Introduction

The prevalence rate of ADHD in Western culture is approximately 5%, and remains the most common psychiatric disorder among young children, with an estimated 50% of these children reporting ADHD symptoms for the rest of their lives (Wolraich 2005; Biedermann 2005). The economic consequences of ADHD persisting into adulthood are significant, with one U.S. analysis finding an average of 35 days of annual lost work performance, resulting in 120 million days of annual lost work in the labor force, equivalent to $19.5 billion lost human capital (Kessler 2005).

Shared concerns about adverse effects of widely prescribed stimulant medications among mental health providers, parents and individuals diagnosed with ADHD have led to studies on a range of alternative modalities (Schachter 2001). More than 50% of parents of children diagnosed with ADHD treat their children's symptoms with dietary modification or one or more alternative therapies but few disclose this to their child's pediatrician (Berman 2009). Many individuals diagnosed with ADHD use alternative therapies alone or in combination with a medication, often without regard to the research evidence (Slatkoff 2006).

This article is offered as a concise review of current evidence for dietary modification and natural product supplements for treating ADHD.

Dietary modification

Early studies suggested that artificial food colorings were associated with ADHD; however, a meta-analysis of studies spanning a 35-year period failed to confirm this relationship (Nigg 2012). The oligoantigenic diet (OAD) is a highly restrictive multiple elimination diet that excludes food colorings and additives, in addition to dairy products, sugar, wheat, corn, citrus, eggs, soy, yeast, nuts and chocolate. OADs permit a limited number of hypo­allergenic foods, like lamb, chicken, potatoes, rice, banana, apple, cabbage, broccoli, brussels sprouts, carrots, peas, pears and cucumber, as well as salt, pepper, calcium and some vitamins. Several studies on the OAD regimen reported significant reductions in hyperactivity in children diagnosed with ADHD when specific food items were eliminated from the diet (Egger 1992, Carter 1993, Schmidt 1997). A recent meta-analysis of studies on restrictive diets in childhood ADHD concluded that roughly one-third of hyperactive children may benefit from some form of an elimination diet (Nigg 2012). The American Academy of Pediatrics does not currently endorse elimination diets because of inconsistent findings of efficacy and concerns that highly restrictive diets do not provide balanced nutrition. Parents who are considering restrictive diets should consult with a qualified nutritionist, and highly restrictive diets should not be continued longer than two weeks in the absence of noticeable improvements in ADHD symptoms (Arnold 2010).

Omega-3 essential fatty acids

The omega-3 essential fatty acids EPA and DHA play important roles in healthy brain function and have established anti-depressant effects. Most studies on omega-3 in ADHD have reported negative findings and a few studies suggest that high doses of EPA or combined EPA/DHA are beneficial in some cases. One large study reported positive results on parent-rated measures of ADHD (Sinn 2007). It has been suggested that the use of olive oil as a placebo may mask the beneficial clinical effects of essential fatty acids because an active constituent of olive oil is converted into oleamide which is known to affect brain function (Richardson 2002). Other issues potentially confounding research designs are the short durations and low doses of essential fatty acids used in some studies which may not be adequate to result in long-term changes in neuronal membrane structure required for clinical improvement. The dosage issue has been explored by a small 8-week open-label study in which 9 children diagnosed with ADHD received high dose EPA/DHA concentrates (16.2 g/day) while continuing on stimulant medications (Sorgi 2007). Most children were rated by a blinded psychiatrist as having significant improvements in both inattention and hyperactivity that correlated with reductions in the ratio of the omega-6 fatty acid arachidonic acid (AA) to EPA following 8 weeks of treatment. Current evidence does not support the use of EFA as a stand-alone treatment in ADHD. A meta-analysis (including studies from 1965 to 2010) however confirmed positive effects of adjunctive essential fatty acids in childhood ADHD however, therapeutic benefits were significantly less than for conventional pharmacological treatments (Bloch 2011).

Zinc and iron

Some children diagnosed with ADHD have abnormally low plasma zinc levels which may interfere with optimal information processing and result in difficulties maintaining attention (Yorbik 2008). In a large randomized controlled trial 400 children and adolescents who received a high dose of zinc (150 mg/day) experienced significantly greater improvements in hyperactivity and impulsivity (but not inattention) compared to the placebo group (Bilici 2004). In another placebo-controlled study involving 44 ADHD children, the group receiving zinc (55 mg/day) while taking a stimulant medication reported greater improvement than the group taking a stimulant only (Akhondzadeh 2004). It is important to note that a subsequent study failed to confirm the results of the earlier studies (Arnold et al 2011).

