The following is an educational presentation with little humorous or geek value. Reader discretion is advised.
Greetings assembled sentients! I am Tenzil Kem of Bismoll, although I expect you will all know me from my Legion of Super-Heroes codename Matter-Eater Lad. I'm sure we all recognize that the most expedient passageway to the positive emotional response center is via the sustenance processing mechanism. Certainly the United Planets does, which is why I've been asked to run this seminar on intergalactic diplomacy through the culinary arts. Since bipedal Caucasoids make up a mathematically improbable proportion of known life, we will begin with their nutritional perimeters.
Food is an essential part of the "human" experience, and ranked alongside oxygen within Maslow's hierarchy of needs. The most efficient and often delicious food source for the humanoid is the carbohydrate molecule, composed of carbon, hydrogen and oxygen. A single carb molecule, called a monosaccharide, is so simple and potent that it need not even be digested. However, this simple sugar will cause spikes in energy rather than a consistent resource pool, and should be employed sparingly. A couple of examples are fructose, derived from fruits or honey, and galactose (no relation,) found in the lactate of some animals.
The most important single carb is glucose/dextrose, the blood sugar that powers body cells, which you can combine with a monosaccharide to form a disacchardide. Glucose and galactose form lactose, of which which many humans are sadly intolerant, even though it helps strengthen bone, produce the vitamin K, and promote the growth of helpful gastrointestinal flora. Glucose and fructose form sucrose, often referred to as simply "sugar." Technicians can also convert glucose and fructose into a powerful narcotic which has been outlawed on Earth since the 21st century, but you can still find scofflaws producing high fructose corn syrup from rural stills. You can also string a couple of glucose together, but the resulting maltose isn't naturally occurring, and is mostly used by industry for additional flavoring and color.
You have to include glucose in all disacchardides, and they all break back down into glucose during digestion. Once blood sugar levels rise after eating, the pancreas secretes insulin, which directs glucose out of the bloodstream and into cells. The postprandial period follows a meal, in which bodily processes regulate the flow of glucose to maintain an even keel, sugarwise. Ingested fructose and galactose are converted to glucose and gradually released from the liver as blood sugar levels drop in the body, under the direction of the pancreas when it secretes glucogon.
Once you start getting more complex with your carbohydrate strings, you can really start cooking with polysaccharides. For instance, after plants synthesize glucose, they store some in the form of starch. These can be found in grains, which remain Earth's major food crop, and the foundation of all Earthling diets. There are also starchy vegetables, like potatoes, dried peas and beans. Starches begin to digest through saliva, but most of the work is done in the small intestine. 95% of starch ingested by humans is digested within 1-4 hours. Whatever doesn't pass muster is eliminated through stool.
The animal equivalent to starch is glycogen, but it's tough to come by, because it converts to lactic acid during the slaughtering process. If you get the chance to eat, say, a cow whole, you'll note an unfamiliar sweet tang. You can find a bit in some shellfish, as well. Animals store glycogen as an energy source between meals. The human liver breaks the stuff down to maintain consistent blood sugar levels.
Finally, there's fiber, which cannot be digested by human enzymes. Instead, it helps control blood fats (cholesterol,) serves as an energy source for colon bacteria, and generally aides in waste elimination. It is very important to remember that because fiber varies in solubility and impairs absorption of some minerals, it must be used in moderation. Thirty grams daily is recommended, with plenty of water, or the fiber will bunch up and inhibit elimination.
Per Galactipedia, "Human homeostasis refers to the body's ability to physiologically regulate its inner environment to ensure its stability in response to fluctuations in the outside environment and the weather." Part of your role in this process is to consult the Glycemic Index, which organizes foods based on their impact upon blood sugar. Sugary foods are good for high spirits, but the crash that follows can be leveled out by other foods. Also, your menus should cater to specific needs, as an athlete will burn through massive amounts of carbs, while a diabetic will have to make up for an excess of sugar elsewhere in their diet. Ultimately, glucose metabolism will have to balance out the need to burn energy (catabolism) and build compounds for other bodily purposes (anabolism.) Carbs provide the raw energy payload, with glucose exclusively providing all human brainpower.
In the event that the human body is deprived of carbohydrates, it will begin to devour any resident fats or proteins. Without glucose, fats cannot be completely broken down. The acidic intermediate fat compounds are called ketone bodies, which will accumulate in the bloodstream to cause fatigue, nausea, the absence of appetite and dehydration.
When crafting a human diet, consider that it is recommended that carbohydrates make up 45-65% of total caloric intake, to the tune of about 130 grams daily. Added sugars should not exceed 25% of total calories, and 14g of fiber should be included in every 1,000 calories ingested. Male bipeds typically need more fiber, so you might target them with 38g daily, and fems should receive 25g. Healthy selections include whole grains and fibrous fruits & vegetables.
Humans do have a sweet tooth, which can be accounted for through discretionary calories within a diet and with sugar substitutes. Sugar alcohols are roughly half to three quarters as sweet as sugar. They are incompletely absorbed by the body, so that they only account for 1½-3 calories per gram and are less impactful on blood glucose. They can give folks the runs, though. There are also synthesized nonnutritive sweeteners with zero glucose impact or caloric value.
Already beings, go out there and play with some monosaccharide. We'll meet back here next week to discuss protein...