There’s an irony in living longer — we’re more likely to see our bodies decline. Your immune system itself is not immune. It’s known as immune senescence, which is a term to describe the tendency for an aging immune system to allow more infections, cancers and diseases to take hold.

If you smoke, do everything to stop

If you smoke, quit now. It’s hard to do, but this is the single greatest, avoidable negative influence on your immune system. Your immune system has its own internal clock which has to last us a lifetime. We measure this clock by the length of molecules on our DNA, called telomeres. Smoking and a number of other bad habits shorten our telomeres and run out our immunologic clock before our time.

If your immune system is your Superman that shields you from tiny invaders, smoking is its kryptonite. It destroys antioxidants in your blood, increases autoimmune responses and kills antibodies — your body’s fighter cells that stay on alert for infection. Smoking also causes lung inflammation, using up antibodies that could fight infections elsewhere. This all puts you more at risk for other illnesses, such as pneumonia and flu,

Don’t worship the sun

Avoid exposing your skin to too much sunlight. While vitamin D from sunlight does help support healthy immune function, too much UV radiation can alter your DNA, ultimately boosting your risk of cancer. You also may get more cold sores.

Limit your exposure to chemicals and carcinogens

It’s good to limit your exposure to other carcinogens as well. Avoid burning coal and or cooking too much with charcoal. Also avoid man-made chemicals, including hydrocarbons, as much as possible.

If you’re overweight, work to lose those extra pounds

It’s well known that carrying too much weight puts your body at greater risk in many ways. A weakened immune system is one result. Abdominal fat triggers inflammation and boosts your risk of heart disease and diabetes. As you age, fat can build up in your bone marrow, muscle and liver — further boosting harmful inflammation. Even small amounts of weight loss can have an anti-inflammatory effect.