Whenever we learn something new or experience something pleasurable, our brain’s reward system becomes activated. With the help of natural brain chemicals, several brain areas communicate with each other to help us learn and repeat behaviors that improve our knowledge and well-being.

Relying heavily on the neurotransmitter dopamine, the reward system helps explain several quintessential human experiences, such as falling in love, sexual pleasure, and enjoying time with friends.

However, certain substances, such as drugs, hijack the brain’s reward system, “artificially” activating it. Telling the brain to repeat pleasure-seeking behavior constantly is the mechanism behind addiction.

But is sugar such a substance? And if so, does it help explain sugary food cravings?

A United States scientist named Theron Randolph coined the term “food addiction” in the 1950s to describe the compulsive consumption of certain foods, such as milk, eggs, and potatoes.

Since then, the studies exploring this concept have yielded mixed results, and some experts argue that speaking of food addiction is a bit of a stretch.

New research helps shed some light on the matter, as Michael Winterdahl, associate professor at the Department of Clinical Medicine at Aarhus University in Denmark, and his colleagues examined the effect of sugar intake on the reward circuitry in the brains of pigs.

The researchers published their findings in the journal Scientific Reports.

‘Major changes’ after 12 days

The scientists analyzed the effects of sugar intake on seven female Göttingen minipigs, using complex PET imaging techniques with opioid receptor agonists and dopamine receptor antagonists to examine the animals’ brain reward systems.

The team gave the minipigs access to a sucrose solution for 1 hour on 12 consecutive days and then retook the scans 24 hours after the last sugar dose.

In a subgroup of five minipigs, the team applied an additional PET scanning session after the first exposure to sugar.

“After just 12 days of sugar intake, we could see major changes in the brain’s dopamine and opioid systems,” reports Winterdahl.

“In fact, the opioid system, which is that part of the brain’s chemistry that is associated with well-being and pleasure, was already activated after the very first intake,” adds the study’s lead author.

Specifically, there were alterations in the “striatum, nucleus accumbens, thalamus, amygdala, cingulate cortex, and prefrontal cortex” after the sugar intake.

Why sugar may be addictive after all

The findings, conclude the researchers, imply that “foods high in sucrose influence brain reward circuitry in ways similar to those observed when addictive drugs are consumed.”

The lead researcher explains that the findings contradicted his initial expectations. “There is no doubt that sugar has several physiological effects, and there are many reasons why it is not healthy.”

“But I have been in doubt of the effects sugar has on our brain and behavior, [and] I had hoped to be able to kill a myth.” He continues by emphasizing the addictive aspects of sugar intake.

“If sugar can change the brain’s reward system after only 12 days, as we saw in the case of the pigs, you can imagine that natural stimuli, such as learning or social interaction, are pushed into the background and replaced by sugar and/or other ‘artificial’ stimuli.”

Michael Winterdahl

“We’re all looking for the rush from dopamine, and if something gives us a better or bigger kick, then that’s what we choose,” he explains.

Are pig models relevant?

The researchers also explain their choice of minipigs as a model in which to study the effects of sugar on the brain.

They say that previous studies have used rats, but even if these rodents do have a penchant for sugar, their homeostatic mechanisms — which help regulate weight gain and metabolism — “differ significantly from those of humans.”

“It would, of course, be ideal if the studies could be done in humans themselves, but humans are hard to control, and dopamine levels can be modulated by a number of different factors,” explains Winterdahl.

“They are influenced by what we eat, whether we play games on our phones, or if we enter a new romantic relationship in the middle of the trial, with potential for great variation in the data.”

“The pig is a good alternative because its brain is more complex than a rodent and […] large enough for imaging deep brain structures using human brain scanners.”

According to the World Health Organization, cancer is the second leading cause of death worldwide — in 2018, it was responsible for approximately 9.6 million deaths.

Reducing behavioral or dietary risks associated with cancer is an important way of lowering the total number of cancer deaths; however, finding effective treatments is also crucial.

Doctors usually treat cancer with chemotherapy, but this often has significant side effects. For example, some chemotherapy medication can wipe out a person’s white blood cells, leaving their immune system compromised and open to infection.

Although chemotherapy treatment can be successful, there is always a risk that a person’s cancer might return.

