Translation:Is soy milk really healthy?
If you want to complicate things a little : what Chinese people call 豆浆 is something closer to "crushed soybean juice" and doesn't refer to the the drink we find in Western supermarkets. The Western "milky" version is being sold now more and more in China too and it says 豆奶 (even though it's dairy free) on the package to distinguish it from the Chinese 豆浆.
Zhen on its own means real, true, authentic (etc.) Zhen de means Really or Actually. Zhen de is more like one word, instead of zhen + de.
I honestly just called it doujiang all this time. Have they really been the same thing this whole time? :o