Can I write about different topics on main domain where subdomain has another niche?

I have a domain which is like www.example.com; and I have a subdomain for that domain too. I have a great blog on that subdomain. But now; I would like to use my main domain to create another blog. My domain is related to Textiles & Fashion and have a related keyword on main domain.

Now my question is that- Can I use my root domain for making a blog with different niche? Suppose; I want to blog about Health on the root domain. If I start; will Google affect negetively on my site? Will I have any problem regarding SEO or any other things? This question has raised as; the subdomain is a fashion blog and the root domain is going to be health related blog. Sounds good or worst?

Any suggestions/ consultation would be highly appreciated.

Advanced thanks mates.

 

Personally I don't think it matters.. The sub domain and the main domain are seen as two seperate websites unless you cross link them heavily which if they are different niches I don't see why you would. I have a main domain that is just a place holder for all the sub domains. All the sub domains are different and not linked together. Not even the main domain is linked from the sub domain and it doesn't cause any problems for me.