Recent advances in cancer treatment include immunotherapy, which involves using a person’s immune system to fight cancer cells. However, this does not always work or may only slow down the growth of cancer, so it cannot yet replace chemotherapy.

Copper nanoparticles

In the new study on mice, the scientists combined immunotherapy with copper-based nanoparticles. This combination treatment destroyed the tumor cells without the use of chemotherapy. Most importantly, however, the tumor cells did not return after treatment ceased.

The team of scientists — from KU Leuven in Belgium, the University of Bremen, the Leibniz Institute of Materials Engineering both in Germany, and the University of Ioannina in Greece — found that tumors in mice are sensitive to copper oxide nanoparticles.

Typically, these nanoparticles are toxic when inside an organism. The scientists found that by using iron oxide to create the nanoparticles, they could control which cells the nanoparticles destroyed, leaving healthy cells unaffected. They recently published their findings in the journal Angewandte Chemie International Edition.

Prof. Stefaan Soenen and Dr. Bella B. Manshian from the Department of Imaging and Pathology at KU Leuven worked together on the study. They explain how “any material that you create at a nanoscale has slightly different characteristics than its normal-sized counterpart.” They continue:

“If we ingest metal oxides in large quantities, they can be dangerous, but at a nanoscale and at controlled, safe concentrations, they can actually be beneficial.”

The scientists began by using only the nanoparticles to target the tumor cells. As expected, the cancer returned. However, the team discovered that the nanoparticles could work in conjunction with the mice’s immune systems.

“We noticed that the copper compounds not only could kill the tumor cells directly, they also could assist those cells in the immune system that fight foreign substances, like tumors,” said Dr. Manshian.

Blocking cancer’s return

When the scientists combined the nanoparticles with immunotherapy, the tumor cells died and did not return.

To confirm the results, the scientists injected the mice with new tumor cells. The mice’s immune systems immediately destroyed the new tumor cells.

The researchers believe that a combination of nanoparticles and immunotherapy could work as a vaccine for lung cancer and colon cancer, which were the two types of cancer the scientists studied.

However, they think that this technique could treat up to 60% percent of cancers, including breast cancer and ovarian cancer, that develop from the same gene mutation.

“As far as I’m aware, this is the first time that metal oxides [have been used] to efficiently fight cancer cells with long lasting immune effects in live models,” Prof. Soenen says. “As a next step, we want to create other metal nanoparticles and identify which particles affect which types of cancer. This should result in a comprehensive database.”

Results derived from animal testing do not necessarily work when it comes to humans, and to take the research further, the team intends to test the treatment on human tumor cells. If that is successful, they will conduct a clinical trial.

However, according to Prof. Soenen, there are still several hurdles along the way:

“Nanomedicine is on the rise in the United States and Asia, but Europe is lagging behind. It’s a challenge to advance in this field because doctors and engineers often speak a different language. We need more interdisciplinary collaboration so that we can understand each other better and build upon each other’s knowledge.”

As scientists have become increasingly interested in the role of gut bacteria, so have the public. In parallel with the microbiome’s rise to fame, probiotics have grown ever more popular.

Probiotics are live organisms that manufacturers add to a range of foods, most commonly yogurts. Their marketing information often contains an array of health claims, from improving digestive health to boosting the immune system.

Probiotics are now big business. In 2017, the probiotics market in the United States was worth more than $40 billion, according to the authors of the recent study.

Claims and accuracy examined

As with many products today, online sales and marketing play a significant role. With this in mind, researchers from the Brighton and Sussex Medical School in the United Kingdom and the Université libre de Bruxelles in Belgium assessed online claims about these products for accuracy.

To investigate, they collected information from top-ranked webpages in Google searches. Co-author Prof. Michel Goldman explains that “often, the public will not go past the first 10 results — these will, therefore, have a higher visibility and impact.”

First, the authors analyzed the pages for “accuracy and completeness.” Next, they checked the information against the Cochrane library, which is a database of evidence-based medical information, including clinical trials and meta-analyses.

Prof. Goldman explains their approach: “We assessed the first 150 webpages brought up by a Google search for ‘probiotics’ and recorded where they originated from and the diseases they mentioned. The scientific evidence for health benefits of probiotics against these diseases was then examined for scientific rigor.”

