“suggested I just ate/eat a banana”

The following is an extract from a passage, the emboldened sentence being the phrase of interest:

Coming in a minimalistic white pouch, the meal-replacement powder blends things like rice, peas and flaxseed. Add water, shake it up, and there’s your lunch, dinner or breakfast, or all three. I ordered a week’s supply, telling friends about my exciting discovery. Comments ranged from outraged to encouraging (‘this makes a lot of sense’). My mum suggested I just ate a banana.

Although it sounds harmonious, I'm interested in knowing why exactly the word "ate" was chosen to be used as opposed to its present-tense counterpart (eat). Which grammar rule has a hand in this and where can I read more about it?

EDIT: To clarify, this has been taken from a CAIE (Cambridge) examination question insert. The entire passage (text A) can be found on page 2 of this document (and the sentence on line 10).

Solution 1:

I was going to write up an answer citing The Cambridge Grammar of The English Language (by Huddleston and Pullum) on what H&P call covert mandatives. But I found out that @Araucaria already wrote an excellent answer on ELL more than three years ago.

I suggest you go read that answer. [subjunctive or covert mandative!]

One notable point of the answer along with the comments is that although H&P claims "Clear cases of the covert construction are fairly rare", which claim is inclusive of British English usage, the actual British English corpus data suggests that covert mandatives are more productive than should-mandatives (...that I should just eat a banana) as well as subjunctive mandatives (...that I just eat a banana) . [Note in this sentence "are more productive" is not a covert mandative.]

This corpus data seems to be in line with my own limited exposure to British English where I've noticed some British prime ministers and politicians use covert mandatives in their public speeches.

So I find it perfectly fine for a test based on British English to use covert mandatives.

Solution 2:

By instinct, I would not use ate in that sentence.

British English prefers the structure with should + infinitive after suggest in the past. Cambridge does not even record the use of past tense after suggested:

Suggest + that-clause When we suggest an action to someone, we can use a that-clause. In informal situations, that is often left out:

• I suggest (that) you leave here around four o’clock. The traffic gets very bad from about 4.30 onwards.

When suggest is in the past, we can use should in the that-clause:

• Her doctor suggested that she should reduce her working hours and take more exercise.

However, the use of past tense after suggested is not banned. On Englishgrammar you will find a description of how the verb suggest behaves. Among other things it says:

When the verb in the main clause is in the present tense, we can use a present tense in the that-clause after suggest. When the verb in the main clause is in the past tense, a past tense is possible in the that-clause as well.

• His doctor suggests that he stops smoking.
• His doctor suggested that he stopped smoking.

In both these examples that can be omitted.

At the question if the sentence

The boss suggested we left early yesterday.

is correct, BBC answers:

It is perfectly correct. You could also say:

• The boss suggested (that) we leave early.
• The boss suggested (that) we should leave early.

All these forms are possible with little or no difference in nuance, although the subjunctive form, suggested we leave, is a touch more formal.

There is yet another site that states that past simple is correct in British English after suggested:

In British English, we may use both the present simple and past simple tenses.

• Mark suggested that I called him.

All that being said, I think your sentence may well be called a covert mandative, but it can also be reported speech at the same time. Gngram finds instances of past after suggested, so it does exist. If the mother said

I suggest you just eat a banana.

the reported speech can occur as

My mum suggested I just ate a banana.

although according to most grammars the only options of reported speech are considered the following

• My mum suggested I just eat a banana.

or

• My mum suggested I should just eat a banana.