Water

The conventional guideline of drinking eight glasses of water a day has proven to be a myth. But there is such thing as drinking too much water. Water intoxication occurs when a person drinks so much that the water dilutes the concentration of sodium in the blood, creating an electrolyte imbalance.

Water intoxication, known as hyponatremia, is mostly a risk for endurance athletes. A 2005 article in the New England Journal of Medicine found that 13 percent of 488 runners in the 2002 Boston Marathon developed hyponatremia from drinking too much water. According to the researchers, a relatively simple strategy to reduce that risk would be for runners to weigh themselves before and after training runs, in order to gauge their overall fluid intake and ensure they do not drink too much water during exercise.

An unusual and fatal case of water intoxication occurred in 2007 when a California woman reportedly drank too much water during a "Hold Your Wee for a Wii" radio station contest.

Nutmeg

The light dusting of nutmeg on your eggnog has practically no effects aside from making your beverage more delicious. However, trouble kicks in when the spice is consumed in excessive quantities as a low-cost hallucinogenic drug.

Unpleasant side effects usually appear three to eight hours after ingestion, and can include anxiety, fear, and a feeling of impending doom. According to a case report published in Emergency Medicine Journal in 2005, some people may also experience acute psychotic episodes, detachment from reality and visual hallucinations.

Nutmeg, even in doses as high as 20 to 80 grams of powder, is rarely deadly. There were only two reports of fatal nutmeg overdoses in medical literature. The first was reported in 1908 and involved about 14 grams ingested by an 8-year-old. The second case involved a 55-year-old and was reported in the journal Forensic Science International in 2001. Toxicology tests found traces of myristicin (a compound found in the essential oil of nutmeg) and flunitrazepam (a powerful sedative) in her blood. Her death was likely due to the combined toxic effect of both substances, the report said.

Carrots

Carrots are full of vitamins, minerals and fibers that are good for your health. But eating too many carrots can bring in too much beta-carotene the molecule responsible for carrots' bright orange hue and a precursor of vitamin A. This can lead to excess blood carotene which can discolor the skin.

Known as carotenemia, the condition occurs because carotene is a fat-soluble molecule. Excessive quantities of it tend to accumulate in the outermost layer of skin, resulting in yellow- or orange-pigmented skin, particularly in the palms, soles, knees and nasal area.

Although carotenemia occurs mostly in infants when they are fed too much pureed carrot baby food, it can occur in adults as well. In a case report published in The Journal of Dermatology in 2006, a 66-year-old woman's skin turned yellow-orange after she took too many carotene oral supplements. One cup of raw chopped carrots has about 15 mg of carotene, according to the U.S. Department of Agriculture's Nutrient Database, so you'd need to eat half a cup of chopped carrots every day for months, in order to turn to her shade of yellow.

Despite such dramatic outward appearance, carotenemia is a mostly harmless condition and it is often reversible.