Unlike some of the studies you will be looking for, there is not a specific limiter to add to your searches to limit to just quantitative articles. One way you can narrow down to these studies is to add a search term of quantitative to your search string. See example below:
"heart disease" AND diet AND quantitative
Then you will need to read through the article abstracts of the results to determine if the study meets the criteria of a quantitative study.
In order to increase the likelihood of finding a quantitative article, be sure to use filters to narrow your search results to peer-reviewed, scholarly, or research articles. Each database will have different filters that can be used, but most will have something that will allow you to limit to these types of articles.
If you are looking specifically for randomized controlled trials, which are a specific type of quantitative study, there are tips for finding these on the Randomized Controlled Trials page of this guide.