Originally published as “Essential fatty acids (5), notes” on March 27, 2020. Restored November 9, 2026, with the original wording preserved. These are the notes discussed in Essential Fatty Acids: There Is a Lot to Explain.
Evidence annotations added November 9, 2026. The original 2020 notes below are unchanged. Each indented evidence note links to peer-reviewed research and explains what it supports, what it does not establish, and where a hypothesis or contrary finding needs to be kept in view. These are selected studies, not a systematic review. Some were published after the original notes. Summaries were checked against the published abstracts and, where available, full text.
Abbreviations: EFA, essential fatty acid; EFAD, essential fatty acid deficiency; LA, linoleic acid; ALA, alpha-linolenic acid; AA, arachidonic acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid.
IV glucose w/o fat induces EFA deficiency w/ accompanying symptomatology
Fat-free feeding and deficiency
Direct human evidence, under specific feeding conditions. Wene, Connor, and DenBesten (1975), Journal of Clinical Investigation, gave healthy men calorie-maintaining, fat-free glucose/amino-acid diets by continuous intravenous or nasogastric feeding. Plasma fatty-acid changes indicating deficiency developed within two weeks. This demonstrates that adequate calories and existing body fat do not necessarily prevent biochemical deficiency during continuous fat-free feeding.
Clinical signs are a separate endpoint. In Goodgame, Lowry, and Brennan (1978), Surgery, two of 32 patients receiving intravenous nutrition developed skin lesions suggestive of EFA deficiency. These studies support the note in the context of fat-free nutritional support; they do not show that an ordinary glucose-containing meal causes deficiency.
Hydrogenated coconut oil and tallow are used to induce EFA deficiency in lab animals
The experimental diet matters
Direct animal evidence, with a qualification about tallow. Ling and colleagues (2010), Prostaglandins, Leukotrienes and Essential Fatty Acids, compared fat-free diets with diets containing hydrogenated coconut oil in rats. Both produced biochemical EFA deficiency within two weeks, although their effects on individual tissues and fatty acids differed.
Iritani, Ikeda, and Fukuda (1984), Journal of Nutritional Science and Vitaminology, used hydrogenated beef tallow in a linoleic-acid-deficient feeding protocol after prior depletion. That distinction matters: this supports the use of deliberately EFA-poor experimental fats and diets, not the claim that ordinary tallow inevitably induces deficiency regardless of the rest of the diet.
PUFA induced NAFLD seems to be dependent on what mouse model is being used, for example, diabetic prone mice already have deranged EFA metabolism, as a result EFA would be implicated much like cholesterol is implicated in various disease states but interventions fail, flawed logic, do you biology? LOL.
Metabolic context and fatty liver
Support for model dependence; not for dismissing adverse findings. Wang and colleagues (2006), Journal of Lipid Research, found different patterns of hepatic elongase/desaturase expression in chemically induced diabetes, diet-induced glucose intolerance, and genetically obese mice. The metabolic background is therefore a meaningful experimental variable.
However, Deol and colleagues (2015), PLOS ONE, reported fatty liver and metabolic disease in C57BL/6 mice fed a high-fat soybean/coconut-oil mixture compared with a predominantly coconut-oil diet. This was not simply a comparison in mice already made diabetic. Neither study establishes that pre-existing EFA dysfunction explains away the liver injury, nor that all PUFAs have the same effects. The oil mixture, dose, background diet, species, and measured outcome all need to travel with the conclusion. The cholesterol analogy is an interpretation, not a result of these experiments.
Symptoms of EFA deficiency take weeks not years to appear (even when nutrition is adequate)
How quickly deficiency develops
Strong evidence for rapid biochemical change; symptoms are less uniform. Goodgame and colleagues (1978), Surgery, found abnormal linoleic- and eicosatrienoic-acid measurements after one week of fat-free intravenous nutrition; all patients studied at four weeks had an elevated triene:tetraene ratio. Only two developed the reported skin lesions.
