How stress affects our metabolism: heart rate & headaches (pt1)
Our heart rate and breathing rate are controlled by two different parts of the brain. The medulla (as part of the brain stem) and the hypothalamus both exert control over our heart rate and breathing rate. We can also consciously and deliberately control our breathing rate. We can deliberately move our skeletal muscles, but we cannot deliberately control our heart rate.
Our medulla changes our heart rate and breathing rate in response to “pressure” and “CO2/O2 levels” that our brain gets from the neurons associated with the smooth muscle of our blood vessels. If we start moving fast, our muscles will use more O2 and produce more CO2. This causes the CO2/O2 ratio to rise, the increased CO2/O2 ratio sensory information is processed by our medulla, and our medulla sends out signals that make our hearts beat faster and us breathe faster. This helps more O2 get to the moving muscles faster.
If we did not increase our heart rates and breathing rates in response to increased CO2, our blood would become too acidic and our bodies would start shutting down. It is important that our hearts can beat faster and that we can breathe faster during times that we’re trying to move.
Our hypothalamus changes our heart rate and breathing rate in response to “emotional” stimuli. This can be things like “I’m late for class” (you may feel like this is a fact and not an emotion, but the processing is similar) or “I saw something out of the corner of my eye that I need to run from” (this is part of a reflex response that also involves the superior colliculi of the brain stem, but has an emotional component) or “I’m stressed out” (a more obvious emotional component).
Our bodies are built to run away from our problems (literally). When we get “stressful” stimuli, our hypothalamus releases signals to prepare us to run. While our medulla will respond to signals like increased CO2 once we’ve started running and increase our heart rate, our hypothalamus will respond to signals that say we should start running and increase our heart rate.
What happens when our hypothalamus sends signals to increase our heart rate in anticipation that we’ll start moving, but we don’t actually start moving? Our hypothalamus has sent signals to increase our heart rate and breathing rate to prepare us to move. This allows our heart rate and breathing rate to deliver more O2 to our muslces before the CO2 levels rise.
So what happens if we don’t start moving? If we aren’t moving, our muscles won’t be using extra O2 to produce energy, so they won’t have CO2 to put into the blood. Now, our CO2/O2 ratio is going to drop – a signal that we have too much O2 in our blood.
Our medullas will sense that there’s not enough CO2 and will try to even our bodies back out so that there’s the right amount of CO2 in our blood. Just like we can’t let our blood get too acidic with too much CO2, we also can’t let our blood get too basic with not enough CO2.
Can our medullas get our hearts to slow down if our hypothalamus is telling our hearts to speed up? No. Our ability to try to predict what we need to do next is so strong that as long as we think we need to move fast away from something, our hypothalamus will win and keep our heart rates up. It will also try to keep our breathing rate up. But then how does our body deal with the CO2/O2 problem?
Our medulla can’t change our heart rate if the hypothalamus is increasing it, but it can change our blood pressure. Our medulla will sense that we need to get our CO2/O2 levels back to a normal range. The options are to slow down our heart rate (which our hypothalamus won’t let happen), start moving (which we have decided to not do), or to drop our blood pressure. The medulla will send signals to our blood vessels to open up and get wider (vasodilate) so that it takes more pressure to push blood around. This slows down how fast the blood comes back to the lungs and gives the blood more time to give up O2 to the muscles and pick up CO2.
Rapid changes in blood pressure can make us lightheaded. If you have ever been really stressed out and gotten dizzy, it’s because your blood pressure dropped rapidly in response to your medulla trying to even out your CO2/O2 levels while your hypothalamus is telling your heart to beat faster. This is also why some people end up hyperventilating when they’re stressed – their hypothalamus is telling them to breathe faster but there’s nowhere for the air to go because, if they aren’t moving, there’s not much CO2 to exhale.
Can we do anything about this mismatch between the hypothalamus, the medulla, and our movement? Yes.
Our systems will reset themselves if:
1. the stressful stimulus is taken away,
2. we bring our heart rate down,
3. we restore our CO2/O2 levels back to normal.
