Food as medicine (आहारस्य महाभेषजत्वम्)
The term Ahara (आहारः) in Samskrit refers to the food or diet. Any food that is consumed to gain energy or to continue the survival is called as Ahara in Ayurveda. Anna (अन्नम्), Bhojana (भोजनम्), Ashana (अशनम्) are some synonyms commonly used to refer Ahara in Ayurveda. Ahara has been identified as that entity which is responsible for sustenance of life of a person. It provides nourishment, strength, health and at the same time can cause various diseases if not consumed in an appropriate way. Thus, it is counted as the first among 3 supporting pillars of life i.e. Trayopasthambhas (त्रयोपस्तंभाः).
आहारस्य महाभेषजत्वम्॥ Ahara as medicine
Various diseases develop due to intake of inappropriate and unwholesome ahara (food). Therefore it is counted as one of the causative factors for diseases. But at the same time, appropriate changes in such food articles and their consumption manners can also cure these diseases. Therefore, Ahara is believed to be the equally consequential medicine in Ayurveda. Administration of right diet plan in a patient with any disease gives fast relief and many a time offers permanent cure. Thus Ayurveda Vaidya always recommends do's and dont's in Ahara while giving treatment for any disease. These are known as Pathyas & Apathyas.
चिकित्साभेदः ॥ Medicine category
Chikitsa(चिकित्सा) i.e. treatment is said to be of 3 types in Ayurveda literature. Daivavyapashraya (दैवव्यपाश्रया), Yuktivyapashraya (युक्तिव्यपाश्रया) and Satvavajaya (सत्वावजया). Among these 3 types, use of wholesome food articles and administration of diet plan is counted under the Yuktivyapashraya type of a chikitsa.
युक्तिव्यपाश्रयं- पुनराहारौषधद्रव्याणां योजना.. (Char. Samh. 11.54) yuktivyapāśrayaṁ- punarāhārauṣadhadravyāṇāṁ yojanā.. (Char. Samh. 11.54)
आहार एव औषधम् ॥ The only medicine in certain conditions
Ahara is the only medicine to regain strength during recovery from diseases. Many acute severe or chronic diseases affect the person in such a way that the person recovering from them becomes weak, looses strength and remains incompetent to perform routine activities. In many instances the strength of the patient is lost due to the strong medicines used for treatment of the disease which in turn make the person weak. In such conditions Ayurveda scholars have identified and emphasized the role of ahara as medicine. In spite of using any medicine to boost strength, it is advised to use different types of food recipes that will boost energy and strength. In such cases, ghee, meat soup, milk, soups/broths etc.
भेषजक्षपिते पथ्यमाहारैरेव बृंहणम्|....
..तथा स लभते शर्म युज्यते चायुषा चिरम्||२३|| Cha.Su. 16.22-23
bheṣajakṣapite pathyamāhāraireva br̥ṁhaṇam|....
..tathā sa labhate śarma yujyate cāyuṣā ciram||23|| Cha.Su. 16.22-23
Going further the benefit of administering such diet in diseases individuals, Ayurveda acharyas have mentioned that, it helps to balance the the body-mind-energy complex and increase the longevity.
रोगनिवारणे आहारस्य कार्यम्॥ Role of ahara in management of diseases
Any medicine used to treat a roga (disease) in Ayurveda, is believed to act chiefly on doshas and dhatus. It helps to re-establish the equilibrium of these components responsible for laying the foundation of disease. Samanya vishesha siddhanta is commonly used to select the dravyas (medicinal substances) to treat that disease. Therefore when ahara is to be used to manage a certain ailment or in addition to medicines, food articles, recipes and combinations are selected which will help to reduce the aggravated doshas, increase the depleted dhatus etc. Since Ahara and shariram as well as its component like doshas and dhatus are also panchabhautika in nature, 5 elements are the basis of this type of activity of ahara. 5 mahabhutas in ahara help to increase or reduce the disturbed 5 mahabhutas in shariram.
