What follows here is the verse by verse translation. You can also read a detailed on this topic here.

Thanian:

The vEdhaantha dEsikar,  the one with the grace of Ethiraajaa stood like a lion and triumphed over many
debating adversaries;  researched the vEdhaas and saasthraas, with the view to guide us in choosing foods
that ennoble us and avoid foods that debase us, has given us this prabhandam called aagaara niyamam.  I shall
wear His flower like thiruvadi as an ornament on my head.

[1]
All chEthanaas must understand that there are two kinds of foods, those that are ennobling (saathveega) and those
that are debasing (thaamasa).   These are described by KaNNan in sri bagavath geethai, by Ethiraajaa in
srimadh geethaa bhaashyam, and by many rishees in many saasthraas and smrithees.  By following these
principles, ajakaran attained mOksham.  Likewise, we must understand and follow these rules.

[2]  Forbidden foods:
-    Foods that are not brought into the house through the main door.
-    grains such as varagu, etc.
-    foods that mingle with stuff that have fallen from  the mouth
-    remainder of what was put into the mouth
-    foods seen by immoral people
-    foods that are burnt
-    foods touched by clothes, or contaminated by  saliva or sneeze.
-    foods seen or touched by dogs
-    foods cooked on days such as Ekaadhasi

[3]  forbidden foods continued...
-    foods smelt by animals or people
-    foods touched by people with decease
-    foods that are not offered with kindness
-    foods contacted by fly, worm, thread, hair, and  nail
-    foods offered by sanyaasi or touched by his vessel
-    foods touched by the mouth of people, rats,chicken, crow, and cat.

[4]
This paasruam lists the vegetables that are forbidden.  I can't recognize many of them.  Of the ones I am able to
recognize, I don't know the English names.  The rest are listed below.

     white eggplant, lotus stem, garlic, certain kinds of spinach, mushroom, certain kinds of drumstick

[5]  More forbidden foods:
Vegetables taken from other's garden without permission,  portion that is set aside for oneself prior to
the partaking of the rest of the group, foods that are exceedingly bitter, salty, pepper hot, or sour.

[6]  More forbidden foods:
Foods that were not offered to our Lord, foods that were not offered to the guests, foods that were cooked without
first cleaning them, foods earned in immoral ways, cooked with other foods that are forbidden, cooked by
unclean children, and foods that are contaminated by excrements.

[7] forbidden foods continued...
-    foods intended for dEvathaas
-    foods offered to dEvathaas such as Sivan
-    foods that harm our praaNan and indhriyam
-    foods that are unrecognizable
-    foods that are intolerably hot
-    foods that are not palatable to the mind
-    vegetables and flowers that bloom in an untimely  fashion dirty salt.

[8] forbidden foods continued...
-    Calcium (suNNaambu) extracted from sea shells
-    bubbles and froth from water
-    foods that are not offered to our Lord
-    harvested from the stems that were previously  harvested
-    foods avoided by learned persons with pure heart

[9] forbidden foods continued...
-    Foods from which the essence is taken out, except buttermilk
-    viLaam fruit and popped rice during the day
-    foods prepared with curd and sesame seed oil, during night time
-    foods that are said to give magical powers
-    no foods on Ekaadasi days, and at dusk or  midnight.

[10]  Do not eat,
-    before your shower and sandhya japam
-    alone, eat with a group of bhakthaas
-    foods that are mashed by someone else
-    under the moonlight or fire
-    husband and wife together
-    while staring at inferior individuals
-    with your left hand
-    anything that is avoided by religious people.

[11]  Do not eat,
-    ghee that is served after you have begun eating
-    foods that have been cooked twice (reheated?)
-    foods served by bare hand or spatulas made of  iron, uncooked foods may be served by bare hand
-    foods already bitten into,
-    old, and spoilt foods
-    foods prepared in someone else's house (no potluck)
-    foods that someone else wanted or rejected
-    foods with smell of earth, or separated by finger nails, salt that you can see
-    separated for one self and guests
-    sap coming out of trees, except asafoetida.

