Sunday, 6 January 2013

Tomato, leek and barley soup with japanese yam and kale

The Lure of lycopene

Arguably one of the greatest accomplishments of the last century was the control of infectious diseases in the developed world owing to the discovery and development of vaccines, antibiotics and other antimicrobial agents (CDC). With the advancement of microbiology and the reduced impact of harmful bugs on the lifespan of human beings, other threats to human health have emerged including cancer, diabetes and the number one killer - heart disease. 

Genetics and age have an immovable impact on our cardiovascular systems but countless other environmental factors also impact the health and longevity of our hearts.  The biggest environmental factors contributing to the decline of our central, blood pumping organ is lack of exercise, weight-gain, low fruit/vegetable consumption and smoking - all of which we do have control over when it comes to our fitness. Unfortunately, for many, tackling these issues is easier said than done.

Another inconspicuous player in cardiovascular health is carried inside the bellies of one of my favorite foods, the tomato, and is called lycopene. Watermelons, guava, grapefruit and papaya are other great sources of lycopene. One early sign that lycopene might positively impact our heart was the knowledge that in regions of the world where a Mediterranean diet is consumed, there is a decreased risk for heart disease compared to the rest of the world. Tomatoes are a major component of the Mediterranean diet that was found to contribute to this decreased incidence of heart disease and lycopene is abundantly present in this fruit.

Lycopene is a molecule that is classified as a carotenoid. Carotenoids are natural pigments that are produced by plants and often contribute to the particular colour of a fruit or vegetable.  Each carotenoid has a specific structure that contributes to the pigment associated with it.

The characteristics of carotenoids do not end in their colour however; in plants they are responsible for absorbing light which is used to make energy and they also protect the plant's energy-making machinery from damage. In people, carotenoids play a similar protective role as an antioxidant, meaning they absorb harmful, reactive molecules that can cause damage to our cells. Humans, for the most part do not make carotenoids and so we depend on the consumption of fruits and vegetables to get these important antioxidants into our bodies.

Sidebar: Antioxidants are protective molecules that can bind and neutralize reactive oxygen species (also known as a free-radicals) that cause oxidative damage. Charged, oxygen-based molecules are released as by-products of many molecular reactions that are constantly happening in and around us. When oxygen species become charged they become reactive, meaning they like to bump into things and damage the things that they run into, like our cells and our DNA. Carotenoids, which act as 'anti'oxidants can capture these reactive oxygen molecules and prevent them from damaging our critical cellular systems.

Getting back to heart disease, it is now thought that many environmental factors that increase our risk for cardiovascular pathologies actually promote oxidative stress and ensuing damage. In other words, things like smoking, obesity and diabetes increase the levels of damaging reactive molecules in our bodies. Increased oxidative stress causes damage to the tissues in our body that are required for keeping our cardiovascular system running smoothly. 

Coming back full circle, it is obvious then why it is so important to eat plenty of fruits and vegetables - to get these antioxidants into our blood streams, to scavenge excess reactive oxygen species and to promote the health of our cells that make up our organs.

Many studies have been done to examine the relationship between lycopene and heart disease; the results have been mixed. Although many studies do support the claim that lycopene positively affects heart health, other studies have failed to find a link. Either way, the protective effect of antioxidants is well documented. For reasons I do not fully understand, simply taking these molecules as a supplement is not as beneficial as consuming them naturally from fruits and vegetables. For one thing, other components of fruits and vegetables, such as vitamins and carotene, may also be playing unique and complimentary roles in protecting us from disease. Also, in many cases it is found that other components of fruits and vegetables are needed for carotenoids to be properly absorbed.

As an example, lycopene is not easily released and taken up into our blood stream following consumption of raw tomatoes. Lycopene is more easily absorbed from cooked tomato products like tomato sauces and tomato juice. Also, it has been found that the bioavailability of lycopene is increased when tomatoes are eaten and prepared with certain types of oil, such as olive oil. This is especially interesting considering olive oil is another Mediterranean diet staple, and that this diet is linked to a healthy cardiovascular system.

You have heard it before, but it is worth repeating, eating as many fruits and vegetables as you can is important for a healthy body. Lycopene sourced from tomatoes, to scavenge damaging free-radicals, is a specific example of how and why this is so important.

And with that, here is a wonderfully heart healthy recipe packed with nothing but all that is good in the world: tomatoes, leeks, barley and kale. Lycopene absorption from this recipe should be maximized with the initial sautéing in olive oil, followed by blending of the tomatoes and a long, slow cooking step.

Tomato, leek and barley soup with japanese yam and kale
The sage drizzle in this recipe is simply gratuitous. The soup tastes great without it, making a great meal eaten right off the stove or the next day packed in a lunch

  • 8 medium tomatoes
  • 2 tbsp olive oil
  • 1 large leek, end trimmed and chopped
  • 1/2 onion, chopped
  • 3 cloves garlic, minced
  • 10 cups water
  • 4 organic, vegetable stock cubes
  • 1/2 cup dry barley
  • 1/2 cup dry small pasta shape
  • 1 small japanese yam, small cubes
  • 2 large kale leaves, stems torn off and leaves chopped
  • Sage drizzle (optional) (Combine in a food processor: 5 sage leaves, 1 tsp white balsamic vinegar or lemon juice and 3 tbsp of olive oil)

  1. Bring a large pot of water to boil.
  2. Cut small, shallow crosses into the skin at the bottom of the tomatoes.
  3. Immerse the tomatoes in the boiling water for 1 minute.
  4. Drain and add the tomatoes to cold water with ice, to cool the tomatoes
  5. Slide the skins off of the tomatoes and discard the skins.
  6. Chop and roughly puree the tomatoes in a food processor or blender then set aside.
  7. In a large frying pan, heat 2 tbsp of oil over medium-low heat and add chopped leeks, garlic and onion and sauté for about 10 minutes until soft.
  8. Add the tomatoes and bring to a simmer, cover and cook about 30 minutes.
  9. Meanwhile in a separate large pot, bring 10 cups of water to boil and add 4 vegetable bouillon cubes (or use 8 cups of prepared stock plus 2 cups of water).
  10. Lower heat, stir in the barley, cover and simmer to cook for 15 minutes.
  11. Next stir in the pasta to the broth and cook 5 minutes before stirring in the chopped yam.
  12. Finish the cooking by simmering the broth for another 5-10 minutes, until the yams are tender.
  13. In a food processor, blend the tomato and leek mixture until roughly smooth and then stir the tomato mixture into the broth.
  14. Season the soup with sea salt and a few tablespoons of honey or other sweetener. I suggest start by adding a few turns of salt from a salt grinder and one or two teaspoons of sweetener into the soup, then scoop a few spoonfuls of the soup into a small bowl and taste. Add more salt or sweetener if needed and repeat until desired taste is achieved. 
  15. Remove the soup from the stove to cool and stir in the chopped kale.
  16. Serve soup warm and if desired, garnish with sage-oil drizzle.

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