Heart health: Part II – Heart rate, variability and food
Resting heart rate – slower is better
As your heart gets more efficient and stronger – it can pump more blood with each stroke (and, potentially, require less energy to do that). Eventually, what this leads to is slower resting heart rate. Remember, the heart rate is a product of the demand for oxygenated blood and your heart’s ability to satisfy that demand. As this ability improves, the heart doesn’t need to beat as fast.
This is precisely where the benefit of exercise comes in. Exercise not only strengthens the heart itself and makes it more efficient in accessing oxygen in the blood (by growing more mitochondria) – but it also triggers the growth of new mitochondria (as well as improvement in oxidative capacity of existing mitochondria) at the periphery (i.e. – within the target tissue). All of that means that tissues in need of oxygen could now use less of it to satisfy the same demand for energy – which means your heart doesn’t need to beat as fast.
What benefits does slower heart rate have? There may be a couple:
- Slower heart rate means a bigger “buffer” between current and maximum heart rate to keep up with more demanding situations when the heart needs to beat faster. Remember – the maximum rate is a finite number for everyone – your heart can’t just beat faster and faster in response to the demand – because the heart itself needs oxygen from blood to perform the work. Faster heart rate means higher energy demand for the heart muscle itself – and at some point, the ability to fuel this process by oxygen delivered by the blood will be limited by the supply of that freshly oxygenated blood and the speed at which it is utilized within the aerobic metabolism pathways. No available energy at any given moment means no ability to contract. So a slower heart rate potentially means more energy-efficient heart and a higher capacity to increase that rate to address spontaneous demands for blood delivery;
- As we have already mentioned, muscle contraction requires energy – which comes from oxidation of fat, glucose or ketone bodies. Cellular energy metabolism – while being absolutely essential for life – also generates several chemical and electrical by-products that, in large amounts, can be harmful. For instance – we have already discussed positive hydrogen ions (H+) generated by muscle contraction that raise the acidity of the cell. Also, cellular metabolism generates reactive oxygen species that are known to inflict damage to cell’s DNA and cause various disorders. It follows, then, that less energy required for resting heart rate means less of such by-products – which, by the way, may contribute to the wear and tear and, as a result – the longevity of the heart itself. Perhaps it is no coincidence that animals with generally slower heart rates live longer?
In the end – slower heart rate is not something you specifically strive for – it is merely a side effect of training and an indication that your heart is getting more efficient.
Heart Rate Variability (HRV)
Although diet and exercise play a huge role in your heart health, there is another very important factor that influences it – along with other organs and systems in your body – your stress levels. And, when it comes to the heart, there is a reliable method of measuring your level of stress and, thus, predicting and preventing negative consequences.
Most people know that heart rate speeds up and slows down in response to your activities – but think that, at rest, the heart beats at relatively the same pace. This is actually not the case – heart rate is usually measured in beats per minute, but the actual time between each beat does not remain constant – that is, until something goes wrong. In a healthy heart, there is an ever so slight (usually measured in milliseconds) natural variation in the time interval between heartbeats, called Heart Rate Variability.
Why is this important? Because low HRV (i.e. – lack of variation in those time intervals) may be able to predict the risk of a heart attack – and in those who already had a heart attack, it can be a predictor of mortality in the next three years. It is also associated with other conditions, such as hypertension, diabetes and chronic obstructive pulmonary disease, among some others.
Generally speaking, because HRV reflects the state of your autonomous nervous system (ANS) and the ANS (comprised of the two main branches that control the body’s stress and recovery processes) is tied to many automatic processes in the body that regulate blood sugar, body temperature, blood pressure, sweat, digestion, and much more – HRV helps you gain an understanding of the state of your ANS at any given moment. High HRV indicates dominance of the parasympathetic response (the branch that promotes relaxation, digestion, sleep, and recovery). Low HRV indicates dominance of the sympathetic response, (the “fight or flight” branch), associated with stress, overtraining, and inflammation.
When you heart is stressed, your HRV disappears and the beats become more evenly spaced. So, measuring and comparing your HRV to a healthy baseline can tell you a lot. Too little variation indicates age-related system depletion, chronic stress, pathology, or inadequate functioning in various levels of self-regulatory control systems.
