Gamma linolenic acid (GLA): What is it & how can it benefit health?

In this week’s blog, our Nutritional Therapist, Ruth, explores in detail all things gamma linolenic acid. GLA for short!

What is GLA?

Gamma-linolenic acid (GLA) is an omega-6 fatty polyunsaturated fatty acid (PUFA). Omega-6 fatty acids are considered essential fatty acids, as they are necessary for human health, but the body cannot make them. You therefore need to get them through diet. Along with omega-3, omega-6 PUFAs play a crucial role in brain function, and normal growth and development. Both omega-3 and omega-6 PUFAs regulate inflammation, immunity, blood vessels, platelets, synaptic plasticity, cellular growth, pain, sleep and many other bodily processes⁸.

Over the last few decades, the publicity in the area of healthful fatty acids has been dominated by omega-3 fats, and more specifically EPA and DHA found in oily fish. This publicity is based on a large body of scientific evidence that links omega-3 fatty acids to a decreased risk of several chronic diseases such as cardiovascular disease, diabetes, cancer, cognitive decline, depression, as well as a supportive role in visual and neurological development, and maternal and child health¹.

Omega-6 fatty acids: Health threat or health friend?

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Evidence on the health benefits of omega-3 PUFAs very often depicts omega-6 fatty acids in a negative light; even as a potential health threat. The basis for this conclusion is the evidence that an imbalanced ratio between omega-6 to omega-3 fatty acids can lead to a range of health concerns^4-6. The average ratio of omega-6: omega-3 in the Western diet is approximately 20:1, whereas in the palaeolithic times (and up to around 100 years ago) the ratio was thought to be closer to 4:1⁶.

Omega-3 and Omega-6 fatty acids ratio in modern day dietary intake

One reason for this imbalanced ratio is the low intake of oily fish in the Western diet, coupled with a high dietary intake of the omega-6 fatty acids linolenic acid (LA) and arachidonic acid (AA).

Because it is synthesised in plants, LA is found in high proportions in foods of plant origin. For example, many seeds, nuts, and plant oils are rich in LA; these include safflower, sunflower and pumpkin seeds, walnuts, corn, and sunflower, safflower and soybean oils².

Conventionally reared meat, such as chicken and pork are often fed a diet high in LA, including corn and soy, and thus contain high levels of omega-6 fatty acids in their meat⁷.

For the last few decades, following widespread recommendations to eat unsaturated fatty acids as opposed to saturated fatty acids, intake of fatty acids in modern society has been shifted from saturated fatty acids (butter, lard) to vegetable oils rich in LA and poor in omega-3 fatty acids⁸, which is likely to be one of the reasons that led to a remarkably significant increase in the ratio of omega-6/omega-3.

LA and AA combined account for the majority of omega-6 dietary intake, to which the potential negative effects of the imbalanced fatty acids ratio are linked.

GLA, however is only present in small amounts in the diet but has the potential to have similar benefits to omega-3 fatty acids – evidence of which we will discuss below.

GLA is present in some plant seed oils including evening primrose, blackcurrant, and borage oils (where it contributes about 9%, 17%, and 21% of fatty acids, respectively)³.

Fatty acids, inflammation and prostaglandin creation:

One of the key compounds generated from fatty acids are hormone-like substances called prostaglandins. The primary role of prostaglandins is to support the healing process by balancing inflammatory and anti-inflammatory processes. They are found in almost every cell and tissue throughout the body and are essential to proper functioning.

The three major prostaglandins in the body include PgE1, PgE2 and PgE3:

• PgE1 (anti-inflammatory) – formed from omega-6 fats; either LA or GLA sources
• PgE2 (inflammatory) – primarily derived from AA
• PgE3 (anti-inflammatory) – formed from omega-3 fats; either ALA or more directly from EPA sources

GLA is converted into ‘dihomo’ GLA or DGLA and this is incorporated into cell membrane phospholipids. GLA is metabolized into prostaglandin E1 (PGE1), a potent anti-inflammatory mediator that can modulate immune responses and reduce inflammation⁹.

PgE1 is the most potent anti-inflammatory prostaglandin in the body. It is produced through the metabolism of LA into GLA, however this reaction is slow and can be impaired by a variety of factors such as stress, poor diet and various medications. Furthermore, proper digestive, liver and enzymatic function are essential for ensuring that the fats consumed in the diet can be converted into prostaglandins. By directly supplementing with GLA, one can bypass this inefficient conversion process, ensuring a more reliable and effective increase in DGLA levels.

