The use of complementary and alternative medicine (CAM), such as nutritional supplements, is common in children with ADHD, despite limited evidence for its effectiveness. Many consumers use these treatments, often without telling their physicians. Asking patients about them allows for a discussion of the risks and benefits.
Nutritional supplements include macronutrients such as proteins, fats, and carbohydrates, as well as micronutrient products such as vitamins and minerals. Among randomized controlled trials (RCTs) evaluating nutritional supplements for ADHD treatment, few are of high quality, and study results are frequently inconsistent.
Macronutrients for ADHD
Essential Fatty Acids. The essential fatty acids (EFAS) include the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and the omega-6 fatty acids arachidonic acid (AA) and gamma linolenic acid (GLA). Children with ADHD may have low levels of EFAS, especially DHA and AA. While there have been a number of well- designed studies of EFAS in children with ADHD, there is limited evidence that fatty acids improve core symptoms in such children.
A 2011 meta-analysis of 10 RCTs (699 participants) comparing omega-3 fatty acid supplementation with placebo found omega-3 to be modestly effective (0.31 effect size) on inattentive and hyperactivity ADHD symptoms, especially with a higher EPA dose (Bloch MH & Qawasmi A, J Am Acad Child Adolesc Psychiatry 2011;50(10):991-1000).
A 2012 Cochrane review, which included 13 RCTS (seven overlapping with the 2011 meta-analysis) did find that there was evidence of improvement in a pooled analysis of two trials (with a total of 97 participants) of combination omega-3 and omega-6 fatty acids.
None of the other RCTS in the review showed benefit to supplementation (Gillies et al, Cochrane Database Syst Rev 2012; Jul 11:7). The differences in results are likely related to the variability of EFA supplements used, and to methodological differences.
Overall, a growing body of evidence supports the use of an EFA supplement for children who have ADHD. In general clinical practice it is reasonable to embark on a trial of EFAs—especially when parents are ambivalent about medications, or medications are not effective or poorly tolerated—as there are a number of positive studies and the risks are low.
It is best to use combination EFAs, such as fish oil. Phosphatidyl serine might also be a good source, but has limited data at this time.
Fish oil is a more efficient source of EFAs than flaxseed oil. Fish oil is inexpensive and comes in a variety of flavors and chewables for children. The label should specify that the product is mercury free. An acceptable dose is 1,000 mg to 2,000 mg (with at least 500 mg of EPA) per day from preschool age and up.
At least three months should be allowed to see results, and results may be optimal at six months. The most common side effects of fish oil include abdominal pain, belching, and a fishy aftertaste.
L-Carnitine and Acetyl L-Carnitine (ALC).
L-carnitine is synthesized from lysine and methionine amino acids. It is a semi-essential nutrient involved in transporting fatty acids into mitochondria. While two foreign RCTs showed benefit, two American RCTs failed to show benefit on intent-to-treat analyses; however, those with inattentive subtype responded better than others.
So, while the evidence to support use of L-carnitine is weak at this time, it might be beneficial for children with the inattentive subtype of ADHD. Doses used in research study were 500 mg to 1,500 mg BID, depending on weight, and no safety concerns or side effects were reported (Amato A et al, J Child Adolesc Psychopharmacology 2007;6:791).
Micronutrients for ADHD
Zinc. Zinc is an essential mineral and is a cofactor for many enzymes. In the brain, zinc inhibits dopamine uptake when it binds to the dopamine transporter. Zinc deficiency symptoms include concentration impairment and jitters. Several studies suggest that zinc levels might be low in children with ADHD, and that optimal stimulant response might depend on adequate baseline zinc levels. Zinc increases the affinity of methylphenidate for the dopamine transporter.
Two RCTs conducted in Turkey found benefit from zinc monotherapy in ADHD. A large RCT found that zinc supplements reduced hyperactive, impulsive, and impaired socialization symptoms, but did not improve symptoms of inattention. This study used a high dosage of zinc for a period of 12 weeks and more than 50% of placebo and zinc groups dropped out of the study.