# Ritucharya: the classical rationale for seasonal regimen

> Canonical version of this page: https://nighantu.ageayurveda.com/concept/ritucharya-rationale/

## How much weight this concept bears

What the modern references carried here establish is that human physiology and disease incidence vary with the time of year. That is not in dispute, and it is not an Ayurvedic proposition. Dopico 2015 found seasonal expression profiles in more than 4,000 protein-coding mRNAs in white blood cells and adipose tissue; Ter Horst 2016 found annual seasonality in stimulated cytokine responses across 534 healthy subjects; Sheth 1999 found January peaks in myocardial infarction and stroke mortality across 300,000 Canadian deaths. None of the three was designed to test ritucharya, none uses the six-season division, and none measures anything corresponding to vata, pitta or kapha. Offering them as support for 'the premise behind ritucharya' credits the classical scheme with evidence it has not been given, so this record does not offer them that way. The generic claim these papers support is one nobody disputes; the Ayurvedic claim is the specific one, that physiology varies in the particular doshic pattern Charaka Sutrasthana 6 and Sushruta Sutrasthana 6 assert, with the two half-years as the driver, and no reference here speaks to that. Two of the three point away from a calendar-fixed regimen rather than towards one. Dopico's seasonal expression pattern is inverted between Europe and Oceania, and the blood-composition changes that might explain it differ between the United Kingdom and The Gambia; an effect whose sign depends on latitude is evidence against a fixed six-season calendar anchored to north India being the operative variable. Ter Horst's cohort is single-site Dutch and carries no latitude information at all. Sheth's winter peak is a Canadian winter, in months that Sushruta's scheme splits across hemanta and shishira. Nothing retrieved here tests the scheme itself: not the six-season division, not the dosha-to-season assignments, not the chaya-prakopa-prashama sequence, not ritusandhi, not the claim of spontaneous seasonal remission, and none of the per-season dietary or behavioural prescriptions. What the searches returned is set out with dates and hit counts in modernCoverage.searchBound: a Europe PMC query for 'ritucharya' on 2026-10-06 returned 68 records, of which exactly one carries the publication type 'Controlled Clinical Trial', and that one tests a prophylactic polyherbal kit rather than a seasonal regimen; the same query restricted to publication type 'Randomized Controlled Trial' returned nothing. Sixty-seven of those 68 were read as metadata only. On that basis this record states what those searches returned and does not state that no trial exists, and the Ayurvedic-side pattern it can report is the one its own references show: narrative reviews that restate the classical scheme in the vocabulary of chronobiology or the gut microbiome, propose a biomarker or a microbiome study as future work, and stop, of which the gut-microbiome review cited here, not even PubMed-indexed, is the clearest example. The honest summary is that ritucharya is a classically coherent scheme resting on a real and generic phenomenon, with no modern test of the scheme itself, and with the one latitude-resolved modern finding pointing against its calendar being exportable.

Ritucharya is the classical prescription that diet and conduct be changed with the season. The rationale, as the retrieved passages state it, has three parts. First, the year is divided into two solar half-years, adana (the sun's northern course, when the sun and dry winds take up moisture and human strength declines) and visarga (the southern course, when moisture is restored and strength increases), each subdivided into three two-month seasons. The causal chain the texts give is environmental before it is doshic: solar and wind action alters the qualities of water and plants, which alters food, which alters the body. Second, the doshas are held to run a three-stage cycle keyed to season: accumulation (chaya) in one season, aggravation or manifestation (prakopa) in the next, and subsidence (prashama) in a third. Whether the regimen for a season is therefore aimed at the dosha accumulating in it or at the one manifesting in it is NOT settled by the passages retrieved here: Charaka's autumn prescription reads as anticipatory, Sushruta's chapter closes by directing that the deranged dosha be checked in the season of its prakopa before it manifests as illness, and the two are not reconciled in anything retrieved. See contested. Third, suitability is defined relationally: what is appropriate is what has qualities contrary to those of the place of habitation and of the existing disorder, though Kaviratna footnotes a textual variant at exactly that verse (see notKnown). The seasons named are those of the north Indian calendar, defined by named lunar months, and the texts do not address latitudes where that calendar does not apply.

