An opiate, according to Wikipedia, "describes any of the narcotic opioid alkaloids found as natural products in the opium poppy plant." So, an opiate must be an alkaloid, and must come from the poppy plant. Examples of opiates are morphine and codeine. Heroin is a synthetic opiate made from morphine. Prolonged use of opiates causes physical dependance and addiction. Death can occur from overdose. Abrupt abstinence from opiates causes withdrawal symptoms including agitation, headaches, sweats, cramping, diarrhea, nausea, and vomiting.
An opioid, according to Wikipedia, is a "psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract." So opioids are a larger class of chemicals that include opiates. Our bodies can make their own opioids, e.g. endorphins. Depending upon the particular opioid, prolonged exposure can lead to physical dependance and addiction; death can occur from overdose (e.g. the poppy derivatives); and abrupt abstinence can spur withdrawal symptoms. The effect of the opioid depends upon its chemical structure, the actions its receptors initiate, the exposure level, the genetic makeup of an individual, and an individual's gender, age, and biochemistry. There are clearly a number of variables to assess when determining an opioid's effect.
Opiates and Opioids In Food
Dr. William Davis of the Track Your Plaque site, and author of the recent "Wheat Belly," says that wheat contains an opiate which is responsible for what he describes as wheat addiction. He identifies the protein gliadin as the opiate, and says:
"This opiate, while it binds to the opiate receptors of the brain, doesn’t make us high. It makes us hungry."From the definitions at the beginning of this post, I wouldn't have said gliadin was an opiate because it doesn't originate from the poppy plant and it is not technically an alkaloid, although it does contain nitrogen.
- Opiate Of The Masses, April 18, 2012
However, when the body digests gliadin, it produces a fragment peptide that can act like an opioid, called gliadorphin or gluteomorphin.
Gluten, another protein in wheat (gluten is composed of gliadin), when partially digested produces fragment peptides that can also act as opioids, called gluten exorphins.
There is a protein in cow's milk called casein which, when partially digested, produces a fragment peptide that acts like an opioid, called casomorphin.
There are proteins in whey called α-lactalbumin and β-lactoglobulin, which, when partially digested, produce fragment peptides that act as opioids, called α-lactorphin and β-lactorphin.
There is a protein in blood called hemoglobin which, when partially digested, produces a fragment peptide that acts like an opioid, called hemorphin.
There is a protein in green plants, algae, and some bacteria called RuBisCO. It's an enzyme that assists in taking carbon from the atmosphere and converting it into carbon-containing energy molecules like glucose. RuBisCO, when partially digested, produces fragment peptides that act as opioids, called rubiscolins. The structure of 2 rubiscolins have been identified in spinach, although RuBisCO from which rubiscolins are derived is abundant in nature.
Salt, Sugar, and Fat: The Hyperpalatable Combination
All of the opioid peptides above come from outside the body and are thought to be short-lived. In healthy people they're broken down soon after formation and "have limited physiological activity." Also, peptides are fairly large molecules and don't easily squeeze through a healthy, selectively permeable intestinal wall.
When it comes to food cravings, opioids that come from inside the body may be the real players. Former FDA Commissioner and Harvard trained doctor Dr. David Kessler, in his book, The End of Overeating, says that salt, sugar, and dietary fat trigger opioids in the brain which can contribute to overeating.
"The neurons in the brain that are stimulated by taste and other properties of highly palatable food are part of the opioid circuitry, which is the body's primary pleasure system. The "opioids," also known as endorphins, are chemicals produced in the brain that have rewarding effects similar to drugs such as morphine and heroine. Stimulating the opioid circuitry with food drives us to eat."Here's an interview where he summarizes the ideas in his book:
In addition to their stimulating effects the opioids produced by eating high-sugar, high-fat foods can relieve pain or stress and calm us down.
In a cyclical process, eating highly palatable food activates the opioid circuits, and activating these circuits increases consumption of highly palatable food."
Dr. David Kessler, Author Of The End of Overeating, On Why We Can't Stop Eating
Two other points from Kessler's book:
1. It is the combination of sugar and fat in food which makes us crave it. Sugar alone and fat alone do not produce the same strong cravings as sugar and fat combined.
2. Variety may be doing us in:
"After eating a certain amount of one food, animals typically become satisfied with its taste and stop eating it - but they'll keep on eating if something else is available."
Josh Wooley, a neuroscientist at the University of California, San Francisco, demonstrated this with chocolate- and banana-flavored food pellets called Supreme Mini-Treats, which consist primarily of sucrose and fat.
He first allowed his test animals to eat as much chocolate as they wanted for an hour. Then he gave them ninety minutes of unrestricted access to both banana and chocolate, and he observed that the animals chose to eat significantly more banana. Apparently their initial exposure to chocolate had reduced but not eliminated further interest in that flavor, but left them enough appetite for the novel taste of banana. the same thing happened in reverse: When exposed first to banana, an animal later ate more chocolate when given the choice of flavors."
- Wheat does not contain opiates.
- Many foods contain chemicals that have the potential to engage our opioid circuitry (wheat, milk, cheese, yogurt, meat, spinach, lettuce, and other greens), but the effect in a healthy person, if any, is probably weak and short-lived.
- The body's endogenous opioids are pretty powerful.
- Stimulating the brain's opioid circuitry performs a useful function - it drives us to eat. But stimulating it often, with highly palatable foods, can drive us to overeat.
*Here's the follow-up: Food And The Brain. In a few words, eating a particular food often causes us to crave that food, in a positive feedback loop.