How does nutrition affect intelligence?

Many ways: Low intake of omega-3s for example, would deny the brain access to dha, an important fatty acid, certain vitamins, like B12 and e are needed for normal nerve and brain function. Low iron can also cause brain related problems. Certain antioxidants, like the anthocyanins in blueberries can reduce brain inflammation. Get your nutrition from whole foods and never from pills if avoidable.