## At a glance

| Field | Value |
| --- | --- |
| Subject area | Regimen and prevention |
| Domain, as recorded | prevention |
| Contested questions | 4 |
| Stated as not known | 15 |
| Classical citations | 12, 12 quoting the text |
| Research papers assessed | 4 |
| Citations checked | 2026-10-08 |

## What is contested, and by whom

These are the questions on which the sources genuinely disagree. Each position is given as
its source states it. No position is presented as the settled answer, because none of them is.

### Where do the boundaries of adana and visarga fall, and which season starts the year?

This is contested.

- Charaka's Sutrasthana 6 runs adana from the dewy season (shishira) through summer, and visarga from the rains through hemanta, and describes the seasons in that order. Charaka Samhita, Sutrasthana 6, prose aphorisms 1-2 in Kaviratna's edition, quoted in full in this record. Kaviratna's own footnote to this passage lists the six seasons beginning from hemanta, which is a third ordering and is the translator's, not Charaka's.
- Sushruta's Sutrasthana 6 lists the six seasons beginning with winter (Magha-Phalguna) and defines the ayanas by the sun and moon changing course at the tropics, giving a different narrative entry point. Modern textbooks reconcile these, but the two chapters are not identical in ordering or emphasis. Sushruta Samhita, Sutrasthana 6, Bhishagratna p. 46, unnumbered prose, quoted in full in this record; the account of the two ayanams follows immediately on p. 47.

### Does a dosha accumulating in a season need treating in that season, or only when it manifests in the next?

This is contested.

- Sushruta states the accumulated doshas 'should be checked as soon as they become aggravated (manifest themselves)' in the following season, which reads as intervention at prakopa. Sushruta Samhita, Sutrasthana 6, Bhishagratna p. 50, quoted in full in this record.
- Charaka's autumn prescription is framed as acting on pitta 'stored' during the rains, and the general logic of the chapter is anticipatory: eat contrary to the season now so that nothing accumulates. Practitioner traditions differ on whether purificatory measures are timed to chaya or prakopa. Charaka Samhita, Sutrasthana 6, aphorisms 32-33 of the renumbered verse series, quoted in full in this record. No source is cited here for the practitioner traditions; that sentence rests on nothing retrieved and is retained only as a report of disagreement, not as a sourced position.
- A third reading, added from the chapter's own closing sentences: Sushruta ends by directing that the deranged kapha be checked in spring, pitta in autumn and vata in the rains, that is in the season of prakopa, 'before they develop themselves in any patent or manifest bodily ailment'. That is intervention at prakopa but ahead of overt disease, which is neither of the two positions above and does not resolve them against Charaka. Sushruta Samhita, Sutrasthana 6, the chapter's closing sentences immediately before the colophon, quoted in full in this record.

### How should ritucharya be applied outside the north Indian calendar and climate?

This is contested.

- The texts define seasons by Indian lunar months and do not address the question; Charaka's okasatmya rule, suit food and conduct to the place of habitation, arguably licenses local adaptation. Sushruta Samhita, Sutrasthana 6, Bhishagratna p. 46 for the month definitions; Charaka Samhita, Sutrasthana 6, aphorisms 40-41 of the renumbered verse series for the okasatmya and contrary-qualities rule. Both quoted in full in this record. Note the textual variant Kaviratna flags at aphorism 41.
- Modern seasonality data show the human seasonal transcriptome inverts between northern and southern hemispheres and that the underlying blood-composition changes differ again between the UK and The Gambia, which means a month-anchored regimen cannot simply be exported. No classical or modern source retrieved here resolves how to re-anchor it. PMID 25965853, carried in this record's modern section.

### Is 'unseasonal weather causes epidemics' a public-health observation or a moral doctrine?

This is contested.

- Sushruta's practical instruction, avoid contaminated water and produce during an epidemic, is sound and matches modern outbreak practice. Sushruta Samhita, Sutrasthana 6, Bhishagratna p. 51, quoted in full in this record.
- The aetiology he gives for the unseasonal weather itself is collective sin and malign destiny, and the passage continues into depopulation by curse, spell and demoness. Modern Ayurvedic writing generally reports the first half and omits the second; recording only the first half misrepresents the source. Sushruta Samhita, Sutrasthana 6, Bhishagratna pp. 51-52; the sentences on curse, anger, spell and poisonous pollens follow directly on p. 52 and were read on 2026-10-06.

## What is not known

Stated rather than left out. Where a negative has actually been searched for rather than
assumed, the entry says so.

