In the last few years, I’ve gotten sick very infrequently. When I’ve had cold symptoms, it was invariably after pulling an all-nighter, or a weekend of relative debauchery. In other words, I had it coming. And when I say “cold symptoms", I mean some of the mildest sniffles and coughing you’ve ever seen.
And the common cold is, well, common. Americans suffer through a billion colds every year. Adults tend to get on average two to four colds per year. How is it that I am getting only very mild colds, and at only about half the rate of the average adult?
I’ve always lived a relatively healthy lifestyle compared to most, but I’ve never been the kind of person who controls every last variable in my environment, or eats only clean foods, never drinks alcohol, etc. I added one very simple, cheap, and easy behavior to my lifestyle in January 2013 which seems to have done the trick: vitamin D supplementation! Soon after that, I added zinc to my supplement regimen, which provided further immune benefits.
I plan to cover about a gazillion different things you can do to improve your immune function in this article. However, as a big proponent of the 80/20 rule, I figured I’d give away my “secret" right at the beginning. Simply adding the cheap supplements of vitamin D and zinc to your routine could provide an incredible bang for your buck, immunity-wise.
Oh, and one other quick tip. Drink a ton of water. Seriously. Not only is staying hydrated important for immune function, but it provides the double “benefit” of making you need to pee frequently, and thus provides a very easy reminder to wash your hands frequently throughout the day. I used this strategy recently while working in an urgent care clinic, and the close proximity to all sorts of diseased people didn’t affect me one bit!
In what is to follow, I will walk you through reams and reams of different tips, tricks, and lifestyle modifications that will make you impervious to all infectious diseases, guaranteed! (Warning: not really a guarantee.)
Nutrition: What to Consume
The first step towards a healthy immune system is to make sure that you are getting enough of certain nutrients.
You know how people tend to get sick in the winter more often than other seasons? I know I’ve always been told that this was because the cold weather somehow suppressed your immune system. While there is probably some truth to that hypothesis, it doesn’t look like it is entirely convincing.1
A more plausible explanation would be having lower levels of vitamin D. There is quite a bit less UVB light exposure during the winter, which means your body isn’t synthesizing its own endogenous vitamin D in nearly as high levels as it would when you are spending summer days out on the beach. A growing body of literature is showing how important optimal vitamin D levels are for immune function, and how vitamin D can help prevent both autoimmune and infectious diseases.2,3,4,5
Making sure you get enough vitamin D is important, but it’s also pretty easy. During the summer, spend more time out in the sun. Keep in mind that sunscreen prevents your body from synthesizing vitamin D from the sun’s rays, so you might want to consider getting sun protection from the food you eat instead. Of course, since getting sunburn can lead to skin cancer, you’ll need to balance the risks. A short period of exposure to the sun (say, 15-30 minutes without sunscreen) over large portions of your body should do the trick with a minimal risk of burn.
You can also get vitamin D in your diet, with egg yolks and fatty fish being good dietary sources. However, it is difficult for most people to get enough through their diet, particularly if they also lack sun exposure. “Fortified" foods use synthetic forms of vitamin D that are potentially harmful, so don’t rely on them for your vitamin D needs either.
Ultimately, most people will benefit from taking fairly large doses of a vitamin D supplement for much of the year, but particularly during the winter months. I suggest you check the vitamin D status in your city in order to determine how much you’ll synthesize from the sun while you are outside. For some of you it will be sufficient, but I suspect most people reading this will benefit from supplementation.
You should make sure you are supplementing with an oil-based vitamin D3, specifically. Until and unless more research determines that it is okay, you should avoid using other forms of vitamin D (such as D2). The optimal blood level and dosage of vitamin D is up for debate, but over the past few years, as more and more benefits of vitamin D have been discovered, the guidelines have tended to climb. You’ll likely want to take several thousand IU’s of vitamin D supplements on a daily basis, but the only way to know for sure is to get tested. In addition, if you are taking vitamin D in significant amounts, it is imperative that you also take a vitamin K2 supplement, which works synergistically. Taking vitamin D without K2 can lead to nutrient imbalances over time. It is not yet established what the optimal ratio is, but one recommendation is to get at least 100 mcg of vitamin K2 for every 5000 IU’s of vitamin D.
