Introduction
Essential fatty acids are fatty acids that must be obtained through food to achieve optimal health. Two types of essential fatty acids reviewed herein are omega 3 and omega 6. Three varieties of omega 3 fatty acids are alpha-linolenic fatty acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA). And omega 6 fatty acids are linoleic fatty acids.
Essential fatty acids have a physiological relationship with every cell in the body and contribute to the fluidity of the membrane, preventing rigidity, and promotes functional hormone-receptor binding sites. As functional nutrients, essential fatty acids are precursors for eicosanoids which are signaling molecules and regulators of cellular function; they include prostaglandins, thromboxanes, and leukotrienes and can be converted from both omega 3 and omega 6. In particular, DHA converts to eicosanoids, resolvins, and neuroproctectins.
Omega 3 fatty acids boost brain health as they are part of brain and nervous tissue (Gropper & Smith, 2013; Bjerve, 1989). Think of brain cells as electrical wires. Yes, our brains are an electrical system! For safety reasons, electrical wires need an outer layer or coating of protection so the electrical current doesn't go haywire. Brain cells need what is called the myelin sheath for its outer protection. And omega 3s help make up the myelin sheath.
Omega 3 fatty acids also supports eye health as the retinal photo-receptor membrane of the eye is composed of omega 3 (Gropper & Smith, 2013; Bjerve, 1989).
Essential fatty acids are considered cardio-protective (heart healthy) related to its beneficial impact on vasodilation, vasoconstriction, and vascular permeability. This means that omega 3 is beneficial to arteries and veins which moves blood from the heart to the lungs and throughout the body. Additionally, omega 3 has a slight blood thinning affect (for the prevention of blood clots).
Essential fatty acids also positively impact digestive health by aiding gastrointestinal tract motility (Gropper, 2013). Omega 3 is also thought to help treat constipation. Not only does fish oil (omega 3 supplement) act as a natural lubricant but can also help reduce inflammation within the gut.
Keep reading on what happens when we don't get enough omega 3 fatty acids, how to ensure you are getting enough in your diet, and the importance of the omega 6:3 ratio.
In the optimal nutritional state, omega 6 and omega 3 fatty acids work oppositely within the body: omega 6 is pro-inflammatory and omega 3 is anti-inflammatory for whichever the body needs (Patterson, Wall, Fitzgerald, Ross, & Stanton, 2012). While both types of fat are essential for one's health, too much omega 6 within the diet may override the beneficial anti-inflammatory effects of omega 3.
The Importance of the RATIO between Omega 6 and Omega 3 in the Diet
The ratio of omega 6 and omega 3 in the diet seems to be of upmost significance to our health. While there is no upper limit set for omega 3 nor omega 6 fatty acids (DRI, 2005), too much essential fatty acids seems to be most relevant in terms of the [omega 6:omega 3] ratio whereas 10:1 appears to be the upper limit (Patterson, Wall, Fitzgerald, Ross, & Stanton, 2012). Americans tend to eat far more omega 6 fatty acids than omega 3 which puts these two fatty acids out of balance. The standard American diet is around 15:1 (Patterson et al., 2012) therefore the majority of Americans are above the upper limit of omega 6 in particular.
Clinical studies of patients supported by total parenteral nutrition found resolution of signs of deficiency when a parenteral lipid containing a linoleic acid:α-linolenic acid ratio of 6:1 was provided (Holman et al., 1982). The recommended ratio of omega 6 to omega 3 is a range of 5:1 to 10:1 from the World Health Organization and the Institute of Medicine (FAO/WHO, 1994).
The reason the ratio has significance on nutrition status is because fatty acids compete for enzymes. If the ratio is out of balance, eicosanoids are out of balance (Thompson, Manore, & Vaughan, 2014). Too much omega 6 in the body can cause a functional deficiency of omega 3 (Emken et al., 1994). The inadequacy of omega 3 and the excessiveness of omega 6 can be problematic to one's health as essential fatty acids impact every cell of the body. This imbalance can negatively impact the body affecting anywhere from the skin, brain, or vision to cardiovascular health (Gropper & Smith, 2013).
The function of omega 6 is pro-inflammation as this is sometimes necessary in the body while the function of omega 3 is anti-inflammatory, the two fatty acids work together like ends of a seesaw for whichever the body needs at the time. Too much omega 6 can dominate over omega 3. Excessive intake of omega 6 fatty acids primarily lead to chronic, inflammatory conditions such as cardiovascular disease (heart disease), inflammatory bowel disease, and the metabolic syndrome including obesity and high triglycerides in the blood (consequences of too much omega 6 is further explored under the subtitle below "Omega 3 and Omega 6 Toxicity").