- Whether following a seasonal regimen changes any clinical outcome. No trial of one was returned by the searches listed in modernCoverage.searchBound, and those searches were English-language, Europe PMC only, and did not include any trial registry.
- Whether the classical dosha-to-season assignments correspond to anything measurable. No biomarker of seasonal dosha accumulation has been proposed and validated in anything retrieved here.
- Whether the claim of spontaneous seasonal remission (pitta disorders easing in hemanta, kapha in summer, vata in autumn) holds for any defined modern disease category. This is a directly testable claim and no test of it was found.
- How ritucharya should be adapted for southern-hemisphere, equatorial or temperate-continental climates, or for people living in climate-controlled environments year round. Charaka's okasatmya rule licenses adaptation in principle and supplies no procedure for it.
- Whether the seasonal foods prescribed carry any effect beyond ordinary seasonal food availability and energy balance.
- Whether the seasonality documented in immune gene expression and in stimulated cytokine responses has any causal relationship to the seasonal variation in disease incidence, let alone to Ayurvedic categories. Dopico and Ter Horst measure immune variables, Sheth measures deaths, and nothing retrieved connects them.
- Whether seasonal variation in vitamin D, rather than season as such, is what drives the seasonal immune findings this record relies on. Ter Horst 2016 reports vitamin D's mediating effect as limited and alpha-1-antitrypsin as a partial mediator, in one single-site Dutch cohort. That is one result, not a settled confound. A generic Europe PMC search for the seasonal vitamin D literature on 2026-10-06 returned well over a thousand records and none of them was appraised, so this record cannot separate 'season affects immunity' from 'sunlight exposure affects immunity'.
- Whether a primary interventional study of a seasonal regimen exists in the literature the searches reached. Of the 68 Europe PMC records matching 'ritucharya' on 2026-10-06, 67 were classified by publication type only and not read in full; the one typed as a controlled clinical trial (PMID 36052011) tests a prophylactic polyherbal kit, not a seasonal regimen. A primary study could be sitting in one of the 67, or in the non-English and non-indexed literature that was never searched at all.
- Whether the adana/visarga mechanism as the texts state it, solar and wind action altering the qualities of water and plants and thence of the body, has ever been measured. No search for it was run. The mechanism now has quoted classical loci in this record and no modern reference whatever.
- Whether Charaka Sutrasthana 6's closing rule governs qualities contrary to the PLACE only, or contrary to the place and the existing DISORDER. Kaviratna footnotes a textual variant at that aphorism, 'Doshanam' against 'Deshanam', and judges 'Deshanam' correct while translating both. No second edition, no Sanskrit original and no commentary (Chakrapani or otherwise) was consulted on the point, so the record cannot say which reading the tradition carries.
- What the rest of Ashtanga Hridaya Sutrasthana 3 says. Only verse 58 was retrieved and read. Vagbhata's own seasonal prescriptions, his ordering of the seasons and his account of bala are not covered by this record, and the wisdomlib page for the chapter is Cloudflare-blocked.
- Whether the Das-Emmerick e-text's verse numbering for Ashtanga Hridaya matches any printed critical edition. The ritusandhi verse is numbered 58 there and no collation was done, so 'AH Su 3.58' is reported as the e-text's address and not as a printed-edition address.
- Whether Bhishagratna's chaya/prakopa vocabulary reflects Sushruta's Sanskrit or Bhishagratna's own glossing. The words naming each state as the 'excited state' of a particular dosha appear in his footnotes rather than his text, and the Sanskrit original of Sushruta Sutrasthana 6 was not consulted during this work.
- Whether Charaka's and Sushruta's two orderings of the year are reconcilable in the texts themselves rather than only in modern textbooks. Nothing retrieved here reconciles them; see contested.
- Whether the three-way assignment of bala to position within a half-year (strongest in hemanta and shishira, weakest in the rains and summer) has any measurable correlate. Charaka states it, Vagbhata appears to state something similar at Sutrasthana 3.7 which was seen but not read closely, and no modern reference here addresses it.

