My girlfriend was told by a guy she works with that if you drink water (or whatever) with your meal, you prevent your body from absorbing the nutrients in the food because you are flushing it away with the beverage? Is this true? What if you are eating tacos? Are you supposed to enjoy them for the sheer taste of it… and just let your mouth burn and burn and burn?
The guy your girlfriend works with is an idiot with no knowledge of anatomy or nutrition. Wash the nutrients away to where? The system is rather lengthy, and complex. Any nutrients “washed away” from the stomach would be caught by the intestines. Drink all you want, be it water or wine. It won’t hurt you nutritionally.
ps: for hot foods, drink milk, or eat yogurt. Water just aggravates the problem.
Alcohol
I wouldn’t say “drink all the wine you want”. Alcohol is a mild toxin, which in large doses can affect nutient absorption. With moderate consumption, the effect is modest and can be ignored (a normal balanced diet contains more than adequate amounts of essential nutrients; a slightly better absorption rarely makes any difference, because we are rarely balanced on the cusp between adequate and inadequate) Heavy alcohol consumption is associated with malabsorption syndromes and poor nutrition. It was once believed that this was because “alcoholics don’t eat well” but this seems to have been an over-simplification. heavy drinkers can develop anemia due to malabsorption (and other causes), and often have gastrointestinal and liver complications, since the GI tract and liver bear the full brunt of all alcohol you consume
Alcohol also specifically interferes with cell membrane processes in general. This is the major theory for intoxication: unlike many intoxicants, alcohol and its metabolites do not have a specific receptor in the nervous system or elsewhere, but achieves its effects because, as a small molecule that is less polar than water, it can enter or partly disrupt membranes in neurons, which are heavily membrane dependent (the neural electrical impulse is actually just a tightly controlled transfer of a tiny number of the ions closest to the membrane - NOT an electric current like an electric wire)
absorption of nutients is also heavily cell-membrane dependent. The luminal side of the intestinal lining (the “inside” surface) is sudded with transport molecules that actively and passively absorb various substances, and the vascular side (the “outside”) is similarly specialized to pump those nutrients into the blood. Mess with membranes too much, and you mess with absorption, especially since the cells are suffering the other mildly toxic effects of alcohol as well.
But again - there’s nothing wrong with modest alcohol consumption with meals. It may actually have health benfits - but moderation is crucial!.
Water
Drinking water with meals actually aids digestion. Mechanically, it assists the stomach in liquifying the meal, which aids further processing and absorption in the intestines. Chemically, it assists the primary breakdown process of digestion: hydrolysis.
Both enzymes and stomach acid primarily break down proteins (into amino acids) and complex carbohydrates (into by simple sugars) by “breaking bonds and adding a water molecule” (hydrolysis), because the fundamental reaction in building starches and proteins is a “dehydrating condensation” - fancy talk for “break a -OH off one molecule, break a -H off the other molecule, and stick the broken ends together” (the leftover -OH and -H then form H-OH or H2O, water) If you want to recover the amino acids or sugars, you have to add the (broken) water molecule back.
I’ll summarize the chemistry in a box for those who care, but feel free to skip over it, if you don’t.
If you don’t drink water with your meal, your GI tract will secrete enough to do the job, but adding the water with the meal is useful, both mechanically and chemically.
BLOODSTREAM
Perhaps more to the point, where does the water you drink come out?
Sure, some comes out in your feces (resorbing water is part of your colon’s job) or evaporates from your eyes, mucous membranes, lungs (in your exhaled air) or sweat – but if you’re drinking enough water, most comes out as urine. The kidneys produce urine by filtering your blood, so nutrients can’t be "washed away in urine unless they were in your blood. If they were in your blood, they were available to your body - which is all you can ask for, right?
This last principle applies to all nutrients (vitamins, minerals, etc.)
This is old, but it enjoyed a renewal of popularity some years ago with Harvey Diamond’s “Fit for Life.” Another of his pillars (like “don’t drink water with your meals, etc.”) was certain foods should not be eating in combination with certain other foods. Something about they cause your body to produce conflicting enzymes or something like that, with the result being that your body doesn’t derive all the nutrition that it could.