Observing signs and symptoms, awareness of mild to severe presentations as well as either acute and chronic altered nutrient status can further our understanding of deficiency and imbalance of these fatty acids.
Deficiency of Essential Fatty Acids
As essential fatty acids are a part of every single cell and tissue in the human body, deficiency can affect many body systems. Deficiency signs and symptoms can be found below in Table 1.
Observations of individuals with essential fatty acid deficiency caused by non-lipid total parenteral nutrition, the body is receiving energy from dextrose which prevents fat from the adipose tissue from being mobilized (Jeppesen, Hoy, & Mortensen, 2000). Great insight can be attained from these observations on the nature of essential fatty acid deficiency.
Most obvious to the eye is the essential fatty acid deficiency manifestation of the skin. As essential fatty acids provide integrity to cell membranes, a deficiency can cause scaly skin lesions that are hemorrhagic (prone to bleeding) (Gropper & Smith, 2013). In this case with administration of non-lipid parenteral nutrition, essential fatty acid deficiency can be considered acute and severe. Some studies have shown that the skin lesions manifested while on non-lipid total parenteral nutrition were resolved following supplementation with cod liver oil and soybean oil or ethyl linolenate (Bjerve et al., 1987a, 1987b). Scaly and hemorrhagic dermatitis can resolve in two weeks of treatment (Jeppesen, Hoy, & Mortensen, 2000).
Cells of the eye, in particular, retinol photo-receptor membranes, rely on essential fatty acids. In deficiency, as seen with patients on total parenteral nutrition without lipids (fat), poor vision can occur and can also be corrected in 2 weeks with adequate initiation of lipids (Bjerve, 1989).
Essential fatty acids support neural health by providing membrane integrity of the neuron as well as supporting the composition of the myelin sheath (Gropper & Smith, 2013). Studies have associated essential fatty acid deficiency with Alzheimer’s disease (Ruidavets, Bongard, & Dallongeville, 2007), a condition of brain deterioration.
Importantly, the cardioprotective properties of essential fatty acids go awry in deficiency. When too many omega 6 fatty acids are consumed, fatty acid enzymes are occupied and bypass the converting of omega 3 fatty acids. The deficiency of omega 3 fatty acids is an inhibition of the anti-inflammatory, anti-thrombotic, and anti-arrhythmic functions which compromises heart heath and can even lead to a heart attack (Gropper & Smith, 2013).
Underdeveloped countries that subsist on rice and a lack of variety of foods are at higher risk of essential fatty acid deficiencies.
In developed countries, acute essential fatty acid deficiency is extremely rare. Though, chronic deficiency of omega 3 coupled with excess omega 6 (a surplus of omega 6 foods in the Western world) is chronic and not uncommon.
Classifications:
Mild, Moderate, Severe, Acute, Chronic in the
DEFICIENCY of Essential Fatty Acids
In order to stage deficiency manifestations, it is important to understand the signs, symptoms, and latency periods of mild, moderate, and severe deficiency.
Non-lipid total parenteral nutrition has given science information towards understanding essential fatty acid deficiency. Within the first 2 weeks of essential fatty acid deficiency on non-lipid total parenteral nutrition, hyperosmolar nonketotic hyperglycemia may occur first (McLaren & Meguid, 1988). This creates a compounded condition in which fat is not mobilized within the body in addition to not receiving any additional dietary fat and, in this case, parenteral lipids.
Early clinical manifestations of a fatty acid deficiency include rough, scaly skin. As the deficiency is prolonged, the state of the skin progresses to dermatitis (Jeppesen et al., 1998). This skin rash, scaly skin, and ectopic dermatitis that manifests have been demonstrated in patients on 2-4 weeks of total parenteral nutrition without fatty acid (DRI, 2005).
In 3 months on non-lipid parenteral nutrition, essential fatty acid deficiency can present biochemically and clinically (McLaren & Meguid, 1988). In case studies of total parenteral nutrition with safflower oil as the lipid (which is very low in omega 3), eye and neural changes took place including sensory neuropathy and vision problems (McLaren & Meguid, 1988).
Signs of an advanced stage of omega 3 fatty acid deficiency include severely scaly and hemorrhagic dermatitis, hemorrhagic folliculitis of the scalp, impaired wound healing, and growth retardation (in infants and children) (Bjerve, 1989).
Omega 6 is typically much more common in dietary sources than omega 3 especially with the abundance of processed foods. Omega 3 deficiency is more common than an omega 6 deficiency as the two compete for the same fatty acid enzymes, and when there is much more omega 6 intake than omega 3 (beyond the ideal ratio reviewed above), omega 6 will dominate the use of these enzymes resulting in dietary omega 3 that is less functional. Additionally, omega 6 is released from adipose tissue in states of starvation so deficiency is rare (Bjerve, 1989). Otherwise, omega 6 deficiency results from non-lipid total parenteral nutrition related to the constant flux of intravenous dextrose preventing the mobilization of stored omega 6 (Bjerve, 1989). With this we can conclude that an over-the-counter omega 6 supplement is largely unnecessary to achieve optimal health in the majority of people.
