How to Have a Strong Immune System Over Time

Aging can impact health in many ways, including on the immune system. Fortunately, one can bolster their immune system over time by reducing harmful habits and adopting others to support a healthy lifestyle.

How to have a strong immune system is frequently a hot topic. Understandably so, its buzz worthiness nearly tripled these past couple of years.

However, supporting the immune system is a lifelong affair since it is our greatest defense against acute and chronic illness. Just like many practices weaken the immune system, various habits strengthen and optimize it. 

Furthermore, it is perhaps even more important to bolster immunity as one ages because immune function tends to decrease over time.

What Is the Immune System?

The immune system is a complex network of cells and proteins that help protect the body against outside invaders like viruses, bad bacteria, fungi, and toxins. Working together, humans have an innate immune system and an acquired immune system. 

The main parts of the immune system include adenoids, bone marrow, lymph nodes and vessels, Peyer’s patches (lymph tissue in the gut), spleen, thymus, tonsils, and white blood cells.

The innate immune system is inherited and the first to respond when an invader is detected. Cells called phagocytes typically surround and engulf the offenders and kill them inside the immune system.

On the other hand, the acquired immune system is largely composed of B lymphocytes that produce antibodies in response to an invader. It can take several days for antibodies to develop, but after the first exposure, the immune system will remember the invader and defend against it should they interact ever again. Because this system is based on exposure, it can drastically change throughout life. 

Abnormalities of the immune system may lead to allergies (food and environmental), autoimmune diseases, and immunodeficiencies. Interestingly, allergies and autoimmune conditions are actually related to overactive immune systems, whereas immunodeficiencies typically result from genetic inheritance, medication, diseases like HIV/AIDS, and poor lifestyle habits.

What Weakens the Immune System?

In general, the same lifestyle habits that increase the risk for chronic disease also decrease the immune system, mostly because they are closely interconnected. Nonetheless, there are several unique factors that also contribute to suboptimal immunity.

1. Lack of Sleep

Getting enough quality sleep is imperative, as rest is when the body produces proteins and other compounds, some of which fight infection. If the body can not make enough because it does not have enough time overnight, the immune system will suffer. 

In fact, the only time the body releases cytokines, proteins that bolster the immune system is during sleep. Focus on getting 7 to 9 hours of quality sleep per night.

2. Anxiety/Stress/Depression 

The gut and mood are inextricably linked, and because a small immune system exists in the gut– not to mention gut health correlates with immune health– it is no surprise that poor moods weaken the immune system. 

Although the mechanism is not totally understood yet, research shows that acute stress can diminish the immune system in 30 minutes or less. Chronic stress makes it harder to fend off many viruses including the flu, herpes, shingles, and more.

3. Low Vitamin D Status

Vitamin D deficiency is associated with reduced immunity. This fat-soluble vitamin that is also an antioxidant is most bioavailable from the sun. 

Many Americans do not get enough sunlight or eat enough high vitamin D foods like free-range, organic eggs, wild-caught fatty fish, or fortified cereal, thus deficiency runs rampant. Aiming to get 10 to 15 minutes of sunlight sunscreen-free largely combats this issue.

4. Low-Quality Fats

Highly refined vegetable oils and poor quality saturated fat typically from processed meats and processed/packaged foods are largely to blame here. These low-quality fats can hinder the production of enough white blood cells. Over time, they can also alter gut bacteria, which are highly correlated with immunity. 

Instead, include plenty of healthy fats in olive oil and avocado and get omega-3 fatty acids from fatty fish, walnuts and other nuts and seeds, edamame, and algae.

5. Alcohol and Smoking 

Over-consuming alcohol just once slows the body’s ability to fight infection up to 24 hours. Thus, drinking too much too often is basically a recipe for disaster when it comes to immune health. 

Likewise, smoking harms cellular function and blunts the body’s ability to repair itself. Hence why most smokers die prematurely. Consider ways to stop smoking and decrease alcohol consumption to no more than one drink per day for women and two per day for men.

What Strengthens the Immune System?