The next most important element of an immune-system boosting regimen is the highly underrated and under-appreciated mineral, zinc. It is instrumental in having a healthy immune system, and a deficiency makes you far more susceptible to illness. An estimated 17.3% of the world’s population is at risk for zinc deficiency; this risk is lower in high income areas (as low as 7.5%), but is gigantic in other regions (30% in South Asia, for instance).6
Supplementation with zinc can go a long way towards reducing your chance of illness by shoring up your immune system. As Fraker et al shows,
“…short periods of zinc supplementation substantially improve immune defense in individuals with these diseases. Mouse models demonstrate that 30 d[ays] of suboptimal intake of zinc can lead to 30–80% losses in defense capacity. Collectively, the data clearly demonstrate that immune integrity is tightly linked to zinc status."7
When it comes to zinc supplementation, please be mindful of your dosages. It is very difficult to get too much zinc from dietary sources alone, but easy while supplementing. I recommend getting this zinc supplement, but only taking half a pill per day, or about 25 mg. I accidentally took too much one day and had to uncomfortably sweat it out for the next few hours. Don’t repeat my mistake!
Maintain A Healthy Gut Microbiome
The next most important thing to do is to make sure you have a healthy gut microbiome by consuming enough probiotics and prebiotics. Having a healthy ecosystem of friendly gut bacteria is one of the more effective things you can do to avoid getting sick and improve your immune system.8,9 And lactic acid bacteria specifically help your immune system, so taking probiotics (which often contain lactobacillus) is beneficial.10
Fermented foods such as yogurt, kefir, kombucha tea, sauerkraut, and kimchi contain loads of healthy bacteria. You can also use probiotic supplements; I recommend using a greens powder that also contains loads of other healthy stuff. In general, eating a good probiotic yogurt a few times per week should suffice.
You’ll also want to make sure that all those bacteria have something to munch on of their own. Prebiotics are indigestible to you, but make a nice food source for all the healthy bacteria in your gut. Prebiotic foods include garlic, onions, Jerusalem artichokes, jicama, asparagus, and under-ripe bananas. As a general rule, consider adding high-fiber foods to your diet for a similar purpose; just don’t eat too many grains. Focus on berries, almonds, cruciferous vegetables (broccoli, cauliflower, brussels sprouts), and root vegetables.
Other Nutrients That Help Your Immune System
Making sure you have adequate levels of vitamin D and zinc, as well as making sure you take care of your gut bacteria, should go a long way towards ensuring that your immune system is healthy and strong. But there are many other nutrients that can enhance immune function.
When most people think about supplementation to improve their immune system, they think of vitamin C. There is definitely some evidence that vitamin C protects the immune system,11 but taking extra doses in response to a cold appears misguided, despite being a common practice. However, for people who undergo lots of physical stress, like heavy weight-lifters or marathon runners, some extra vitamin C may be effective in improving immune function.12
An old review article found that other important nutrients for your immune system include copper, selenium, iron, vitamins A, E, B-6, and folic acid.13 Additionally, increasing your antioxidant consumption in general is helpful.14 In other words, you’ll want to eat a varied and healthy diet, making sure that you are not deficient in any particular nutrients. Eat your vegetables!
Here are a handful of other suggestions:
- Drink green tea. Boosting your immune system is only one of many of the benefits of drinking green tea. It’s loaded with antioxidants and other goodies that will keep you healthy.
- Drink loads of water.
- Eat dark chocolate. It’s also loaded with antioxidants and dramatically reduces inflammation, which may explain why dark chocolate prevents so many diseases.
- Add garlic to your diet. My girlfriend and I love garlic and add it to just about everything. And why not? It’s delicious! More importantly for our purposes here, garlic also helps stimulate your immune system.15
- Use coconut oil. Coconut oil is another one of those can’t-endorse-it-enough superfoods, which happens to have strong anti-bacterial, anti-viral, and anti-fungal properties. It can be fairly expensive in most places, but you can get a humongous tub of it on the cheap here.