There are several dedicated devices on the market, as well as smartphone apps, which (whether with a help of a simple and inexpensive heart rate monitor strapped to your body or without it) help you easily measure your HRV. Heart rate variability is best measured in a rested state (demanding physical activity – being a stressor – actually temporarily reduces HRV).
So what do you do if you determine you have low HRV? First and foremost (if several measurements throughout the day confirm this), talk to a cardiologist – you may be on the verge of a heart attack and not know it.
But there are also measures that you may take on your own. Heart rate variability is something that is regulated by autonomous nervous system – and you can’t really consciously control it. But when you monitor and receive real-time biofeedback on the results of what you think or do, you can learn to raise HRV through techniques such as conscious breathing, meditation, or physical relaxation.
In addition, you can follow a few guidelines to help maintain high HRV (or improve a low HRV). The goal is not to have HRV that is constantly high (this would mean you never exercise and never experience any stressors – some of which are beneficial), but if you have any reason for concern (i.e. – your HRV is often low), the following may help:
- Get enough sleep and recover sufficiently after exercise. You probably noticed that this is a common theme in many articles – but that’s because it is THAT important! If you don’t get enough rest and recovery – it raises your stress levels, compromises your athletic results, lower your immunity and wreaks all sorts of havoc on your body. When you are emotionally or physically stressed or tired and in need of recovery after exercise – getting more sleep and reducing the frequency of (potentially too intense) is a great solution.
- Do not overdo it with exercise. By now you should know that recovery after exercise may be even more important than exercise itself. You can’t just keep pushing yourself – or the results will be the opposite of what you expect. Your post-exercise recovery may depend on your age, hormonal balance, fitness level and other factors – so you should not just copy some else’s schedule – but ignoring proper recovery after a workout adds up to the stress of the exercise itself and your autonomous nervous system will confirm this through lower HRV. Remember – this is an indicator that something is wrong – do not ignore this!
- Try to eliminate unhealthy habits. No matter what you may have heard about the benefits of red wine for your heart (as long as it’s based on resveratrol – it’s a myth), alcohol is a stressor and a toxin. True, your body is equipped with necessary enzymes that metabolize it, but they created a few quite toxic by-products (such as acetaldehyde) and depletes important minerals (such as magnesium) in the process. Some argue that this creates a hormetic response that builds all sorts of resilience in your cells – but it’s hard to argue the facts: alcohol does impact the HRV negatively and that should tell you something. While you can get away with occasional drink – as little as two glasses of wine may affect your HRV. Given that too much alcohol also impairs sleep quality (thus, undermining the rule in first bullet point above) – you should be really careful with it;
- Some compounds, like L-theanine found in green tea, have been shown to positively impact HRV – so don’t ignore those. The effect is probably not very pronounced, but – in combination with other things – they can be beneficial;
- Generally – and it may be easier said than done, but try really hard – to the best of your ability, remove known stressors form your life. Practice meditation (this doesn’t have to be anything overly complicated or structured – sometimes just relaxing and trying to calm your mind and focus on slow breathing can help a lot), find a better job, a rewarding hobby, spend more time with people you love, get more sunlight and find what makes you happy and stick with it. This is a loaded statement – but only you can figure out what it is
Lose fat for a healthy heart
It’s no secret that obesity is directly associated with heart disease (as well as a whole bunch of other medical conditions). Whether it is a direct cause of heart problems or simply accompanies and indicates conditions that lead to heart problems doesn’t really matter – the point is, if you are obese or overweight, your risk of heart disease increases.
When you are obese, every activity requires more energy. Going up the stairs or even walking briskly requires your muscles to move a potentially significant amount of weight – for which they need energy that needs to be generated by oxidizing macronutrients delivered (immediately or with a bit of a delay) in the blood. The more energy you exert – the more of that blood supply you need – and the more your heart has to work. At some point, if the heart is not trained and the effort exerted is really high compared to your level of preparedness – the heart can fail to deliver sufficient amount of oxygenated blood to itself to support the elevated energy requirements for pumping more blood throughout the body, leading to myocardial infarction (heart attack).
