The weather has been very (very) wet this May in France and I spent a lot of time reading with my dog curled up beside me. Fortunately, there is no shortage of interesting news to keep our minds busy. (Go here for Curious Cook: Observations about food in France in May – Part 1)
A large study in China (conducted between 2004 and 2008 with 416,213 participants aged between 30 and 79 years) concluded that eating an egg a day reduced the risk of death via strokes by 28% and heart attacks by 18% across a wide demographic. Oddly, this food study provided no additional supporting dietary data.
So this extraordinary claim has to be viewed cautiously, because an earlier 2015 Korean study of 23,417 adults found that eating eggs actually increased artery calcification (a leading indicator of heart disease) – though it also noted that this was observed more in people who were overweight/obese and/or ate few vegetables. Statistically it is a common mistake to credit a single item (such as eggs) without considering all other associated factors which can affect predicated outcomes.
Therefore the safest interpretation of the China study is: eating an egg daily is fine for people on good diets and who are not overweight, which as it turns out, is something we already know anyway.
Fasting intermittently and diabetes?
As someone prone to sinusitis, every few months I restrict my calorie intake to around 200 calories a day for three to five consecutive days. This appears to reset the immune system and then I am fine for another few months – if you are curious, more details are somewhere in here.
I therefore follow a very intermittent fasting (IF) strategy, and not the more common IF diets which prescribe stuff like semi-fasting two days out of every week.
So headlines like “Fasting Diets Can Increase the Risk of Diabetes” emanating from a widely-reported talk at the 2018 European Society of Endocrinology Annual Meeting in Barcelona piqued my interest – especially as it asserted: “intermittent fasting diets may actually damage the pancreas and affect insulin function in normal healthy individuals, which could lead to diabetes and serious health issues”. This is a striking claim which would be remiss of me not to investigate.
Searching for study papers revealed the University of São Paulo had not published any. All that was available was a short transcript which noted that the research was conducted on Wistar rats, which have a totally different diurnal (daily) feeding cycle to humans. Starving a rat for just one day is roughly similar to starving a human for two to three weeks, starving mammals often react by developing insulin resistance which helps minimise weight loss – and there was no mention of the fasting period(s) used.
In any case, the research seemed to focus on markers associated with insulin resistance and it was unclear if any rats actually developed diabetes.
To be fair, I will review the paper when it is published but it is extremely likely the “normal healthy individuals” cited in Barcelona referred to rats rather than humans. Phew.
In any case, I had earlier bookmarked a paper from MIT which claimed that fasting boosts intestinal stem cells’ (ISCs) ability to regenerate, even in aged subjects. If you are curious, it was suggested fasting conditions may somehow cause ISCs to boost/re-activate the peroxisome proliferator-activator receptors (PPAR) responsible for fatty acid oxidation. This may be plausible as a lack of food should promote a more efficient digestive environment – however, the research was based on young and old mice, not humans. So until there is confirmation the same effect happens in humans, it is probably best to leave it as an interesting conjecture.
The spleen and baking soda
A paper from the Medical College of Georgia, USA, in the Journal Of Immunology claimed that ingesting sodium bicarbonate (NaHCO3, or baking soda) can reduce inflammation in both test rats and humans. This paper reads like an unfinished detective story.
The plot started originally with test research into slowing kidney failure rates by reducing blood acidity via the introduction of an alkaline compound, NaHCO3 – note that kidney failure causes increases in blood acid levels. Promising results led to a detailed, complex investigation of NaHCO3’s unexpected side effect on general inflammation.
The surprising outcome was a conclusion that NaHCO3 stimulated the mesothelial cells on the surface of the spleen (an organ involved in the immune system), and this had the effect of shifting the balance in the body from M1 (inflammatory) to M2 (anti-inflammatory) macrophages (which are special white blood cells involved in clearing pathogens, defective cells and other cellular debris from the body).
How this M1-to-M2 switch happens may be due to the production by the spleen’s mesothelial cells of acetylcholine, an important neuro-transmitter associated with reducing inflammation as well as learning and memory. This is an intriguing piece of research, with two additional notable items.
One is the apparent anti-inflammatory response is destroyed if the spleen is perturbed or damaged in any way; the second is the humans studied was a small group of 18 healthy young adults, and therefore probably statistically irrelevant.
I have read well over a thousand scientific papers, and the impression is that not all the research done was strictly warranted or worthwhile. However, if asked to choose the most intriguing paper of the month, this would probably be it, although it is a long way before further peer-reviewed research can confirm the findings reported.
An opinion piece from researchers in Oxford University in Nature magazine explored the reasons why human behaviours may be modified by the human gastrointestinal microbiota (HGM).
While such behavioural change may not be as extreme as, say, the changes invoked by the rabies virus, there are certainly bacteria in the HGM producing compounds which can make humans feel good or lousy.
Organisms that co-exist symbiotically within a host are known as symbionts – and symbionts are likely to have a major influence on host evolution by influencing host behaviour in a manner which benefits the symbionts and (hopefully) also the host.
Why I bracketed the word “hopefully” is because of an odd situation. Rodents infected with the brain parasite Toxoplasma gondii lose their aversion to the scent of cat urine, making them more likely to be caught and killed by cats. The reason is because the parasite can only reproduce in felines and it therefore needs to sacrifice its rodent host to be eaten by a cat.
This is not only a cat and mouse issue. Thirty to 50% of all humans today currently have toxoplasmosis, which means their brains are infected by Toxoplasma gondii.
Perhaps as a result of human immune responses to this infection, several conditions have been associated with toxoplasmosis. They include leukaemia, various neuro-degenerative diseases, neuroticism, aggression, impulsive behaviours, suicidal tendencies, etc – though one should note correlation is not necessarily proof of causation. Generally, toxoplasmosis is asymptomatic and the vast majority are not even aware of infection, though it might help explain why many humans like cats irrationally (as witnessed by the number of cat items on YouTube and Instagram).
The HGM situation is different as it comprises of many species of bacteria clustered together, which limits each individual strain’s ability to influence the host – any self-initiated aggressive attempt to boost an individual species is likely to be met with counter-measures from other bacteria. Therefore, quorum sensing generally keeps a healthy HGM in balance. More about this on: https://www.star2.com/living/viewpoints/2016/03/13/curious-cook-a-quorum-of-flavour-part-1/.
The HGM also resides within the Enteric Nervous System (ENS), a huge conglomeration of neurons stretching from the oesophagus to the anus and linked to the Central Nervous System (CNS) via the vagus nerve.
Hence, the HGM can transmit good and bad signals via the ENS to the CNS, and these signals can influence behaviour. An example is the tension-induced “butterflies in the stomach” feeling, which can provoke odd coping behaviours.
Pleasant signals may result from neurotransmitters (or precursors to neurotransmitters) created by certain species in the HGM in response to ingested food.
Less pleasant signals can arise from other HGM bacteria which spawn uncomfortable immune system responses as a result of stress or poor diet – note that for now, we exclude the different, strident reactions to external pathogenic invasions or chemically-disruptive events (eg. smoking, alcohol, pollution, etc).
Both good and bad signals may alter (and reinforce) host behaviour in ways to benefit different bacteria within the HGM. Feeling good may cause the host to seek and ingest more food linked to pleasure.
Bad feelings may lead to the host also ingesting more to compensate for feeling lousy or malnourished. Either way, such changes in host behaviour can benefit certain adept bacteria in the HGM without being disruptive to other bacteria.
So if you are certain the brain in the head is always in charge of making decisions, you might want to think again.