Foods that may be accepted are listed now.
[12] Accept without hesitation,
-    foods with the saliva of one's father, teacher, and  first older brother
-    Saliva in the sOmaa vessel during sOma yaagam
-    foods with husband's saliva for wife, if such food is contaminated with hair, worm, or thread, these
     may be removed properly and the food accepted
-    maadhuLangaay, only during our Lord's muga vaaSa soorNam
-    all prohibited foods during calamitous times
-    water, roots, ghee, milk, havis from yaagam, nimandhraNam, guru's teachings, and medicine
     may be accepted even during fasting days.

[13] Accept without hesitation,
-    sugar cane juice, yogurt, milk, ghee, beetle nut, pepper, honey, cardamon, water made from snow
-    anything until you realize its blemish
Dip in the ocean is permitted on full moon day and new moon day.  During times of lunar and solar eclipse all
waters will be considered equal to gangaa water;  water in rivers, even if it carries horses, donkeys and cadaver,
will become purified with current.

[14]  Accept without hesitation,
-    foods cooked without water
-    fruits ripened on their own accord
-    boiled rice
-    vadaam, snacks such as appam, seedai, rotti, even  if they are old, but tasty; do not accept foods that
     are fresh, but not tasty

[15]    Accept without hesitation,
-    Foods prepared with milk, like thirattuppaal
-    snacks like thEnkuzhal, muRukku, etc.,
-    medicines prescribed by physicians, flower,  vellam, wheat
-    old rice that is soaked in clean water may be taken  with buttermilk, ghee, milk, yogurt

[16]    Accept without hesitation,
-    snacks made of yogurt and juice of flower, vegetables, and fruits; these are OK even if they
     are slightly spoilt.
-    foods that are spoilt may be taken during calamitous times by cleansing them and adding
     ghee and honey.  If these foods are further contaminated with hair or other unclean stuff,
     cleanse them with sand and water.

[17]  Forbidden milk
-    milk from one hoofed animals like horse or donkey
-    cow that has twin calf, or camel milk
-    salt added milk
-    milk from women
-    milk from pregnant cow
-    milk extracted with the help of calf that does not belong to the cow
-    cows that belong to temples (?)
-    goat milk, milk bought from brahmins
-    milk kept in copper vessels, burnt milk

[18]  Forbidden water
-    Water from previous day, except gangaa water
-    remainder of water used for cleaning feet
-    murky water
-    heated coconut water
-    water gathered in a ditch
-    water offered in "water-sheds"
-    doubtful water, water taken from where
     washermen work
-    water contaminated by saliva
-    water from conch
-    rain water that has not fallen on the ground

[19]  about beetle leaves
-    don't chew beetle nut without beetle leaves
-    don't consume the bottom, stem, or tip of beetle  leaves
-    don't chew beetle leaves and nuts at the same time
-    widows, sanyaasi, and bachelors must not  consume beetle leaves
-    don't consume the beetle leaf used to keep calcium
-    never use beetle leaves on fasting days such as Ekaadasi
-    don't drink water while chewing beetle leaves

[20]
A particular food item may be acceptable or forbidden based on the caste, stage in life, geography, time of
eclipse, individual dharmam, etc., etc.  For example, it is said that milk from kapilai cow is acceptable for
brahmins, but forbidden for shudraas.  Therefore, one must approach learned people and get your doubts
clarified.

[21]
For the benefit of people who live in this world characterized by lack of wisdom, Lord kaNNan showed
many principles in saasthraas.  After consulting with aachaaryaas these principles have been laid out in this
prabhandam.   Guard yourself against the agnostics who believe only in this transient body and world.  Consume
only those saathvega foods that helps us amplify our devotion to the thiruvadi of pEraruLaaLan.

Simple free translation by SrI.P.Dileepan.

Written By SrI.Anbil Ramaswamy, USA

Right from Vedic literature down to the Itihasas and Puranas, we find scattered references to vegetables and other edibles that can be consumed and those that are better avoided in order to ensure augmentation of Satva and preclusion of Rajo and Tamo.