We don’t have conscious or deliberate control over the stimulus or our heart rate, but we can do things that reduce how stressful we perceive things to be (hard and takes a long time – but is worth is) and we can do things to restore our CO2/O2 levels to normal (easy and takes a short time – and helps with the first thing).
Questions:
1. Name two things you think you can physically do to bring your CO2/O2 levels back to normal when you’re stressed out? These should be physical activities that you have deliberate control over and that you can do immediately.
2. How do you think that consciously taking deep breathes can make us feel “calmer”?
3. Find your pulse and take your current heart rate. Then find a comfortable seat somewhere and put one hand on your chest and one hand on your belly. Take 5 – 10 “box breathes”. Take your pulse again. Did it change?
References:
Arthur, W. and GC Kaye. (2000) The pathophysiology of common causes of syncope. Postgraduate Medical Journal. Vol 76.
Whitworth, JA. et al. (2005) Cardiovascular consequences of cortisol excess. Vascular Health Risk Management. Vol 1.
“Get to 25 grams Guide” for Fiber
Make nutrition count more and calories count less by designing a diet that focuses on protein & fiber first. (Not sure how much protein you actually need? Check out this guide.) The daily recommended fiber is 25 grams (g) a day (or, 14g for every 1000 cal, if you like extra math. That’s just the minimum, there’s no harm in getting more). According to data the USDA collects, the average American gets 10-15g of fiber a day - less than half of the minimum recommended value.
We all know to “eat our veggies” but how much do we actually need to eat to get our 25 grams? Here are some resources to help get to 25g of fiber/day (click here for downloadable PDFs).
How to use the guide: An easy way to design your diet is to make a list of the foods you like eating & can easily incorporate into your day. Then add snacks until you get to 25g. You can do this to plan different meals each day, or to build a checklist of things you’ll eat commonly. The checklist can have enough snacks/foods that you know if you eat 7 out of the 10 or 12 of your “fav foods” on it, you’ll hit 25g. This is a great time-saver for people who don’t want to keep a food log every day.
Examples of “designer diets” that get you to 25g of fiber in a day: These are some example meals, only the fiber is listed. Obviously, when you think about your diet as a whole, you also want to consider protein and have simple carbs in proportion to your training goals/how much you’re moving. Want help designing the rest of your diet? Schedule a consult.
Example 1 (29g total fiber): Breakfast is Kashi Go cereal (7g). Lunch includes a sandwich using multi-grain bread (3g) and an avocado (15g) plus whatever else you want on a sandwich - maybe eggs (protein) with kale (vitamins/minerals). Mid-afternoon snack is an apple (4g) with cheese. Dinner includes a serving of lentils (7g) as a side, a warm addition to a soup or salad, or on top of your protein of choice. I like making a batch of something like spicy chicken in the crockpot so I can add the chicken (protein) to a pile of lettuce (vitamins/minerals) with cheese (more protein, fat to feel full), and some lentils for a filling salad.
Example 2 (26g total fiber): Breakfast is whole rolled oatmeal (4g) with sliced almonds (3g) and some raw honey and cinnamon (flavor). Lunch includes plain (or low sugar) Greek yogurt (protein) with mixed berries (4g) and 1 tbsp chia seeds (4.5g). Mid-afternoon snack can be a banana (3g) with dark chocolate (70% or higher; 3g). Dinner includes butternut squash (4.5g) maybe paired with some salmon (protein) or crispy tofu (also protein) and arugula (vitamins/minerals).
Example 3 (26g total fiber): Breakfast is shredded wheat (8g) with raspberries (8g). Lunch includes multigrain bread. (3g) - maybe for grilled cheese (protein) with arugula (vitamins/minerals). Mid-afternoon snack is a mango (3g) and dinner includes a sweet potato (4g). Maybe the sweet potato replaces the bun for a burger (protein) or grilled portobello mushroom (vitamins/minerals).