- Consume apple cider vinegar. Admittedly, I have not tried it myself, but there are some who believe that it has immune-boosting properties.
- Spice up your food. Many spices are loaded with antioxidants and have antimicrobial properties, so try to include some spices in every meal. Turmeric is generally a good choice.
- There are many herbs that have antimicrobial properties or are said to enhance the immune system in some way.16,17 Echinacea is probably the most famous for this effect, but there are many others. I have little experience in this area, and would advise anyone who is interested to do their own research. Consider that many herbs have powerful chemicals that can have serious health effects, including interacting with medications. Be careful.
You’ll get the most bang for your buck by focusing on vitamin D and zinc, but there are clearly many other nutrients that impact your immune system.
Nutrition: What Not To Consume
Not only are there nutrients that you must make sure you consume in sufficient quantities to maintain a healthy immune system, but there are also foods that you should deliberately avoid. If you are interested in this subject, I strongly suggest reading this 11-page paper by Dr. Ian Myles, which summarizes modern research on how our diets can adversely impact our immune system. It’s ridiculously fascinating.
Here are a few rules:
- Try to avoid eating out at restaurants as much as possible. Obviously, there are many good reasons to go to restaurants, but your health is simply not one of them. They may be adding things to your food that are bad for you, and you would have no idea. You also don’t know what kind of sanitation practices they use.
- When shopping for food, you should tend towards the organic options if you can afford it. Pesticides can wreak havoc on your immune system.18 Organic is more expensive, but you don’t need to get everything organic. Certain foods are more important to purchase organic, but you should do your own research to determine how important this is to you.
- Avoid all processed foods, gluten, and sugary foods and drinks. According to Dr. Myles, these foods lead to increased inflammation, reduced control of infection, increased rates of cancer, and increased risk for auto-inflammatory diseases and allergies. They are also really bad for your gut bacteria.
Seriously, you should avoid sugar like the plague. According to Dr. Sears,
“Eating or drinking 100 grams (8 tbsp.) of sugar, the equivalent of two- and-a-half 12-ounce cans of soda, can reduce the ability of white blood cells to kill germs by 40 percent. The immune-suppressing effect of sugar starts less than thirty minutes after ingestion and may last for five hours."
Unfortunately, you’ll want to avoid artificial sweeteners as well, which tend to pulverize your gut bacteria.19 Splenda (sucralose) seems to be particularly bad.20 So if sugar is bad and artificial sweeteners are bad, getting your sweet-tooth on may be a bit challenging. Stick with real fruit and dark chocolate. Alternatively, stevia is a natural sweetener that does not have the problems associated with artificial sweeteners.21 If you simply need added sweetness, use stevia.
Exercise Guidelines To Optimize Immune Function
Exercise provokes a huge number of physiological changes in the human body, including quite a few changes that directly impact the functioning of the immune system. For the nerds who are interested in learning more about these physiological changes, read this paper. It’s dense, but interesting.
Physical exercise is generally considered necessary to maintain optimal health and fitness. But the relationship between exercise and the immune system is more complex.
Acute bouts of exercise create a stress response in humans, suppressing the proper functioning of the immune system. This stress response is so strong that researchers will sometimes use exercise as a means of simulating a traumatic event in their experiments! Therefore, a given bout of exercise will tend to make it more likely that you will get sick. Heavy acute exercise loads can depress immune function for 3-72 hours post-exercise.22 Moderate physical activity does not tax the body’s immune system to nearly the same degree.
High-intensity training absolutely should NOT be ruled out based on this – you just need to weigh the pros and cons. The anti-inflammatory effect of exercise may potentially make up for the increased susceptibility to infection. High intensity exercise will most certainly reduce your risk of chronic degenerative diseases, even if short term infections might increase.
There is a perception among athletes that long-term, moderate exercise improves their immune systems. While there is some evidence of this, there isn’t enough to draw any significant conclusions for the average person.23 Perhaps the ideal form of long-term exercise for immune function would be yoga, which improves immune system markers by reducing the body’s response to stress.24,25
Additionally, there is some evidence that supplementation with glutamine, carbohydrate consumption, probiotics, and antioxidants may reduce the negative immune system impact of heavy exertion.26,27 Normally I wouldn’t recommend most carbohydrates, but consuming them at around the same time you are exercising isn’t the worst idea in the world.
