Self & Other · The Things That Actually Help

Sunshine and Vitamin D

If you have specific medical conditions that affect your immune system, the vaccine question for you is more nuanced and should be discussed with the doctors who know your situation. For most people, most of the time, the schedule recommended by your country’s public health authority is the right answer.

Sunshine and Vitamin D

Vitamin D plays a real role in immune function, and a substantial fraction of people in northern latitudes are at least mildly deficient, particularly in winter. Severe deficiency is associated with worse immune outcomes, including higher rates of certain infections.

What the evidence less clearly supports is that taking large doses of vitamin D when you are not deficient will improve your immune function or prevent disease. Most studies attempting to show such an effect have produced modest, mixed, or null results. The strongest case for supplementation is in correcting genuine deficiency, particularly in people who get little sun exposure, who live at high latitudes, who have darker skin, or who are older. For these groups, modest supplementation — typically a thousand to two thousand IU a day, though the right amount varies — is often reasonable, and a doctor can help you determine it, ideally after a blood test.

The other thing sunshine does, beyond vitamin D, is help maintain your circadian rhythm — the daily clock that, as we mentioned, regulates much of how your immune system runs. Getting some natural light early in the day, especially within the first hour or two of waking, helps anchor this rhythm. The effect is real even on cloudy days; ambient outdoor light is many times brighter than typical indoor lighting. Getting outside briefly, every day, is one of those small things with surprisingly strong cumulative effects.

People

This is the section that, in a popular health book of twenty years ago, would not have appeared. The evidence has changed.

Loneliness and social isolation have, in the last fifteen years of careful research, been shown to have measurable effects on immune function. People who report being chronically lonely have higher levels of certain inflammatory markers, lower antibody responses to vaccines, and somewhat worse outcomes in a range of conditions. The size of the effect, in some studies, is comparable to that of well-known risk factors like smoking and obesity. This is not metaphor. It is biology.

The mechanism is not fully understood, but a working picture has emerged. Chronic loneliness appears to register, biologically, as a chronic stress signal. The signal raises baseline cortisol and certain inflammatory cytokines. The chronic elevation shifts the immune system into a state that is somewhat better at responding to physical injury (the body, in evolutionary terms, may be expecting a fight) and somewhat worse at responding to viral infections and at controlling inflammation generally. Over years, the wear shows up as measurable health effects.

The implication is not that you have to be popular. The evidence is about felt isolation, not objective social network size. People with one or two close, sustained relationships do not show the loneliness penalty. People who live alone but feel connected do not show it. What seems to matter is whether you have, somewhere in your life, a sense of being known by people who would notice if you disappeared. The biology of that is real. The intervention is not therapy, though therapy can help; it is the slow, ordinary work of staying in touch, joining the things that bring you into contact with others, and not letting the people who matter to you drift further than you mean to let them. Old-fashioned advice. Also one of the more medically relevant pieces of guidance in this chapter.

The Boring Foundations

A few things no popular wellness book leads with, but that have stronger evidence than most of the things popular wellness books do lead with.

Wash your hands. Especially before eating, after using the bathroom, and during respiratory illness season. The reduction in transmission of common infections from this single behavior is large and well-documented. Soap and water work better than hand sanitizer for most situations, but hand sanitizer is fine when soap and water aren’t available. Not glamorous. In pure cost-benefit terms, one of the highest-leverage things humans can do.

If you smoke, stop. Smoking damages the cilia that clear pathogens from the airways, suppresses certain immune cell functions, increases inflammation, and accelerates many of the chronic diseases we discussed in Chapter 8. It is a confirmed risk factor for several autoimmune diseases, particularly rheumatoid arthritis. There is no version of this advice that is gentle. There are good resources to help; the gain is real.

Take care of your teeth. Chronic dental and gum infections produce ongoing low-grade inflammation, which Chapter 8 named as a contributor to several major chronic diseases. The link between gum disease and cardiovascular disease, in particular, is now well established. Brushing, flossing, and seeing a dentist regularly are not just cosmetic choices.

Manage chronic conditions. People with diabetes who keep their blood sugar in good control have substantially fewer infections. People with HIV on consistent antiretroviral therapy have nearly normal immune function. People with autoimmune conditions whose treatment is well-managed have fewer flares and lower complication rates. The single highest-leverage thing many people with chronic disease can do for their immune function is take their medications consistently and stay engaged with their care. Unglamorous. Also more important than most of the lifestyle changes that get more attention.

Stay up to date on your vaccinations. (We covered this; it bears repeating.)

A Note for Readers with Chronic Conditions

If you have an autoimmune disease, a primary immunodeficiency, are on immunosuppressive therapy, are undergoing cancer treatment, or have any of the other conditions we discussed in earlier chapters, this chapter applies to you in modified form.

The interventions that help everyone help you too. Sleep is, if anything, even more important when you are managing a chronic condition. Movement, in whatever amount and form you can sustain, is broadly beneficial. Eating well supports your overall resilience. Connection with people matters as much for you as for anyone, possibly more.

But there are specific considerations. Some autoimmune patients on certain medications need to avoid live vaccines. Some immunocompromised patients need extra protective steps during respiratory illness seasons. Some people on biologics need to be alert to specific kinds of infections. Some chemotherapy patients need to be especially careful about food safety. The general advice here is the foundation; the specific modifications depend on your situation, and they should come from the doctors who know it.

What we said in the autoimmune chapter is worth repeating, because the framing matters. Doing all of these things will not cure your condition. Failing to do them did not cause it. They make any human life a little better; they do not, by themselves, address the specific medical realities of any chronic immune-related disease. Treat them as foundations, not as cures.

If you have read this chapter looking for the special trick — the supplement, the diet, the protocol, the secret — you will probably feel a little disappointed. The honest version of immune-related lifestyle advice is mostly things you have heard before: sleep, move, eat real food, see your friends, get your shots, wash your hands. The reason these are the recommendations is that these are what the evidence supports. The reason they don’t sell as well as more elaborate protocols is that they are not patentable, not glamorous, and not particularly profitable.

What you can do for your immune system, on the available evidence, looks remarkably like what you can do for your general health. The body is a single organism, and the immune system is woven through every part of it.

The next chapter is the negative space of this one. It is about what does not help, what only sounds like it helps, and what is being sold to you on premises the science does not support. It is the chapter that will save many readers a lot of money.

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