Diet and immunity: What’s the connection? – A three part series by Robyn Chuter

Fat chance of defending yourself – Part two

Excess fat intake raises the production of the inflammatory prostaglandin E2. The omega six fat arachidonic acid is found primarily in animal products and processed foods. If we eat too many vegetable oils it alters the balance of fats in the membranes of our immune cells, disrupting their function.

Saturated fats are even worse, because of their impact on toll-like receptors, a crucial element of the immune system designed to evaluate what specific type of invader – bacterial, viral, or fungal – is threatening the body. A high dietary intake of saturated fats announces to the rest of the immune system that a bacterial invader is present which incites inflammatory activity to combat it.

This misguided attack on saturated fat causes intestinal hyperpermeability (‘leaky gut’), further increasing immune dysfunction and worsening infection control. It’s also a major factor in triggering autoimmune disease.

Being overweight – or even just having a higher than ideal body fat percentage – compromises your immune function in several ways:

Firstly, fat cells are constantly pumping out inflammatory substances. Over time, this constant release of substances that should be deployed only when there’s an infection to fight, may result in a ‘boy who cried wolf’ situation. The immune system becomes so blasé about the constant warnings of danger that it doesn’t respond to a real threat when it should.

Secondly, obese people have been found to have significant abnormalities in the number and activity of their infection-fighting white blood cells compared to lean individuals. They have fewer natural killer cells (which kill tumour cells and virus-infected cells) and reduced T and B cell activity which give the immune system its ‘memory’ – that is, its ability to rapidly respond to bugs it has encountered in the past, so it’s able to fight them off without your body actually getting sick.

So, if you’re carrying extra fat mass, you’re more likely to pick up an infectious disease; you’ll feel sicker when you have it (because it’s the inflammatory compounds produced by your immune system, not the bug itself, which cause the malaise, lassitude, fatigue, numbness, coldness, muscle and joint aches, and reduced appetite you suffer when you’re fighting off a bug); and you’ll be sicker for longer.

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