They published their findings in the journal Frontiers in Medicine.

Site type matters

The scientists found that the majority of the top 150 websites were news-based or commercial — 31% and 43%, respectively. Overall, news and commercial sites were the least reliable sources of information as they rarely mentioned regulatory issues or side effects for vulnerable individuals, such as those who are immunocompromised.

Of the 150 webpages, only 40% mentioned that the benefits of probiotics need more research, 35% referenced scientific literature, only 25% listed potential side effects, and just 15% mentioned regulatory provisions.

In the four categories covered above, commercial websites scored lowest. In Google’s top 10 results, the scores were higher.

The authors explain that Google’s algorithms do a relatively good job of ensuring that reliable health portals come at the top of searches: in the top 10 search entries in Google, reliable health portals took up the majority of slots.

However, as author Prof. Pietro Ghezzi explains, “the fact that there is such a large amount of commercially-oriented information is problematic for consumers who are searching for honest answers.”

Evidence is lacking

The researchers investigated specific health claims in more detail, checking these claims against the Cochrane database. Although websites make claims about probiotics treating a range of ills, the evidence is severely lacking.

To date, evidence only supports the use of probiotics to treat a handful of conditions, including infectious diarrhea and necrotizing enterocolitis in preterm infants. Even in these cases, it is necessary for scientists to do more research.

Overall, 93 of the 150 websites claimed that probiotics could enhance the immune system. In reality, as the authors explain, this “has been barely investigated in clinical trials.”

Similarly, a significant number of websites claim that probiotics might help relieve mental disorders and reduce the risk of cardiovascular disease. Again, scientists have carried out very little research into these topics.

In all, there were 325 specific health claims on the webpages that the scientists investigated. Scientific evidence substantiated only 23%, and 20% had no evidential support to back them up. These findings are important, as the authors explain:

“In the current era where distrust in medical experts and health authorities is widespread, individual consumption of over-the-counter health products is largely guided by information collected on the internet.”

They continue, “Since probiotics escape scrutinization by regulatory authorities, it is of utmost importance to get insight into the level of trustworthiness provided by online information on their benefits and risks.”

Misfolded alpha-synuclein proteins in the brain are the hallmark sign of Parkinson’s disease.

Many experts believe that these toxic protein clumps lead to the progressive loss of brain cells that control movement.

But the science is not clear-cut, and the underlying mechanisms that cause Parkinson’s remain elusive.

Without an effective way of preventing or curing Parkinson’s, treatment primarily focuses on alleviating symptoms.

A recent line of research has been looking into a possible link to the gut microbiome, the trillions of microbial species that populate our intestines.

Could changing a person’s gut microbiome be a way of modifying their risk of developing Parkinson’s or even serve as an effective treatment?

A group of scientists from the Universities of Edinburgh and Dundee, both in the United Kingdom, set out to investigate.

Maria Doitsidou, a fellow at the University of Edinburgh’s Centre for Discovery Brain Sciences, is the senior study author, and the team’s research features in the journal Cell Reports.

Probiotic ‘inhibits and reverses’ aggregation

For their study, Doitsidou and her colleagues used a nematode worm model that scientists had genetically engineered to express a human version of the alpha-synuclein protein.

These worms normally develop aggregates, or clumps, of alpha-synuclein at day 1 of their adulthood, which is 72 hours after they hatch.

However, when the researchers fed worms a diet containing a probiotic bacterial strain called Bacillus subtilis PXN21, they observed “a nearly complete absence of aggregates,” as they state in their paper. The worms still produced the alpha-synuclein protein, but it did not aggregate in the same way.

In worms that had already developed protein aggregates, switching their diet to B. subtilis cleared the aggregates from the affected cells.

The team then followed a set of worms through their lifespan and compared a B. subtilis diet with a conventional laboratory diet.

“The maximum number of aggregates reached in animals fed with B. subtilis was far lower than that observed on the [standard] diet, indicating that B. subtilis does not simply delay aggregate formation,” the authors explain in the paper.

“B. subtilis PXN21 inhibits and reverses [alpha-synuclein] aggregation in a [roundworm] model,” they note.