अनया चोक्त्या आहारः शरीरगतानां भावानां समानगुणानां गुणद्वारेण वर्द्धनहेतुः,विपरीत गुणानां च क्षयहेतुः इति प्रतिपादयति ----
यथास्वं ते च पुष्णन्ति पक्वा भूतगुणान् पृथक्| पार्थिवाः पार्थिवानेव शेषाः शेषांश्च देहगान् (Asht. Hrud. 3.60)
anayā coktyā āhāraḥ śarīragatānāṁ bhāvānāṁ samānaguṇānāṁ guṇadvāreṇa varddhanahetuḥ,viparīta guṇānāṁ ca kṣayahetuḥ iti pratipādayati ----
yathāsvaṁ te ca puṣṇanti pakvā bhūtaguṇān pr̥thak| pārthivāḥ pārthivāneva śeṣāḥ śeṣāṁśca dehagān (Asht. Hrud. 3.60)
प्राणाः प्राणभृतामन्नम्॥ Vital nature of Ahara
Ahara has been acclaimed for its role in every aspect of persons life in Charaka Samhita (चरक संहिता). Acharya Charaka has described the multivariate importance of Ahara or Annam in the verse below.
प्राणाः प्राणभृतामन्नमन्नं लोकोऽभिधावति| वर्णः प्रसादः सौस्वर्यं जीवितं प्रतिभा सुखम्॥
तुष्टिः पुष्टिर्बलं मेधा सर्वमन्ने प्रतिष्ठितम्| लौकिकं कर्म यद्वृत्तौ स्वर्गतौ यच्च वैदिकम्॥
कर्मापवर्गे यच्चोक्तं तच्चाप्यन्ने प्रतिष्ठितम्॥ (Char. Samh. 27.349-51)
prāṇāḥ prāṇabhr̥tāmannamannaṁ loko'bhidhāvati| varṇaḥ prasādaḥ sausvaryaṁ jīvitaṁ pratibhā sukham॥
tuṣṭiḥ puṣṭirbalaṁ medhā sarvamanne pratiṣṭhitam| laukikaṁ karma yadvr̥ttau svargatau yacca vaidikam॥
karmāpavarge yaccoktaṁ taccāpyanne pratiṣṭhitam॥ (Char. Samh. 27.349-51)
Meaning: The source of life for all living beings is food and thus all the world seeks (runs behind) food. Complexion, clarity, good voice, long life, understanding, happiness, satisfaction, growth, strength and intelligence are all established in food (can be attained by eating right food). Whatever is beneficial for worldly happiness, whatever pertains to the vedic sacrifices leading to higher abode and whatever actions lead to spiritual salvation are said to be established through food.
आहारः प्रीणनः सद्यो बलकृद्देहधारकः ॥ आयुस्तेजःसमुत्साहस्मृत्योजोग्निविवर्धनः ॥ (Sush. Samh. 24.68-69)
āhāraḥ prīṇanaḥ sadyo balakr̥ddehadhārakaḥ ॥ āyustejaḥsamutsāhasmr̥tyojognivivardhanaḥ ॥ (Sush. Samh. 24.68-69)
Meaning: Ahara is nourishing, instantly energizing and body bearer. It promotes longevity, energy, freshness, memory, ojas and Agni. At the same time, Ayurveda acharyas have also identified the nuisance value of ahara if it is not consumed methodically. It is because of some inappropriate practices of consuming food, it can also become a cause for disease development and thus might create trouble. Acharya Charaka has pointed out this interesting aspect of Ahara by comparing it with liquor and poison by showing the similarity between them skillfully in the verse below.
किन्तु मद्यं स्वभावेन यथैवान्नं तथा स्मृतम्| अयुक्तियुक्तं रोगाय युक्तियुक्तं यथाऽमृतम्॥
प्राणाः प्राणभृतामन्नं तदयुक्त्या निहन्त्यसून्| विषं प्राणहरं तच्च युक्तियुक्तं रसायनम्॥ (Char. Samh. 24. 59-60)
kintu madyaṁ svabhāvena yathaivānnaṁ tathā smr̥tam| ayuktiyuktaṁ rogāya yuktiyuktaṁ yathā'mr̥tam|॥
prāṇāḥ prāṇabhr̥tāmannaṁ tadayuktyā nihantyasūn| viṣaṁ prāṇaharaṁ tacca yuktiyuktaṁ rasāyanam॥ (Char. Samh. 24. 59-60)
Meaning: (Ayurveda has identified alcoholic drinks or fermented preparations as one of the medicinal formulations e.g. Asavas and Arishtas. Thus how Madyam can be utilised as medicine and when it can give trouble was well-known to Ayurveda scholars which they skillfully applied in practice of medicine. The same applies to use of poison. In this reference this verse has been added) But liquor by nature is similar to the food. It causes disorders when consumed improperly; while it is like amritam (elixir) when consumed properly. Food is like the vitality of life for the human beings; but the same may be fatal if ingested improperly. The poison is fatal, but it can be rasayana if used sensibly.
