RH BLOOD TYPE, what are healthy foods to eat? Is kelp one of them? Would it help to become a vegetarian?

Regardless of your blood type, a plant-based diet is linked to better overall health.  The only blood type-cancer link I'm aware of is a lower risk for pancreatic cancer for people with O type.  

You don't have to become a full vegetarian to eat healthy foods, but make the majority of your diet plant-based.  For example, make your plate 50% vegetables and fruits, 25% whole grains and beans, and the last 25% lean protein (egg, fish, chicken, dairy, or plant protein).

Kelp is a great food, as all seaweeds, and is a fantastic addition to a healthy diet.

See more tips on healthy diets at:  The Daily Crunch: Healthy Eating

Hello.  Eating for blood type is an unusual way to choose a diet, however, many people have propagated this thinking.  85% of people have the Rh antigen.  An antigen is a substance that evokes an immune response.  As far as I know, this Rh antigen does not evoke an immune response for any foods.  However, looking at your dietary intake to improve health is an awesome project for anyone.  I would suggest looking at how often do you eat fruits and vegetables, and a variety of whole grains?  Also looking how much added fat and sugar are in your diet?  These two are culprits for the developing obesity, cardiovascular and diabetes conditions in many people around the world.

I would suggest having a well rounded diet that maintains a healthy weight as the best goal, and eating semi-vegetarian, or vegetarian is a healthy way to maintain metabolic fittness.