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Avoid THIS and Cut Your Risk of Cold and Flus

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Sugar has been blamed for a number of negative effects on human health and there is good evidence to suggest that it can also raise the risk of cold and flu. However, there is an ongoing debate over the influence of sugar on the immune system and whether that translates into increased risk of cold and flu. Can sugar truly depress the immune system? How does sugar affect the body’s defense mechanism? Are complex carbohydrates also linked to cold and flu? Read on to find out.

Cold, Flu and the Immune System

The best immunity against the microbes that cause diseases is still the natural immunity provided by such immune cells like T cells, B cells, and Natural Killer cells. Ideally, these immune cells can hold up the body’s defenses and keep the viruses that cause cold and flu at bay.

One reason why there are more cases of cold and flu are during certain seasons and certain periods of the year is because environmental conditions can affect our immune system.

For example, there is strong evidence to show that the reduced production of vitamin D in the skin during the winter months contributes significantly to the high occurrence of flu during the cold, sunless days of winter.

Studies have shown that vitamin D encourages the production of antimicrobial peptides known as cathelicidins and also boosts the immune system. These effects can improve the activities of immune cells and enhance their abilities to protect against cold and flu viruses.

In fact, the underlying principle behind flu vaccines is the training and enhancement of the immune system to recognize influenza viruses and defend the body against them.

Therefore, any food, drug, supplement, herb or lifestyle choice that boosts the immune system can reduce the risks of cold and flu.

On the other hand, anything that suppresses the immune system can increase your chances of coming down with cold and the flu.

Sugar and the Immune System

Sugar as an immune system depressant is a hotly debated topic in medical circles. Strangely, there are only a very few studies done to investigate the link between sugar and the immune system.

The best known study in this area of research is still the first one, the one most often quoted and the genesis of the debate. It was published in The American Journal of Clinical Nutrition in 1973.

The 1973 Study

For this study, researchers collected blood samples after an overnight fast and also at selected intervals (30 minutes, 1 hour, 2 hours, 3 hours and 5 hours) after different morning meals.

Meals Tested

100 g of carbohydrate from

  • Glucose
  • Fructose
  • Sucrose
  • Honey
  • Orange juice
  • Starch

These blood samples were incubated in suspension cultures containing the bacterium, Staphylococcus epidermis.

Thereafter the incubated samples were examined under a microscope. The researchers counted the number of bacteria found in the neutrophils of each blood sample to calculate the phagocytic indices of each food-blood sample.

The phagocytic index is a measure of the extent of phagocytosis due to a population of white blood cells. In this case, the white blood cell observed is the leukocyte known as a neutrophil.

Neutrophils are the major immune cells that engulf and destroy (phagocytosis) bacteria.

The results of the study showed that all of the sources of carbohydrate tested except starch significantly reduced the ability of neutrophils to engulf and destroy S. epidermis.

In addition, the result showed that the greatest inhibition of the antimicrobial ability of neutrophils occurred within 2 hours of consuming the sources of sugar. However, this inhibition was still significant 5 hours after consuming the sugar meals.

The researchers confirmed that sugar did not reduce the population of neutrophils but rather their function.

This study showed that simple carbohydrates such as sugar can depress the immune system for hours. Complex carbohydrates, on the other, do not affect the immune system in this way.

The observed inhibition of white blood cell phagocytosis in this study suggests that those who regularly consume simple sugars every day may continuously suffer from impaired immune functions.

It is also worth noting that the researchers only observed the effect of sugar on the immune system for 5 hours. Therefore, it is possible that sugars may depress the immune system further than 5 hours.

Since 1973

This study has been endlessly quoted and criticized by different health experts. One of the criticisms leveled against this study was that it was done in the lab rather than in the body.

Observing the same effect on humans would have been better but in vitro studies such as this are commonly used to make medical decisions too. Therefore, suggesting that the results do not apply because they were obtained from an in vitro study is a weak criticism.

