Relationship between polyunsaturated fatty acid and eating disorders: Systematic review and meta-analysis

Highlights

• The current meta-analysis addressed that the patients with eating disorders were associated with significantly higher plasma total omega-3 fatty acids than those in controls.

• Also, the patients with eating disorders were associated with significantly plasma lower levels of total omega-6 fatty acids and lower red blood cell membrane levels of total omega-6 fatty acids than those in controls.

• Polyunsaturated fatty acid supplements were associated with a benefit to body weight outcomes but not disease severity and mood symptoms in interventional trials.

Abstract

Objectives

Eating disorders result in poor nutrition, poor physical conditions and even suicidality and mortality. Although polyunsaturated fatty acids (PUFAs) have attracted attention in the emerging field of nutritional psychiatry, their role in eating disorders remains unknown. This meta-analysis investigates the differences of PUFA levels between patients with eating disorders and healthy controls, and the potentially beneficial effects of PUFAs in such patients.

Methods

We conducted a systematic literature search and meta-analysis under the random effects model.

Result

Eleven studies were included in the current meta-analysis. Compared with controls, 379 patients with eating disorders had significantly higher plasma levels of alpha-linolenic acid, eicosapentaenoic acid, stearidonic acid, osbond acid, palmitoleic acid, oleic acid, and total omega-3 fatty acids; and lower levels of total omega-6 fatty acids and omega-6/omega-3 ratio. Eating disorders were associated with significantly higher red blood cell membrane levels of palmitoleic acid and oleic acid and lower levels of adrenic acid, arachidonic acid, and total omega-6 fatty acids. In addition, PUFA supplements were associated with a benefit to body weight outcomes but not disease severity and mood symptoms in interventional trials.

Discussion

This meta-analysis indicates abnormal levels of PUFAs in peripheral blood tissues in patients with eating disorders. The relationship between PUFAs and eating disorders should be interpreted cautiously considering the specific lipid metabolism under starvation state. To investigate the role of PUFAs on psychopathological and therapeutic effects in eating disorders, further larger clinical studies are warranted.

Introduction

Eating disorders are serious illnesses that particularly affect young women and can result in poor nutrition, significant physical conditions, and even suicidality [1], [2], [3], [4]. Development of eating disorders is reportedly influenced by multiple factors, including genetic, biological and psychosocial factors, and individual personality traits. Recently, several human and animal studies have attempted to elucidate a biological basis of eating disorders [5], [6]. In eating disorders, disturbance of the striatal circuit and receptors and transporters of dopamine and serotonin have been reported in neuroimaging studies [7]. Notably, psychological stress leads to abnormal activity of serotonin in the hypothalamus and this influences appetite [8], [9]. Other studies have reported a relationship between eating disorders and reduction of serum brain-derived neurotrophic factor (BDNF) levels [10], genetic abnormalities of BDNF [10], increase of serum and plasma level of pro-inflammatory cytokines [11], and genetic abnormalities relating to inflammation [12].

Polyunsaturated fatty acids (PUFAs) have attracted attention in the field of psychiatry due to their neuroprotective effects, such as increased levels of BDNF [13], enhancement of membrane fluidity [14], and antioxidant [8] and anti-inflammatory effects [15]. Evidence on the relationship between eating disorders and PUFAs has gradually accumulated. Abnormal levels of PUFAs in individuals with an eating disorder have been reported in recent studies [16], [17], as well as abnormal activity of fatty acid desaturase, an enzyme that metabolizes PUFAs [16], [17], [18], [19]. These data highlighted the involvement of PUFAs in the pathology of eating disorders. Consistent results have not yet been reached, however, because subject characteristics, sample sizes, and outcome measures have varied between studies.

The importance of interventions other than pharmacological therapies has recently been discussed in the field of nutritional psychiatry. In individuals with psychiatric disorders, nutritional interventions are particularly expected to provide holistic benefits for both physical and psychiatric symptoms. PUFAs, for example, have been suggested to exert therapeutic effects on eating disorders [20], [21]. Regarding their association with appetite, intake of fish oil reportedly contributed to increased appetite in healthy individuals [22]. In cancer cachexia, administration of omega-3 fatty acids has been associated with improvements in appetite, weight gain, and inhibition of lipolysis and proteolysis [23], [24], [25]. Increased body weight as a result of PUFA administration has been reported in clinical studies on eating disorders [21], [26], and improvement in eating disorder assessment scores in addition to body weight have also been reported [20]. On the other hand, some studies described no effect on psychopathological indicators [26], [27]. A consensus has therefore not yet been reached and most interventional studies on eating disorders have been limited by small sample size and high dropout rate.

From the viewpoint of neurotrophic factors and neuroinflammation, PUFAs may be closely associated with eating disorders. As previous observational or interventional studies have not reached consensus, the present study aims to elucidate a potential relationship between PUFAs and eating disorders and the potential benefit of PUFAs in such diseases by meta-analysis.