Many children and adolescents in Western countries have iron deficiencies. Abnormally low serum ferritin levels may be associated with hyperactivity in non-anemic ADHD children, but not with deficits in cognitive performance. In a placebo-controlled study 23 ADHD children with abnormally low serum iron levels were randomized to an oral iron supplement (ferrous sulphate 80 mg/day) versus placebo. Children treated with the iron supplement showed progressive improvements in ADHD symptoms compared to the placebo group (Konofal 2008). A 2012 systematic review of studies on iron in ADHD children found mixed results in the relationship between serum iron levels and symptom severity, and inconsistent responses of ADHD symptoms to iron supplementation (Cortese 2012). Two studies reviewed suggested that serum iron deficiency may reduce the effectiveness of stimulants.

Acetyl-L-carnitine (ALC)

The amino acid acetyl-L-carnitine (ALC) is required for energy metabolism and synthesis of fatty acids. In a multisite study of 112 ADHD children randomized to placebo vs. ALC 1000 to 3000 mg/day, children with predominantly inattentive type ADHD experienced greater improvement over placebo (but there was no differential benefit on primary outcomes in children with combined type ADHD) (Arnold 2007).

Herbal medicines

A patented product derived from the bark of the French maritime pine tree that has established anti-oxidant and anti-inflammatory properties may be beneficial for ADHD. In one study 61 ADHD children taking the product reported reduced hyperactivity, increased attention and increased visual-motor coordination (Trebaticka 2006). Further investigation of French maritime pine bark found a significant effect on symptoms of hyperactivity from a re-analysis of the sample (Sarris 2011). However, a small crossover study on an adult population found no significant effects of FMPB (1 mg/0.5 kg/day) over 3 weeks administration compared to placebo.

An 8-week placebo-controlled study by Li et al (Li et al 2007) evaluated the efficacy and safety of a traditional Chinese herbal medicine preparation (Ningdong: NDG) vs. methylphenidate in 72 ADHD children. NDG significantly reduced ADHD symptoms and caused fewer side effects than methylphenidate. A four-month randomized double-blind placebo-controlled trial evaluated the efficacy of a patented, compound herbal preparation (Nurture and Clarity) for improving attention, cognition and impulse control in 120 children newly diagnosed with ADHD (Katz 2010). The main active ingredients included the herbals White peony (Paeoniae alba), ashwagandha (Withania somnifera), Gotu kola (Centella asiatica), Spirulina (Spirulina platensis), Water hyssop (Bacopa monnieri) and lemon balm (Melissa officinalis). At the end of the study the group receiving the herbal formula showed statistically significant improvement in inattention, impulse control and cognition compared with no improvement in the control group. The herbal formula was well tolerated.

Last words

The high prevalence rate and social and economic burden of ADHD and shared concerns about the effectiveness and safety of widely used stimulant medications have led to studies on a range of non-pharmacologic treatments. Currently, there is no consensus on which non-pharmacologic treatments should be recommended for treating symptoms of ADHD.

The most promising alternative treatments are zinc, iron, and an extract of French maritime pine bark. Certain elimination diets and restrictive diets may be beneficial for hyperactive children. Omega-3 supplementation may reduce ADHD symptoms however large studies testing different doses are needed to determine whether higher doses and specific ratios of fatty acids are more effective than others.

Children and adolescents with ADHD should be checked for deficiencies in zinc, iron and omega-3s however it may be unlikely that in cases of deficiency that supplementation will result in greater improvement than a healthy diet.

There is emerging evidence that select botanicals may be effective against ADHD. For example, preliminary findings suggest that some compound herbal formulas used in Chinese medicine may reduce symptoms on ADHD.

In sum, most findings on non-pharmacologic treatments of ADHD should be regarded as preliminary pending confirmation by large well-designed placebo-controlled studies.

Finally, even though the evidence for omega-3s is inconsistent it is appropriate to recommend omega-3 supplementation to individuals with ADHD because of their established anti-inflammatory and neuroprotective benefits.