What is Candida Overgrowth and what causes it?
A yeast overgrowth is when Candida Albicans grows out of control in your gut. If the balance of bacteria in your gut is altered and there is not enough good bacteria (lactobacillus acidophilus and Bifidobacterium), then yeast has the freedom to grow. Candida yeast attaches its roots to your stomach lining and grows and if there are not enough good bacteria, then the yeast will infiltrate into other areas of the body such as organs and tissues, including the brain and kidneys. The yeast feeds off sugar allowing it to grow, so the more sugar you consume, the more of an issue there will be.
The following are causes of Candida Overgrowth:
A high-refined sugar diet
A western diet provides vast amounts of sugar that Candida needs to survive and thrive. That includes sugar itself, foods containing sugar, and also anything that converts to sugar. Refined carbohydrates, like white flour, and even fruits can all contribute to Candida overgrowth. If you have a great immune system, then you should not experience Candida problems, but if you have a high sugar diet, then you are depressing your immune system leaving it vulnerable to yeast problems.
When we take antibiotics we take them to kill off an infection and the bad bacteria that is causing the infection. Unfortunately, the antibiotics cannot differentiate between the good bacteria and the bad bacteria. Therefore, the antibiotics kill everything in sight within the area of infection, which causes the balance of good bacteria versus the bad bacteria to be affected. As with everything, we need balance but by killing them all off, the alter in balance allows for harmful bacteria’s to grow at a rapid pace. If you do not replace the good bacteria, then you can overtime encourage the bad bacteria to multiply by eating too many refined sugary foods and drinking too much alcohol.
Sometimes my vaginal thrush would flare up if I was stressed. Stress affects your body and it can lead to excess Candida. One of your body’s first reactions to a stressful situation is to release Cortisol, a hormone that depresses your immune system and raises your blood sugar level.
The Candida yeast feeds on the extra sugar, while your weakened immune system is powerless to stop it. Stress gives it the chance to overpower the existing gut flora in your small intestine. 
High consumption of alcohol
Alcohol use in excess kills off friendly bacteria, increases toxic overload of the Liver, and allows Candida overgrowth. Yeast is an alcohol by-product. People with extreme Candida overgrowth can have high blood alcohol levels and be drunk, just from eating sugar. This moderate “high” is one explanation for intense sugar cravings. There is another intriguing aspect to alcohol and yeast. Every living thing that eats must create waste on the other end. Usually, that waste is toxic (poisonous) to the organism. Not so with yeast. The alcoholic by–products it creates can serve as a fertiliser to help it grow further, and this explains why various researchers have indicated that everyone who drinks alcohol regularly (daily or a few times weekly) is likely harbouring Candida overgrowth. 
Low immune System
A weak immune system means that the body’s ability to fight various threats and disease is impaired. What is less known about a low immune system, is that overtime, having a weakened immune system can lead to dangerous health conditions that are usually easy to prevent, but much harder to treat once developed. Candida is one of those health conditions. 
The Contraceptive Pill
In other sufferers, the contraceptive pill can link to Candida. The intestines are delicate organs, containing a broad mixture of microorganisms and yeasts that all help to process and digest food. They depend on the right environment to support them, and this equilibrium can be thrown off by the hormonal imbalances caused by the contraceptive pill. By disturbing this balance, the contraceptive pill opens the door for Candida to again outgrow its competitors in the gut. Oestrogen, the main ingredient in the contraceptive pill, is known to promote the growth of yeast. If you need evidence of how this can happen, see how many women get regular yeast infections while on the pill. It’s precisely the same principle and is documented by multiple research studies. 
Science can now prove that during pregnancy the flora in our gut is altered. According to Live Science and Ruth Ley of Cornell University:
“They found that bacteria typically linked with good health decreased over the course of pregnancy, while bacteria associated with diseases generally increased. In addition, signs of inflammation in the gut increased. These changes in gut bacteria may play a role in changing a pregnant woman’s metabolism, the researchers said. Two changes that happen during pregnancy are an increase in the amount of body fat, and reduced sensitivity to insulin, the hormone that controls blood sugar.” With the changes to the bacteria in our gut and an increase of the bad bacteria, then it is likely that as a result we will experience a yeast infection (vaginal thrush).