Wene and colleagues (1975), Journal of Clinical Investigation, likewise demonstrated biochemical deficiency during calorie-maintaining feeding in healthy men. These findings support a timescale of days to weeks in those settings. They do not establish a universal timetable for visible symptoms in people eating mixed diets, or make biochemical deficiency and symptomatic illness interchangeable.
Reversal of EFA deficiencies with sources of LA and ALA largely resolve acute symptomatology within weeks not years, the idea it takes years to deplete PUFA stores is unrealistic
Recovery is not the same as emptying fat stores
Repletion evidence supports the first idea, but not the inference about turnover. Goodgame and colleagues (1978), Surgery, reported rapid correction of biochemical abnormalities after intravenous fat was supplied. Holman, Johnson, and Hatch (1982), American Journal of Clinical Nutrition, described disappearance of neurological symptoms after an ALA-containing emulsion corrected a child’s omega-3 deficiency. Neither report supplies a universal recovery time for every symptom.
Arner and colleagues (2011), Nature, used radiocarbon measurements to study human adipose triglycerides and found turnover on a much longer timescale—about six renewals during a fat cell’s average ten-year life. This was not a PUFA-specific depletion experiment. Correcting a limiting supply and replacing stored fat are different processes; fast recovery cannot by itself establish how long either total fat or a particular PUFA remains in adipose tissue.
Common symptoms of chronic EFA deficiency are hair loss, increased shedding, and skin abnormalities, hair and skin is one of the most metabolically active tissues, the idea that EFAs slow metabolism is an unrealistic mechanism; same for improvements in skin quality
Skin, hair, and metabolic rate
The skin connection is well supported; the metabolic inference is too broad. Zheng and colleagues (2011), Journal of Biological Chemistry, identified a linoleate-dependent pathway required to construct the epidermal water barrier. A human report by Kim and colleagues (2005), Journal of Korean Medical Science, described skin disease and alopecia with combined fatty-acid, protein, and borderline zinc deficiencies. Because several nutrients were replaced, that case cannot isolate EFA deficiency as the cause of the hair loss.
Rafael, Patzelt, and Elmadfa (1988), Journal of Nutrition, found higher resting respiration but impaired cold tolerance in EFA-deficient rats; additional linoleate above the control intake did not raise basal metabolism. A higher metabolic rate was not synonymous with better function. Skin or hair improvement alone cannot establish the direction of whole-body metabolic change.
LA and ALA seem to spare the B vitamins and vice versa
Interaction with vitamin B6
Evidence of interaction, not demonstrated reciprocal sparing. Maranesi and colleagues (1993), Prostaglandins, Leukotrienes and Essential Fatty Acids, studied rats receiving little dietary EFA with or without vitamin B6 deficiency. B6 deficiency changed kidney phospholipid composition and increased renal prostaglandin E2 under those conditions.
This is relevant because it shows that vitamin status can change the handling of fatty acids and their signaling products. It does not demonstrate that LA or ALA reduces a measured B-vitamin requirement, that B vitamins reduce EFA requirements, or that the interaction extends to every B vitamin. “Sparing” remains a stronger proposition than this experiment tested.
Symptoms of EFA deficiency are reminiscent of hypothyroidism (thinning of hair, thinning of outer eyebrows)
Similar signs do not establish a shared cause
Clinical overlap, with limited specificity. In 460 people with diagnosed hypothyroidism, Keen, Hassan, and Bhat (2013), Indian Journal of Dermatology, documented dry skin and diffuse hair loss among the common findings. The combined-nutrient-deficiency case reported by Kim and colleagues (2005) illustrates that nutritional illness can also affect skin and hair.
These observations support the resemblance at the level of outward signs. They do not show that the underlying mechanism is the same, that EFA deficiency causes hypothyroidism, or that thinning of the outer eyebrows specifically identifies EFA deficiency. The eyebrow detail is not established by these citations.
