Life adapts when necessitated by changing conditions that impact survival. These are evolutionary pressures, with nutrition being probably the strongest. Flora bend toward the sun and plunge rooty tendrils deep into soil in search of moisture and minerals, while mobile organisms walk, run, fly, crawl, scrounge, or swim for food. Herbivores prefer to go where the vegetation is the densest and most nutritious, while predators follow close behind. Life is in constant flux, then, with food availability as the invisible hand directing traffic.
Flux is great, exciting stuff, but it makes for difficult research into cause and effect. It heralds the introduction of myriad variables. So we often go to the lab for sterile, randomized controlled trials in an attempt to limit these variables and in a desire for scientific certainty. But real life is messy, complex and difficult to model. This is why isolated populations in actual, natural environments are so valuable.
Enter the moose of Isle Royale in Lake Superior, Michigan. Their ancestors swam to the island about 100 years ago, presumably in search of food. It’s the story of life, right? Food they found, but, with Isle Royale being an island and all, it was finite. Flux happens. Population rises, food becomes more scarce, population drops, and so on. Wolves, one of the moose’s few natural predators, get involved, of course. It was a situation ripe for research (isolated population, ability to account for most variables, etc.), and so a fifty-year (ongoing to this day) study was begun by a group of researchers.
As the moose population increased, the availability of food naturally decreased (because, you know, it was being eaten by all the moose). A shrinking supply of food was spread across a growing population of moose until the population stopped growing and it began to tip toward the other end of the scale. This is all basic stuff that you’d expect to see in an island population with a limited food supply.
There was more, though. Researchers also found (PDF) that osteoarthritis incidence increased in moose who were borne in times of population excess and nutritional hardship. Baby moose weaned on substandard amounts of food were more likely to develop osteoarthritis later in life. Arthritis, eh? That’s the classic wear-and-tear affliction. I know wear-and-tear. When osteoarthritis ended my promising running career many years ago the docs told me it was the high miles I was putting in day-in, day-out. So what about these moose? Why, I bet those moose were playing too much basketball on outdoor courts and were consistently failing to get properly fitted for quality athletic footwear. Or maybe they were going farther afield in search of food. Except that the arthritic moose had access to plenty of food as adults, so they weren’t moving any more than the moose with healthy joints. Or maybe they were obese moose, munching on too much lichen and moss, and their tender joints simply couldn’t take the added weight. That’s what seems to happen to humans, who, as they gain weight, also suffer from more osteoarthritis. Except that wasn’t it, since arthritic moose were, if anything, smaller than healthy moose.
They were also malnourished as youngsters. We can tell this by examining the length of the metatarsal bone in moose, which is a strong index of early nutrition in animals. The moose with osteoarthritis as adults had shorter metatarsal bones, which indicates poor early nutrition. Low metatarsal length is also strongly linked with poor longevity, so it may be that malnutrition early in life has even stronger ties to adult osteoarthritis; we’d never know since many moose with short metatarsal bones died relatively young, too.
The authors go on to propose a similar explanation for increased osteoarthritis in colonized Native Americans. Spanish colonization brought agriculture, especially corn-based agriculture, to ancestral hunter-gatherers. It also brought osteoarthritis, a relatively rare affliction for pre-colonial peoples living on animals and wild plants. Popular science has held that forced slave labor caused the well-documented increase in osteoarthritis through wear-and-tear, but the authors of the moose study suggest malnutrition – going from meat and plant-based nutrition to corn-based nutrition – also played a role. It makes sense, especially since the arthritic joints in the Isle Royale moose were identical to the arthritic joints in humans with osteoarthritis, suggesting a similar root cause. They even propose that malnutrition is at the heart of modern osteoarthritis.
Some might balk at that. After all, humans, especially humans in the US, don’t appear to be malnourished. They’re fat! Even the homeless are overweight! And, stats have shown, being overweight is one of the top risk factors for osteoarthritis in this country. Surely a fat guy isn’t malnourished, right?
Malnutrition is a bit of a nebulous word. What’s the first thing you think of when you hear it? I don’t think I’m alone in assuming “insufficient amounts of food.” Starvation. Children with bloated bellies and limbs like stick figures. Buzzing flies and lurking buzzards. Those are the commonest connotations, but the actual word can mean several different things. It can mean inadequate intake of nutrients. So, if a kid is stuffing him or herself with plenty of calories but failing to get any appreciable amounts of vital vitamins and minerals, that’s also malnutrition. It can also refer to an imbalanced intake of nutrients. Imagine a hyper-vigilant parent with a familial history of osteoporosis and a spotty understanding of how the disease works stuffing his kid full of large amounts of calcium supplements while totally ignoring the need for vitamin D and magnesium. That would also be malnutrition. At the heart of malnutrition is bad nutrition. Heck, it’s right there in the word itself: “mal,” which in Latin (and most of its offshoots) means bad or evil. You could be eating 4000 calories a day and still be subject to classic malnutrition if all you’re eating is candy, soda, and fast food. In fact, most people eating terrible modern diets are walking (or, rather, limping, driving, sitting, slumping) examples of malnutrition, even though they appear incredibly well-fed. Just look at the homeless in this country, who tend to be fairly overweight. They’re not lacking for calories, but they’re certainly malnourished. Eating convenience store fare and processed food will do that to you. You don’t have to be skinny to be malnourished.
I doubt wear-and-tear, except in the most extreme cases, is enough to explain osteoarthritis. Statistics consistently show that the more active you are, the less osteoarthritis you have. In my case it could be that the half gallon of ice cream and other carbs I was ingesting (on the order of 1000 grams a day) to fuel my insane volume of Chronic Cardio was enough to put me down the path of osteoarthritis gene expression, and that pounding away, mile upon mile, on the pavement was less of a contributing factor. Our joints are built to withstand duress. They’re meant to deflect it and mitigate it. A common fact mentioned online is that cartilage is several times more slippery than ice. Repeated incorrect usage of one’s joints can surely lead to articular degradation, but it’s not easy to do. You need to weaken the cartilage first. You need to really mess with the wiring, because the human joint is an elegant and effective setup.
What we’re dealing with is a perfect storm of joint stressors: poor form (when people do exercise); inactivity (like bones and muscles, you gotta put your joints to work or they’ll atrophy); poor childhood nutrition; and, in my opinion most importantly, poor overall nutrition. Next week, I’ll go into some other possible causes of osteoarthritis and outline some strategies for avoiding it, if you don’t have it, and improving it, if you do.