पुरुषवृद्धिकरः आहारः ॥ Role of Ahara in controlling various aspects of life
Ayurveda has recognized the role of Ahara in various aspects of life.
हिताहारोपयोग एक एव पुरुषवृद्धिकरो भवति, अहिताहारोपयोगः पुनर्व्याधिनिमित्तमिति ॥ (Char Samh 25.31)
hitāhāropayoga eka eva puruṣavr̥ddhikaro bhavati, ahitāhāropayogaḥ punarvyādhinimittamiti ॥ (Char Samh 25.31)
Meaning: Hita Ahara (Favorable/suitable Food) is identified as the one and only source of Purusha Vrddhi (Growth of body-mind-energy system of a person).
This statement underlines the importance of Ahara in nourishment of not only physical body but also manas (मनः। mind). Ahara has also been identified as one of the extremely important causative factor for disease development. The origin, sustenance and destruction of life is rooted in Ahara. It is Ahara which causes growth, generates strength, health, wellness when consumed appropriately, on the other hand, inappropriately consumed food leads to illness.  Thus, role of ahara in all these aspects of life, health and well-being is discussed step-wise in brief.
शरीरवृद्धौ आहारः ॥ Role of Ahara in Sharira vruddhi
Shariram (शरीरम्। Physical body) of a person is made up of Ahara. Therefore Sharira vrddhi (शरीरवृद्धिः p hysical growth), strength building can be achieved essentially through ahara. Ahara undergoes the process of digestion and it is transformed into Rasa dhatu. (रस धातुः) This Rasa dhatu which is the essence of ahara is then circulated through various channels in the body to provide nourishment to each and every body component. Thus nourishment & growth of body, sustenance of metabolic functions and preservation of life is accomplished by Ahara through Rasa dhatu.  Owing to this, the root of living beings, their balam (बलम् । strength) and Varnam (वर्णम् । Complexion) appears to be in Ahara. All these vital activities are carried out by Ahara with the help of its Rasa(रसः), Guna (गुणः), Veery (वीर्यम्)a and vipaka (विपाकम्). These properties are based on dravya (द्रव्यम्) i.e. ingredient or substance which is consumed as a food. Therefore, what food you select and consume is extremely important. Physical body appears good when it is in proper shape and size. The disproportionate increase or reduction in size and shape of the body is unpleasant and leads to illness as well. Thus obesity and emaciation (frail/lean body structure) both conditions are displeasing to the person. Ayurveda too opines that such body types are unfavorable and suggests that Ahara is one of the extremely significant causative factors in this which needs to be properly addressed. The other important factor is Nidra (निद्रा । sleep). Overall, for the growth of the physical body known as Sharira in Ayurveda, the role of Ahara was well known to the Ayurveda scholars and thus it has been counted as one among the factors responsible for Sharira Vrddhi (शरीरवृद्धिः । physical growth). These factors are collective known as Sharira Vrddhikara Bhavas (शरीरवृद्धिकराः भावाः). At this place it is once again communicated that not just any ahara but Aharasampat (आहारसंपत्) i.e good quality of Ahara is responsible for body growth.
कार्त्स्न्येन शरीरवृद्धिकरास्त्विमे भावा भवन्ति; तद्यथा- कालयोगः, स्वभावसंसिद्धिः, आहारसौष्ठवम्, अविघातश्चेति ॥ (Char Samh 6.12)
kārtsnyena śarīravr̥ddhikarāstvime bhāvā bhavanti; tadyathā- kālayogaḥ, svabhāvasaṁsiddhiḥ, āhārasauṣṭhavam, avighātaśceti ॥ (Char Samh 6.12)
अग्निरक्षणे आहारः ॥ In agni palanam
Ayurveda shastra gives immense importance to the status of Agni (अग्निः) in a person. Agni is believed to be the moola (मूलम् b ase/root) of the life like that of Ahara. Ahara taken from outside is converted in the form of energy by Agni and this energy is responsible for all vital functions of our body. If the agni is in a balanced state, the person would be healthy and would lead a long, healthy, happy life. On the other hand, the any vitiation or disturbances in agni the entire metabolism of the body is disturbed resulting in illness and poor quality of life. Once the function of agni stops, the life ends. Thus Agni is critical for one's life. It the cause of health, nourishment, strength, lusture, ojas, (ओजः) teja (तेजम् । energy) and prana (प्राणः । life energy). One can also find that the similar description on impact of Ahara on Life is noted in Ayurveda treatises.     Therefore it is clear that Agni and Ahara both impact the life equally in every aspect. Their targets are similar also because agni and ahara are basically interdependent. Ahara can not impact life without process of agni neither agni can help individual without ahara. These two components control each other and bring about the final effect. How food controls the strength of agni has been explained in Ayurveda with a simple example. Agni can become strong and steady when it is offered Ahara which is nourishing and suitable with a tinge of unctuousness like the wood-fire becomes strong and steady with the help of heart wood / hard wood coated with some unctuous material.
