Nitrogen balance is a measure of nitrogen input minus nitrogen output: 

Nitrogen Balance = Nitrogen intake - Nitrogen loss

Nitrogen is a fundamental component of amino acids, which are the molecular building blocks of protein. Measuring nitrogen inputs and losses can be used to study protein metabolism. 

Lysine was shown to enhance the nutritive value of gluten for humans. 

The mean nitrogen balance index for gluten was 0.62. For gluten plus lysine, it was significantly higher, 0.76, approaching the value for casein.

Depending on which measurement system they used, wheat gluten protein was 80-100% digestible by (healthy) humans.

Based on what is currently known, it's a big leap to attributing autism and other problems to gluten, and an even bigger one to prescribing gluten-free eating as a treatment. It's possible that some people benefit from a gluten-free regimen for reasons that have less to do with gluten and much more to do with the structure involved in planning and sticking to such a strict eating plan.

In the context of celiac disease, gluten refers to the protein of grains capable of provoking an autoimmune response. Other grains also contain protein, but wheat, barley, rye, and spelt contain varieties that aren't broken down by digestive enzymes:

• in wheat, the difficult-to-digest protein is gliadin;
• in rye- secalin; 
• in barley - hordein.

In people with celiac disease, when they get absorbed into the walls of the small intestine, the immune system misreads the situation, views them as intruders, and unleashes a furious inflammatory response that damages tissue. 

For satiety choose whole fruit over smoothies and juices.

Solid fruits affect feeling of fullness more than pureed fruit or juice. Adding naturally occurring levels of fiber to juice do not enhance satiety.

Gut microbial composition depends on different dietary habits just as health depends on microbial metabolism, but the association of microbiota with different diets in human populations has not yet been shown.

Significant differences were found in gut microbiota between European children (EU) and that of children from a rural African village of Burkina Faso, , where the diet is high in fiber content, and is similar to that of early human settlements at the time of the birth of agriculture.

Burkina Faso children showed a significant enrichment in Bacteroidetes and depletion in Firmicutes, and a unique abundance of bacteria from the genus Prevotella and Xylanibacter, completely lacking in the EU children. Enterobacteriaceae (Shigella and Escherichia) were significantly underrepresented in Burkina Faso children.

In addition, we found significantly more short-chain fatty acids in Burkina Faso children. 

Gut microbiota might have coevolved with the polysaccharide-rich diet, allowing to maximize energy intake from fibers while also protecting from inflammations and noninfectious colonic diseases. 

One study found that 0.85 mg of calcium was lost for each gram (1 g) of protein in the diet. A meta-analysis of 16 studies in 154 adult humans on protein intakes up to 200 g found that 1.2 mg of calcium was lost in the urine for every 1g rise in dietary protein. A small but more focussed study showed a rise of 40 mg in urinary calcium when dietary animal protein was raised from 40 to 80 g. Urinary calcium to dietary protein ratio is 1 mg to 1g. The empirical observation that each 1 g of protein results in 1 mg of calcium in the urine agrees very well with the phosphorus content of animal protein (about 1 percent by weight).

This means that a 40 g reduction in animal protein intake from 60 to 20 g would reduce calcium requirement by the same amount as a 2.3 g reduction in dietary sodium, i.e. from 840 to 600 mg. 

How animal protein exerts its effect on calcium excretion is not fully understood. 

With the exception of calcium deficiency rickets in Nigeria, no satisfactory explanation has been found for the apparently low prevalence of osteoporosis in countries on low calcium intakes. On international comparisons on a larger scale, it is very difficult to separate genetic from environmental factors. Osteoporosis was largely a disease of affluent industrialized cultures. Hip fracture prevalence (and by implication osteoporosis) is consequently related to animal protein intake, but also, paradoxically, to calcium intake because of the strong correlation between calcium and protein intakes within and between societies. This could be explained if protein actually increased calcium requirement. 

Fracture risk has recently been shown to be a function of protein intake in North American women. There is also suggestive evidence that hip fracture rates depend on protein intake, national income, and latitude. Vitamin D deficiency in hip fracture patients in the developed world was established. Such fractures can be successfully prevented with small doses of vitamin D and calcium. It is therefore possible that hip fracture rates may be related to protein intake, vitamin D status, or both.

A survey of naturally occurring plant-derived food sources with high Vitamin B12 contents suggested that dried purple laver (nori, Porphyra yezoensis) is the most suitable Vitamin B12 source presently available for vegetarians.

The amount of total vitamin B12 in the dried purple laver was estimated to be 55 -59 mcg / 100 g dry weight. The purple laver contained 5 types of biologically active vitamin B12 compounds (cyano-, hydroxo-, sulfito-, adenosyl- and methylcobalamin), in which the vitamin B12 coenzymes (adenosyl- and methylcobalamin) comprised about 60 % of the total vitamin B12: 

• cyanocobalamin
• hydroxocobalamin 
• sulfitocobalamin 
• adenosylcobalamin 
• methylcobalamin 

Dried purple laver also contains high levels of other nutrients that are lacking in vegetarian diets, such as iron and n-3 polyunsaturated fatty acids. Dried purple laver is a natural plant product and it is suitable for most people in various vegetarian groups.

Food energy is chemical energy that animals derive from their food and molecular oxygen through the process of cellular respiration. Humans and other animals need a minimum intake of food energy to sustain their metabolism and to drive their muscles.

Organisms derive food energy from carbohydrates, fats and proteins as well as from organic acids, polyols, and ethanol present in the diet. Some diet components that provide little or no food energy, such as water, minerals, vitamins, cholesterol, and fiber, may still be necessary to health and survival for other reasons. 

Using the International System of Units, researchers measure energy in joules (J) or in its multiples; the kilojoule (kJ) is most often used for food-related quantities. An older metric system unit of energy, still widely used in food-related contexts, is the "food calorie" or kilocalorie (kcal or Cal), equal to 4.184 kilojoules. 

<>Fats and ethanol have the greatest amount of food energy per mass, 37 and 29 kJ/g (8.8 and 6.9 kcal/g), respectively. Proteins and most carbohydrates have about 17 kJ/g (4.1 kcal/g). 

Conventional food energy is based on heats of combustion in a bomb calorimeter and corrections that take into consideration the efficiency of digestion and absorption and the production of urine.