The reason why a person with POTS may feel faint, dizzy or lightheaded is because the condition causes less blood to return to the heart after they change position. Although symptoms usually improve as one gets older, changing diet can greatly help to ease them, especially with regards to the severity and how frequent they occur.
Luckily, POTS usually resolves on its own.
This book contains the essential information you need if you're looking for a nutritional guide for POTS. It answers questions such as what a POTS diet should look like, some modifications and lifestyle interventions that can help you on your road to recovery.