EFAs are required for proper epithelial differentiation and proliferation, this not only has implications for hair and skin but ALL epithelial cells including the GI tract along with gut permeability
Epithelial structure and the intestinal barrier
Direct evidence in specific tissues and animal models. Christon and colleagues (1991), Reproduction Nutrition Development, found altered intestinal villi, crypts, epithelial ultrastructure, and brush-border fatty-acid composition in rats fed a low-linoleate diet. This extends the question beyond skin to the gut.
Stroud and colleagues (2009), Journal of Lipid Research, found skin and intestinal ulceration in mice unable to convert LA into its longer-chain products; dietary arachidonic acid prevented those lesions. The parent fatty acid and the downstream products therefore need to be distinguished. Neither experiment directly establishes a single requirement governing differentiation and proliferation in all epithelial cells, or quantifies intestinal permeability in humans.
EFA deficient animals manifest with slowed wound healing, this is a problem as the longer a wound takes to heal the more susceptible one is to infection and scarring
Wound healing
Direct animal evidence, with important differences between wounds. Hulsey and colleagues (1980), Journal of Pediatric Surgery, compared normal and EFA-deficient rats across skin incisions, intestinal anastomoses, and burns. Control burns healed by 21 days, whereas deficient animals’ burns remained incompletely healed at 120 days; wound contraction was impaired. Some other endpoints, including intestinal bursting pressure, did not differ significantly.
The study supports impaired healing, especially of skin, under experimental deficiency. It did not directly establish increased wound infection or greater eventual scarring. Those are additional proposed consequences, not outcomes that can be assigned to this paper.
The immune system requires LA and ALA to function properly, immune cells hoard EFAs and use the peroxides generated from EFAs to disable viruses and bacteria
Antimicrobial lipids use more than one mechanism
Mechanistic support for particular fatty acids and pathogens. Beavers and colleagues (2019), mBio, showed that arachidonic acid killed Staphylococcus aureus through lipid-peroxidation products that damaged bacterial molecules. Antioxidants reduced this toxicity. This is direct support for an antimicrobial role of lipid oxidation in that system.
Chouinard and colleagues (2013), Journal of Leukocyte Biology, found that AA and 2-arachidonoylglycerol stimulated human neutrophils to release factors active against bacteria and two viruses. That response involved leukotriene B4 signaling and antimicrobial peptides; it was not a demonstration that peroxides killed the viruses. Together these papers support lipid-dependent host defense, but not the claim that every effect belongs directly to LA/ALA or that immune-cell “hoarding” describes a single established mechanism.
EFAs are required for the proper metabolism of saturated fatty acids (the mechanism is not clear yet)
An example involving saturated phospholipids
A specific experimental connection, not yet a general rule. Nakamura, Kawamoto, and Akino (1980), Journal of Nutritional Science and Vitaminology, studied lung phosphatidylcholine in EFA-deficient rats. They found reduced palmitate in this lipid, fewer dipalmitoyl molecules, altered incorporation of labeled palmitate, and altered alveolar phosphatidylcholine turnover. Dipalmitoyl phosphatidylcholine is an important component of lung surfactant.
This provides a concrete example of EFA status affecting the processing and distribution of a saturated fatty acid in a functional membrane lipid. It does not demonstrate that all saturated-fat digestion, oxidation, or metabolism requires EFAs in the same way. The original note is broader than the experiment.
EFAs are required for myofibrillar and sarcoplasmic hypertrophy
Muscle growth signaling
Cell-culture evidence; necessity in humans is not established. Markworth and Cameron-Smith (2013), American Journal of Physiology—Cell Physiology, added arachidonic acid to cultured mouse muscle cells and observed larger myotubes and increased protein accumulation. Blocking cyclooxygenase-2 blunted the growth response, implicating downstream prostaglandin production.
This makes fatty-acid-derived signaling relevant to muscle growth. However, adding AA to cells is not the same experiment as demonstrating that dietary LA and ALA are required for a particular form of training-induced hypertrophy. The study did not separately establish myofibrillar and sarcoplasmic hypertrophy in humans. That specific claim remains unverified here.