Is this effect specific for B. subtilis PXN21, though? To answer this question, the team compared a number of different strains of the bacterium and found that they had similar effects.

Several pathways working together

To find out how B. subtilis is able to prevent and clear alpha-synuclein aggregates, the team used RNA sequencing analysis to compare the gene expression of animals receiving a standard diet with that of those receiving the probiotic.

This analysis revealed changes in sphingolipid metabolism. Sphingolipids are a type of fat molecule, and they are important components of the structure of our cell membranes.

“Previous studies suggest that an imbalance of lipids, including ceramides and sphingolipid intermediates, may contribute to the pathology of [Parkinson’s disease],” the authors comment in the paper.

Yet, changes in sphingolipid metabolism were not the only pathways that the researchers identified.

They also saw that B. subtilis was able to protect older animals from alpha-synuclein aggregation through both the formation of complex structures called biofilms and the production of nitric oxide. In addition, the team saw changes in the dietary restriction and the insulin-like signaling pathways.

Importantly, when the team switched animals that had first received a standard diet over to a B. subtilis diet, their motor skills improved.

“The results provide an opportunity to investigate how changing the bacteria that make up our gut microbiome affects Parkinson’s. The next steps are to confirm these results in mice, followed by fast-tracked clinical trials since the probiotic we tested is already commercially available.”

Maria Doitsidou

Nepeta cataria, or “catnip,” is an herb belonging to the same plant family as mint. Although it originated in parts of Europe and Asia, the plant is now common across several continents, including North America.

Because, like regular mint, catnip proliferates easily, many cat owners grow the plant in pots as a special treat for their feline friends.

As part of the mint family, fresh catnip also smells minty, though this is not the case for the dried catnip sometimes present in commercial cat treats or toys, which may smell more like dried grass.

Why is catnip such a special treat? People who share their life with a cat will know that this plant often has a marked, and sometimes very funny, effect on these beloved animals — not unlike the effect that a mild recreational drug might have on humans.

Do all felines react to catnip? Why does this plant affect cats, exactly? Is it really akin to recreational drugs? Read on to find out.

1. Why does catnip affect cats?

In his book Intoxication: The Universal Drive for Mind-Altering Substances, psychopharmacologist Ronald Siegel estimates that around “70% of domestic cats respond to catnip,” and that those who do have reached sexual maturity. Cats reach sexual maturity at around 6 months of age.

Cats who react to catnip will sniff the plant, or any toys that contain it, and then start chewing on it. Following this, they may start rubbing their head against the plant or toy, and then roll or flip from side to side.

“Both of [my cats] love it, and it makes them go crazy,” one reader told Medical News Today. “[The female] likes to lick it, then she attacks the toy it’s on, often adopting the bunny leg attack. [The male] goes more soppy with it, often rolling around with the toy in his paws,” they said.

Although in most cases, when it does affect them, catnip stimulates cats in a pleasurable way, the American Society for the Prevention of Cruelty to Animals deem it “toxic to cats.” They warn that some domestic felines may experience adverse reactions after coming into contact with this plant. These effects can include vomiting and diarrhea, as well as states of sedation.

Some cats may even become aggressive when they encounter the plant. Another reader told MNT that she avoids giving her cat any catnip for this very reason. “[My cat] just gets a bit like she wants to fight me [and] starts punching my foot,” they said.

For the many cats that respond well to catnip, Siegel notes, this may be “an example of animal addiction to pleasure behavior.” Both male and female cats respond to catnip in a way that is reminiscent of sexual arousal among these felines.

Because of these similarities, some researchers have suggested that the plant may once have been a timely and natural enhancer of reproductive behaviors.

“These displays have prompted naturalists to speculate that catnip once served the evolutionary function in the wild of preparing cats for sex, a natural springtime aphrodisiac.”

Ronald Siegel

He explains that the molecules that carry catnip’s scent, called terpenoids, are what causes the reaction. Catnip features a specific type of terpenoid called nepetalactones. These molecules, Siegel explains, can be toxic. However, they are usually harmless in the quantity in which they are present in catnip.

