If your desired "trademark" makes it difficult to describe the goods then the patent and trademark office will likely not issue the desired "trademark". For example, you cannot trademark "Apple" for apples. The term "Apple" for apples is considered generic as "apple" exactly describes the product "apple". You can trademark "Apple" for computers as it is nonsensical UNTIL Apple made Apple Computers famous (so to speak).
Now, as long as the name you wish to call your cakes is not generic or too "descriptive" of the product then you can trademark the name.
Yes, it is possible to patent a cake with health benefits as long as:
(1) the same thing has not been done before;
(2) your cake is not an obvious variation of a previous product;
(3) you came up with the design (i.e. you invented the cake);
(4) you have not been making and/or selling the cake for more than a year (before filing a patent application);
(5) if you will not tell on yourself in (4) above, the issue becomes if someone else can prove you were making and/or selling the cake for more than a year before filing a patent application;
Basically, if you have been making your cake for more than a year and/or selling same for more than a year, no one, including you, can get a patent on such a cake.
Keeping your ingredients a trade secret may be the best call assuming others cannot discover your ingredients or guess same from your advertisements and marketing.
Lots of fact specific issues to consider when it comes to patent law.
Please keep asking questions until you are satisfied with my answers.