EFAs are required for some hormone production, especially some of the stress hormones, a failure in the production of stress hormones would inhibit the stress response, thus adaptation, leading to maladaptive and degenerative state
Stress hormones—suggestive and contrary findings
A human case supports the possibility; an animal experiment limits the generalization. Bistrian and colleagues (1981), Journal of Parenteral and Enteral Nutrition, described probable glucocorticoid insufficiency and blood abnormalities during prolonged fat-free feeding, alongside biochemical EFA deficiency. The abnormalities responded to fat repletion. A single case suggests a connection but cannot establish a universal requirement or isolate every contributing factor.
In contrast, Vahouny, Hodges, and Treadwell (1979), Journal of Lipid Research, found normal stimulated corticosterone output from adrenal cells of EFA-deficient rats despite major changes in stored fatty acids. The proposed chain from deficiency to failed stress response to degeneration should therefore be read as a hypothesis, not a consequence demonstrated across organisms and settings.
EFA deficiencies manifest psychologically with the following traits: depression, aggression, hostility, changes in attention, motivation, changes in reactivity to stimuli and reward, general personality disorders such as obsessive compulsive behavior, apathy, and eating disorders
Neural function and behavior
A plausible mechanism in mice, not validation of the entire symptom list. Lafourcade and colleagues (2011), Nature Neuroscience, found that lifelong dietary omega-3 insufficiency disrupted endocannabinoid-mediated synaptic plasticity in the prefrontal cortex and nucleus accumbens of mice and was associated with altered emotional behavior.
This connects a defined nutritional manipulation to specific neural signaling and behavioral outcomes. It does not establish that EFA deficiency causes all the listed human psychiatric conditions, or that those conditions identify an EFA deficiency. Depression, aggression, attention changes, compulsive behavior, and eating disorders are distinct outcomes requiring their own evidence. The long list should be treated as a set of research questions rather than a validated deficiency syndrome.
EFAs required for proper sex organ function and development in both males and females
Reproduction and membrane composition
Strong experimental evidence in a defined mouse model. Stoffel and colleagues (2020), Molecular Metabolism, studied male and female mice lacking FADS2, an enzyme needed to make longer-chain PUFAs from dietary precursors. The mice developed disrupted ovarian and testicular membrane organization and infertility. Sustained combined AA and DHA feeding restored the relevant structures and fertility, including in adult animals.
This supports an important role for PUFA composition in reproductive function and shows that precursor supply alone may be insufficient when conversion fails. It does not establish identical requirements in ordinary human diets, nor that supplying more LA or ALA treats every cause of infertility.
EFA metabolism is complex, supplemental EFAs can resolve EFA symptomatology in most cases, however, perturbations of desaturase and elongase activity such as those seen different disease phenotypes can prove difficult to treat though because the underlying machinery is deranged
Supply and conversion are separate problems
Direct proof of principle in genetically modified mice. In Stroud and colleagues (2009), Journal of Lipid Research, mice without delta-6 desaturase developed disease despite ample dietary LA; AA prevented the skin and intestinal lesions. In the same type of model, Roqueta-Rivera and colleagues (2010), Journal of Lipid Research, found that DHA restored male fertility more effectively than AA.
These experiments show why adding the parent fatty acid may fail when a required conversion step is missing, and why the appropriate downstream product can sometimes bypass that block. They do not establish that every disease-associated change in a desaturase or elongase creates the same bottleneck. They also argue against treating impaired conversion as necessarily irreversible or untreatable.
EFA derangement is seen in the following conditions, alloxan and streptozotocin treated diabetic rats, diabetes, vitamin E and selenium deficiencies, cystic fibrosis, copper deficiency, Kwashiorkor, adult respiratory distress syndrome, chronic and acute carbon tetrachloride poisoning, multiple sclerosis, most chronic and acute neurological diseases, LEC rat models of fulminant hepatitis, hepatic cancer, Wilson’s disease, sudden cardiac death, beta-Thalassaemia major, abnormal umbilical cord blood cells
A map of disease associations, not one deficiency syndrome
Several associations are documented, but the findings are not interchangeable. “Derangement” can mean altered blood concentrations, different tissue composition, changed enzyme activity, or oxidation products. Those measurements do not all establish dietary EFA deficiency. The papers below provide specific entry points into this long list.
