One of the greatest parts about problem based learning is that I constantly revisit familiar topics. It’s amazing to me how often I thought I learned something well only to discover bits and pieces and “aha” moments about subjects that I’d learned not too long ago. Nutrition is definitely one of those! Now that I have a better understanding of a wider range of problems within the body, coming back to nutrition has synthesized concepts in the coolest way.
I’ll apologize in advance for being so nerdy about this stuff. But people always talk about the associations between poor diet and chronic disease, and no one ever explains why. What’s the mechanism? That’s a question we ask a lot in school, and one that is frequently tested on our board exams. Wouldn’t you want your doctor to be able to explain the how’s and why’s of medicine?
I’d like to start by talking about estrogen. Before medical school, I had no idea it was linked to diet and nutrition. And there are consequences for men too! Here’s the thing: fat cells make estrogen. They have a special enzyme called aromatase that picks up extra hormones your body produces and converts them to estrogen. This happens in both men and women. So, when we have excess fat cells, we produce too much estrogen. In men, excess estrogen can lead to what we call gynecomnastia (translation: man boobs) and infertility; basically, the cells in breast tissue get messages from estrogen to grow, and cells within the brain get messages to eventually lower testosterone (which is needed for adequate sperm). In women, excess estrogen can increase the risk of breast and uterine cancer because it is a chemical signal to influence cell division and growth. And the definition of cancer is disordered and excess cell division and growth.
Another interesting topic is fiber. The main way our body gets rid of fats and cholesterol that it doesn’t need is by creating a substance called bile in the liver and storing it in the gall bladder. Bile is kind of like a garbage truck. It drives the trashed fats and cholesterol over into the intestines, and then 95% of the bile trucks drive back to pick up another load. The 5% that remains in the intestines is made primarily of a substance called lipopolic acid. This acid, it turns out, is carcinogenic to the bowel (irritates the cells lining our gut) and can eventually lead to colon cancer. Because of its chemical properties, fiber (once ingested) will suck the lipopolic acid into its center and form a protective coat around it. This prevents the acid from coming into physical contact with the intestinal wall and therefore reduces the risk of colon cancer. And a bonus? Fiber can also trap excess estrogen. So if your body happens to be making too much estrogen, fiber ensures that it is eliminated completely from the body rather than taking a round trip with the bile garbage truck.
Now, we can talk about prescription drugs. Most (but not all!) prescription drugs get metabolized by an enzyme family in the liver called CYP. If there is less CYP (generally), you get a larger dose of drug floating around your system. If there is too much CYP, you get a much smaller dose of drug, because all the CYPs are digesting it and making it inactive (there are exceptions, but I won’t go into those). It turns out that CYPs are also very important for digesting our bodies own garbage. If they are overactive, however, they can quickly start to digest substances that the body needs. A notable example is Vitamin D. If you are taking a prescription drug that “induces” (increases) the number of active CYPs, then these CYPs are simultaneously chopping up all of your vitamin D and throwing it in the trash (your intestines and kidneys). Because your body needs vitamin D to form strong bone, a lack of vitamin D over time can lead to a loss of bone mass- which leads to osteopenia and osteoporosis. So just make sure you and your doctor know if the medication your doing can influence this!
The last interesting tid bit is also kind of crazy. It turns out that anorexia, bulimia, and obesity can all lead to the same problem: heart failure. In anorexia, patients are simply not getting enough energy. The heart requires energy in order to pump blood through circulation and, if severe, can eventually just stop working. In bulimia, vomiting leads to a loss of stomach acid. The acid is important in maintaining the pH of blood. When a patient looses acid, he or she will “compensate” by breathing faster. Breathing faster will cause a drop in oxygen, which the heart also doesn’t like. The drop in oxygen affects heart function and can eventually lead to cardiac arrest. In terms of obesity, the excess weight can lead to high blood pressure, which forces the heart to work much harder to pump blood. Over time, the extra work the heart does can cause it to grow. The growth means that the heart will need more oxygen, but there is no way to get it. And this can lead to heart failure.
Isn’t it crazy how intertwined our bodies are with our lifestyles? I mean really at a biological level! I hope that you found this at least somewhat as interesting as I did, and that maybe it will motivate you to stick with healthy choices.
Are there any fun facts you have to share about nutrition and biology? Feel free to comment!