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In order to study the relationships among variables, observational studies are performed. Unlike controlled experimental designs where only certain variables are allowed to vary (at prespecified levels), in observational studies the variables are observed and recorded. Often some of the variables are controlled as much as possible. Consider a long term study on a drug involving humans where a variable that needs to be controlled is diet. The diet guidelines are set but these will probably be broken from time to time (or maybe often) by some of the human subjects. Contrast this with a lab setting, where the diet of animals can be controlled. In observational studies, cause and effect are hard (often impossible) to establish. But associations and predictabilities among variables can be investigated. Such associations and predictabilities may be further studied in a lab setting.

A sleep disorder characterized by the repetitive collapse of the pharyngeal airway during sleep yielding hypoxia and hypercapnia, with arousal being required to re-establish airway patency.

Not manifest or detectable by clinical methods alone

Ochratoxin A, B, and C are mycotoxins produced by some Aspergillis species and Penicillium species. Ochratoxin A, a human carcinogen, is known to occur in food and beverages such as cereals, coffee, dried fruit and red wine.

Painful swallowing

A type of elimination diet used to test for multiple food intolerances by selectively limiting food choices.

A carbohydrate which on hydrolysis yields a small number (from two to four or as many as 10, according to various authorities) of monosaccharides. Two examples are fructo-oligosaccharide (FOS) and galacto-oligosaccharide (GOS).

A subnormal concentration of spermatozoa in the penile ejaculate.

The maximum amount of weight that can be lifted one time with correct form during a standard weight lifting exercise.

The loosening of the nail from the nail bed.

The softening of the nails.

The splitting of the nail in layers.

Opinion and column page usually opposite the editorial page.

An open-label study is where both the researchers and the study participants know which treatment each individual is receiving.

Itching and swelling in the mouth and oropharynx associated with pollen allergies, especially to birch, grass, ragweed and mugwort as a result of eating a fruit or vegetable which cross-reacts with pollen.

Special combinations of water, carbohydrate, sodium, potassium, chloride, and a base precursor in an osmolar or hypoosmolar solution that help rehydrate the body when fluid has been lost due to diarrhoea. ORS vary primarily in their carbohydrate and sodium content.

The preferred method of treating dehydration in infants who have diarrhea due to acute gastroenteritis. It includes a rehydration phase in which stool losses of fluid and electrolytes are rapidly replaced enterally with an oral rehydration solution (ORS), and a maintenance phase, which involves replacement of continuing fluid and electrolyte losses with ORS to prevent further dehydration, and continued feeding to achieve adequate dietary intake

Pesticide category that persist in the environment long after use. Banned pesticide orgnochlorines include DDT, aldrin, dieldrin, and heptachlor. Some of these chemicals were banned as pesticides in the 1970s.

The pathological obsession with eating biologically pure and healthy food. Ref: Bratman S. Original orthorexia essay.

a bone-forming cell

A condition of impaired mineralization caused by vitamin D and calcium deficiency.

A condition of too little bone mass during any stage of life.

Outcomes research seeks to understand the end results of particular health care practices and interventions. End results include effects that people experience and care about, such as change in the ability to function. In particular, for individuals with chronic conditions—where cure is not always possible—end results include quality of life as well as mortality. Outcomes research is also referred to as medical effectiveness research or outcomes and effectiveness research.

An allergen found in egg white. Ovalbumin is a glycoprotein.

Adults: BMI greater or equal to 25 kg/m2 Children and adolescents: BMI for age = 85th percentile and < 95th percentile

An eating pattern based on grains, vegetables, legumes, seeds, nuts, and eggs but excludes meat, fish or fowl and dairy or products containing these foods.

An allergen found in egg white. Ovomucoid is a glycoprotein.

Oxidative Stress is defined as an imbalance between the production of various reactive species and the ability of the organism's natural protective mechanisms to cope with these reactive compounds and prevent adverse effects.