## The terms this concept is built from

| Term | What it names |
| --- | --- |
| shad ritu | The six seasons of two months each: shishira (winter/dewy), vasanta (spring), grishma (summer), varsha (rains), sharad (autumn), hemanta (late autumn/cold). Bhishagratna's Sushruta names the constituent months explicitly and is quoted for it in this record. |
| adana kala (uttarayana) | The sun's northern course, covering shishira, vasanta and grishma in Charaka's reckoning. The sun and dry winds take up moisture; the juices generated become dry, bitter, astringent and pungent; human strength declines. |
| visarga kala (dakshinayana) | The sun's southern course, covering varsha, sharad and hemanta. The sun's power is weakened, moisture that is cool, sour, saline and sweet increases, and human strength increases. |
| [bala](https://nighantu.ageayurveda.com/lexicon/bala/) | Seasonal strength. Charaka states men are weak in the first season of visarga (rains) and the last of adana (summer), intermediate in the two middle seasons, and strongest in the last of visarga (hemanta) and the first of adana (shishira). |
| [chaya](https://nighantu.ageayurveda.com/lexicon/sanchaya/) | Accumulation. A dosha builds quietly in one season without producing disease. Sushruta: pitta accumulates in the rains, kapha in hemanta, vata in summer, and in each case by way of the qualities that water and vegetables take on in that season. |
| [prakopa](https://nighantu.ageayurveda.com/lexicon/dosha-prakopa/) | Aggravation or manifestation. The accumulated dosha is liquefied or agitated by the following season's conditions and produces disease. Sushruta: pitta in autumn, kapha in spring, vata in early rains (pravrit). |
| prashama | Subsidence. Sushruta states that disorders of bile, phlegm and wind are respectively ameliorated in hemanta, summer and autumn 'by natural causes', which Bhishagratna glosses in brackets as variations of temperature and rainfall. |
| okasatmya / viparita guna | Suitability by habituation, and the rule that suitable conduct and food are those with qualities contrary to the place of habitation and to the existing disorder. Kaviratna's own footnote to the second of these two aphorisms records a textual variant, 'Doshanam' against 'Deshanam', and he judges 'Deshanam' (of places) the correct reading while his English renders both place and disorder. The 'existing disorder' half of the rule as usually taught therefore rests on a reading Kaviratna himself rejects; no second edition or commentary was consulted here. See notKnown. |
| ritusandhi | The junction of two seasons, defined as the last week of the outgoing season and the first week of the incoming one, at which the earlier regimen is to be given up and the later taken up gradually. The verse was RETRIEVED, in Sanskrit, at Ashtanga Hridaya Sutrasthana 3.58 of the Das-Emmerick machine-readable text, and is quoted in this record's classical section. The standard attribution to Ashtanga Hridaya Sutrasthana 3 therefore holds. It is still true that no public-domain English translation of Vagbhata exists, so no English quotation is offered, and that the e-text has not been collated against a printed critical edition. |
| vishama ritu | Unseasonal or contrary season. Sushruta treats this as a cause of epidemic disease, and attributes the unseasonal weather itself to collective moral cause. |

## The classical passages

Each citation gives its address so a reader can check it in a printed edition, our account
of what it establishes, and the result of reading it against its source.

### Charaka Samhita Sutrasthana 6 (Tasyashitiya; printed 'Tasyapitiya' in Kaviratna's own colophon and summary):aphorisms printed 1 and 2 in the chapter's PROSE series, the numbers printed after each aphorism, checked against the source

> Of him who is acquainted with the opportuneness of conduct and food with seasons, strength and complexion (and happiness and period of life) increase, in consequence of his food, &c., (being taken with propriety). For the purposes of this lesson, the year should be known as consisting of six portions, divided according to the seasons. Of these, the three seasons commencing with the season of dews and ending with summer constitute the period when the Sun travels in the region lying to the north of the equinoctial. That is again the period when the Sun takes (i.e., sucks up the liquid portion of every earthly object). The three other seasons commencing with the season of rains and ending with Hemanta constitutes the period of the Sun's southerly course. That is, besides, the time when the Sun gives (or yields moisture to all earthly objects).

tr. Avinash Chandra Kaviratna (1896-1913)

The adana/visarga frame and the six-season division, stated as the organising structure of the chapter. This is a cited locus for the two half-years themselves, not for the prescriptions derived from them. The claimed outcome is strength, complexion, happiness and lifespan.

Source: https://archive.org/download/BIUSante_47357/BIUSante_47357_djvu.txt

### Charaka Samhita Sutrasthana 6 (Tasyashitiya):aphorism printed 5 in the chapter's PROSE series, the number printed after the aphorism, checked against the source

> In the period of Taking, the Sun, by means of his rays, sucks up the moisture of the universe; and keen and rough winds also dry up the same. Besides, (both the Sun and) the winds, in the seasons of Sisira, Vasanta, and Grishma, gradually developing the property of roughness, and generating juices that are dry, bitter, astringent, and pungent, contribute to the weakness of mankind.

tr. Avinash Chandra Kaviratna (1896-1913)

The adana half of the mechanism. The stated causal chain is environmental: solar and wind action alters the qualities of plants and water, which alters the qualities of food, which alters the body. The doshic account is downstream of an environmental one.