दीप्तो यथैव स्थाणुश्च बाह्योऽग्निः सारदारुभिः | सस्नेहैर्जायते तद्वदाहारैः कोष्ठगोऽनलः ॥ (Asht. Hrud. 10.79)
dīpto yathaiva sthāṇuśca bāhyo'gniḥ sāradārubhiḥ | sasnehairjāyate tadvadāhāraiḥ koṣṭhago'nalaḥ ॥ (Asht. Hrud. 10.79)
Thus it is always believed in Ayurveda that, not just the food but its digestion and transformation also should be given equal importance while considering health and illness.
बलवृद्धौ आहारः ॥ In Balam Vruddhi
Balam (बलम्) in Samskrit refers to the strength of the body. It also indicates ability of the body or part of the body, to protect oneself against various harmful factors. As mentioned in previous sections, Ayurveda has given immense importance to Ahara and agni to acquire and maintain balam.    Grossly, Balam is the product of the strength of all the dhatus (धातवः । body tissues). Therefore strength and quality of each dhatu contributes in balam which in turn depends on the ahara. Ultimately, Ahara becomes one of the crucial contributing factors in building and maintaining strength. Ahara is thus listed on eamong the crucial factors for building strength. These factors are called as Balavrddhikara bhavas (बलवृद्धिकराः भावाः) in Ayurveda.
बलवृद्धिकरास्त्विमे भावा भवन्ति| तद्यथा- बलवत्पुरुषे देशे जन्म बलवत्पुरुषे काले च, सुखश्च कालयोगः, बीजक्षेत्रगुणसम्पच्च, आहारसम्पच्च, शरीरसम्पच्च, सात्म्यसम्पच्च, सत्त्वसम्पच्च, स्वभावसंसिद्धिश्च, यौवनं च, कर्म च, संहर्षश्चेति ॥ (Char. Samh. 6.13)
balavr̥ddhikarāstvime bhāvā bhavanti| tadyathā- balavatpuruṣe deśe janma balavatpuruṣe kāle ca, sukhaśca kālayogaḥ, bījakṣetraguṇasampacca, āhārasampacca, śarīrasampacca, sātmyasampacca, sattvasampacca, svabhāvasaṁsiddhiśca, yauvanaṁ ca, karma ca, saṁharṣaśceti ॥ (Char. Samh. 6.13)
Fundamentally there are 3 types of balam based on its source viz Sahaja (सहजम् । Natural, Present right from the birth), Kalaja (कालजम् । Present due to particular season and age) and Yuktikrita (युक्तिकृतम् । Obtained by deliberate efforts to acquire strength like use of diet, exercise, medicines). Ahara is believed to develop Yuktikruta type of Balam. This means with proper application of knowledge about which food should be taken and how it should be consumed, one can certainly increase the strength. E.g Inclusion of ghee, milk, meat and certain strength building recipes in diet under a Vaidya's supervision can help one build strength and stamina.  
स्वास्थ्यरक्षणे आहारः ॥ In Prevention of diseases
Ahara is one of the highly important factors from one's life that is responsible for maintenance of health and well-being. The entire theory of disease development and health in Ayurveda is based on the effect of food and lifestyle factors on various body components. Therefore, the role of ahara in prevention of diseases has also been identified by Ayurveda. Various Ayurveda scholars at multiple places in literature have clearly stated that the one who consumes the appropriate and suitable food regularly can stay away form diseases and live a healthy life.
