How Nutrition Influences The Immune System

Nutrition can play a fundamental role in the health and functionality of the immune system. Sometimes this can be as simple as supplying adequate nutrients for normal cell function, right through to directly stimulating and upregulating specific immunological functions.

Polysaccharides

Polysaccharides are very large, complex sugar molecules. They are a type of sugar that in many cases do not get broken down and utilised in the same manner that sugars do (we at least the variety that we are concerned with here don’t). They play a whole host of other biological roles, from acting as prebiotic agents, through to delivering immunomodulatory activity. Polysaccharides may actually prove to be the most exciting dietary component for immunomodulation. These compounds, particularly the beta glucans that are found in mushrooms.

Beta glucans have been studied for over 40 years. Much of this research has been done in Japan and the USA. These compounds have been shown to have a staggering effect upon immune function. Polysaccharides are known to stimulate the production of NK cells, and also regulate Th cells in some interesting ways. For many years it was believed that beta glucans delivered their activity on a kind of lock and key basis. It was thought that there were receptor sites on the surface of specific leukocytes, that bound with beta glucan in order to instigate an effect upon the cells, which impacted their behaviour. However, this theory was scuppered when beta glucan was found intact in stool samples. It came straight through the digestive tract intact, yet still delivered its physiological effects of increasing NK cell numbers and interacting with Th sub group expression. How did it do this? By interacting with the Peyer’s patches! Remember, the Peyer’s patch is like a surveillance station whose job it is to monitor gut contents, and continually report this to the immune system. When the polysaccharides pass over the Peyer’s patches, they seem to trigger some kind of of chain reaction. Almost like an alarm response. Exactly why this occurs is yet to be determined, but one of the theories is that mushroom polysaccharides are similar in structure to polysaccharides displayed on the outer surface of some types of bacteria. immune cell lines residing in the peyers patches detect this as being a bacterial attack, and as such begin to send out chemical messengers, called cytokines, to recruit and stimulate the correct immunological responses. This sequence of events is believed to be the key.

Best sources of Beta Glucan polysaccharides

• Shiitake Mushrooms
• Oyster Mushrooms
• Maitake Mushrooms

Zinc
Zinc is now a very common ingredient in many cold and flu formulae in recent years. And for good reason. Some nutrients that are known to interact with immune function, seem to have performed haphazardly in clinical trials for treating the common cold. However, zinc has consistently performed very well in trials, delivering a reduction in the duration and severity of colds and upper respiratory tract infections. So, how does it deliver these effects? Zinc is used by most of the white blood cells within our immune system, to actual code their genes. These genes regulate all of the internal processes that will control the way in which the white blood cells respond to pathogens and troubled tissues. Zinc is also used to regulate phagocytosis, and the production of cytokines. Zinc in and of itself also has an antimicrobial effect. As such it is found in the mucous secretions of the upper respiratory tract.

Best sources of zinc

• Shellfish
• Pumpkin seeds
• Eggs
• Beef
• Almonds
• Cashews
• Cheese
    

Vitamin C

Vitamin C is probably the single most thought of nutrient when it comes to immune health. Unlike zinc, vitamin c often performs poorly in trials focused on treating the common cold. That being said, vitamin C still is an important nutrient for the overall health and functionality of the immune system, regardless of whether it shortens the duration of a cold or not. It affects immune function in several ways. Firstly, vitamin c stimulates the production and activity of neutrophils, phagocytes, and leukocytes. It stimulates their motility as well as the phagocytic processes. Several cell lines also accumulate vitamin C to protect them from oxidative damage during their normal responses when faced with pathogens. Vitamin C also regulates a specific immunological response called the oxidative burst. This is where leukocytes release a cloud of reactive oxygen species when faced with pathogens.

Best sources of vitamin C

• Peppers
• Spinach
• Broccoli
• Goji berries
• Kiwi Fruit
• Citrus fruit

Essential fatty acids (EFA’s)

The essential fatty acids omega 3 and omega 6 are very closely linked to immune function, for several distinct reasons. Firstly, as you will have learned on the heart module for example, they play a key role in the regulation of the inflammatory response. Inflammation serves several purposes in immunity, such as increasing the passage for white blood cells in to tissues. This is done by dilation of the blood vessels, which makes them more porous, allowing white blood cells to squeeze through and enter infected tissues. Inflammation also draws our attention to an affected area. Fatty acids influence inflammation drastically. Different fatty acids will influence inflammation in different ways, due to their metabolic end products - a class of compounds called prostaglandins. There are three types of prostaglandins series 1, series 2, and series 3. Series 1 and series 3 prostaglandins reduce inflammation, whereas series 2 prostaglandins activate and exacerbate inflammation. Different fatty acids are metabolised to form different types of prostaglandins. Omega 6 fatty acids are metabolised to form the pro-inflammatory series 2 prostaglandins. Omega 3 fatty acids, particularly EPA are metabolised to form series 3 prostaglandins. There are another group of newly discovered inflammatory mediators called resolvins, made from omega 3 fatty acids. E Resolvins from EPA, and D Resolvins from DHA. These compounds reduce active inflammation. In any kind of issues that deliver excessive inflammation, increasing intake of omega 3 fatty acids will have a notable anti-inflammatory activity, due to the increased expression of series 1 and 3 prostaglandins, and the resolvins. Essential fatty acids also benefit immune function because of their importance to cell membranes. EFA’s are incorporated into cell membranes and as such modulate vital cellular processes such as cell signalling and receptor function.

Best sources of essential fatty acids

• Oily Fish

Other important nutrients

Other nutrients are also important for healthy immunity, but dont really fill their own paragraph. Vitamin E for example regulates B and T lymphocyte function. Vitamin A, B1, B6, B12, and Folic Acid are all vital for healthy white cell function.

Garlic

Garlic as an ingredient contains several elements beneficial to the immune system. Many are simple nutrients such as B vitamins and vitamin C. However, there are other compounds that are non nutritional but biologically active that give garlic its age old reputation as an antiviral. These compounds are sulphur based compounds that are responsible for the pungent smell of garlic. These substances, once through the digestive system, can only be removed from the body via one route and one route alone. They arent water soluble so dont get excreted via the urine. They arent fat soluble so they dont leave via the bowel. They need to be removed via the respiratory tract. That is why a night out at a restaurant can leave you smelling like Buffy the Vampire Slayer’s pocket. As these substances are breathed out, they can pick of susceptible bugs and viruses that are clinging to the mucous membranes.