After drinking "true athlete" natural protein powder in a shake, I had pretty bad heartburn.. In the shake I also added milk, bananas, and strawberries. It's not the brand of whey protein powder because this has happened with other brands as well. I also tried it with just water, and the same thing happened. I'm a runner and I work out, drinking the protein shakes post work out. Lastly the whey powder I have now is very natural and has no additives. Is there anything I can do to not have heartburn ?