Why does Islam not tell us to eat less red meat?

It should noted first of all that the Qur’aan’ is a book of
guidance and law-giving, it is not a book of medicine or astronomy, so that
some people want it to mention everything that has to do with medicine,
astronomy, plants or animals. 

Allaah says (interpretation of the meaning): 

“(This is) a Book which We have revealed unto you (O
Muhammad صلى الله عليه وسلم) in order
that you might lead mankind out of darkness (of disbelief and polytheism)
into light (of belief in the Oneness of Allaah and Islâmic Monotheism) by
their Lord’s Leave to the path of the All‑Mighty, the Owner of all praise”

[Ibraaheem 14:1] 

“And this is a blessed Book (the Qur’aan) which We have
sent down, so follow it and fear Allaah (i.e. do not disobey His Orders),
that you may receive mercy”

[al-An’aam 6:155]

With regard to food, the Qur’aan forbids some foods and
mentions them in detail, and some others are mentioned in the Sunnah of the
Prophet (peace and blessings of Allaah be upon him).  

The Qur’aan mentions some general principles that have to do
with food, then all of that is explained in detail in the Sunnah of the
Prophet (peace and blessings of Allaah be upon him). 

Some of the issues that are discussed in detail in the
Qur’aan are the following. Allaah says (interpretation of the meaning): 

“Say (O Muhammad صلى الله
عليه وسلم): ‘I find not in that which has been revealed to me
anything forbidden to be eaten by one who wishes to eat it, unless it be
Maytah (a dead animal) or blood poured forth (by slaughtering or the like),
or the flesh of swine (pork); for that surely, is impure or impious
(unlawful) meat (of an animal) which is slaughtered as a sacrifice for
others than Allaah (or has been slaughtered for idols, or on which Allaah’s
Name has not been mentioned while slaughtering). But whosoever is forced by
necessity without wilful disobedience, nor transgressing due limits; (for
him) certainly, your Lord is Oft‑Forgiving, Most Merciful’”

[al-An’aam 6:145]

“Forbidden to you (for food) are: Al‑Maitah (the dead
animals — cattle — beast not slaughtered), blood, the flesh of swine, and
that on which Allaah’s Name has not been mentioned while slaughtering (that
which has been slaughtered as a sacrifice for others than Allaah, or has
been slaughtered for idols) and that which has been killed by strangling, or
by a violent blow, or by a headlong fall, or by the goring of horns — and
that which has been (partly) eaten by a wild animal — unless you are able to
slaughter it (before its death) ‑ and that which is sacrificed (slaughtered)
on An‑Nusub (stone‑altars). (Forbidden) also is to use arrows seeking luck
or decision; (all) that is Fisqun (disobedience of Allaah and sin)”

[al-Maa’idah 5:3]

With regard to some principles, Allaah says (interpretation
of the meaning): 

“and eat and drink but waste not by extravagance,
certainly He (Allaah) likes not Al‑Musrifoon (those who waste by
extravagance)”

[al-A’raaf 7:31]

This prohibition on extravagance in eating and drinking is
general in meaning and does not apply to any particular type of food or
drink. 

This general prohibition on extravagance is more far-reaching
than simply forbidding extravagance in eating red meat or anything else,
because this general meaning applies to many things. 

Ibn al-Qayyim (may Allaah have mercy on him) said in Zaad
al-Ma’aad (4/213): 

Allaah guided His slaves to consume that which is enough to
support the body of food and drink, and told them that it should be to the
extent that will benefit the body in terms of quantity and quality. If it
goes beyond that then it is extravagance, and both of them pose an obstacle
to health and cause sickness; I mean not eating and drinking, or being
extravagant in them. Preservation of health is included in these two words.
End quote. 

Allaah says, describing the Prophet Muhammad (peace and
blessings of Allaah be upon him) (interpretation of the meaning): 

“he allows them as lawful At‑Tayyibaat (i.e. all good and
lawful as regards things, deeds, beliefs, persons and foods), and prohibits
them as unlawful Al‑Khabaa’ith (i.e. all evil and unlawful as regards
things, deeds, beliefs, persons and foods)”

[al-A’raaf 7:157]

And He says (interpretation of the meaning): 

“They ask you (O Muhammad صلى
الله عليه وسلم) what is lawful for them (as food ). Say: “Lawful unto
you are At‑Tayyibaat [all kinds of Halaal (lawful‑good) foods which Allaah
has made lawful (meat of slaughtered eatable animals, milk products, fats,
vegetables and fruits)]”

[al-Maa’idah 5:4]

So everything that is good is permissible, and everything
that is bad is haraam. 

With regard to the Sunnah, the Prophet (peace and
blessings of Allaah be upon him) forbade the eating of every animal that has
fangs and every bird that has talons, and he forbade eating the meat of
domesticated donkeys, etc. 

The Prophet (peace and blessings of Allaah be upon him)
also explained how the believer should be with regard to food and drink, as
he said: “The human being does not fill any vessel worse than his stomach.
It is sufficient for the son of Adam to eat a few mouthfuls, to keep him
going. If he must do that (fill his stomach), then let him fill one third
with food, one third with drink and one third with air.”

Narrated by al-Tirmidhi and classed as saheeh by al-Albaani
in Saheeh al-Tirmidhi. 

And the Prophet (peace and blessings of Allaah be upon
him) forbade every harmful thing, whether that is food, drink or anything
else. He said: “There should be neither harming nor reciprocating harm.”
Narrated by Ibn Maajah (2340) and classed as saheeh by al-Albaani in
Irwa’ al-Ghaleel (896). 

The food may be halaal in principle, but because of
extravagance in eating it that leads to harm, it may be haraam. This does
not apply only to meat; everything that will cause harm to a person if eaten
is haraam, even dates. 

The scholars also stated that it is haraam to eat anything
that causes harm. 

See: al-Majmoo’, 9/39. 

If it is proven that a certain food is harmful then it is
haraam to eat it, but it should be noted that harmful foods may vary from
one person or country to another, so it is not permissible to say that it is
haraam in general terms, rather it is haraam only for the one who will be
harmed by it, if he eats the amount that will harm him.