Friday, December 5, 2008

Drink enough water, but don't overdo it or you could die

You gotta have water, but don't drink so much so quickly and be sure you're getting enough electrolytes.

Proper hydration and intake of electrolytes are necessary for maintenance of homeostasis. And severe water and electrolyte loss can occur due to excessive sweating, vomiting or diarrhea. If water is replaced by plain water without electrolytes, then body fluids can become even more dilute. For this reason, oral rehydration therapy solutions include a small amount of table salt to avoid body fluid dilution.

Water intoxication occurs when a person consumes water steadily and faster than the kidneys can excrete the water or when renal function is poor. The water accumulates in the body, the excess causes cells to swell, which may produce convulsions, coma and death.

No scientific consensus has been reached on how much water should be consumed daily. The safest recommendation is half your body weight in ounces (e.g. 100 lbs = 50 oz). Drink a little more if you're losing more water daily due to exercise or if it's bloody hot, like in Arizona.


Tortora GJ, Derrickson B. Principles of Anatomy and Physiology, 11th ed; 2006. New York: John Wiley & Sons; p1041.

Thursday, December 4, 2008

Olestra, Frankenstein fat substitute

Who knew that when Procter and Gamble accidentally created Olestra by attaching up to eight fatty acids to regular table sugar, they had also created a monster? While the molecule tastes and looks like fat to the human eye, in the body its freakishly spiderlike structure can't be broken down at all, thus, the intestine cannot absorb it for caloric energy.

After a fatty meal, the body doesn't even really start digesting the triglycerides until they reach the small intestine (although there is a bit done by saliva and stomach fluid) [1].

As fats reach the duodenum, they form into large globules that stimulate secretion of bile from the liver that emulsifies them into tiny globules or droplets [1p716]. A protein called colipase binds to the droplets, which allows various enzymes called lipases secreted by the pancreas to access them more easily [1p779]. Lipases hydrolyze triglycerides freeing a couple of the fatty acids from their glycerol backbone so that both the monoglyceride and fatty acids can be transported by intestinal cells [1p716].

It's not a perfect system. The hydrolysis is absolutely necessary for absorption, but then those fatty acids and monoglycerides are just made into triglycerides again [1p716]. But in the bloodstream they can be hydrolyzed again to be degraded by beta-oxidation into acetyl CoA for production of ATP or, as witnessed by my love handles, can be stored in adipose tissue [1].

Unlike triglycerides, Olestra would never be broken down or absorbed at all because it is unrecognizable to colipase and lipases. The colipases are particular in binding to droplets, and lipases, like all enzymes, are specific in the way of binding to substrates [1p639].

The "fake fat", thus, is pooped out as slimy diarrhea and, along with it, fat-soluble nutrients.  Yes, it's true, those P&G snacks are fortified with extra vitamin A and D to cancel out the leaching. 

But, because they're not vitamins, fortification does not include carotenoids such as lycopene, which is hugely beneficial to prostate and heart health. According to FDA, eating Olestra products can significantly reduce carotenoids in the body.[3]   


1. Denniston KJ, Topping JJ, Caret RL. General, Organic, And Biochemistry, 5th ed. New York: McGraw Hill; 2007.
2. Cutting edge. "Fat Blockers". Interactive Concepts of Biochemistry. Available at Accessed on October 4, 2008.
3. Olestra and the FDA. NEJM. Volume 335:668-670.