नित्यं हिताहारविहारसेवी समीक्ष्यकारी विषयेष्वसक्तः | दाता समः सत्यपरः क्षमावानाप्तोपसेवी च भवत्यरोगः॥ (Asht. Hrud. 4.36)
nityaṁ hitāhāravihārasevī samīkṣyakārī viṣayeṣvasaktaḥ | dātā samaḥ satyaparaḥ kṣamāvānāptopasevī ca bhavatyarogaḥ॥ (Asht. Hrud. 4.36)
The qualities of food that should be looked for while selecting the daily food have been mentioned by ayurveda scholars. Ahara which is nutritious, right in quantity, snigdha (स्निग्धः । having appropriate amount of fats) and madhura rasa (मधुर रसः) dominant is believed to be beneficial to build and maintain strong health. Such ahara should be consumed on daily basis or in other words, the food that is recommended to be consumed on daily basis should have these qualities.
विविधाः औषधी पाककृतयः॥ Specific recipes in specific diseases
The subject of food can not end without recipes. Ayurveda acharya in their treatises have not missed this extremely important aspect of administering food. At many instances they have described recipes of medicinal food articles which would be beneficial for intake in special health conditions. Various recipes have been designed in such a way that not just the food ingredient in it but also its processing method will be adding quality to that recipe which will be desired in that specific health conditions. There are certain classical treatises like Kshemakutuhalam (क्षेमकुतुहलम्) that are entirely dedicated for describing ancient traditional and healthy recipes which have basis of Ayurveda and were commonly followed in Bharata in ancient times. One can find the mention of Sanyawa (संयावः Haluwa), Ghewara (घेवरम् a type of jalebi) and many such interesting preparations in Ayurveda treatises in the context of management of diseases. For example, in the management of certain Shirorogas (शिरोरोगाः diseases of head & neck), use of Sanyawa, Madhumastaka (मधुमस्तक), Ghrutapoora (घृतपूर ghewara) etc has been advocated.  Similarly in certain rogas like Jwara(ज्वरः) Pandu (पाण्डु) use of soups of Mudga (मुद्ग Green gram), Masura (मसूर), Chanaka (चणक), Makushthaka (मकुष्ठक) has been recommended in aharakala (आहारकालम् right time of having food). 
In this way, Ayurveda describes the Ahara, its significance, its types, guidelines for food intake, its role in causing diseases and also its role in management of diseases in depth. Ahara has been given paramount importance when the matter of the life comes forward. Owing to Ahara's crucial role in maintaining the life, one must take utmost precautions while taking food. One should not indulge in intake of unwholesome food out of greed or ignorance. The wholesome food taken in appropriate manner is the key to healthy and long life.
- Charaka Samhita (Sutrasthanam Adhyaya 11 Sutra 54)
- Ashtanga Hrudayam (Sharirasthanam Adhyaya 3 Sutra 60)
- Charaka Samhita (Sutrasthanam Adhyaya 27 Sutras 349-51)
- Available from charakasamhitaonline.com
- Sushruta Samhita (Chikitsasthanam Adhyaya 24 Sutra 68-69)
- Charaka Samhita (Chikitsasthanam Adhyaya 24 Sutram 59-60)
- Available from charakasamhitaonline.com
- Charaka Samhita (Sutrasthanam Adhyaya 25 Sutra 31)
- Sushruta Samhita (Sutrasthnam Adhyaya 46 Sutra 3)
- Sushruta Samhita (Sutrasthanam Adhyaya 14 Sutra 3)
- Charaka Samhita (Sutrasthanam Adhyaya 21 Sutra 51)
- Charaka Samhita (Sharirasthanam Adhyaya 6 Sutra 12)
- Charaka Samhita (Chiktsasthanam Adhyaya 15 Sutra 3-4)
- Ashtanga Hrudayam (Chikitsasthanam Adhyaya 10 Sutra 79)
- Sushrut Samhita (Sutrastanam Adhyaya 15 Sutra 19)
- Charaka Samhita (Sharirasthanam Adhyaya 6 Sutra 13)
- Charaka Samhita (Sutrasthanam Adhyaya 11 Sutram 36)
- Ashtanga Hrudayam (Sharirasthanam Adhyaya 3 Sutra 78)
- Ashtanga Hrudayam (Sutrasthanam Adhyaya 4 Sutram 36)
- Sushruta Samhita (Chikitsasthanam Adhyaya 24 Sutram 98)
- Sushruta Samhita (Uttaratantram Adhyaya 26 Sutras 37-38)
- Sushruta Samhita (Uttaratantram Adhyaya 39 Sutra 150-151)