MILK – YOUR TICKET TO DREAMLAND? Milk contains protein, which helps keep blood sugar stable. Deﬁciency of calcium and magnesium (found in milk), can cause insomnia, plus it’s theorised that the amino acid tryptophan, present in milk and needed for serotonin production, may increase the effect. The effect may also be psychological – if mum tucked you in with a mug of warm milk, you’ll associate it with sleep. However, if you’re allergic or sensitive, it could have the opposite effect.