With regard to foodstuffs and supplements, some people are in fact very sensitive to excesses of certain aliments and medications. For most people who are, the effect (palpitations) occurs after ingestion rather than long term. So if he is sensitive to caffeine, or alcohol, or stimulants such as medications for asthma or nasal congestion, I would expect that the manifestation would be right after the ingestion, rather than in the early morning hours. With time, an individual should be able to observe the things that are bothersome, and the things that aren’t. If beer, coffee, tea, pseudephedrine, ephedra, marijuana, or cocaine trigger the palpitations each time, then they will continue to do so and should be avoided. No special diet is required, nor will one work, unless the problem is due to a chronic metabolic problem that requires dietary management (example, chronic low blood potassium due to excess losses by the kidney or bowel) or dietary overindulgence (binge eating, especially in people with gallstones or hiatus hernia).
With regard to the nightmares and rapid heart beat. This is another matter entirely that requires medical work up. Your brother should be seen by a cardiologist to assure that he is not having dangerous rhythm disturbances rather than just nightmares with the normal increases in heart rate that may be brought about by the fearsome dreams. Although some primary care physicians will feel competent to deal with this problem, I would be uncomfortable with this approach as the average non-cardiologist has neither access to nor ability to interpret the appropriate diagnostic tests and does not have expertise in the most current available therapies. Note also that just because the diagnosis of paroxysmal atrial fibrillation has been made on one occasion, not all palpitations are due to this diagnosis. Sometimes, the problem is as simple as a chemical imbalance (example, low potassium or magnesium from blood pressure pills for which the solution is to give potassium or magnesium), metabolic imbalance (common with benign thyroid conditions), or viral problem. There is not enough information in your question for me to help further. Please make sure that he sees a cardiologist as soon as possible, and if you have any further questions regarding therapy we can go over the options.
Q: How do I determine what a healthy heart rate is when I’m exercising?
There are different formulae to estimate the expected peak heart rate for your age. As a general guideline some people use a heart rate of 220 minus your age (assuming that you are not on drugs which limit your heart rate response such as beta blocking drugs, if you are, ask your physician to give you a more appropriate target rate). When starting an exercise program, aim for a target of 50%. Your goal is to be able to stay in the 65 to 75% of maximum heart rate range for 30 minutes per day, 4 or 5 days per week. The following chart may be helpful.