It was however, left to Swami Sri VEDANTA DESIKA who did deep research in this field (as also in all other fields he touched ) to incorporate in his work entitled "Ahara Niyamam', a catalog for ready reference on what can be consumed, what should not be ingested and what can be taken with certain restrictions and even what go without any restrictions also!. We attempt below to have a glimpse of the various items as gleaned from 'Ahara Niyamam' and Srimad Ramayanam in particular. It should be understood that the prohibition is meant only to enable us to regulate consumption in a conscious, cautious way.

Lord Krishna clearly prohibits food that are too sour, hot, salty, too much bile-producing etc. (BG 17/9)

And again, he advises that they who consume food that are time expired, those that have lost taste, those that emanate stale odor, altered taste, mixed with spittle and those not fit to be offered to the Lord should not be eaten. Sri RAMANUJACHARYA's SRI BASHYAM `Sarvanna Anumatyati Karanam'Sutras 446 to 448 declare - that in times of danger to life one can consume any food and such intake will not go against Pramanas and Smritis.

BUT, SUTRA 449, HOWEVER, CLEARLY AND CATEGORICALLY FORBIDS CONSUMPTION OF LIQUOR EVEN IN THE FACE OF DANGER TO LIFE.7

The case of one Sage USHASTI is alluded to. Due to famine he and his wife were migrating to a far off place. On the way, the Sage was so exhausted due to starvation that he almost swooned and apprehended his end was near at hand. A mahout who passed by on an elephant offered him some horsegram which the sage readily accepted (though ordinarily prohibited). But when the mahout offered water to drink, the sage declined saying that he took the horsegram only for saving himself from starvation-death and taking water thereafter was not proper since at that point of time, the danger to life had disappeared.

A. Items prohibited on hygienic and prophylactic grounds (like our not using tooth brushes used by others)

1. Spittle and food contaminated with spittle
2. Food contaminated by flies, worms, hair, fingernails etc.
3. Food contaminated by excreta
4. Food contaminated by cloth, thread, sneeze etc.
5. Food that has been `smelt' by anybody
6. Food `that has been tasted' by humans, rodent, crow, hen, cat, dog etc.
7. Food that has been partially `bitten' by others
8. Morsel of food partially remaining after eating a portion of it.
9. Vegetables cooked without first being washed
10. Fruits, vegetables etc. cut with finger nails
11. Food prepared by persons who are not clean
12. Food cooked in other people's homes (Parannam)
13. Food that has been found fault with
14. Foods that have been prohibited specifically
15. Food cooked along with prohibited items
16. Foods known to be harmful to vital air and the functioning of sense organs

1. One should not take for self food intended for all
2. Food meant for others (especially a sick person)
3. Food kept apportioned for self and guests
4. Food remaining after feeding a woman in menstruation*
5. Food prepared specifically for a woman who has just delivered*
6. Food that has not been offered to `Bhagavan' in the first place (during Aradhana)*
7. Food before offering to guests (Atiti Satkara)
8. Food offered to lesser deities (Devatantara)
9. Food set apart for offering to such deities as per Sastric injunctions
10. Products (grains, pulses etc.) not offered to God after the harvest
11. Food offered by Sanyasis directly
12. Food taken out from the vessel of Sannyasis
13. Food offered without love and affection
14. Vegetables, fruits etc. cultivated in dirty places *
15. Those that are known to affect concentration and meditation
16. Those that have been specifically advised against by Acharyas and such others
17. Mixed food distributed by hand
18. Ghee should not be served after one commences eating
19. Foods cooked more than once (Punar Pakam)
20. Cooked food served with iron ladles or bare hands
21. Salt served directly by hand
22. Food should not be eaten using left hand
23. Food should not be eaten holding the plate by hand
24. Food should not be placed on a seat
25. Food should not be eaten keeping them on the lap (22 to 25 are precisely what we do during buffet)
26. Should not eat edibles sitting on the bed
27. Food should not be eaten without a lamp burning
28. Moonlight / Fire are no substitutes for a burning lamp
29. Lime used for making chunnam out of seashells
30. Bubbles and foam arising from liquids (as while drinking coke, pepsi, coffee etc)
31. No food can be taken without taking bath and washing hands, and completing ablutions (Parishechanam)
32. Should not leave without completing the final Parishechanam
33. Should not eat out of a broken plate or other vessels that are not clean

