Winter: Storing, Cold, and the One Instruction That Is Not About Food

What changes in the body

Cold changes the circulation first. Peripheral vessels constrict, blood pressure rises, and the heart works against a higher afterload. This is not a small effect: systolic pressure is measurably higher in winter than in summer in most populations, and the incidence of heart attack and stroke peaks in the cold months. If there is one seasonal fact worth knowing, it is that winter is the dangerous season for the cardiovascular system, not summer.

The second change is in the airway. Cold dry air triggers bronchoconstriction in people with asthma and makes exercise harder for everyone; the classical association of winter with the lung is really an association with cold air, and it holds up.

The third is thermoregulation at night. Core temperature has to fall for sleep to begin and rises again before waking, and in a cold bedroom that curve is disturbed — which is why winter sleep is often longer and less refreshing, and why people wake more.

The fourth is behavioural, and it is the one that matters most. Activity falls, light exposure falls, and food intake rises. The result is a modest seasonal weight gain in most temperate populations, a fall in vitamin D, and a shift in sleep timing. The tradition describes winter as a season of storing rather than expending, and the description fits the observed behaviour closely — which is not the same as saying the behaviour is optimal.

What the tradition adds is a claim that the kidney stores the body’s reserves, that winter is when those reserves are replenished, and that depleting them in winter produces problems later. The first two are not testable as stated; the third is a reasonable description of what happens when people stop sleeping and stop moving for three months.

What the classics say

Quoted in the original with our own translation. These are the passages the seasonal advice is built on — we give the whole sentence rather than the fragment usually quoted, because the part that gets cut is often the part that qualifies the claim.

Read the winter passage against the other three and notice what it does not say. It does not mention food at all. Its instructions are about sleep timing (早卧晚起, early to bed and late to rise — the only season where late rising is prescribed), about waiting for daylight before going out, about keeping warm, and about not sweating. The entire tonic-food industry that attaches itself to winter is built on a chapter that prescribes a schedule rather than a menu. The second citation is the tradition’s theory of latency — that a winter insult shows up as a spring illness — and it is worth noting that this is a claim about timing that modern epidemiology has partly vindicated for some infections, and not for the "warm disease" category as a whole.

Patterns that flare now

Seasonal attribution is the weakest link in the traditional chain, and we present it as the tradition does rather than as a claim we can support. What is defensible is narrower: these are the patterns that share a climate, a flavour or an organ assignment with the season, so they are the ones a reader is most likely to recognise in themselves right now.

What to eat, and why

The tradition’s winter advice is warm, cooked, and regular, and the mechanism is simply that heat is lost faster and a hot meal costs the body less. Soups, stews, congee and braises are the appropriate form, and they are also what the season’s vegetables make possible — roots and cabbages keep, greens do not.

The tonic question is where the tradition and the evidence part company. 补 in the classical sense means to support a deficit, not to add richness, and the two have been thoroughly confused. The modern version — a daily dose of deer antler, cordyceps, ginseng or wine-soaked herbs for three months — is not what the chapter asks for, has no outcome data behind it, and carries real risk: several of these interact with anticoagulants, blood pressure medication and immunosuppressants.

Salt deserves its own note because the season pushes it in two directions. The tradition assigns salt to the kidney and uses it in small amounts; the modern problem is the opposite one, that winter food is saltier and blood pressure is higher. If you have hypertension, winter is the season to be more careful, not less.

The genuinely useful winter dietary change is vitamin D and oily fish, and neither is traditional. In northern latitudes, cutaneous synthesis stops for several months, and supplementation is the standard recommendation. This is the clearest case on the site of modern advice being the thing that matters and the tradition being silent.

Sleep, activity, and light

The instruction 早卧晚起 — early to bed, late to rise — is the single most distinctive line in the seasonal chapter, and it is the one nobody follows. Read practically: in a northern winter, the light that sets your clock arrives late, so forcing a 5 a.m. start in December works against the season rather than with it. Sleeping an hour longer in winter and an hour less in summer is the pattern the text describes, and it is also what most people do when they stop fighting it.

Do not go out to exercise before daylight in the cold. This is the 必待日光 line, and the modern reason is not mystical: cold air plus darkness plus a sudden cardiovascular load is the combination in which winter cardiac events cluster. Move the session later, or move it indoors.

Avoid sweating in the cold. The text says 无泄皮肤 — do not let the skin discharge — and the practical version is to layer so that you can remove a layer before you overheat, and to change out of damp clothing rather than sitting in it. This is the one piece of winter advice that is both traditional and straightforwardly correct.

Keep the bedroom cool but not cold, and warm the bed rather than the room. Core temperature has to fall for sleep to begin, and an overheated bedroom produces the dry mouth and broken sleep that gets blamed on kidney yin deficiency. The two explanations point at the same fix.

Light in the morning, even in winter. Ten to twenty minutes outdoors in the first part of the day is the intervention with the best evidence behind it for winter flatness, and it is free.

What the evidence supports

This section exists because most seasonal-advice pages do not have one. Here is what we think survives contact with ordinary physiology, and what does not.

What holds up: blood pressure rises in cold and cardiovascular events peak in winter; cold air triggers bronchoconstriction; vitamin D falls below sufficiency in northern winters without supplementation; sleep timing shifts with light availability; seasonal low mood responds to light treatment.

What does not hold up: that winter is the season to take tonic herbs, or that 补肾 in the classical sense maps onto any measurable kidney function. The classical kidney is a functional category that includes bones, growth, reproduction and reserves; a serum creatinine test says nothing about it. The tonic market depends on that ambiguity, and we do not.

What is unresolved: whether cold exposure itself — as opposed to the inactivity that comes with it — has any adaptive benefit. Cold-water swimming and deliberate cold exposure have small studies with mixed results, mostly on mood and perceived stress, and no convincing outcome data. It is not dangerous for healthy people and it is not a treatment.

Common mistakes

• Chest pain, sudden breathlessness, or a face that droops in cold weather is an emergency. Winter is when these are most common and most often attributed to the cold.
• Do not take tonic herbs alongside anticoagulants, blood pressure medication or immunosuppressants without checking. Ginseng, deer antler and several others have real interactions.
• Do not stop blood pressure medication in winter because readings look better in summer. The seasonal rise is the reason to keep measuring, not to stop.
• Do not use alcohol to warm up. It dilates skin vessels and increases heat loss, which is why hypothermia and cold-water deaths are associated with drinking.
• Do not exercise hard in cold air without a warm-up if you have angina or known heart disease. The combination of cold and sudden exertion is the specific trigger to avoid.