kenkou no tame ni, sarada ni mayoneezu wo kakesuginai you ni site imasu.

健康のために means for health or for the sake of health.

• 健康 = health
• ため = sake, benefit, purpose
• の links the noun 健康 to the noun ため
• に marks the phrase as the reason/purpose for what follows

So the whole phrase sets up the motivation: For my health, ...

In English, we often say for my health, but in Japanese the my is usually left unstated if it is obvious.

Because with かける, the thing you put something onto is often marked with に.

So:

• サラダに = onto the salad
• マヨネーズを = mayonnaise
• かける = to pour on, put on, sprinkle on

So サラダにマヨネーズをかける means to put mayonnaise on a salad.

A useful way to think about it is:

• に = target or surface
• を = thing being applied

Because マヨネーズ is the direct object of かける.

In this sentence, the mayonnaise is the thing being put onto something, so it takes を.

Compare the roles:

• サラダに = onto the salad
• マヨネーズを = mayonnaise
• かける = put on

So Japanese divides the idea put mayonnaise on the salad into:

• the destination/surface: サラダに
• the thing being added: マヨネーズを

かけすぎない is made from:

• かける = to put on / pour on
• すぎる = to do too much
• ない = negative

So:

• かけすぎる = to put on too much
• かけすぎない = to not put on too much

This is different from かけない:

• かけない = not put any on
• かけすぎない = not put too much on

So the sentence does not mean the speaker avoids mayonnaise completely. It means they are trying not to overdo it.

This pattern means I try not to ... or I make an effort not to ...

Here is the structure:

• verb in negative plain form: かけすぎない
• ようにする = to make sure / to try to do so
• ようにしている = to be making a habit of doing so

So:

• かけすぎないようにしています = I try not to put too much on / I make a point of not putting too much on

This pattern often describes a repeated habit or conscious effort, not just a one-time action.

They do different jobs.

• 健康のために = for health
  This gives the reason or goal.

• かけすぎないようにしています = I try not to put too much on
  This shows the action the speaker is deliberately trying to maintain.

So the sentence is structured like this:

• Reason: for health
• Habit/effort: I try not to use too much mayonnaise on salad

They may both look like purpose-related expressions in English, but grammatically they are different.

しています shows an ongoing habit or repeated effort.

So:

• 〜ようにします can sound like I will try to ... or I make it a point to ...
• 〜ようにしています sounds more like I have been trying to ... or I make a habit of ...

In this sentence, しています tells us this is the speaker’s current practice, not just a decision made in the moment.

So the nuance is:

• します = decision or intention
• しています = ongoing habit or continuing effort

Yes, most likely.

Japanese often leaves out the subject when it is clear from context. In a sentence like this, the most natural reading is:

I, for my health, try not to put too much mayonnaise on my salad.

Depending on context, it could refer to someone else, but without extra context, native speakers would usually assume the speaker is talking about themself.

No. They are all に, but each one has a different role.

1. 健康のために
   Here に marks the purpose/reason phrase: for health

2. サラダに
   Here に marks the target surface: on the salad

3. ようにして
   Here に is part of the grammar pattern 〜ようにする, which means to try to make it so that ...

So even though the same particle appears several times, the meaning depends on the expression it is part of.

Yes, but the meaning would change.

• かけないようにしています = I try not to put mayonnaise on it
• かけすぎないようにしています = I try not to put too much mayonnaise on it

The actual sentence is softer and more realistic. It suggests the speaker still uses mayonnaise, but in moderation.

That nuance is important, especially with health-related statements. It sounds like I am being careful, not I completely avoid it.