C.SWAMI SRI DESIKAN HAS DRAWN UP AN ELABORATE LIST OF VEGETABLES / PRODUCTS THAT SHOULD NOT BE EATEN. WE GIVE BELOW THE TAMIL AND POPULAR AND / OR BOTANICAL NAMES OF THESE FOR GENERAL GUIDANCE"

But, please do not be put off by this list. He has given another list of exceptions and relaxations under which even some of the prohibited items could be consumed as also yet another list of items that can be consumed freely without restrictions. (Vide Sections (D) and (E).

        TAMIL NAME                      POPULAR AND/ OR BOTANICAL NAME
1.    Athi                      Varieties -  Ficus Racemosa
2.      Perarku                 Bauhinia Racemosa
3.      Irali                   Ficus Virens
4.      Vellai Kathari          White egg plant | white brinjals
5.      Aal Banyan -
6.      Arasu                   Peepal Ficus Religiosa
7.      Ayil                    Chittagong wood Chickrasia Tabularis
8.      Aarai                   Masculia Quadrifoli a
9.      Naruvili                Cordia Obliqua/M onoria
10.     Pungu                   Dalbergia
11.     Thigaipoondu            A plant that causes confusion in mind
12.     Kurinji                 A shrub Maruthonr i Terminaw a
13.     Tanri                   Bellenica
14.     Kusumbai                Carthamus Tinctoriu m
15.     Velai                   Cleone Pentaphytt a
16.     Sivappu/Nattu Murungai  Drumstick - Hyperanth era Muringa 
17.     Sukam Sukampal 
18.     Tamarai Kizhangu        Lotus bulb Nelumbo Nucifera
19.     Ulli                    Garlic 
20.     Siriya Avarai           Beans 
21.     Thummatti               Callous Leaved Bryonia
22.     Therar Kai              Clearing nut Strychnoo Patatatura
23.     Panai                   Palmyra palm 
24.     Nayuruvi                Achyranth us Aspera
25.     Kadambu                 Eugenica Racemosa
26.     Naikkudai               Mushroom 
27.     Suraikkai               A variety of gourd 
28.     Peerkku                 Ridge gourd 
29.     Sanar Keerai            Hemp
30.     Siru Keerai             Amaranth us Gangeticu s
31.     Sivanda Agathi          Cormilla Grandi Flora
32.     Purasu                  Balia Frundosa
33.     Pasala                  Portulaca Obracora
34.     Vilvakkai               Crataeva Religiosa
35.     Madulankai              Unripe Pomogranate
36.     Varagu                  Paspalum Frumentac eum
37.     Mullangi                Radish Raphenus Sativus
38.     Vengayam                Onion Allium Cepa
39.     Punnakku                Oil cake
40.     Pannai keerai           ! celosia s.p. ! Exact equivalents not
                                        traceable |Yeast. Dried brew|
41.     Noyyir keerai
42.     Seenkadan
43.     Oovaikkai
44.     Rammananthal
45.     Khadi

1. The remnants of food partaken by father, preceptor and eldest brother.
2. The remnants of soma juice tasted through the soma vessel during Somayaga.
3. The remnants of food eaten by wife / husband even if hair, worm, thread etc are found in such remnants, they can be thrown away and the remnants eaten.
4. In times of danger to life, even prohibited items can be consumed.
5. During fasting days one can take water, roots, ghee, milk, sacrificial remnants, medicines - these will not spoil the fast.
6. If it becomes necessary to eat totally prohibited items in order to save life, a bit of ghee or honey could be mixed with them and taken.
7. Even those foods that had become rotten can be taken after mixing with ghee. Even other impurities like hair if noticed therein can be removed and thrown away.
8. Of items that have turned sour, the following can be taken - curds, butter, fruits that became sour due to contact with water, roots, flowers and pickles made out of these (vide Manu Smriti and Srimad Ramayana).