So make sure you focus on getting rid of that fat (not weight, but extra body fat, specifically). It’s really not that hard – and the first thing you need to do is revise your diet (and only then look at exercise).
The best fuel for heart muscle (it’s probably not what you think!)
For decades, most people have been taught that glucose is the best and most efficient fuel for cellular metabolism. All of our cells are able to extract some energy from carbohydrates (glucose or other simple or complex sugars, which, after being broken down by various enzymes, essentially feed into the same pathway) – some aerobically, some anaerobically (without the presence of oxygen).
For some cells (that either have damaged mitochondria or lack them altogether – like red blood cells) anaerobic glucose metabolism is the only possible way to extract energy for cellular processes. But the vast majority of them are also able to produce energy by metabolizing other substrates – fats, ketone bodies and even some amino acids.
Most cells are able to switch between various types of metabolism depending on the current environment (availability of oxygen and the presence of other catalysts). At any given point in time, your body as a whole utilizes multiple metabolic pathways at the same time. In fact, even within the same tissue you may have some cells that extract energy aerobically and some cells that do that anaerobically.
The ability of your cells to use many different substrates to extract energy required for life is a remarkable adaptive mechanism that allows you to survive. But the fact that your body can process a specific type of fuel doesn’t always mean it should. Especially when overloading on that type of fuel has other drawbacks.
Glucose is essential for life – and you cannot survive without it. At any given point in time, even if you take in zero carbs, your body will still synthesize a small amount of its own glucose from other substrates through gluconeogenesis, to support glucose-hungry processes and store a bit as glycogen. But when you take in too much of it (which, unfortunately, is very typical for food habits of a modern man, spoiled by ready-to-eat processed foods using cheap calories as energy) – things may start going off the rails.
The heart can get easily affected by such glucose excess – diabetic heart disease is a general term for a set of conditions and heart issues that develop in people with diabetes. The risk of dying from heart attack for people with Type 2 diabetes are the same as in people who already had heart attacks. Diabetes also leads to neuropathy (nerve damage) – both in the heart itself and in other tissues, including those that control blood pressure (another risk factor for heart disease).
The risk is not specific to diabetics – some studies show that even in non-diabetic patients, elevated blood glucose was strongly associated with heart failure.
Too much glucose means an increased risk of:
- metabolic disorders, such as diabetes;
- glycation of tissue proteins;
- free-radical damage;
- yeast and bacterial overgrowth (as simple sugars are their favorite food);
- and more;
Within the context of the heart tissue itself, studies show that chronic increases in myocardial glucose uptake and oxidation reduce the heart’s metabolic flexibility and render it susceptible to contractile dysfunction.
On the other hand, our old friends – ketone bodies – continue to remain the preferred kind of fuel even for the cardiac muscle (just as they are for your brain, as you would have learned form prior articles). In fact, heart muscle is the highest consumer (per unit mass) of ketone bodies – which are the preferred substrate for energy production.
In fact, ketone bodies may be preferred not just over glucose, but even over fatty acids. Despite the highest theoretical payoff of ATP per each carbon bond within long-chain free fatty acids, given the initial ATP investment required to activate their oxidation and because of some other specifics of complex chemical pathways related to the oxidation of ketone bodies, the latter may be more energetically dense in the end.
Moreover, unrestrained mitochondrial fatty acid oxidation increases the generation of reactive oxygen species (ROS) to levels that exceed scavenging mechanisms – which doesn’t happen to the same extent with ketone bodies. In fact ketone bodies actually diminish oxidative stress by scavenging free radicals.
So, ketones come out on top once again. This doesn’t, of course, mean that ketosis is the only state that guarantees a healthy heart – you don’t necessarily have to go to extremes, but, given the facts above, reduction in carbohydrate/glucose intake (at least compared to a “typical” average level of consumption in a Western diet) – with potential substitution of lost energy for high quality fats and ketone bodies – is definitely warranted.
In Part III – the final part of the series – we will talk about how to slow down aging of the heart and important supplements for heart health.