Special Diets
Evidence and cautions for elimination diets, gluten/casein-free, and other special dietary approaches.
Important to know:
Common special diets reviewed
The claim:
That these proteins cause autism symptoms through opioid-like effects or leaky gut.
What research shows:
- •Cochrane review found insufficient evidence to recommend
- •Some small studies show benefit, but methodology is often poor
- •No evidence for the proposed mechanisms
- •May help a small subset, but no way to predict who
Risks:
- Nutritional deficiencies (calcium, vitamin D, fibre)
- Social restriction around food
- Expense
- False hope
Our view: Not recommended as routine. If trying, do so with dietitian support and for a time-limited trial.
The claim:
That artificial additives cause or worsen ADHD symptoms.
What research shows:
- •Southampton studies showed small effects of colours on some children
- •UK has stricter regulations than US partly due to this research
- •Effect sizes are small
- •Not all children are affected
Risks:
- Modest restrictions, relatively low risk
- Can become overly restrictive
Our view: Reasonable to try if you notice patterns. UK foods already have fewer additives. Don't expect major changes.
The claim:
That identifying and removing trigger foods reduces symptoms.
What research shows:
- •Some studies show benefit for some children
- •NICE notes limited evidence and no long-term data
- •Very difficult to implement properly
- •Requires significant family commitment
Risks:
- Nutritional deficiencies if prolonged
- Extremely restrictive
- Can worsen picky eating
- Social isolation around food
Our view: Only consider with dietitian supervision. Not a first-line approach.
The claim:
That ketones provide better brain fuel and reduce symptoms.
What research shows:
- •Strong evidence for epilepsy (used medically)
- •Preliminary research in autism, mostly animal studies
- •Very limited human data for ADHD/autism
Risks:
- Nutritional concerns
- Difficult to maintain
- Not suitable for children without medical supervision
Our view: Not recommended for ADHD/autism outside of medical research settings.
The claim:
That sugar causes hyperactivity.
What research shows:
- •Multiple controlled studies show no sugar-behaviour link
- •Perceived effects are likely expectation effects
- •Exciting events with sugar (parties) confuse the picture
Risks:
- Minimal if done moderately
- Can become overly restrictive
Our view: Reducing sugar is reasonable for general health, but don't expect ADHD symptom improvement.
Before trying any restrictive diet
Consult a healthcare professional
Discuss with GP, paediatrician, or dietitian before starting restrictive diets.
Assess current nutritional status
Ensure baseline nutrition is adequate. Test for deficiencies if relevant.
Set clear goals and timeline
What improvement are you looking for? How long will you trial? How will you assess?
Plan for nutritional adequacy
How will you replace eliminated nutrients? Consider supplementation.
Consider the whole family
Who will follow the diet? How will you manage social situations?
Track systematically
Food diary and symptom tracking to objectively assess effects.
What guidelines say
- Ask about foods/drinks that appear to influence behaviour
- Consider food diary if clear link suspected
- Dietitian referral if food diary supports dietary management
- Note: limited evidence for "few foods" diet
- GFCF diet: insufficient evidence to recommend
- Artificial colours: small effects in some children
- Few foods diet: limited evidence, difficult to implement
Special diets are not first-line treatments. Evidence is limited, risks are real, and better-supported interventions exist. If you want to try a dietary approach, focus on overall diet quality first, and only consider elimination with professional guidance.
- Most special diets have limited evidence for ADHD/autism specifically
- Risks include nutritional deficiency and worsening relationship with food
- If trying, do so with professional guidance and a clear plan
- Time-limited trials with objective tracking are better than indefinite restriction
- Focus on overall diet quality rather than elimination approaches