1. Sugarcane juice
2. Curds
3. Milk ( /but subject to restrictions listed at H)
4. Ghee
5. Sangam
6. Pepper
7. Honey
8. Cardamom
9. Ice
10. Betelnut (subject to restrictions listed at J)
11. Anything fried in fire
12. Fruits that have ripened on their own
13. Boiled rice
14. Vadam
15. Appam | even if they are old provided they have not lost their taste
16. Seedai |
17. Chappathi |
18. Milk products
19. Thenkuzhal
20. Murukku
21. Medicines prescribed by doctors
22. Jaggery and flour combined edibles even if old
23. Wheat flour combined edibles
24. Side dishes, butter milk, ghee, milk, curds mixed with cooked rice
25. Cooked rice put in a vessel with clean water
26. Edibles prepared with curds, milk etc.
27. Juice of flowers, raw vegetables, fruits, Tender Coconut Water.

1. Food overheated so much as to make it inedible
2. Too much bitter
3. Too much salty
4. Too much hot (like chillies)
5. Too much sour
6. Those that are too hot (temperature)
7. Those that are repulsive
8. All liquids from which the cream has been the essence and has been removed (except buttermilk)
9. Old food that had become rotten
10. Food that smells like mud

1. Food cooked on Ekadasi and other days of fasting should not be consumed
2. Wood apple and puffed rice should not be taken during day time
3. Food mixed with sesame should not be taken at night (also referred in Srimad Ramayana)
4. Food prepared in gingelly oil at night
5. Food prepared with curds at night
6. No food can be taken at sunrise, sunset and midnight (also referred to in Srimad Ramayana
7. Husband and wife should not eat together at the same time

1. Milk of animals like mare , donkey etc. which have single hoof (Vide also Srimad Ramayana)
2. Milk of cow that has given birth to twin calves
3. Camel's milk
4. Milk with which salt has got mixed up
5. Breast milk of women (this is also referred to in Srimad Ramayana)
6. Cow that is pregnant and cow just ready for sexual intercourse (referred in Srimad Ramayana )
7. The milk of a cow whose calf had just died
8. Milk drawn from a cow by showing to it a calf of another cow
9. Milk that had become sour or bad (also in Srimad Ramaynana )
10. Milk of cows bearing names of deities other than those of Sriman Narayana
11. Milk of ewe (Vide also Srimad Ramayana)
12. Milk purchased from a Brahmin
13. Milk kept in bronze vessel
14. Milk overheated to the point of getting charred
15. Milk and curd taken of milk of cow that has just delivered for at least 10 days after delivery
16. Milk of other animals of the bovine family except the buffalo

1. Except Ganges water, no stored up water standing over a day should be used.
2. Water remaining in a vessel after using part of it for washing feet
3. Muddy water
4. Tender coconut water, if heated
5. Water stagnant in a small pool
6. Water running across a road
7. Water given in hotels and water sheds ( Tanneer pandals)
8. Any water purity of which is in doubt
9. Water down from washerman's ghats
10. Water contaminated with spittle
11. Water held in a conch
12. Rain water before it falls to the ground
13. One should not drink water by cupping both the palms (Vide Srimad Ramayana)

1. One should not munch betelnut before putting betel leaves in the mouth
2. The stem, the middle line and the tip of the leaves should be removed before taking betel thambool
3. One should not munch both betel leaves and betel nut together
4. Widows, Brahmacharis and Sannyasis should not use betel leaves
5. One should not take betel leaf on which lime had been kept
6. During Ekadasi and other days of fasting betel chewing should be scrupulously avoided
7. While chewing betel one should not drink water at the same time.

As already mentioned these prohibitions and restrictions are only for general guidance. If you desire to regulate / eliminate the Gunas you may choose to follow the instructions and if you do not follow only YOU are the loser to that extent. The doctor can only help in diagnosing the disease and prescribing appropriate medicines. If the patient desires an expeditious and effective cure, the patient will have to scrupulously follow the instructions, the patient is free either to follow or flout the instructions with attendant consequences.

AND, NOW IT IS IN YOUR HANDS TO CHOOSE EITHER COURSE ON THE ROAD TO YOUR SPRITUAL REGENERATION OR DEGENERATION.