Find this useful? Let me know - and if you’re on IG, tag @ask.a.biochemist and show me your snacks!
Tips for Maintaining Metabolic Balance: Travel Edition!
TRAVEL EDITION: What to do when all options are a compromise?
Real life is flexible and your nutrition plan needs to be too. Following set-in-stone rules or restrictive diets isn’t sustainable and sets us up for failure in the long term. Traveling is one of those times restrictions and rules don’t do us much good. Instead, we can use our Foundational 5 habits, our nutrition decision guide, and what we know about choosing packaged foods to maintain metabolic balance (aka feed ourselves with less stress). Click the links if you haven’t read these yet!
Here are some scenarios you might find yourself in when you’re traveling and how to make the most of them.
Scenario 1: You’re on the go & stop at a coffee shop for breakfast on the way to the airport.
Your choices are: (a) a fluffy donut that looks delicious or (b) a sad bagel and egg sandwich that you aren’t excited about. The donut and bagel have similar amounts of fiber (little), and simple carbs (aka sugar, and there’s a lot). What’s best when you can’t cook yourself or don’t have time to go to a sit-down brunch spot?
Eat the thing you’re excited about and find another source of protein + fiber to round out the morning snack mix. In this case, the egg definitely has more protein than the donut. But if you aren’t excited about it, remember that each individual food makes up just one part of your whole diet. Is there a bodega, convenience store, or quick mart you could stop in? If so, grab some other source of protein like almonds (which also have fiber) or a low-sugar protein drink.
Scenario 2: You’re at the airport and now it’s time to look for lunch.
You made it through security so you can have liquids again. You grab a coffee, which will temporarily boost your cortisol levels & therefore cause a spike in blood glucose levels. Which is fine because you still have to run to your gate. On the way, you pass: (a) a pizza place with actually good pizza, (b) your favorite Chinese take-out chain, and (c) a burrito place where you can customize what goes in your order. What’s best for when you’re about to be stuck sitting still for hours on end (after you finish dashing to your gate)?
If you can, pack ahead with some source of protein (nuts, or hard-boiled eggs, or your fav low-sugar protein drink) and fiber (some berries, an apple). If you can’t, and you don’t have strong feelings about any of these airport options, then get the one that you can reduce the number of simple carbs. In this scenario, it’s probably the burrito since you can get it without rice (Maybe you’ll even be lucky enough to get it as a salad bowl, but maybe not. Airports are not known for their fresh produce options.)
If you can’t reduce the number of simple carbs, can you increase the amount of fiber or other nutrients? Is there a veggie pizza option with extra peppers (vitamin C), broccoli (fiber), or chicken (protein)? Are there stir-fry veggies that can be added to the Chinese take-out?
PRO-TIP: They will not let you bring Greek yogurt or peanut butter through security. Both yogurt and PB are considered “liquids” by the TSA and they will take your lunch from you.
Scenario 3: You’re at an airport snack & magazine kiosk and this is it. You’re eating whatever they have.
Again, look for snacks that will have protein and fiber. Since you’re about to be forced into sitting still for a while, choose snacks with the least amount of refined carbs. They will give you refined carbs on the plane. They will only give you refined carbs on the plane.
Sometimes there are kiosk salads and sometimes those kiosk salads look good. Sometimes they have yogurt with granola cups – I’m personally suspicious of the yogurts because they are often “low fat” aka “high sugar” and have granola that also has a lot of sugar on them. If there’s yogurt you can see the nutrition label for, great, but if it’s all pre-made, be aware that it probably has a lot more sugar than is obvious.
Tips for staying metabolically balanced and not spiking your blood glucose levels while traveling:
- Plan ahead with some healthy, travel-friendly snacks!
- When you are eating on the go, remember that each food is part of a larger plan. Enjoy the donut and add in something with more nutrition with your next snack/meal.
- Remember that coffee - and being dehydrated from flying! - will both raise BGLs and cause glucose spikes. Try not to make it worse by also adding sugary snacks. Stay hydrated out there.