Perhaps the right strategy may be to continue doing high intensity training a couple times a week, but also do yoga a couple other times per week to help balance it out while remaining fit. You might also want to consider going easy on the exercise when you really can’t afford to get sick, or if you are engaging in other “riskier" activities such as poor eating and not getting enough sleep.
Mental Health, Happiness, And The Immune System
This is a blog largely focused on happiness, so how can I not bring up the role that emotions play in immune system health?
As discussed in the previous section, physical stress decreases immune function. But psychological stress has a serious impact as well. Here is a meta-analysis of over 300 empirical studies on psychological stress and immune response. The whole thing is interesting, but I will summarize the most important results. Note that “cellular" corresponds to immune defense mounted against viruses (intracellular), whereas “humoral" corresponds to defense against bacteria and parasites extracellularly. The researchers found that
- Acute stressors that last for only a few minutes have mixed effects, upregulating some markers of immune function and down regulating others.
- Brief naturalistic stressors, such as exams, tended to suppress cellular immune function while preserving humoral.
- Chronic stress suppresses both cellular and humoral measures of immune function.
In another study, higher psychological stress increased the infection rate when subjects were exposed to various respiratory viruses, such as the common cold.28 And on a related note, depression and negative mood states down-regulate the body’s immune response, which can lead to delayed healing and higher susceptibility to infection.29,30
Taking steps to reduce the chronic stress in your life is one of the best ways to reduce your susceptibility to illness. This could involve restructuring certain aspects of your life (job, family, etc.), coming to terms with and accepting certain aspects of your life that you can’t change, and things like meditation that will manage the existing stress and reduce your body’s response to it. I have written extensively about this and related subjects (after all, that’s what this blog is for!), so here are some ideas:
- Accept yourself. But if you are unsatisfied with your life, you can use the starting from zero technique to help you begin changing it for the better. Similarly, use the fear-setting technique to help you overcome the fears you may have related to pursuing your dream life. Then get to work on achieving your goals, but recognize that you’ll never be able to do it all. And when you find yourself slipping, learn how to get back on-course.
- Understand that busyness is a choice.
- Get over your “FOMO", or fear of missing out. On a related note, stop ruining good experiences by wishing for something different or better. In general, you should learn to develop an abundance mentality, which is one of the greatest things you can do to reduce stress.
- Become more mindful. Learn how to meditate. You can also practice mindful eating. One of the better ways to reduce stress that gives you an opportunity to be more mindful is cuddling with a loved one.
- Stop practicing escapism.
- Learn how to reframe your negative thoughts.
- Learn how to accept criticism. Become better at seeing the good in other people.
- Become more resilient in the face of adversity. When something really bad happens, write about your experience. Recognize that negative emotions play an important and positive role in your life.
Negative emotions can clearly have a negative influence on our immune function, but what influence might positive emotions have? The effect of positive emotions on immune function has been studied to a vastly lesser degree than negative emotions and stress. In addition, the studies that have been done have numerous caveats, so we must be cautious trying to extract meaning from their results. For those interested in a review of relevant studies, here is a good paper. It appears that positive mood states lead to improved markers of immune activity. In addition, people who are generally positive (or, in their lingo, “trait positive affect”) tend to have better immune function.
In general, your efforts to improve your life and become happier will also pay off with an improved immune system.
Lifestyle Factors Impacting Your Immune System
It’s a little bit ambiguous what would be considered a “lifestyle factor" and what wouldn’t. I mean, what isn’t a lifestyle factor? Well, whatever. The three subjects I will include here are sleep, the use of certain substances, and hygiene.
Get Enough Sleep
There is certainly a popular conception that sleep deprivation weakens immunity and makes people more likely to get sick. In my personal experience, this is certainly the case. Very rarely do I get sick, unless I’ve pulled an all-nighter or have barely slept for several days.