Cats absorb nepetalactones by sniffing the catnip. The molecules then bind to olfactory (smell) receptors in the nose, which send additional signals to the amygdala, which are two small clusters in the mammal brain. These are linked with both the regulation of emotions and some sexual behaviors.

2. Why do some cats not respond?

About 30% of domestic cats have absolutely no reaction to catnip. One MNT reader exclaimed that it “has no effect on [her cat] whatsoever!”

Why does catnip affects some cats but not others? The difference, Siegel argues, lies in cat DNA. Some cats inherit the “catnip sensitive” gene, while others simply do not.

“The reason for the failure of some cats to become even the least bit excited about catnip and for the exaggerated reaction of others is genetic,” he writes.

“Cats can inherit a dominant gene that guides the reaction to catnip,” adds Siegel. He adds that some studies have demonstrated that the offspring of cats sensitive to catnip are also sensitive to this plant, and that those of cats with no reaction to it also will not respond.

In addition to this, he says, some felines may become avoidant of catnip if they have had a bad experience with it.

For instance, notes Siegel, if a feline has sniffed or chewed on catnip and then injured itself, in the future, it may turn around when encountering the plant, instead of jumping at the occasion of accessing the stimulant.

3. Does catnip affect other felines?

If catnip can have a striking effect on domestic cats, does it also affect larger felines, such as lions, jaguars, and tigers?

The answer is “yes” — and it seems to act, to a much lesser extent, on other cat-like mammals that are not actually felines.

An experiment conducted in the early 1970s at what is now Zoo Knoxville in Tennessee found that lions and jaguars were “extremely sensitive” to catnip.

Some of the tigers, cougars, and bobcats at the zoo also responded to catnip, though not at all strongly. The two cheetahs on site at the time showed no interest in the plant.

Other animals have shown curiosity about catnip, though to a much lesser extent than domestic cats.

Non-felines that have shown an interest in catnip include civets, which are carnivorous animals native to Asia and Africa that look like cats but belong to a different family, called Viverridae.

4. What other stimulants affect cats?

Though catnip is by far the best known cat stimulant, researchers have noted that there are many other plants that can alter felines’ moods and behaviors.

Siegel, for instance, speaks of matatabi, or silver vine (Actinidia polygama). This is a plant native to areas of Japan and China. In an experiment at Osaka Zoo in Japan, large felines exposed to high quantities of the active substance in matatabi showed signs of intense pleasure — and addiction.

“This plant contains secondary compounds closely related in chemical structure and behavioral activity to nepetalactones,” Siegel explains.

“After an initial exposure, the [large] cats became so eager for more that they would ignore whatever else they were doing — eating, drinking, or even having sexual intercourse — whenever the chemicals were made available.”

Ronald Siegel

One 2017 study confirmed that matatabi can be just as, if not more, effective than catnip when it comes to stimulating domestic cats.

The study’s authors also identified two more plants that had a similar effect: Tatarian honeysuckle (Lonicera tatarica) and valerian (Valeriana officinalis).

Almost 80% of the domestic cats in this study reacted to matatabi, and around 50% of cats also responded to Tatarian honeysuckle and valerian root.

Matatabi, the study authors also note, actually elicited a response in 75% of the domestic cats that had no reaction to catnip.

“Olfactory enrichment using silver vine, Tatarian honeysuckle, or valerian root may, similar to catnip, be an effective means to improve the quality of life for cats,” the researchers conclude.

5. Is catnip safe for humans?

Although humans tend to buy or cultivate catnip purely for the entertainment of their feline friends, some people think that the plant can have a soothing effect on their own minds.

For example, some people like to brew catnip tea, and some have even tried rolling the plant into cigarettes and smoking it. “It makes people feel happy, contented, and intoxicated, like marijuana,” an older study notes.

As a supplement, people have also used catnip to treat symptoms such as coughs or toothaches, and as a digestive aid.

Is it safe? This much remains unclear. So far, there has been little research into the effectiveness or safety of catnip when it comes to treating various conditions in humans.

Some specialists suggest that catnip can cause contractions of the uterus, so they recommend that pregnant women avoid this plant.

Given the scarcity of evidence regarding the safety of this plant, however, our readers may be better off saving it for their cats’ enjoyment — that is, if they are part of the majority that do appreciate it.