To their credits, the researchers drew blood from human subjects and properly incubated the blood samples after allowing time for the absorption of sugar into the bloodstream.

In addition, they measured the effects of fasting on the activities of neutrophils and compared it to the effect of carbohydrate consumption on the same group of white blood cells. This means that they established a proper control against which the test samples was compared.

The second criticism of this study was that its claim has not been backed by another independent study.

While it might seem this 1973 study should have been repeated and confirmed by secondary studies, it is worth noting that there are also no studies that refuted the results of this study.

Therefore, there is a clear need to do more studies to investigate the effect of sugar on the immune system.

The only other study to approach this one was a 2009 study published in the journal, Eurosurveillance, which indicated that obesity can raise the risk of fatality from flu caused by the influenza virus, H1N1.

This study is relevant because regular, high consumption of sugars can cause obesity and diabetes. Therefore, when obesity increases the risk of dying from the flu, the mechanism involved is most likely the suppressant effect that sugar has on the immune system.

How Sugar May Affect the Immune System

The two most important questions raised by the 1973 study are: why did simple carbohydrates and not complex carbohydrates, affect the immune system? And how can sugar depress the immune system?

Complex carbohydrates such as starch differ from simple carbohydrates such as glucose because they take longer to get broken down.

Therefore, while simple carbohydrates are ready sources of energy, complex carbohydrates provide a more sustained release of energy. Therefore, complex carbohydrates produce a steady level of blood glucose while simple carbohydrates cause a spike in blood glucose level followed by a crash.

All of this means that complex carbohydrates are healthier since they do not flood the body with excess glucose.

On the other hand, the excess glucose released by simple carbohydrates makes the body work harder.

But how does sugar affect the white blood cells of the immune system? First, we have to understand how white blood cells protect us. These cells search for foreign bodies (such as harmful microbes, microbial antigens, and toxic metabolites) in the bloodstream.

They encircle these foreign bodies, engulf and then destroy them.

In the case of cold and flu, white blood cells can protect us from coming down with these diseases by mopping up the causative viruses from the bloodstream.

However, white blood cells need vitamin C to fulfill their role. Dr. Linus Pauling a proponent of high-dose vitamin C supplementation showed that white blood cells contain 50 times more vitamin C than the amount found in the blood in which these cells are suspended.

Unfortunately, glucose (the simplest form of sugar) is structurally similar to vitamin C. Therefore, excess blood glucose can accumulate in white blood cells.

Since glucose does not improve the functions of white blood cells, the substitution of vitamin C with glucose actually reduces the ability of these immune cells to mop up viruses and bacteria.

The Bottom-Line

So can your sugar intake cause cold and flu? The answer is yes.

Of course, a single intake of sugary foods and/or drinks will not bring you down with the flu. However, continuous and regular consumption of sugar can weaken your immune system enough to impair its ability to fight off infections.

The negative effect of sugar on the immune system is commonly observed in diabetes.

Diabetics usually have a hard time fighting off infections and experiencing complete wound healing. The impairment of the phagocytic (and perhaps other aspects of the immune system) property of white blood cells caused by high blood sugar levels in diabetes lowers resistance to infections.

In the same way, flooding the blood with sugar can temporary impair the functions of white blood cells even in healthy people.

As noted above, sugar is definitely not the sole factor responsible for your risk of cold and flu. In fact, no one factor can bring you down with these diseases but a combination of them will add up.

Therefore, the combination of low vitamin D levels during the winter months and the consumption of sugar can accelerate the onset of cold and flu as well as make the diseases severe.

This does not mean that flu season is the only time to avoid sugars.

Regular consumption of sugar from processed food, soft drinks, fruit juices, candies, cookies, etc. is bad in all seasons. Sugar negatively affects the body in many ways besides impairing the immune system. It promotes weight gain, insulin resistance, obesity, inflammation and affects just above every organ of the body.





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