Risk factors for Essential Fatty Acid Imbalance and Deficiency
Babies, Children, & Pregnancy
Infants and children require essential fatty acids to support their growing brains. Preterm babies are at higher risk for essential fatty acid deficiency than full term babies due to a slower capability of converting omega 3 to functioning nutrients (Gropper & Smith, 2013). Getting enough essential fatty acids during pregnancy can promote the health of the mother but can also promote the health of the infant (Bjerve, 1989).
Gastrointestinal Disorders
Malabsorptive conditions can impact the ability to receive adequate essential fatty acid nutritional status. Cystic fibrosis, due to the overproduction of mucus within the digestive tract, can prevent the absorption of essential fatty acids. Pancreatic insufficiency provides inadequate enzymes for the digestive system to digest fats. Various other gastrointestinal disorders can increase risk of essential fatty acid deficiency due malabsorption such as celiac disease, bowel resection, and cholestatic liver disease. Fecal fat tests are useful in determining if essential fatty acids are not being absorbed efficiently. If there is too much fat in the feces, it will be especially foul-smelling and greasy. This condition is also concerning for malabsorption for vitamin A, E, and K. With some gastrointestinal issues such a celiac disease, constipation may be a problem and some sources indicate that an omega 3 supplement may help for the most basic reason of providing a natural lubricant to also potentially reducing inflammation within the digestive tract.
Total Parenteral Nutrition
Total parenteral nutrition provides carbohydrates, fats, protein, vitamins/minerals/electrolytes and are calculated by the clinical dietitian and pharmacists and is determined based on the patients height, weight, and metabolic needs. These needs may change depending on the patient's acute or chronic conditions, growing needs (children, teenagers), and activity level, so the practitioner should review and update as necessary. This formula can either provide an optimal amount of essential fatty acids, too little, or too much.
Burns & Surgery
In burn and surgery patients, their needs for essential fatty acids are increased for cell repair.
Omega 3 and Omega 6 Toxicity
What happens when we get too much omega 3 or omega 6? Is there such as thing as too much of an essential nutrient?
Omega 3 supplement in excess reduces platelet aggregation and can prolong bleeding time. The platelet count can decline by as much as 35 percent; however, the count does not usually fall below the lower limit of normal (Goodnight et al., 1981). Excessive omega 3 dietary intake (through food sources - not supplementation) has been associated with easier bleeding such as nose bleeds in an Eskimo population with a high marine intake (Clarke et al., 1990). Otherwise, high omega 3 dietary intake is unlikely to cause a toxicity at all.
Prolonged bleeding times have been shown to be beneficial in preventing heart disease, even so, high dose omega 3 supplementation bleeding times can become prolonged enough to result in epistaxis (nose bleeds) and bruising (Clarke et al., 1990). Omega 3 supplement toxicity is of low risk but may become concerning in those taking anticoagulant medications (Buckley, 2004). In this circumstance, all anticoagulant medications and supplementation with blood thinning properties (fish oil, cod liver oil) should be reviewed by a doctor, pharmacist, and/or clinical dietitian nutritionist. Omega 3 supplementation with anticoagulants needs provisioning so that the blood thinning effects are optimal for the patient.
Some surgeons may also recommend discontinuing omega 3 supplementation for an impending surgery to inhibit the potential of easy bleeding, but new research is finding the discontinuation of omega 3 for an operation as unnecessary (Begtrup, Krag, & Hvas, 2017).
Excess of omega 6 is also relevant in the stages of nutritional injury. Linoleic acid is proinflammatory as a result of the eicosanoids that are derived from it (Patterson et al., 2012). In omega 6 dietary abundance (common in an unhealthy diet with high amounts of ultra-processed foods), receptors are triggered, leukocytes infiltrate, and cytokines are produced - all indicators of inflammation (Patterson et al., 2012). Omega 3 works oppositely as an anti-inflammatory and terminates the inflammatory response, but when omega 6 is in excess, the omega 3 conversions are downregulated (Patterson et al., 2012).
Omega 6 toxicity causes damage within the body and is characterized by a chronic inflammatory state (Patterson et al., 2012). This results in the latency disease states of omega 6 toxicity. These diseases include: cardiovascular disease, obesity, rheumatoid arthritis, cancer, Alzheimer’s, non-alcoholic fatty liver disease, inflammatory bowel disease (Patterson et al., 2012), and the metabolic syndrome (Ruidavets et al., 2007).
