Recent studies suggest that an intake of vitamin E in excess of that found naturally in a balanced diet may actually increase the risk of developing certain illnesses, despite the claims of thousands of people who swear by it as a dietary supplement.

a. Recent studies suggest that an intake of vitamin E in excess of that found naturally in a balanced diet may actually increase the risk of developing certain illnesses

b. Recent studies suggest that taking vitamin E in excess of that found naturally in a balanced diet actually increases the risk of developing certain illnesses

c. Certain illnesses may be at a higher risk of development if vitamin E is taken in excess of a balanced diet, according to recent studies

d. According to recent studies, the intake of vitamin E, if in excess of that found naturally in a balanced diet, may actually increase developing certain illnesses

e. Vitamin E, recent studies suggest, if in excess of that found naturally in a balanced diet, may actually increase the development risk of certain illnesses

Why is A better than B?

Also in the non underlined portion of the sentence 'it' should refer to Vitamin E.
B is a better choice as the subject is Vitamin E and 'it' refers to vitamin E - "swear by it as a dietary supplement", whereas in choice A 'it' is refereed to "intake of vitamin E" and this is the subject of the sentence in A.

In my opinion,

issues with Choice B.

that taking vitamin E.....increases the risk....looks awkward
shift from "may actually increase" to "actually increases"!!!!

There is a minor diff b/w a and b

a. Recent studies suggest that an intake of vitamin E in excess of that found naturally in a balanced diet may actually increase the risk of developing certain illnesses

b. Recent studies suggest that taking vitamin E in excess of that found naturally in a balanced diet actually increases the risk of developing certain illnesses

in b "may" is not there which changes the meaning.
a shows probability....bt b dnt..

Hope it helps !

Yes, the big issue with B is that it claims the risk is definitely increased, which is not what this sentence is going for..

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Tim Sanders
Manhattan GMAT Instructor