Leafy Greens For Heart Health: Nature's Cardio Protectors

The importance of heart health cannot be stressed enough, as coronary heart disease (CHD) is the leading cause of mortality. It was the biggest cause of mortality in 2019 and on average 9 million pass away due to this annually. This article will focus on the importance of enhancing your diet with leafy greens to boost your heart health and the various vitamins, minerals, and nutrients often forgotten when considering how to form a balanced diet.

Leafy greens like spinach, kale, and bok choy are high in vitamins, minerals, and antioxidants. They are especially high in vitamin K which contributes to better clotting which plays an important part after injury and improves cardiovascular health. Vitamin K2 has proven to increase the flexibility of the heart vessels and thus decrease cardiovascular death.¹

Nutritional benefits of leafy greens

As mentioned above, leafy greens are rich in vitamins but also in potassium, fibre, phytochemicals, and nitrates. We will now discuss these below looking at the benefits of fibre, potassium, vitamin K, Vitamin C, phytochemicals, and nitrates. This will be followed by the three main green leafy vegetables and some additional contributions to better heart health. 

Fibre

Fibre is a key driver in promoting good heart health as it lowers cholesterol levels, thus lowering the risk of CHD. Cholesterol builds up in blood vessels in the heart, leading to fatty deposits. These cause heart attacks and strokes, and most severe cases would need manual widening of vessels to overcome this.

One plausible theory about fibre benefit is that the glue-like nature of fibre in the intestines increases the feeling of fullness and therefore we consume less food. Another mechanism that is directly linked, is that fibre is broken down by bacteria in the intestine forming short-chain fatty acids which reduce cholesterol synthesis.² 

There is also some evidence in animal studies that it reduces blood pressure. Still, there is not enough evidence in humans so further studies need to be conducted to increase confidence of the correlation between fiber and cholesterol.³

Potassium

The World Health Organisation conducted a review study to form guidance on potassium intake to improve cardiovascular health. This review included children and adults. In both groups, potassium caused a decrease in blood pressure, which was most effective with 90-120 mmol/day consumption in adults.⁴

Potassium is thought to reduce blood pressure by reducing the amount of bone-related proteins and calcium in the blood, which means that the blood vessels do not get stiff. Arterial stiffness is an indicator of cardiovascular death, so this should be taken seriously.⁵ However, excess potassium consumption is a problem for those with kidney dysfunction, as well as it may lead to irregular heart rhythm.⁶

Vitamin K

As mentioned above Vitamin K2 plays an important role in maintaining the flexibility of our blood vessels, thus optimising heart performance. Specifically Vitamin K2’s subtype, MK-7 activates proteins that deter calcium from migrating to soft tissues, like those in blood vessels of the heart, which means there is a reduction in plaque buildup and calcification.⁷

However, Vitamin K2 is more common in fermented food and meat.⁸ In contrast, Vitamin K1, which leafy greens are rich in, has reduced blood vessel calcification and promoted better heart health due to reducing inflammation and insulin resistance.⁹

Vitamin C 

Vitamin C is well known for preventing the oxidation of a form of cholesterol known as low-density lipoprotein (LDL). When LDL is oxidised it triggers the cascade of events that cause plaque buildup in the blood vessels. Other mechanisms of action include helping the blood vessels increase in width and lowering blood pressure.¹⁰

Phytochemicals

Phytochemicals play a similar role to Vitamin C, by acting as an antioxidant.¹¹ Therefore, they reduce oxidative stress and inflammation. The number of phytochemicals in an individual’s diet can be identified using the dietary phytochemical index (DPI).¹²

More recent population-based design studies have used the DPI to study obese patients, in which there is an inverse relationship between DPI and heart disease factors, which emphasises the importance of having a high DPI diet. Not only has it been shown to reduce oxidative stress, but it also plays a major role in maintaining cholesterol levels in many ways, such as inhibiting cholesterol production, promoting the excretion of cholesterol by the liver, and increasing the removal of excess cholesterol from tissues.¹³

Nitrate

Nitrate from the soil is transported through the roots up to the leaves, giving the leaves of plants the highest concentration of nitrates.¹⁴ The European Food Safety Authority has announced that the acceptable daily intake of nitrate for humans is 3.7 mg of nitrate per kilogram of body weight. It is not recommended to over-consume added nitrates from products such as processed meats because it can lead to a condition known as methemoglobinemia in babies and an increased risk of cancer in adults. 

However, nitrates from vegetables have a range of benefits, such as allowing the relaxation of blood vessels and reducing platelet aggregation, thus preventing excessive clotting and reducing blood pressure.¹⁵ You are recommended to eat leafy vegetables high in nitrates to gain these benefits but stay clear from excess consumption of processed meat. This would allow the benefits of nitrates to outweigh the risks.^16,17 

Leafy green examples

Spinach

Spinach is one of the most versatile vegetables to use; for those who don’t enjoy the taste of green vegetables, it can easily be blended into smoothies, curries, and pasta sauce bases. 

You can grow it in your garden or buy it in stores at any time of the year. As per the statistics on the website of the U.S. Department Of Agriculture (USDA), spinach is rich in potassium, sodium, calcium, magnesium, vitamins B, C, and K, and phytochemicals like beta-carotene. 

To preserve the phytochemicals it is best eaten raw, as cooking green vegetables like spinach and kale reduces their total carotenoids which is a form of a phytochemical by 28.2%.^18,19 Spinach is also a source of naturally occurring dietary nitrate, with around 168.5–2350.9 mg per kg.²⁰ 

You can eat it raw by swapping it out for lettuce in salads, shredding it, and tossing it in as garnish or adding it as an ingredient for your smoothie or green juice. It can also be lightly sauteed or added at the end of your omelette to reduce overcooking. Follow these simple recipes both of which can be prepared in under 5 minutes from BBC Goodfood for wilted spinach and a green smoothie.

Kale

Kale is another vegetable that is considered a superfood due to it being rich in calcium, potassium, sodium, magnesium, vitamins A, C, and K, and phytochemicals such as beta-carotene at 2870 µg. It also has high amounts of the most important omega-3 fatty acid called alpha-linolenic acid at 0.18g per 100g.²⁰ 

Humans cannot make alpha-linolenic acid so must be accumulated by your diet and improves heart health by reducing fat buildup and reducing the formation of plaques in the blood vessels.^21,22 There are many easy kale recipes on BBC Goodfood and Jamie Oliver’s website for you to follow for your next meal to gain the benefits of increasing your life expectancy by promoting better heart health.

Bok choy

Bok choy, also known as Pak Choi or Chinese cabbage has high levels of calcium, potassium, vitamin B, especially vitamin B6 at 0.194mg per 100g, vitamin C, and beta-carotene.²³ Vitamin B6 is crucial in helping remove homocysteine.²⁴ 

Some mechanisms of action of homocysteine that contribute to heart disease are changing the internal structure of blood vessels and increasing the number of platelets causing blood clots in the blood vessels. Here are a few interesting bok choy recipes for you to try out from BBC Goodfood and Tesco RealFood recipes. 

Summary

It is clear from the overwhelming evidence that leafy vegetables have a great impact on our heart health, from reducing inflammation, widening our blood vessels, reducing our blood pressure, and lowering cholesterol. It is often a misconception that green vegetables are only rich in vitamins and fibre. This article delves into the many constituents of the green vegetables spinach, kale, and bok choy which contain numerous other vital cardiovascular protectors such as nitrates and omega-3 fatty acids.