GLA can support a balanced level of inflammation in the body through a process called competitive inhibition; DGLA competes with AA for access to enzymes (i.e., cyclooxygenase and lipoxygenase) that create prostaglandins that either promote or resolve inflammation¹¹.

This means that the presence of DGLA in tissues can help lower the output of AA’s prostaglandins by inhibiting their production and/or blocking their transformation¹³, which ultimately translates to lower levels of pro-inflammatory prostaglandins.

It is important to note that both inflammatory and anti-inflammatory prostaglandins are essential, it is only when the system falls out of balance and creates too much PgE2 at the expense of PgE1 and PgE3 that issues arise. Omega-3 and omega-6 PUFAs compete for the same conversion enzymes and so consuming a high level of dietary omega-6 may cause issues even in the context of high dietary omega-3.

What is GLA good for?:

As we have explored, GLA is a unique omega-6 PUFA, which demonstrates a variety of anti-inflammatory properties. The idea that we don’t require GLA due to the high amounts of omega-6 consumed in our diet is a common misconception, when in fact, GLA is vital in order to neutralise and reverse the effects of an excess of AA and LA fatty acids in the diet.

GLA has been used for centuries as part of homeopathic remedies, however, it is only in recent years that the research has caught up and several benefits have been confirmed and discovered:

GLA & hypertension

In one study on post-menopausal women with hypertension, those who received supplementation of 1000mg borage oil, rich in GLA over a 6-month period, saw a significant reduction in the systolic and diastolic pressure as well as a significant change in waist-hip ratio¹⁰.

Gamma linolenic acid & diabetes mellitus

The prevalence of type II diabetes is increasing worldwide and has the potential to affect different organs such as the kidney, brain, heart, amongst others, in chronic stages. A decrease in insulin activity has the potential to reduce delta-6 desaturase and impair the conversion of LA to GLA¹⁶. This phenomenon has a key role in membrane structure and 6-desaturated metabolites, the precursors to prostaglandins.

All of these can lead to cardiovascular complications alongside diabetes, and consequently it has been suggested that high doses of GLA be effective in neuropathy improvement and cardiovascular disorder risk reduction in the condition¹⁶.

Neuropathy is the most common complication among diabetes patients¹⁵. GLA is an essential component of structural phospholipids in neural cell membranes and, as such, is necessary for the maintenance of normal nerve membrane structure and function. One study measured the efficacy of GLA for reducing pain severity in diabetic neuropathy over a 12-week period and concluded that it offered a well-tolerated and effective treatment option¹⁵.

GLA & rheumatoid arthritis (RA)      

RA is one of the most common autoimmune conditions, characterised by pathological changes in the lining of the joints. In RA, the overproduction of the inflammatory molecules PGE2, tumour necrosis factor (TNF), interleukin (IL)-1, and cytokines induce the chronic inflammation that causes pain and swelling in the joints. Several clinical trials have demonstrated a beneficial effect of GLA in alleviating inflammation and disease severity in RA¹⁷.

Gamma linolenic acid and skin health

In one interventional study, 40 men and women received either 1.5g GLA-rich evening primrose oil or placebo. After 12 weeks, those receiving evening primrose oil had significant improvements in skin moisture, elasticity, firmness and trans-epidermal water loss (a measure of barrier integrity) compared to placebo²¹. There is also evidence of GLA supporting specific skin conditions:

Atopic eczema

Atopic eczema is a chronic inflammatory skin condition, which usually develops in early childhood and can have a significant impact on quality of life. The pathology of atopic eczema is multifactorial and has complicated immunological abnormal responses, including damage to the epidermal barrier, genetic factors, and environmental causes.

Some researchers have suggested that atopic eczema may be related to the abnormal metabolism of essential fatty acid, especially in the production of gamma-linolenic acid, and a functional deficiency in delta-6 desaturase has been identified, leading to a decrease in GLA, and consequently a dominance of inflammatory prostaglandins¹⁸.

Supplementing with evening primrose oil, a rich source of GLA has demonstrated improvements in the severity of eczema symptoms¹⁹. Some studies suggest balancing a typical western diet, rich in LA and AA, with GLA and omega-3 fatty acids, which can act to balance the fatty acid composition of membrane phospholipids and/or inhibit the production of proinflammatory eicosanoids²⁰.

Acne

Acne is a common, inflammatory skin condition characterised by excessive sebum production, follicular hyperkeratinisation of sebaceous ducts, and an increased release of inflammatory mediators. It has been estimated that approximately 85% of adolescents have acne; however, this dermatosis may occur in childhood and can persist beyond adolescence.