In addition to addressing the above issues through dietary and lifestyle measures, the following greatly enhance immune function.

1. Eat Plenty of Plants

Whole food plants like fruits, veggies, nuts, seeds, and legumes contribute polyphenols in the form of antioxidants. These potent compounds help decrease inflammation by fighting free radicals. 

In addition, plants supply fiber, known to feed the gut microbiome, and a diverse gut microbiome certainly improves body immunity. Additionally, many fruits and veggies are high in vitamin C, a micronutrient known to help stave off the common colds and flu.

2. Eat More Fermented Foods 

After taking a probiotic supplement, eating fermented foods is the best way to feed the gut and populate it with beneficial bacteria. Research shows that foods like yogurt, sauerkraut, kimchi, kefir, natto, miso, and pickles actually help immune cells to differentiate between healthy substances and harmful invaders. 

Overall, a good gut equates to less autoimmune risk.

3. Reduce Inflammatory Foods

The most inflammatory foods are refined sugar and hydrogenated vegetable oils. Unsurprisingly, obesity, type 2 diabetes, and cardiovascular disease decrease immune function, and because a high intake of refined/added sugar is associated with those diseases, decreasing intake trickles down into an improved, healthy immune system. 

In addition, reducing other inflammatory foods like hydrogenated oils discussed above and replacing them with healthier fats (not eating low fat!) decreases systemic inflammation and bolsters immunity.

4. Exercise Enough, but Not Too Much 

While moderate exercise boosts the immune system, intense prolonged exercise actually suppresses it. This is why many elite long-distance runners frequently suffer from viral infections. 

People tolerate different thresholds of exercise tolerance, so it is important to find the sweet spot of just enough. Generally, people find success aiming for 30 to 60 minutes of some cardio and strength training on most days of the week.

5. Supplement When Necessary

Obtaining all necessary micronutrients from food alone can be challenging, especially when appetite is low in older adults. This is when supplementation becomes beneficial. Certain nutrients are most associated with immune function and include:

  • Vitamin C
  • Vitamin D
  • Zinc
  • Elderberry
  • Echinacea
  • Garlic

Immune System Aging

A recent study conducted by scientists at Stanford and the Buck Institute discovered a way to predict an individual’s immunological decline. These scientists essentially created an inflammatory aging clock that is much keener to predict the strength of immunity compared to biological age.

The article goes on to say that even if 100 people are technically the same age, they may not be biologically the same age. Meaning, some people are more disease prone than others, in large part due to differing rates at which people’s immune systems decline.

As humans age, low grade but chronic systemic inflammation essentially builds up and starts to wreak havoc, causing organ damage and increased risk for disease. But previously, there was no real way to quantify someone’s immune function.

This study determined 50 cytokines, immune signaling proteins, that when applied to a systematic algorithm, sufficiently generated a single-number inflammatory score that correlated with a person’s likelihood of incurring a variety of age-related diseases.

All in all, the research demonstrated that inflammatory age proved superior to chronological age in predicting frailty and disease associated with aging. Hopefully, this provides even more incentive to adopt a healthy diet and lifestyle practices as one ages that improve the immune system! 

The Takeaway

The immune system is a complex network of specific cells and proteins that fight infection and is affected by many dietary and lifestyle factors. Lack of sleep, low vitamin D, and chronic stress diminish immunity while colorful plant foods and anti-inflammatory omega-3 fatty acids, and moderate amounts of physical activity/exercise largely improve it. 

What’s more, it is vital to support the immune system as one ages, especially because new research shows that immunological age is better at predicting frailty and risk of disease than biological age.


Bhargava H. Your Immune System: Things That Can Weaken It. WebMD. Medically Reviewed March 26, 2020.  

Goldman B. Immune System ‘Clock’ Predicts Illness and Mortality. Stanford Medicine News Center. Published July 12, 2021.

Shoemaker S. 9 Ways to Boost Your Body’s Natural Defenses. Healthline. Published April 1, 2020.  

The Immune System. Johns Hopkins Medicine.