components supported by years of clinical research and studies. However, we must explore the entire classification of omega-3 fatty acids both essential and nonessential and avoid crediting all oils with the same benefits.
To further understand their structure, we must explore the chemical structure of oils. All oils are composed of small subunits called fatty-acids that are assembled in a chain-like fashion. The term unsaturated differs from saturated with only one respect – unsaturated fatty acids contain at least one double bond within their chain. The absence of double bonds makes the fat saturated, with the characteristic of being thick and hard even at room temperature. However, unsaturated fatty acids contain the minimum of one double bond within their chain, thereby obtaining the characteristic of being thin and viscous at room temperature. The more double bonds, the more unsaturated the fatty acid, and thus the more thin and fluid the oil. The term omega-3 is assigned when the first double bond within the chain occurs on the 3rdsubunit (carbon).
When we explore the sources of omega-3 fatty acids we find that the plants can provide a source of omega-3’s – in the form of alpha-linolenic acid (ALA). For example, oils derived from flaxseed, pumpkin, soybean, canola, etceteras, are sources of alpha-linolenic. However, as we review documented fatty acid content of plant oils, we find they predominantly hold higher concentrations of omega-6 fatty acids. Furthermore, the plant kingdom can rarely provide unsaturated fatty acids with 3 double bonds.
Fish oils are a rich source of omega-3 oils. However, unlike their vegetable counterpart, fish oils are unique – containing 4, 5, and 6 double bonds, making them essentially super-unsaturated. The omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) hold 5 and 6 double bonds respectively. It is this super-unsaturation that is attributable to the many benefits assigned generally to omega-3 fatty acids, however it is this same characteristic that makes them unique.
As we explore the body’s metabolic processes, we find that omega-3 fatty acids provide us with a source of energy. They can become incorporated as part of our body’s fat, serving as insulation, cushioning, and protecting our vital organs. However, DHA has been even further scrutinized in its role in building and maintaining the integrity of all cells. It is hypothesized that cells are programmed to select and incorporate different fatty acids to maintain and perform cellular functions. Moreover, DHA has the capacity to be converted into prostaglandins, which are hormone-like substances utilized in regulating cellular activity, becoming closely associated to the functioning of membranes, influencing fluidity, and regulating cell receptor sights. However, science has just scratched the surface regarding DHA’s effect and role in neural development, and needs to further investigate its role within specific tissues of the body.
Studies have suggested that DHA levels are lower among patients with retinitis pigmentosa than other individuals in control groups. Differences in serum levels were posted lower in subjects with retinitis pigmentosa by 10-15%. A correlation is reached regarding the concentration of DHA and its ability to enhance the function of the cones and rods within the retina. Currently hypothesized, is a metabolic defect of synthesizing DHA from sources of ALA. Further studies using DHA supplementation as an intervention have reported improvements to neurological functions, as well as the retinal response of some RP patients. The necessity of DHA to support the normal neurological development response is further correlated through studies completed during early infancy.
In order to obtain DHA or EPA from plant sources, our bodies must start with the essential fatty acid called alpha-linolenic acid (ALA). Immediately, many falsely assume that by consuming dietary sources of ALA an equivalent and quantitative increase of DHA and EPA would occur. Unfortunately, this is not true.
Findings from a study showed that subjects given flaxseed oil (a rich source of ALA) over a 4-week period did not have increased blood levels of DHA. It seems rather perplexing that significant increases in ALA did not contribute to increases of blood levels of DHA in spite of specific dietary controls employed to maximize DHA production. It has been established that a special conversion enzyme called delta-6-desaturase is necessary to convert ALA to DHA (see diagram 1). The conversion rate is very slow and delta-6-desaturase (as established within this same study) is considered a limiting enzyme. On the other hand, subjects given fish oils (an excellent source of DHA) posted high blood levels of DHA. The extra steps required for conversion were eliminated when given DHA in a fish oil form, enabling subjects to acquire immediate benefits.
An approximate conversion rate of ALA to EPA has been established at approximately 2.7%. This is a rather slow process due to the rate-limiting enzyme, and may be even further attributed to other fats and oils found within the diet. It is established that specific compounds and fatty acids compete and may attenuate the endogenous conversion of ALA to DHA, cell selectivity may be further compensated. For instance, trans-fatty acids found within hydrogenated oils and omega-6 fatty acids found in abundance within safflower and sunflower oils can inhibit the desaturation and elongation of ALA to DHA by competing for the same delta-6-desaturase enzyme. However, other studies indicate transport and response differences depending on the variation or ratio of dietary fats. For example, when reviewing nutrient transport of fatty acids, we find that omega-6 fatty acids may counter the absorption of some omega-3 fatty acids. To further complicate elongation, we discover that during early infancy, as we age, or within certain individuals, the body does not produce adequate amounts of DHA from ALA sources due to a decrease in the availability of the delta-6-desaturase enzyme.
This should be taken into consideration when choosing dietary supplementation of omega-3 fatty acids. Having mixed proportions of various fats, may interfere with obtaining the benefits of the super-unsaturated fatty acid DHA. We find, as in the study mentioned earlier, the DHA taken in its pure form offers the greatest efficacy. It will not encounter any of its competitive omega-3 fatty acids family members, nor compete with omega-6 fatty acids for elongation. Considering the challenges dietary plant sources of omega-3 fatty acids, choosing an optimal source of the DHA surely would provide the most benefit.
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