Diabetes and malnutrition. Holman and colleagues (1983), PNAS, found higher LA but lower AA in several tissues of streptozotocin-diabetic rats, suggesting impaired conversion. Koletzko and colleagues (1986), European Journal of Pediatrics, found depleted polyunsaturated fatty acids in children with marasmus or kwashiorkor, without a significant difference between those two groups. These are different nutritional and metabolic situations.
Vitamin and mineral status. Balevska and colleagues (1985), Biological Trace Element Research, found altered liver-membrane fatty acids in copper-deficient rats. Buttriss and Diplock (1988), Biochimica et Biophysica Acta, found that vitamin E deficiency reduced membrane PUFA, combined vitamin E/selenium deficiency increased its proportion, and selenium deficiency alone had no consistent effect. “Deficiency” therefore did not produce one uniform fatty-acid pattern.
Cystic fibrosis and multiple sclerosis. Freedman and colleagues (2004), New England Journal of Medicine, found altered AA/DHA ratios in CFTR-expressing tissue from people with cystic fibrosis. Holman, Johnson, and Kokmen (1989), PNAS, reported altered plasma profiles in 14 people with multiple sclerosis. Neither observation establishes that insufficient dietary EFA caused the disease. The MS study cannot support the much broader phrase “most chronic and acute neurological diseases.”
Lung injury and toxic liver injury. Quinlan, Evans, and Gutteridge (1994), Free Radical Research, observed linked declines in plasma linoleate and protein thiols in nine of eleven ARDS patients, consistent with oxidative damage. Carreau and colleagues (1980), Lipids, measured reduced hepatic desaturase activity after carbon-tetrachloride poisoning in rats. These concern injury-associated changes, not proof that either illness begins with dietary deficiency.
LEC rats, Wilson’s disease, and liver cancer. Shibata and colleagues (1999), Anticancer Research, found that safflower- or perilla-oil-supplemented diets delayed hepatitis in LEC rats; that dietary intervention is not itself a diagnosis of EFAD. Azbukina and colleagues (2020), Metabolites, identified altered plasma lipid/oxylipin profiles in people with Wilson’s disease. Qiu and colleagues (2015), Lipids, found altered plasma and tissue fatty-acid profiles in hepatocellular carcinoma. The human studies are associations, not demonstrations of a shared cause.
Cardiac death and blood cells. Luostarinen, Boberg, and Saldeen (1993), Atherosclerosis, found higher LA but lower AA and several other PUFAs in coronary arteries after sudden cardiac death; the cases also had more atherosclerosis. Rachmilewitz, Shohet, and Lubin (1976), Blood, documented altered red-cell lipids in beta-thalassemia major. Mackay and colleagues (2012), Hypertension, found lower erythrocyte long-chain PUFAs in mothers and offspring in preeclampsia and growth-restricted pregnancies. This last result addresses a defined pregnancy context, not the undefined category “abnormal umbilical cord blood cells.”
Boundary of this annotation. These examples support investigating fatty-acid metabolism across diseases. They do not establish the entire original list as a single syndrome, independently verify its alloxan-specific claim, or show that EFA supplementation prevents or treats each condition.
Mead acid is increased during EFA deficiency, the largest reservoir of mead acid is the cartilage, after stores of oleic acid are exhausted soft tissues particularly in the joints are robbed of mead acid stores, it is plausible this can lead to joint degeneration, stiffening of joints, loss of flexibility, calcification of joints
Mead acid—established synthesis, unverified depletion story
The biochemical observation is supported; the proposed joint mechanism is not. Ichi and colleagues (2014), Biochimica et Biophysica Acta, identified enzymes and pathways involved in making Mead acid from oleic acid, explaining its appearance during EFA deficiency. This is evidence of synthesis, not evidence that tissues must be stripped of pre-existing Mead acid.