Source: https://archive.org/download/BIUSante_47357/BIUSante_47357_djvu.txt

### Charaka Samhita Sutrasthana 6 (Tasyashitiya):aphorism printed 6 in the chapter's PROSE series, the number printed after the aphorism, checked against the source

> In the season, however, of rains, of Sarat, and of Hemanta, when the Sun begins his southerly course, and his powers become weakened by time, by the virtue of his track itself, by the winds generated by the clouds, and by the downpours (from the cloudy regions), when the Moon also appears with unabated vigor, and (lastly) when the heat of the universe becomes cooled by the water that falls from the clouds, moisture that is cool, sour, saltish, and sweet, increases gradually, and the strength of human beings increases.

tr. Avinash Chandra Kaviratna (1896-1913)

The visarga half of the mechanism, in the same environmental terms as the adana half: weakened solar power and cloud-borne water change the qualities available in food and drink, and strength follows. Added so that both half-years, and not only adana, carry a quoted locus.

Source: https://archive.org/download/BIUSante_47357/BIUSante_47357_djvu.txt

### Charaka Samhita Sutrasthana 6 (Tasyashitiya):aphorism printed 1 in the chapter's RENUMBERED VERSE series, the first aphorism after the words 'On this topic are the following verses', checked against the source

> It should be said that during the first season of the Giving period, (viz., the season of rains), and the last season of the Taking period, (viz., summer), men become weak. In the two intermediate seasons of both the periods, (viz., Sarat and Vasanta), men become neither very weak nor very strong. During the last season of the Giving period, (viz., Hemanta), and the first of the Taking period, (viz., Sisira), the strength of men is at its highest.

tr. Avinash Chandra Kaviratna (1896-1913)

The seasonal strength (bala) sequence, which the original record asserted in its components list with no quote behind it. Note that strength here is assigned by POSITION within a half-year, not by climate description, which is part of why the scheme does not travel to other latitudes.

Source: https://archive.org/download/BIUSante_47357/BIUSante_47357_djvu.txt

### Charaka Samhita Sutrasthana 6 (Tasyashitiya):aphorisms printed 32 and 33 in the chapter's RENUMBERED VERSE series, checked against the source

> The bile of men whose bodies are exposed to the cold of the rainy season, and who suffer themselves to be suddenly exposed to the rays of the Sun, becomes stored. This bile, in the season of Sarat, becomes injurious. Those that desire their own benefit should, therefore, in the season of Sarat, take food and drink, agreeably to the proper measure, and that are sweet, light, cool, with (at times) things that are bitter and that check bile.

tr. Avinash Chandra Kaviratna (1896-1913)

The accumulate-then-manifest logic in Charaka's own words, and the derived rule that the autumn regimen targets pitta stored during the rains. This is the clearest retrieved statement that the regimen looks back at what accumulated, though it does not settle whether intervention belongs to the season of accumulation; see contested.

Source: https://archive.org/download/BIUSante_47357/BIUSante_47357_djvu.txt

### Charaka Samhita Sutrasthana 6 (Tasyashitiya):aphorisms printed 40 and 41 in the chapter's RENUMBERED VERSE series, the last two before the chapter-summary verse, checked against the source

> That which produces happiness or yields not torture, in consequence of the system being inured to it, is known by the name of okasatmya. They that are conversant with this topic of assimilation (or suitability of practices to the system), regard that conduct and that food to be suitable which have virtues contrary to those of the place of habitation and of the disorders (to which the system is subject).

tr. Avinash Chandra Kaviratna (1896-1913)

The relational definition of suitability, which is the third part of the rationale and the only part that licenses adapting the regimen to a different place. Added; the original record cited 'Charaka Sutrasthana 6' for it in a component gloss with no quote.