Optimal Intake of Essential Fatty Acids
Recommendations for dietary intake of omega 3 and omega 6 are categorized in “adequate intake” only – no Recommended Daily Allowance (RDA), Estimated Average Requirement (EAR), or Upper Limit (UL) exists (DRI, 2005). This is due to a lack of data to set these parameters and is not because excess is not a concern.
Recommendations for Essential Fatty Acids
The recommended ratio of omega 6 to omega 3 is a range of 5:1 to 10:1 from the World Health Organization and the Institute of Medicine (FAO/WHO, 1994), and this ratio seems to be of upmost relevance to health as previously reviewed here under the subtitle "The Importance of the RATIO between Omega 6 and Omega 3 in the Diet".
Adequate intake for linoleic acid (omega 6) is 14-17g/d for men and 11-12g/d for women, and adequate intake for alpha-linolenic acid (omega 3) is 1.6g/d for men and 1.1g/d for women (DRI, 2005).
When a medical doctor or clinical dietitian nutritionist recommends an omega 3 supplement, it is often due to its benefits in lowering blood triglycerides levels of >500mg/dL and for its cardioprotective effects as omega 3 has beneficial anti-thrombotic, anti-inflammatory, and anti-arrhythmic properties (Gropper & Smith, 2013). Beginning or stopping an omega 3 supplement while a patient is taking blood thinning medications should be provisioned by a medical doctor due to the possibility of altering blood thinning effects (Buckley, 2004; Thorngren and Gustafson, 1981). Omega 3 from food sources does not have any known negative effects on anticoagulant and antiplatelet medications.
Omega 3 is also considered a probiotic for the simple reason that it promotes the growth of healthy bacteria within the gut. It also can be supplemented as a potential treatment of constipation as it provides a natural lubricant and helps reduce inflammation of gastrointestinal disorders.
Considering that omega 3 is so essential to brain health, it would make sense that ensuring adequate consumption of omega 3 even through supplementation would be supportive of mental health and special considerations for mood states such as anxiety, depression, ADHD, and other psychiatric conditions but more research is needed.
Omega 6 is an essential fatty acid which means it is of importance to get enough omega 6 in the diet for one's health as well as omega 3; however, consuming enough omega 6 in industrialized nations (such as the USA) is no problem as omega 6 is found in abundance in ultra-processed foods and plant oils. Omega 6 deficiency is very rare. Therefore, omega 6 supplementation (i.e. Evening Primrose Oil) is discouraged as too much omega 6 can counteract the benefits of omega 3.
Best food sources for omega 3
Fish tops the list of best sources of omega 3 fatty acids especially fatty fish such as salmon and tuna, and most nutrition textbooks and google searches will confirm this; however, all other seafoods I have reviewed such as tilapia, crab, and shrimp also have beneficial amounts of omega 3. For optimal omega 3 consumption, consume seafood at least twice per week. Chia seeds, walnuts, and flaxseeds (and their oils) are excellent sources of omega 3 as well as canola oil.
While I was conducting this research on omega 3 fatty acids, I thought to myself, what parts of the body are omega 3s especially good for? The brain! So would that mean cow brain is a good source of omega 3? I looked up the fat profile of cow brain in a nutrition database. Yes, it is an excellent source of omega 3; cow brain, lamb brain, and pig brain too.
Other foods that are less well-known but have optimal omega 6:omega 3 ratios are as follows:
Milk of all types (whole milk, 2% milk, cheeses, yogurts with fat, goat's milk, sheep's milk - in general, milk from animals that eat grass), pork, beef hot dogs (Oscar Meyer brand), turkey, beef, pork bologna, bison
Important to note, 100% grass-fed beef has double the amount of omega 3s. Most beef in the grocery store is corn-finished rather than grass-finished unless labeled otherwise.
Beans (kidney, pinto, & black) and green peas do not have much fat in general but the fat they do have is a good ratio of omega 6 to omega 3.
Foods to Limit
The following are not good sources of omega 3 or have a less-than-ideal omega 6:omega 3 ratio and are as follows: peanut oil, soybean oil (aka vegetable oil), potato chips (fried in soybean oil), corn oil (tops the list at worst)
Best food sources for omega 6
Great sources of omega 6 that are not detrimental to the omega 6:omega 3 balance are all the foods listed as sources for omega 3s as well as eggs, avocado, and olive oil.
Vegetable and nut oils such as sunflower, safflower, corn, soy, and peanut are good sources of omega 6 but the ratio of omega 6:omega 3 is not in a good range (ideal range: <10:1), so it is recommended to not overdo these oils; however, choosing these oils in their whole food forms in reasonable amounts (corn, peanuts, sunflower seeds) appears harmless in the context of essential fatty acid content.
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