GLA is thought to be supportive in acne, not only due to its anti-inflammatory properties, but also since DGLA can reduce follicular hyperkeratinisation²².

One study found that GLA from borage oil was comparable to EPA and DHA for improving acne lesions and found that it presented a safe and tolerable adjuvant treatment for mild to moderate acne²³. GLA has also shown to have a protective role on the skin barrier and maintains skin hydration in those who are treated with the acne medication isotretinoin²².

There are more and more promising studies in favour of combined GLA and omega-3 PUFAs supplementation showing the highest potential in diminishing inflammatory processes and ameliorating chronic inflammatory skin diseases²².

GLA & female health

Premenstrual Syndrome (PMS)

PMS is a condition, which is associated with somatic, emotional and behavioural symptoms before or during menstruation. Anxiety, depression, acne, fatigue, and headache are common symptoms of PMS and around 85% of women of menstrual age are thought to be affected by the condition.

Low levels of PgE1, as the result of a deficiency in essential fatty acids is thought to cause high sensitivity to prolactin, and high prolactin levels throughout the menstrual cycle, which is thought to contribute to the symptoms of PMS²⁴.

One review of the research highlighted eight studies that compared evening primrose oil with a placebo for PMS and one study comparing GLA with a placebo. The evening primrose oil study showed a significant decrease in PMS severity, while the GLA study showed a shortened duration and decreased severity of PMS symptoms²⁴.

Mastalgia

Mastalgia, or breast pain, is a common condition among premenopausal women, which can lead to significant impairment in daily living. The pathology of cyclical mastalgia is likely to be multifactorial and include hormonal fluctuations (particularly variations in oestrogen and progesterone), breast tissue sensitivity, inflammation, cyclic changes in breast anatomy, psychological factors, nerve sensitivity, and fibrocystic changes²⁵.

GLA’s beneficial role in mastalgia is thought to be due to its ability to modulate prostaglandin synthesis and promote hormonal balance, thus alleviating breast pain²⁵.

Gamma linolenic acid, menopause transition and post-menopause

Menopause is a natural transition in a woman’s life that typically takes place between the ages of 45 and 55 and is triggered as a woman’s oestrogen levels begin to decline. For many women this natural stage in life can become a time of physical and emotional discomfort, and the most common symptoms include hot flushes, night sweats, insomnia, anxiety, mood swings and weight gain.

As mentioned, GLA authorises the synthesis of anti-inflammatory substances such as 15-hydroxy-eicosatrienoic acid and prostaglandin E. Prostaglandins function as central neurotransmitters and influence the hypothalamic pituitary axis, and GLA is thought to help counter menopausal hormonal changes by increasing the production of prostaglandins²⁷.

One study, examining the effects of evening primrose oil on hormonal levels in menopause found a decrease in follicle stimulating hormone, and increase in oestradiol and improvements on the “menopause rating scale” after 2 months of use²⁷.

Another study demonstrated improved mood and decreased psychological symptoms such as low mood, irritability, anxiety and mental exhaustion upon taking evening primrose oil. The authors suggest that this is likely to be due to the high level of GLA in the oil²⁶. Evening primrose oil has also shown improvements in the severity of hot flushes in post-menopausal women²⁸.

Gamma linolenic acid and neurodivergence

There is a wealth of evidence of a supportive role of PUFAs in neurodivergent conditions such as attention deficit hyperactivity disorder (ADHD). Evidence has typically focused on omega-3 PUFAs, but a supportive role of GLA in neurodivergence is emerging.

Due to its anti-inflammatory properties, GLA has demonstrated a supportive role in ADHD and associated symptoms, particularly when it is combined with omega-3 PUFAs.

In particular, a combination of EPA and DHA with the addition of GLA in a 9:3:1 ratio appears to be associated with improvements in ADHD symptoms. It is hypothesised that this may be due to omega-3 PUFAs preventing the accumulation of serum AA in response to GLA¹².

Gamma linolenic acid and children’s health

When combined with an omega-3 fish oil and vitamin D supplement, GLA from blackcurrant seed oil demonstrated benefits in children with atopic dermatitis after 4 months of treatment. The benefits included a significant reduction in eczema symptoms, a reduced need for topical corticosteroids and improvements in itch, sleep quality, and overall quality of life¹⁴. This combination has been suggested as a safe and effective intervention that may help to reduce the severity of symptoms of atopic eczema in children.

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Last updated on 21st November 2024 by cytoffice