For a short, fascinating discussion of how sleep and the immune system are related, see this. Disruptions in the circadian rhythm have negative effects on your immune system,31,32 so maintaining a consistent sleep schedule is important. You don’t want to get too much or too little sleep; there is a sweet spot, somewhere between 6 and 9 hours per night, usually between 7 and 8.
I’ve personally found that having a morning routine is the best way (for me) to maintain a consistent sleep schedule. I suggest picking a specific time to wake up each day, but going to sleep whenever you are tired. If you struggle with sleep, take a look at these resources:
- The Definitive Guide to Sleep from Mark’s Daily Apple
- Key Strategies for Optimizing Your Sleep from Dr. Joseph Mercola
- Strategic Napping…from me! This post will cover everything you need to know about how to get the most out of your naps.
Reduce Alcohol And Tobacco Usage
Smoking tobacco suppresses the immune system, both for heavy and light smokers.33,34 But there is good news: quitting smoking for just 31 days restores some measure of immune function.35 And after three months without smoking, there is a substantial recovery of the immune system.36
For optimal immune function, you simply shouldn’t smoke. But the relationship between alcohol use and the immune system is slightly more complex. You can find an interesting discussion of alcohol’s effects on the immune system here, but I will summarize the most important findings.
- Both acute and chronic alcohol consumption can weaken the immune system.
- Alcoholism can lead to malnutrition and vitamin deficiencies, but is also related to immune suppression independent of these factors.
- The effects of acute drinking are less certain, but do appear to have negative effects on the immune system.
A night of binge-drinking will weaken your immune system, as will drinking regularly. On the other hand, light alcohol consumption, such as a single glass of red wine with dinner, may actually have positive effects on your immune system.37
You’ll also want to consider the impact of any drugs (licit or illicit) or medications you might be taking. There are far too many possible substances to discuss individually here; however, it’s a pretty decent bet that whatever you might be taking or thinking of taking, it probably will weaken your immune system.
Practice Good Hygiene
Don’t let the relative position of hygiene in this article fool you about its significance; good hygiene is likely the #1 thing you can do to prevent yourself from getting sick. Of course, it is way less exciting than the other strategies for improving your immune system, so it is getting shoved way at the bottom of this article!
A massive literature review of over 100 years of studies says that hand-washing is a critical means of preventing infections.38 In fact, hand-washing with soap can reduce the risk of contracting diarrheal diseases by over 40%!39 And while you and I have likely never spoken, I feel confident in assuming that you are the kind of person who doesn’t like diarrhea.
Speaking of diarrhea, here are some hygiene tips to help prevent you from getting sick:
- Wash your hands all the time, particularly after being in contact with sick people or touching public things.
- Use a towel to open bathroom doors and to turn on the tap.
- Avoid touching your face, especially during flu season.
- Keep your keyboard and car steering wheel clean by wiping them down with an antibacterial.
- Cough and sneeze into your elbow. And yell at other people when they don’t do this. Seriously, it’s one of my biggest pet peeves. How can people not be doing this in this day and age?
As I mentioned in my introduction to this article, one tip is to drink tons and tons of water. Water is good for your immune system in and of itself, but it’ll also force you to go to the bathroom more often, and thus (hopefully) wash your hands more frequently.
This has been a very dense post, detailing many possible ways for you to optimize your immune function. Having covered so much ground, let’s take a moment to summarize the most important things you can do.
- Get enough vitamin D and zinc. Supplement if you have to. You probably do have to.
- Drink lots of water. No more soda.
- Be mindful of your physical activities – if you feel like you might be coming down with something, don’t work out too hard. Try adding yoga to your exercise regimen.
- Take steps to structure your life such that chronic stressors, such as unhappiness at work, are minimized. Find ways to manage your stress in a healthy way, such as through meditation, yoga, taking walks, reading, etc.
- Have a consistent sleep schedule. Make sure you get the right amount of sleep for you. For most people, that is about eight hours.
- Quit smoking, and don’t abuse alcohol. Drink in moderation.
- Follow good hygiene practices. Make sure you wash your hands frequently.
By following these steps, you ensure that your body is in the best possible position to fight off any illnesses that life tries to throw your way.