Junk food messed up immunity in mice, in lasting ways — and darkened people's moods
We know that fast food puts on pounds and harms brain, heart, and metabolic health.
But new findings suggest junky foods also alter your immune system in ways that cause persistent inflammation.
The unhealthful consequences of that persistent inflammation include higher risks for cardiovascular disease, dementia, autoimmune disorders, and diabetes.
It's proven that poor diets promote inflammation — but troubling new findings suggest that pro-inflammatory genetic changes caused by junk foods may persist.
And it ain't easy to reject junk foods, which trigger your dopamine-driven “reward” system — the same mechanism that sparks and sustains addictions to gambling and sugar.
Fast food damaged rodents’ immune systems
A recent rodent study from Germany's University of Bonn produced the troubling new findings.
The German team put mice on a fast-food diet that was high in sugar and fat but low in micronutrients and fiber (Christ A et al. 2018).
In short order, the mice suffered strong inflammation throughout their bodies, akin to the potent inflammatory response triggered by dangerous infections.
Worse, this intense inflammatory response reprogrammed the body’s immune cells at the genetic level, making them prone to generate inflammation without good reason.
As you might expect, when the mice returned to their normal, grain-based chow diet — high-fiber, low-sugar and low-fat — symptoms of acute inflammation disappeared.
However, despite returning to a normal, healthy diet, the adverse genetic reprogramming of the rodents’ immune cells persisted.
In other words, the genes “switched on” by the fast food diet — which put the animals’ immune systems on a hair trigger — remained active and kept stimulating inflammation.
How can junky diets reprogram your immune system?
The study’s leader, Prof. Dr. Eicke Latz, explained why the fast food diet produced a long-lasting change to the animals’ immune systems.
As he said, “It has only recently been discovered that the innate immune system has a form of memory. After an infection, the body’s defenses remain in a kind of alarm state, so that they can respond more quickly to a new attack.”
This normal, healthy “training” of your body’s innate immune system — its first line of defense — helps you fight infections more rapidly and robustly.
Unfortunately, junky diets altered the genetic programming rodents’ innate immune systems in ways that produced inappropriate, damaging, persistent inflammation.
Beyond producing abnormal inflammation, the fast food diet also changed the way genetic information was “packaged” and stored in the animals’ cells.
The German team explained that the genetic material in DNA normally occurs in strands, which typically wrap around particular proteins, in essence “hiding” them from the body so that they’re not readable until needed.
However, the unhealthy diet caused some of these “hidden” strands of DNA to unwind, making them easier for the immune system to read, thereby maintaining durable and damaging inflammation.
Alterations of your genetic code caused by external factors like diet and exercise are called “epigenetic” changes. And — at least in rodents — a fast food diet caused an immediate rise in inflammation and long-term, adverse epigenetic changes.
Dr. Latz said this about the German team’s findings: “The foundations of a healthy diet need to become a much more prominent part of education than they are at present. Only in this way can we immunize children at an early stage against the temptations of the food industry.”
Spanish study linked fast food to depression
Six years ago, researchers from Spain’s University of Las Palmas de Gran Canaria and University of Granada reported disturbing findings about the effects of junky diets on mood (Sánchez-Villegas A et al. 2012).
Their findings linked diets high in commercial bakery items (such as croissants and doughnuts) and fast food (such as hamburgers, hotdogs, and pizza) to higher risk for depression.
They found that — compared to people who eat little or no fast food — people who consume lots of fast food were over 50% more likely to develop depression.
The study involved nearly 9,000 adults who’d never been diagnosed with depression or taken antidepressants.
They were followed for six months, then reevaluated to see whether they received a diagnosis of depression or a prescription for antidepressants.
And those who were eating relatively junky diets were significantly more likely to develop depression.
The strength of this finding was bolstered by the fact that the team detected a dose-response relationship between fast food and depression — the participants who ate the most fast food were at greatest risk for developing depression.
The research team points out that little is still known about the role that diet plays in developing depressive disorders.
However, as they wrote, “… previous studies suggest that certain nutrients have a preventative role. These include group B vitamins, omega-3 fatty acids, and [extra virgin] olive oil. Furthermore, a healthy diet such as that enjoyed in the Mediterranean has been linked to a lower risk of developing depression.”
Most of us eat some junky fare: Tips to keep inflammation at bay
Thanks to their antioxidants and fiber, colorful vegetables and fruits, whole grains, nuts, seeds, and other whole plant foods constitute key anti-inflammatory allies.
Almost without exception, whole plant foods are rich in fiber and antioxidants, including carotenes, polyphenols, and vitamins C, E and A in the form of beta-carotene.
Vegetable oils, seeds, nuts, and green leafy vegetables rank among the best sources of vitamin E (tocopherols and tocotrienols) which play critical roles in controlling inflammation.
As we’ve noted before, foodborne antioxidants mostly work indirectly, by influencing our “working” genes, in ways that moderate inflammation and boost the body’s internal antioxidant system: see Aging Theory Gets a Radical Makeover.
The nutritional metal selenium is a key inflammation-fighter because it’s essential to some of the body’s key internal antioxidants, including glutathione peroxidases.
Selenium is most abundant in fish, crab, oysters, organ meats, garlic, nuts, whole grains, meat, mushrooms, and eggs — selenium levels can vary widely in grains and garlic, due to soil conditions.
To learn more, see Selenium Seen as Key Anti-Aging Ally.
Omega-3 fatty acids from seafood
There is clear, solid evidence that omega-3s are essential to moderating and resolving excessive inflammation — and may even help the body recover after the effect of years of aggressive immune response.
As they wrote, “[Other] studies, plus our current study in a representative U.S. population, provide evidence for the anti-inflammatory effects of long-chain omega-3 PUFAs in humans.”
The ancient Indian medicine tradition known as Ayurveda prizes turmeric root.
The orange-yellow "curcuminoid" compounds that give turmeric its rich hue are largely responsible for the root's health benefits.
Among other modes of beneficial action, curcumin turns off gene switches involved in excess in chronic inflammation.
Modern epidemiological evidence and its ancient healing tradition have triggered extensive research into the possible health-promoting properties of curcumin.
To learn more, see Curcumin: Miracle or Myth?.
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- Sánchez-Villegas A, Toledo E, de Irala J, Ruiz-Canela M, Pla-Vidal J, Martínez-González MA. “Fast-food and commercial baked goods consumption and the risk of depression. Public Health Nutr. 2012 Mar;15(3):424-32. doi: 10.1017/S1368980011001856. Epub 2011 Aug 11. PubMed PMID: 21835082.