When you look at health news today you may see statements such as, "Fiber reduces your risk of colon cancer", "Get more Vitamin D3 to boost immunity", or "Exercise your way to a healthy heart". This approach to health is ridiculous and one of the primary drivers of our current healthcare problem. The way these statements are phrased is completely wrong, they are phrased in a manner that essentially assumes poor health is the default condition. It is not the normal course of events to grow old, get sick, and die. In fact, a few thousand years ago if you made it to 40 years old and didn't get killed in the normal manner of getting a wound that got infected, you had a far greater chance of making it to 75 than you do today. Let's look at what's wrong with all three of these statements one by one.
Fiber reduces your risk of getting colon cancer
Correct me if I'm wrong, but I just don't remember that many people dieing of colon cancer when I was a kid. And while it may have been present a few thousand years ago, I highly doubt cavemen were doubling over and dieing of colon cancer. While we would never know for certain, we do know that modern hunter gatherers have little to no incidence of colon cancer unless they adopt a westernized diet high in processed foods. While fiber is something you should get, you should get it from whole, unprocessed foods as it is these very foods that shaped our genome over 2 million ears of evolution. We literally evolved to run on them.
Vitamin D3 to boost immunity
There have been multiple studies looking at Vitamin D3 and immunity with mixed results. In my opinion, the mixed results come from poor controls in clinical studies. Vitamin D3 probably isn't a helpful supplement to someone who is not deficient in it. Someone who is outside in the sun regularly with a significant amount of skin exposed probably won't have much use for supplementing with it unless they live on the east coast and it's winter (UVB rays that carry D3 are reflected back toward the sun so we don't get them during those months). In other words, Vitamin D3 doesn't improve immunity, a Vitamin D3 deficiency compromises it. Those are 2 different things, the first one states your immune function will be improved with Vitamin D3, the second that proper functionality of your immune system is dependent on it. Again, poor immunity isn't the default condition, it's the pathological one.
Exercise your way to a healthy heart
My roots are in exercise. I love to exercise and it is more or less my job. However, exercise in it's current form is ineffective for preventing heart disease or improving health in general. Given what we know about evolution and natural selection, sitting at a desk all day is not the default condition. If it were we wouldn't be here because food doesn't find itself. Regular, daily physical activity is the default condition and we are not talking about 2 hours at the gym 3-5 days a week. We are talking about being on your feet for a majority of the day and not sitting for stretches of 4-8 hours without getting up. Your 6-10 hours a week at the gym are not going to make up for the 158 hours you spend lying around. Couple that with a bad diet and a reliance on insulin to shuttle glucose in to cells and you are basically destroying your cardiovascular system.
The way we view health in the US is terrible. We assume that the default condition is to sit in an air conditioned room out of the sun in a chair for 8 hours a day. If you buy in to the notion that we evolved via natural selection (I hope you do or you've found the wrong blog), it makes perfect sense that we are optimized for whole foods high in fiber, constant movement and plenty of sun exposure. We spent 99.999975% of our time here getting just that, to assume that you can undo the fine tuning that occurs over the course of 1,999,950 years of evolution with a few supplements and a couple of hours of activity is foolish.