Source: https://archive.org/download/BIUSante_47357/BIUSante_47357_djvu.txt

### Sushruta Samhita Sutrasthana 6 (Ritucharyadhyayam):unnumbered prose, Bhishagratna vol. I p. 46, immediately after the definition of the units of time and immediately before the account of the two ayanams, checked against the source

> The twelve months such as, Magha, etc. are divided into six seasons such as, Winter, Spring, Summer, Rains, Autumn and Hemanta, each consisting of two months. The two months known as Tapas and Tapasya (Magha and Phalguna) constitute the season of winter. Spring consists of two months called Madhu and Madhava (Chaitra and Vaishaka). Summer is marked by two months known as Shuchi and Shukra (Jaistha and Ashadha). The rains or the rainy season is marked by two months called Nabhas and Nabhasya (Shravana and Bhadra). The two months known as Isha and Urja (Ashvina and Kartika) constitute what is called the season of Autumn. Hemanta is marked by two months called Sahas and Sahasya (Agrahayana and Pousha).

tr. Kunja Lal Bhishagratna (1907-1916)

The seasons are defined by named months of the Indian lunar calendar, not by climate variables. This anchors ritucharya to a specific latitude and calendar, which is the central difficulty in applying it elsewhere.

Source: https://archive.org/download/b24758619_0001/b24758619_0001_djvu.txt

### Sushruta Samhita Sutrasthana 6 (Ritucharyadhyayam):unnumbered prose, Bhishagratna vol. I pp. 49-50, the three consecutive paragraphs on the rains, Hemanta and summer that precede the summary of the triad, checked against the source

> ... the bile originated and accumulated during the rains, is liquefied by the rays of the sun and gives rise to bilious diseases. ... Hence water and vegetables partaken of in Hemanta are divested of their properties of acid reaction after being assimilated in the human system, but they give rise to an accumulation of phlegm in the body owing to their heaviness, sliminess, and cooling and oily character. In spring, the phlegm thus accumulated in the body is liquefied and ushers in diseases due to a deranged state of that bodily humour. ... The sun's rays dry up the natural moisture of the human system, and accordingly water and vegetables largely partaken of in summer, give rise to an accumulation of wind in the system owing to their lightness, dryness, or expansive and drought-making properties. Subsequently wind thus accumulated in the summer, is agitated by the rains and cold winds in the forepart of the rainy season (Pravrit) when the ground is flooded with water and thus gives rise to diseases which are incidental to a deranged state of the bodily wind.

tr. Kunja Lal Bhishagratna (1907-1916)

The dosha-to-season assignments themselves, dosha by dosha, each with its stated environmental mechanism: pitta accumulates in the rains and manifests in autumn, kapha accumulates in hemanta and manifests in spring, vata accumulates in summer and manifests in pravrit. Added because the summary passage alone cannot carry these assignments: its English list order does not read respectively.

Source: https://archive.org/download/b24758619_0001/b24758619_0001_djvu.txt

### Sushruta Samhita Sutrasthana 6 (Ritucharyadhyayam):unnumbered prose, Bhishagratna vol. I p. 50, the summary of the triad, immediately before the mapping of the parts of the day onto the seasons, checked against the source

> The fundamental bodily humours such as, wind, bile, etc. augmented and accumulated during the rains, Hemanta and summer, should be checked as soon as they become aggravated (manifest themselves) in autumn, spring, or in the forepart of the rainy season (Pravrit). Diseases which owe their origin to a deranged state of bile, phlegm and wind, are respectively ameliorated in Hemanta, summer, and autumn by natural causes, [such as the variations of atmospheric or earthly temperature, rainfall, etc.]. Thus far we have discussed the accumulation, excitation and pacification or alleviation of the deranged bodily humours.

tr. Kunja Lal Bhishagratna (1907-1916)

The triad named as a triad, and the prashama assignments. It also contains the claim of seasonal remission without treatment, which is testable and has not been tested. What it does NOT by itself establish is which dosha accumulates in which season: its first sentence lists 'wind, bile, etc.' against 'the rains, Hemanta and summer' in non-matching order, so the assignments come from the preceding paragraphs, quoted separately in this record.

Source: https://archive.org/download/b24758619_0001/b24758619_0001_djvu.txt

### Sushruta Samhita Sutrasthana 6 (Ritucharyadhyayam):unnumbered prose, Bhishagratna vol. I p. 51, after the mapping of the parts of the day onto the seasons and before the account of depopulation by curse, spell and poisonous pollen, checked against the source

> Water and vegetables retain their natural properties when the seasons are natural, and do not exhibit contrary features, and they then tend to increase the appetite, vitality, strength, and power of the human system. Contrary or unnatural seasons are but the consequences of sin committed by a whole community and portend the workings of a malign destiny. A season, exhibiting unnatural or contrary features, affects or reverses the natural properties of water and vegetables peculiar to it, which, drunk or partaken of, cause dreadful epidemics in the country. The best safeguard lies in not using such defiled water and vegetables when an epidemic breaks out in the country.

tr. Kunja Lal Bhishagratna (1907-1916)

Seasonal derangement is the classical bridge to epidemic disease (janapadodhwamsa). It is worth recording plainly that the stated cause is collective moral fault, and the stated remedy is avoidance of contaminated water and produce. The remedy is sound public health; the aetiology is not.

