i suffered from terrible fatigue and brain fog for a couple of years. there were days it was so bad my entire body hurt, i could hardly move or think. tehre were days i couldn't even drag myself from my bedroom to the bathroom.
i experimented with whatever i could find, such as liver cleansing and natural stimulants and homeopathy etc., but nothing helped
i realize now that i stayed stuck with teh wrong general practitioner for too long, who didn't take me evry seriously and blamed it all on stress (i didn't even have any stress in my life, apart from my health).
i finally was so lucky to end up with a homeopath who suggested i took a food allergy test. I didn't even believe in food allegies, but i accepted, although 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 semi-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 dairy, but toally eliminating it: if you have a serious allergy, the tiniest bit can provoke the same reaction as a big amount.
i hope this helps some people.