How to understand japanese sentence step by step

Question

野菜を食べることが大切、と言われる理由は大きく三つあります。

一番目は野菜に含まれる成分のうち、体内に吸収されて重要な役割を演じる物質が摂取できるからです。ビタミン類やミネラル類はもちろん,最近はこれら以外のわずかに含まれる成分にも注意が集まっています。

1. 一番目は野菜に含まれる成分のうち

   First component that was contained in vegetables

2. 体内に吸収されて重要な役割を演じる物質が

   So I cut this part 体内に吸収されて / 重要な役割を演じる物質 -> is it true(?)

   And this mainly talk about 物質 as subject.

   The substance that was absorbed into the body which plays an important role 摂取できるからです-> I'm a bit confused because 摂取 and 吸収 have pretty same meaning -> but I think refers to 野菜含まれる成分(？) and there is "から" at the end, so it means a component (成分) that intake.

3. The component that intake The substance that was absorbed into the body which plays an important role(?)

4. It refers to vitamin and mineral

I don't know if this true or not, and I'm pretty confuses about who is the subject in this sentence.

If it's wrong please help me revise it.

Answer 1

1. 一番目 refers to one of the three reasons why they say it's important to eat vegetables.
   一番目は～～～からです。 means "The first reason is that ～～."

「[野菜に含まれる成分のうち(の)]、[体内に吸収されて重要な役割を演じる]物質」
(体内に吸収されて重要な役割を演じる is a relative clause that modifies 物質.)
"substances [in/among the elements contained in vegetables][which are absorbed into body and play important roles]"

2. 「[体内に吸収されて重要な役割を演じる]物質」
   "substances [which are absorbed into body and play important roles]"

3. 「一番目は・・・[(体内に吸収されて重要な役割を演じる)物質が摂取できる]からです。」
   "The first reason is that [you can take in the substances (which will be absorbed into body and play important roles)]."

4. Yes, 体内に吸収されて重要な役割を演じる物質 refers to vitamins and minerals, and also other micronutrients (= これら以外のわずかに含まれる成分).

Answer 2

野菜を食べることが大切、と言われる理由は大きく三つあります。

there are three main reasons why it is said that eating vegetables is important

So we can break the next sentence like this:

一番目は???です。

The first reason is ???.

一番目は???が摂取できるからです。

The first reason is because we can intake ???.

一番目は重要な役割を演じる物質が摂取できるからです。

The first reasons is because we can intake the substance that plays an important role

The above is the main sentence. The rest adds a little more details to the main sentence.

体内に吸収されて重要な役割を演じる物質
the substance that is absorbed into body and plays an important role

野菜に含まれる成分のうち体内に吸収されて重要な役割を演じる物質

among the elements contained in vegetables, the substance that is absorbed into body and plays an important role

The next sentence is an independent sentence. The 物質 in the first sentence doesn't necessarily refer to ビタミン類やミネラル類in the second sentence:

Not only Vitamins and Minerals(not only these well known elements), other elements (in vegetables) are recently getting attentions as well.

ビタミン類やミネラル類はもちろん,最近はこれら以外のわずかに含まれる成分にも注意が集まっています。