Heart rate variability (HRV): The role of diet

If you use wearable health tech, you may have encountered the term “heart rate variability” (HRV). But what does HRV measure, and does it really matter for health? 

In this article, we’ll answer these questions and investigate whether diet can improve your HRV.

What is heart rate variability?

HRV measures the gap between your heartbeats and how much that gap varies.

As you probably know, your heart rate increases during exercise or stress and decreases during periods of relaxation. But even at rest, the gap between heartbeats varies, and this variability differs between people.

Thanks to wearable tech, it is now relatively easy to assess your HRV.

How does your body control HRV?

Many factors contribute to HRV, but your brain is ultimately pushing the levers. Using sensory signals — sights, sounds, and so on — and other inputs, like whether you are moving or sleeping, your brain lets your heart know what’s required.

The ANS is split into two complementary systems:

• Sympathetic nervous system: Controls “fight-or-flight” responses, like boosting heart rate and blood pressure when you’re in danger.

• Parasympathetic nervous system: Slows heart rate and lowers blood pressure during relaxation.

These two systems work in tandem. For instance, if you are running for a bus, your sympathetic system boosts your heart rate to make sure your muscles get enough blood as you sprint. Then, once you’re on the bus, your parasympathetic system returns things to normal as you relax.

So, the sympathetic and parasympathetic systems have broadly opposite effects, meaning they need to be well balanced, with neither system overpowering the other. 

Why does HRV matter?

As we’ve seen, your body’s requirements vary, so your heart rate needs to adapt quickly. And HRV measures how responsive and flexible your autonomic nervous system is. 

That's why a higher HRV seems to be linked to better health: It’s a sign that your body is primed and ready to adapt when needed. Lower HRV, on the other hand, is a sign that your nervous system (and, therefore, your body) struggles to adapt to changes. 

Indeed, research shows that a higher HRV is associated with a lower risk of heart disease, while a lower HRV is linked to an increased risk.

Although HRV isn’t routinely used in medicine, advances in technology have made it easier to study the links between HRV and physical health. And these links are growing stronger.

Conversely, people who are physically fit or follow a healthy lifestyle tend to have higher HRV.

There is also growing evidence that a greater HRV might be a marker of better mental health resilience — your ability to adapt to difficulties in life. Along these lines, research shows that people with symptoms of depression or anxiety are more likely to have lower HRV.

Can diet improve your HRV?

This is a tricky question because many factors influence HRV, including age, physical and mental health conditions, current medications, and nutrient deficiencies. 

Additionally, there are multiple ways to measure HRV, making it difficult to compare the results of different studies.

However, there are several studies on this topic, so let’s look at some of the findings.

Nutrients and HRV

The most studied nutrients so far are omega-3s, which are essential fatty acids primarily found in oily fish.

A review focusing on individual vitamins and minerals concludes that there’s not enough evidence to prove that any micronutrients definitely improve HRV.

However, they also write that the best evidence so far is for “vitamins D and B12, where a deficiency was associated with reduced HRV.”

So, while being deficient in these compounds may decrease your HRV, increasing your intake may not improve HRV if you already have healthy levels of those nutrients. It’s also likely that an overall healthy dietary pattern rather than individual nutrients that’s most important. 

We need more research.

Almonds and HRV

ZOE’s Chief Scientist, Prof. Sarah Berry, published a study on HRV in 2020.

For the 6-week study, the scientists recruited adults with an above-average risk of developing cardiovascular disease. While their main diet stayed the same, the researchers changed their snacks. 

They ate either whole almonds or specially designed muffins. The muffins contained the same calories as the almonds and similar amounts of fat, protein, and sugar as average snacks consumed in the United Kingdom.

At the start and end of the study, the scientists measured participants’ HRV while resting and during a mentally stressful task.

This is further evidence of the importance of snack choice. If you'd like to learn more about snacking, ZOE conducted a fascinating study on the topic that you can read about here.

Dietary patterns and HRV

At ZOE, we know that your whole dietary pattern is most important for health, and some researchers have looked at this relationship. 

For instance, a 2009 study on 586 older men found that a higher intake of green leafy vegetables was associated with higher HRV. And a review from 2020 found a link between increased fruit consumption and higher HRV.

Another study from 2010 investigated the Mediterranean diet and HRV in 276 adult twins. The researchers assessed how closely their eating patterns aligned with the Mediterranean diet and measured their HRV for 24 hours.

After controlling for a number of factors, they concluded that those who followed the Mediterranean diet most closely had the highest HRV.

It is now well-established that the Mediterranean diet is associated with better heart health, and the authors suggest that this benefit might be due — at least in part — to its improvement of HRV.

What should you do?

Scientists need to conduct much more research into the role diet plays in HRV. However, as it stands, it seems that a plant-based, Mediterranean-style diet might be beneficial.

We also know that this type of diverse fruit-and-veg-heavy dietary pattern supports many aspects of health.

So, while we wait for evidence to come in, following this approach is still likely to benefit your health, whether it influences HRV or not.

If you’d like to increase your plant diversity, we have a guide to eating 30 plants each week and a wide range of delicious plant-heavy recipes to try.