You are probably drinking too much water. Dr. Laszlo Boros strongly warns against drinking water habitually or in large quantities without the natural cue of thirst. This directly contradicts much of the conventional hydration advice that encourages people to drink three liters of water per day, a gallon per day, or hit a predetermined hydration target. He considers environmental water one of the sneakiest sources of deuterium because it enters the body directly. Unlike food, it arrives without carbon. It absorbs into tissues and mixes directly with your cytoplasmic water. This matters because the body is already designed to produce its own deuterium-depleted water. Every day. As mitochondria combine protons with oxygen, they create metabolic water inside the mitochondrial matrix. According to Dr. Laszlo Boros — Hungarian medical biochemist, retired professor at UCLA School of Medicine, author of 100+ peer-reviewed papers and one of the world's leading deuterium researchers — this is the most important water in the body. And the amount of metabolic water you produce depends heavily on the fuel you burn. Approximately 100 grams of fat generate around 110 grams of metabolic water. 100 grams of carbohydrates produce only around 55 grams. Nearly half as much. Fat produces substantially more metabolic water per unit of food consumed. This is one reason Boros spends so much time discussing fat metabolism and follows a carnivore ketogenic diet himself. Excessive water intake creates a different problem. According to Boros, drinking too much water — especially without salt — lowers blood osmolarity, which causes the brain to swell. The pituitary gland sits inside a tight bony compartment at the base of the skull called the sella turcica. When the brain swells from excess water, it physically compresses the pituitary gland inside this rigid bone. That can shut down its ability to release crucial hormones. Because the pituitary regulates sex hormones, fertility hormones, and thyroid-stimulating hormones, overdrinking can disrupt the entire endocrine system and contribute to chronic conditions like infertility and autoimmune thyroid issues. The most critical hormone affected is antidiuretic hormone (ADH), also called vasopressin. ADH normally signals the kidneys to reabsorb and preserve the body's own deuterium-depleted metabolic water. Without ADH, your body cannot hold onto its clean water. Boros points out that if you drink a liter of water in 30 minutes, you will simply pee it right back out. Because people constantly suppress ADH by forcing themselves to drink water, Boros notes that the average American has an ADH level of about 0.6, compared to a normal level of 1.0. In his view, the general population has essentially given itself a water-wasting disease called diabetes insipidus. Diabetes insipidus is a condition where the body cannot properly balance fluid levels, leading to excessive production of large volumes of urine and intense thirst. The downstream consequence is not just water loss. The suppression of these metabolic regulators can contribute to the buildup of visceral and subcutaneous fat. To show how dangerous overriding thirst can become, Boros gives an extreme example. A mother in New Jersey took her kids on a mountain walk and drank approximately 1.5 liters of water in 15 minutes. The rapid water influx caused severe brain swelling. By the time she drove back to her garage, she fell into a coma and died. Extreme case. But the principle is clear. More water is not always better. Now, the natural objection arises: "What about the studies showing performance drops before thirst kicks in? You can't rely on thirst — it lags behind the actual need." Boros addresses this directly. His argument: Those studies were almost certainly run on subjects whose ADH system was already suppressed from years of chronic overdrinking. If you have spent years forcing yourself to drink 3-4 liters a day whether thirsty or not, you have gradually damaged your hypothalamic cells' ability to produce ADH. It takes approximately six months of gradually reducing water intake to restore ADH production to normal levels. A subject with suppressed ADH entering a dehydration study will show impaired performance before thirst — not because thirst lags, but because their thirst signal itself is broken. They lost the ability to produce sufficient ADH — the key hormone in the hypothalamic system that drives both water retention and thirst signaling. Prime the subjects correctly — gradually restore their ADH production before the study begins — and Boros argues you would see a completely different result. The studies are not wrong. They are measuring the wrong population. Boros does not see a reason to drink water when you are not thirsty. Thirst is the signal. It tells you when to drink. It also tells you when to stop. His argument is not that people should restrict water. His argument is that people should stop overriding the signals that evolved to regulate it. This is an important distinction. Boros is not saying: Don't drink water. He is saying: Drink when thirsty. Drink enough. Then stop. Even Dr. Gabor Somlyai's deuterium-depleted water protocols in his book "Deuterium Depletion" recommend around 1.5–2 liters per day. Not a gallon per day. Not constant hydration. This is the researcher who has followed 2,649 cancer patients over 32 years and whose company sells deuterium-depleted water. If anyone had an incentive to recommend drinking more of it, it would be him. Yet his protocols still recommend around 1.5–2 liters per day. Thirst is a precise physiological signal. Just like hunger. Like sleepiness. You don't go to sleep just because a bed is in the room. The body already knows when it needs water. The problem begins when we stop listening.