Source: https://archive.org/download/b24758619_0001/b24758619_0001_djvu.txt

### Sushruta Samhita Sutrasthana 6 (Ritucharyadhyayam):unnumbered prose, the chapter's closing sentences, immediately before the colophon 'Thus ends the sixth chapter of the Sutrasthanam', checked against the source

> The bodily humours such as wind, etc. are disturbed and aggravated by the contrariety, excess or variations in the characteristic features of the seasons. Hence it is prudent to check the deranged phlegm in spring, to conquer the deranged bile in autumn, and to subdue the deranged bodily wind in the rains, before they develop themselves in any patent or manifest bodily ailment.

tr. Kunja Lal Bhishagratna (1907-1916)

How Sushruta's own chapter ends on the question the record leaves contested: the dosha is to be dealt with in the season of its PRAKOPA, but before it becomes a patent illness. That is neither the purely anticipatory reading nor treatment of established disease. Added because the original record said no retrieved passage bore on the question, and this one does, without settling it against Charaka's autumn prescription.

Source: https://archive.org/download/b24758619_0001/b24758619_0001_djvu.txt

### Ashtanga Hridaya Sutrasthana 3 (rtucarya-adhyaya):58, as numbered in the Das-Emmerick machine-readable text (AH Su 3.58), checked against the source

> ṛtvor antyādi-saptāhāv ṛtu-saṃdhir iti smṛtaḥ | tatra pūrvo vidhis tyājyaḥ sevanīyo 'paraḥ kramāt || 58 ||

Sanskrit mūla

The ritusandhi rule, retrieved at last. Working rendering: the last week of one season together with the first week of the next is known as the junction of seasons; there the earlier regimen is to be abandoned and the later one taken up, by degrees. This is the verse universally attributed to this chapter in modern Ayurvedic teaching, and the attribution holds. The e-text also carries a variant line at this verse, 'ṛtvor antyādi-saptāhād a-sātmya-jā hi rogāḥ syuḥ sahasā tyāga-śīlanāt', to the effect that diseases arise from unsuitability when the change is made abruptly.

Source: https://gretil.sub.uni-goettingen.de/gretil/corpustei/transformations/plaintext/sa_vAgbhaTa-aSTAGgahRdayasUtra.txt

## What the research actually shows

Every paper located for this concept, with what it measured and what it does and does not
establish. The assessment is ours.

### Widespread seasonal gene expression reveals annual differences in human immunity and physiology.

Nat Commun · 2015 · PMID 25965853 (https://pubmed.ncbi.nlm.nih.gov/25965853/)

Dopico and colleagues, Nature Communications 6:7000. More than 4,000 protein-coding mRNAs in human white blood cells and adipose tissue show seasonal expression profiles, 'with inverted patterns observed between Europe and Oceania'; the blood cell-composition changes that could explain the periodicity 'differ between the United Kingdom and The Gambia'; and the immune system shows a pro-inflammatory transcriptomic profile during European winter with increased soluble IL-6 receptor and C-reactive protein.

**How much it shows.** A large, well-powered, multi-cohort transcriptomic study, and the strongest evidence carried here that human physiology has a genuine annual rhythm. It is a COMPARATOR, not a validation: it does not test ritucharya, does not use the Indian six-season division, and measures nothing that corresponds to vata, pitta or kapha. Its two between-population results point AGAINST a calendar-fixed regimen rather than for one: an effect that inverts between hemispheres and differs again between the UK and The Gambia is an effect whose sign depends on latitude, which is precisely what a regimen anchored to Magha-through-Pausha at north Indian latitude cannot accommodate. The original version of this record cited the confirming half of this paper in its evidenceState and left the disconfirming half in this field; both halves now appear in evidenceState.

