i see this is an old thread yet i choose to reply because my experience may be useful to some people out there.
i suffered from terrible fatigue and brain fog for a couple of years. there were days it was so bad i could hardly move or think. of course my general practitioners didn't take me seriously and i experimented with whatever i could find, such as liver cleansing and natural stimulants and homeopathy etc., but nothing helped
then i ended up with a homeopath who suggested i took a food allergy test. I didn't even believe in food allegies, but i accepted, even though that sort of blood test isn't reimbursed by health insurance. The test showed a big allergy against milk, yoghurt, cheese and ferments. As a vegetarian, i used to eat big amounts of dairy and fermented soy...
I immediately removed all dairy and ferments from my diet, and in a few days time all fatigue was completely gone.
It's been for 8 months now that i'm on my new diet, and there hasn't been a single day of fatigue or brain fog, apart from a few times when i experimented eating a tiny bit of yoghurt or cheese, and a few times that i ate it without realizing it.
I wouldn't believe it if I hadn't experienced it, but even the tiniest bit of dairy makes me feel posioned: totally exhausted, almost as if I've drunk a bottle of alcohol.
Of course not everybody who suffers from fatigue suffers because of dairy allergy or intolerance, but i am sure that there must be more people for whom it's the case.
I think it's regrettable that doctors do not automatically test for food allergies. And i recommend everybody who suffers from fatigue to have such a test done, or to experiment leaving out all dairy.
Remember, it's not a matter of reducing: if you have a serious allergy, the tiniest bit can provoke the same reaction as a big amount.
