How can a 7 year old boy increase his height?

Wait. Besides consuming a solid diet with enough calories, vitamins and minerals, there's not a whole lot you can do to increase your height naturally. And it's not as though consuming extra multivitamins or the like will actually increase your height- by getting enough vitamins, you'll avoid a potential deficiency that could delay your growth. Consuming more vitamins than you need won't help and might hurt other aspects of your health.