### Host and Environmental Factors Influencing Individual Human Cytokine Responses.

Cell · 2016 · PMID 27814508 (https://pubmed.ncbi.nlm.nih.gov/27814508/)

Ter Horst and colleagues, Cell 167(4):1111-1124, from the Human Functional Genomics Project. Cytokine responses to 19 bacterial, fungal, viral and non-microbial stimuli were measured in 534 healthy subjects. 'Annual seasonality is found to be an important environmental factor influencing cytokine production. Alpha-1-antitrypsin concentrations partially mediate the seasonality of cytokine responses, whereas the effect of vitamin D levels is limited.'

**How much it shows.** Added in answer to the critic's 'missing' finding on both the cytokine-seasonality literature and the vitamin D confound. Large for a functional immunology study, with stimulated-response readouts rather than resting transcriptome, so it is independent evidence that seasonality reaches immune FUNCTION and not only gene expression. Two limits matter here. It is a single-site Dutch cohort, so it carries no information about latitude and cannot be read either for or against a calendar-anchored regimen. And its vitamin D result is one cohort's mediation analysis, not a settlement of the confound: it weakens the claim that seasonal immune variation is simply sunlight acting through vitamin D, in this cohort, for these readouts. It tests nothing Ayurvedic, and alpha-1-antitrypsin is not a dosha.

### Increased winter mortality from acute myocardial infarction and stroke: the effect of age.

J Am Coll Cardiol · 1999 · PMID 10362193 (https://pubmed.ncbi.nlm.nih.gov/10362193/)

Sheth, Nair, Muller and Yusuf, Journal of the American College of Cardiology, pp. 1916-1919. Analysis of 300,000 deaths in the Canadian Mortality Database for 1980-82 and 1990-92: acute myocardial infarction deaths peak in January (RR 1.090) and trough in September (RR 0.904); stroke deaths peak in January (RR 1.113) and trough in September (RR 0.914); the seasonal swing widens markedly with age.

**How much it shows.** Large and robust for what it measures, but ecological and observational, using administrative death records with no individual-level exposure data. It establishes that disease incidence really is seasonal, which is the premise ritucharya assumes. It does not establish that the classical dosha-season assignments are correct, and a Canadian January peak does not map onto Sushruta's kapha-accumulation-in-hemanta scheme in any testable way.

### Untitled

2021 · doi:10.1186/s42779-021-00078-4 (https://doi.org/10.1186/s42779-021-00078-4)

Journal of Ethnic Foods, volume 8, issue 1, published 13 May 2021: 'Adopting seasonal regimen (Ritucharya) to modulate the seasonal variation in gut microbiome'. Proposes that seasonal diet shifts could be used to steer gut microbiota and links this to the classical concepts of shadkriyakala, agni and ama.

**How much it shows.** A NARRATIVE REVIEW with no primary data; the abstract describes itself as a review. It proposes a mechanism as future work and stops, which is the dominant pattern in this literature. The journal is not indexed in PubMed and the article returns no Europe PMC record, so it carries no PMID. It is recorded here because it is the most-cited modern attempt at a mechanism for ritucharya, and because its status as hypothesis rather than finding should be stated plainly.

## Open questions on this record

Recorded rather than resolved.

- Whether this project can publish the Ashtanga Hridaya Sanskrit quotation at all. The GRETIL e-text is distributed under CC BY-NC-SA 4.0 over a transcription marked 'Copyright 1997 R.P. Das and R.E. Emmerick'. Attribution is easy; the non-commercial and share-alike conditions are a licensing decision for the project, not a citation question, and the verse should not go to publication until that decision is made. If share-alike is unacceptable, the alternative is to quote the verse from a public-domain printed Sanskrit edition, which would also supply the collation this record says it lacks.
- Whether to consult the Sanskrit of Charaka Sutrasthana 6.41 and of Sushruta Sutrasthana 6 before publication. Two of this record's notKnown entries exist only because the Sanskrit was not read: the Doshanam/Deshanam variant, and whether Bhishagratna's chaya/prakopa labelling is his or the text's. Both would likely close with one pass over a Sanskrit edition.

## Citation

Age Ayurveda Nighantu, "Ritucharya: the classical rationale for seasonal regimen", https://nighantu.ageayurveda.com/concept/ritucharya-rationale/, CC BY 4.0.
Whole concept set: https://nighantu.ageayurveda.com/concepts.json and https://nighantu.ageayurveda.com/concepts.csv.

Educational reference only. This page describes what a body of theory claims and how well it
is evidenced. Nothing here is advice, and nothing here describes how any condition should be
treated.