You may not be aware, but the majority of the immune system is located in the gut. It means the health of one will inevitably affect the other and can impact everything from your skin, to your mood. The surprise effects of your gut don't end there, nutritional therapist Claire Barnes tells Bazzar. If you're suffering from any of these issues, there's a chance your gut might hold the answer...

1. Low mood

"There is a strong association between depression and our digestive system. Often when we are feeling low, we lose our appetite or crave comfort food, and instead of eating regular meals we satisfy ourselves with quick processed, often sugary foods. A poor diet can lead to an altered gut flora, which can further affect our mood. Certain strains of bacteria produce toxins which may be able to cross both the intestinal barrier and the blood brain barrier, therefore affecting our wellbeing. Meanwhile, beneficial bacteria can produce serotonin in the gut, which is often referred to as our happy neurotransmitter."

2. Frequent colds and viruses

"The immune system within the gut is our first line of defence against harmful viruses entering into the bloodstream and making their way around the body. Firstly, ensure that you are eating a healthy diet of whole foods, consuming a rainbow of different coloured vegetables and healthy proteins such as oily fish, grass-fed meats and legumes, alongside drinking plenty of water. Additionally, consuming fermented foods daily such as sauerkraut and kimchi which contain high numbers of beneficial bacteria could help to keep our gut flora in balance and improve digestive and immune function."

3. Eczema

"If there is an overgrowth of bad bacteria in the gut, this could lead to inflammation and damage to the intestinal lining. The intestinal barrier acts as our first line of defence keeping out toxins, undigested food particles and pathogens from entering into the bloodstream. If there is damage to this lining, the immune system, which is located in the gut, will need to be on high alert to try and stop these harmful products getting into the blood. An imbalanced gut flora, leaky gut and food allergies have all been associated with eczema."

4. Heartburn

"Heartburn happens when stomach acid is pushed up into the oesophagus causing a burning sensation. It is believed the cause is due to a relaxed sphincter between the stomach and oesophagus. Recently, another hypothesis suggested that in many cases it could be too little stomach acid which causes heartburn. This theory suggests that it takes longer for the stomach to break down the food; the undigested food then begins to ferment in the stomach producing gas which results in pushing up the stomach acid into the oesophagus. Increasing digestive enzymes and stomach acidity may help to alleviate heartburn caused by low stomach acidity. These can be taken in supplement forms, or could potentially be increased naturally by drinking hot water and lemon or apple cider vinegar."

5. Bloating

"When bloating occurs, it suggests that the digestive system is not functioning optimally. Foods are not being broken down sufficiently, which slows digestion and increases bacterial fermentation leading to increased gases and gut distention. Live bacteria supplements, such as Bio-Kult, may help to improve digestion through the release of certain enzymes such as lipase, which breaks down lactose (milk sugars). They further help to increase acidity, which helps improve absorption. Always eat when you feel relaxed and turn off any distractions so you and your body can fully concentrate on digesting the meal in front of you."

6. Poor sleep habits

"Keeping a regular routine each day is beneficial for our natural circadian rhythm. Part of this routine includes eating at regular intervals through the day and avoiding eating too late at night. Eating foods rich in protein, especially those containing the amino acid tryptophan, can help to increase melatonin in the brain. Melatonin is our important 'relaxation' hormone necessary for us to get a good night's sleep. It is produced in the body in increasing quantities during the evening."

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7. UTIs

"More than 80% of cases of urinary tract infections (UTIs) such as cystitis are caused by the overgrowth of the bacteria E. coli normally originating from the digestive system. The consumption of cranberry has long been recommended for the prevention and treatment of UTIs including cystitis."

8. Thrush

"The predominance of lactobacilli in the vagina is known to create an acidic environment that protects women from infection. Studies have shown that vaginal flora low in lactobacilli may lead to conditions such as bacterial vaginosis, thrush and UTIs. Beneficial, good bacteria are known to reinforce the gut and vaginal flora."

9. Weight gain

"The bacteria in our guts can have a huge influence on what foods we crave and how much weight we gain. An imbalance in the intestinal microbiota and lower bacterial diversity is repeatedly observed in obese compared to lean individuals. The microbiome of someone obese appears to have an increased capacity to harvest energy from the diet."

10. Hay fever

"Hay fever is associated with an oversensitive immune system, of which 70% is located in the gut and influenced by the diversity of our gut microbes. It is not surprising therefore, that there appears to be a link between the severity of such allergies and the health of our gut. Probiotics have been shown in studies to help rebalance the gut flora and support a healthy immune response. One study reported that hay fever sufferers given a lactobacilli probiotic for just five weeks saw significant improvement in quality of life, and in particular a reduction in runny eyes."

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<p>Think that 100-percent whole-grain English muffin with peanut butter is going to satisfy you 'til lunch? Not a chance. "'Whole-grain goodness' is anything but," says Perlmutter. "Bread, even the whole-grain kind, is extremely high on the glycemic index and will elevate your blood sugar even more than a Snickers bar."  </p><p>It sounds crazy, but it's true: Whether it's a candy bar or whole-grain foods, bombarding your body with too many carbs will raise your insulin levels, which  in turn can lead to weight gain and more serious health conditions like insulin resistance and eventually diabetes. "Insulin is a hormone produced by the pancreas that ferries glucose (or sugar) into the cells, where it can be used as fuel," explains Perlmutter. In a healthy body, when all the glucose and nutrients from food are absorbed, insulin levels drop and remain at a normal, low level, keeping hunger in check. </p><p>But if you overload on too much glucose, eventually your cells <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1083868/">become resistant</a> to insulin's signals to retrieve glucose from the blood. This forces your body to store that excess glucose as fat, you gain weight, and your appetite goes unchecked.</p>