I edited a bit and removed some parts as i saw fit. Here is the Visuddhimagga
I think it is pretty self-explanatory and easily "modernized" to reflect our actual experience in what regards nutriment in our lives.
Bhikkhus, to the bhikkhu practicing the perception of loathing food and abiding much in it, the craving for tastes keep away, it shrinks and rolls away. The mind stretches out and gets established in equanimity or loathing.
“Bhikkhus, when there is physical nutriment, there is greed (lust), there is
delighting, there is craving; consciousness being planted therein
grows. Wherever consciousness being planted grows, there is the
combination of mind-and-matter. Wherever there is the combination of
mind-and-matter, there is ramification of formations. Wherever there
is ramification of formations, there is production of further becoming
in the future. Wherever there is production of further becoming in the
future, there is future birth, aging and death. Wherever there is
future birth, aging and death, bhikkhus, the end is sorrow, I say,
with woe and despair” (S II 101; cf. S II 66).
id emphasise being assailed and afflicted by various disagreeable perceptions and dangers such as;Repulsiveness in going [for food]:
I must now turn my back on such a charming place and go abroad for the sake
of food; Senses will be assailed. This repulsive [experience] [has to be undergone]
for the sake of nutriment.
Afflicted with what? With cold & heat & hunger & thirst, with the touch of flies, mosquitoes, wind, sun, & reptiles. Because it is afflicted, it is called form.
I also think this is a good time to reflect thus;"[He reflects:] ''I am now being chewed up by feeling... perception... fabrications... consciousness. But in the past I was also chewed up by consciousness in the same way I am now being chewed up by present consciousness. And if I delight in future consciousness, then in the future I will be chewed up by consciousness in the same way I am now being chewed up by present consciousness.' Having reflected in this way, he becomes indifferent to past consciousness, does not delight in future consciousness, and is practicing for the sake of disenchantment, dispassion, and cessation with regard to present consciousness.
"What do you think, monks — Is form constant or inconstant?" "Inconstant, lord." "And is that which is inconstant easeful or stressful?" "Stressful, lord." "And is it fitting to regard what is inconstant, stressful, subject to change as: 'This is mine. This is my self. This is what I am'?"
"... Is feeling constant or inconstant?" "Inconstant, lord."...
"... Is perception constant or inconstant?" "Inconstant, lord."...
"... Are fabrications constant or inconstant?" "Inconstant, lord."...
"What do you think, monks — Is consciousness constant or inconstant?" "Inconstant, lord." "And is that which is inconstant easeful or stressful?" "Stressful, lord." "And is it fitting to regard what is inconstant, stressful, subject to change as: 'This is mine. This is my self. This is what I am'?"
"Thus, monks, any form whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every form is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'
"Any feeling whatsoever...
"Any perception whatsoever...
"Any fabrications whatsoever...
"Any consciousness whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every consciousness is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'
Repulsiveness in seeking:
So this [experience] beginning with the entry into the
village and ending with the departure from it, which is repulsive
owing to the water, mud, etc., that has to be trodden in and seen and
endured, [has to be undergone] for the sake of nutriment: “Oh,
nutriment is indeed a repulsive thing!”
Repulsiveness in using:
dipped his hand in and is squeezing it up, the sweat trickling down his five fingers wets any
dry crisp food there may be and makes it sodden. And when its good
appearance has been spoilt by his squeezing it up, and it has been
made into a ball and put into his mouth, then the lower teeth function
as a mortar, the upper teeth as a pestle, and the tongue as a hand.
When thus mashed up and besmeared, this peculiar compound now
destitute of the [original] colour and smell is reduced to a condition
as utterly nauseating as a dog’s vomit in a dog’s trough. Yet,
notwithstanding that it is like this, it can still be swallowed
because it is no longer in range of the eye’s focus. This is how
repulsiveness should be reviewed as to using.
Repulsiveness in secretion:
when [the food] has arrived at the stage of being eaten and it enters inside, then in one
whose secretion of bile is in excess it becomes as utterly nauseating
as if smeared with thick madhuka oil; in one whose secretion of phlegm
in excess it is as if smeared with the juice of nágabalá leaves; in
one whose secretion of pus is in excess it is as if smeared with
rancid buttermilk; and in one whose secretion of blood is in excess it
is as utterly nauseating as if smeared with dye. This is how
repulsiveness should be reviewed as to secretion.
Repulsiveness in the receptacle:
When it has gone inside the belly and is smeared with one
of these secretions, then the receptacle it goes into is no gold dish
or crystal or silver dish and so on. On the contrary, if it is
swallowed by one ten years old, it finds itself in a place like a
cesspit unwashed for ten years.
In what is uncooked (undigested)?
After this nutriment has arrived at such a place for its receptacle, then
for as long as it remains uncooked it stays in that same place just
described, which is shrouded in absolute darkness, pervaded by
draughts, tainted by various smells of ordure and utterly fetid and
loathsome.The pit becomes covered with froth and bubbles, so too, what has been
swallowed that day and yesterday and the day before remains there
together, and being smothered by the layer of phlegm and covered with
froth and bubbles produced by digestion through being fermented by the
heat of the bodily fires, it becomes quite loathsome.
In what is cooked?
When it has been completely cooked there by the
bodily fires, it does not turn into gold, silver, etc., as the ores16
of gold, silver, etc., do [through smelting]. Instead, giving off
froth and bubbles, it turns into excrement and fills the receptacle
for digested food, like brown clay squeezed with a smoothing trowel
and packed into a tube, and it turns into urine and fills the bladder.
How as to fruit?
When it has been rightly cooked, it produces the
various kinds of ordure consisting of head hairs, body hairs, nails,
teeth, and the rest. When wrongly cooked it produces the hundred
diseases beginning with itch, ring-worm, smallpox, leprosy, plague,
consumption, coughs, flux, and so on. Such is its fruit.
How as to outflow?
On being swallowed, it enters by one door, after which it
flows out by several doors in the way beginning, “Eye-dirt from the
eye, eardirt from the ear” (Sn 197). And on being swallowed it is
swallowed even in the company of large gatherings. But on flowing out,
now converted into excrement, urine, etc., it is excreted only in
solitude. On the first day one is delighted to eat it, elated
and full of happiness and joy. On the second day one stops one’s nose
to void it, with a wry face, disgusted and dismayed. And on the first
day one swallows it lustfully, greedily, gluttonously, infatuatedly.
But on the second day, after a single night has passed, one excretes
it with distaste, ashamed, humiliated and disgusted. Hence the
Ancients said: The food and drink so greatly prized— The crisp to
chew, the soft to suck— Go in all by a single door, But by nine doors
come oozing out. Men like to eat in company, But to excrete in secrecy.
The food and drink so greatly prized— The crisp to chew, the soft to suck— These a man
eats with high delight, And then excretes with dumb disgust. The food
and drink so greatly prized— The crisp to chew, the soft to suck— A
single night will be enough To bring them to putridity.
How as to smearing?
At the time of using it he smears his hands, lips, tongue
and palate, and they become repulsive by being smeared with it. And
even when washed, they have to be washed again and again in order to
remove the smell. when eaten it rises up during its
cooking and simmering by the bodily fire that pervades the whole body,
it turns into tartar, which smears the teeth, and it turns into
spittle, phlegm, etc., which respectively smear the tongue, palate,
etc.; and it turns into eye-dirt, ear-dirt, snot, urine, excrement,
etc., which respectively smear the eyes, ears, nose and nether