Cleland and colleagues (1995), Lipids, found distinctive fatty-acid patterns in human and sheep cartilage, including more Mead acid in fetal than mature cartilage. They did not measure cartilage as the largest whole-body reservoir or demonstrate its mobilization after oleic-acid stores were exhausted. Neither paper links that proposed sequence to joint calcification or degeneration. Those parts of the note remain speculative.
LA and ALA are the only known essential fatty acids (in humans, mice have different available desaturase and elongase enzymes, as do other species along with varying capacities), other fatty acids sometimes associated with EFAs such as DHA, EPA, AA, are what are known as ‘conditional essential fatty acids’
Essential precursors and conditional requirements
Human evidence for distinct precursor needs; downstream requirements depend on context. The fat-free feeding study by Wene and colleagues (1975), Journal of Clinical Investigation, demonstrated linoleate depletion and biochemical deficiency. Holman, Johnson, and Hatch (1982), American Journal of Clinical Nutrition, described an omega-3 deficiency that developed despite a linoleate-rich feeding regimen and improved when an ALA-containing emulsion was supplied. The two fatty-acid families are not interchangeable.
Human tracer experiments by Burdge and Wootton (2002), British Journal of Nutrition, demonstrate conversion of ALA into longer-chain products. Conditional essentiality concerns situations in which synthesis cannot meet a particular requirement; it should not imply that AA, EPA, and DHA have identical status in every life stage or disease. Species differences in conversion also do not mean ordinary mice possess a pathway for manufacturing LA or ALA from scratch.
Contrary to the antioxidant hypothesis, Vitamin E may not be involved with stabilizing polyunsaturated fat i.e. reducing its proneness towards oxidation, rather Vitamin E is involved with the function of desaturation ezymes, which of course is a more plausible mechanism
Vitamin E can affect enzymes and protect against oxidation
An enzyme effect is documented; the proposed exclusion of antioxidant action is contradicted. Despret and colleagues (1992), Neuroscience Letters, increased vitamin E in rat microsomal preparations and observed increased delta-6 desaturase activity in brain preparations but reduced activity in liver preparations. This supports a tissue-dependent interaction, not a universal alternative explanation for vitamin E’s function.
Carlson and colleagues (2016), Redox Biology, found that vitamin E rescued mice lacking the lipid-peroxide-detoxifying enzyme GPX4 in hepatocytes; protection was lost when vitamin E was withdrawn. Their results support protection against damaging lipid peroxidation. The possibility of enzyme regulation does not displace this antioxidant role. The original note’s either/or framing should not be read as an established conclusion.
LA probably is an important part of the mammalian antioxidant system
Oxidized linoleate as a signal
A specific mechanistic basis for the idea, with a crucial distinction. Wang and colleagues (2009), Prostaglandins, Leukotrienes and Essential Fatty Acids, found that EKODE, a particular oxidized metabolite of LA, activated an antioxidant-response pathway in neuroblastoma cells and cerebrocortical neurons. The response required NRF2 and PI3-kinase and increased expression of protective genes. LA itself did not activate the response in that screen.
This supports the narrower idea that a product of lipid oxidation can help signal an adaptive defense. It does not make LA itself a conventional antioxidant, show that every oxidation product is beneficial, or establish that increasing dietary LA produces the same response in a person.
There are sex differences in EFA metabolism that are proportional to muscle mass
Sex differences are supported; proportionality to muscle is not
Human evidence points to hormonal regulation. Giltay and colleagues (2004), American Journal of Clinical Nutrition, found a higher DHA proportion in women than men eating controlled diets. In hormone-treatment groups, oral ethinyl estradiol increased DHA and testosterone reduced it; transdermal estradiol did not show the same increase as oral treatment.
These findings support sex- and hormone-associated differences in fatty-acid status. They do not establish that those differences are proportional to muscle mass, or that muscle mass explains the hormonal effects. The proportionality claim remains unverified rather than a finding that can be attributed to this study.