Call me kohlrabi

Pea and halloumi burgers with kohlrabi carpaccio; the science of nutrition and the microbiome

Makes: 4 burgers, with leftover carpaccio
Takes: 15 minutes for carpaccio; another 20 minutes for burgers

Pea and halloumi burgers with kohlrabi carpaccio

Ingredients

Kohlrabi carpaccio
1 medium-sized kohlrabi
150 g greek yoghurt
150 g feta
1 clove garlic
5 pitted olives (eg kalamata)
zest of 1/2 lemon
juice of 1/2 lemon
extra virgin olive oil
pepper and salt
~6 mint leaves

Pea and halloumi burgers
4 burger buns of choice
4 round halloumi slices
zest of 1/2 a lemon
150 g cooked quinoa (or rice)
250 g frozen (or fresh) peas
2 eggs
10 g fresh mint leaves
pepper and salt
pinch dried chile flakes
oil for cooking

Method

1. Wash kohlrabi and cut off roots. Slice as thinly as you can into rounds, using a mandolin if you have one.

2. Finely chop or microplane a clove of garlic and add to blender along with 150 g greek yoghurt, 150 g feta, 5 pitted olives and zest of 1/2 lemon. Blend until smooth, seasoning to taste.

3. Spread the yoghurt mixture out onto a serving plate, then lay out the kohlrabi in overlapping circles. Drizzle over olive oil. Top with juice of 1 lemon, seasoning, dried chile flakes, additional lemon zest and mint leaves. Place in refrigerator.

4. For the green pea burgers, blend 150 g cold, cooked quinoa, 250 g peas, 2 eggs, 10 g fresh mint leaves and zest of 1/2 lemon, until smooth and fluffy. Season to taste.

5. Heat up a frying or griddle pan with a bit of oil. Once hot, spoon out the pea burger mix into rounds the size of your burger buns. The mix will seem liquid but it will set almost like mini soufflés thanks to the eggs (try using linseed and oats as a vegan replacement). Cook on each side until browned.

   

6. Rip a few mint leaves over the halloumi and cook over a griddle pan if you have one, or in a frying pan. The trick to cooking good halloumi is to grease the griddle properly and make sure the cheese is well browned before turning it over. At a medium heat, this will take around 5 minutes each side. Cooking halloumi like this completely transforms the flavour.

7. Just before you are ready to serve, cut bread buns in half and heat them face down in the frying pan, so they can soak up any remaining flecks of halloumi or oil.

8. To serve, place the carpaccio on the table along with burger ingredients. Allow people to make their own burgers, drizzling over the thick, yoghurty sauce and using a piece of halloumi, a pea burgers and a few slices of the carpaccio for each bun.

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The science of nutrition and the microbiome

What does it mean to eat healthily? Does what we eat really matter for our health? We obsess over these questions. But the science of nutrition is complex. Studies so often focus on one discrete habit or measure one nutritional component. Or more holistic studies may demonstrate correlation but struggle to prove causation. For example, people writing on the so-called ‘blue zones’ seek to extrapolate eating and lifestyle recommendations from the habits of people in communities with the oldest populations in the world. But critics note that it is very difficult to isolate what, if any, diet or lifestyle factors are the causes of longevity. What about intangibles like the joy we get from eating? Do they also impact on the science of nutrition?

There is some evidence that nutrients are more likely to be absorbed from food you are familiar with, as opposed to food you eat rarely. Ruby Tandoh suggests in her book Eat Up, that “the enjoyment we get from our food is intimately connected to the nutritional power of that food”, which may be why people who lose their sense of smell are more prone to depression or weight problems. One of the studies she cites is a famous 1970s study that showed that Thai woman eating a popular spicy Thai dish, who were also more at ease with the level of spice, were able to absorb nearly 50% more iron from the same food than a group of Swedish woman.¹ Of course there could be multiple explanations for this curious result. But we might speculate that the microbiome of the Swedish women was less well adapted to extracting nutrients from spicy food that they did not usually eat.

I’ve long been interested in the concept of the microbiome. The microbiome refers to the trillions of microorganisms (also called microbiota or microbes) that co-exist with humans (and many other species), including bacteria, fungi, parasites, and viruses. They live on the skin and throughout the body. But they play a particularly important role in the digestive system, with the largest number occurring in the small and large intestines. The microbiome has been recognised as a supporting organ since its functions are so integral to human health.

I’ve eaten almost no meat since I was only seven or eight years old. Is my gut microbiome even capable of extracting nutrients from meat anymore? There was a moment in my early twenties when I felt like I should give meat a go to see if my strong childhood dislike had changed. It hadn’t. I tried a bite of steak, leading to some rather dramatic and rapid digestive difficulties and terrible gas. I’ve always wondered whether my microbiome was responsible.

Scientists are just now beginning to understand the outsized role that the microbiome plays in both our physical and mental health. The relationship between our gut and our brain is not a one-way street, where we just make decisions with our brain and communicate them to our limbs and organs. Instead, there is growing evidence that our brain, microbiome and the gut are connected, in surprising, bi-directional ways. As a recent Nature article pointed out, we used to think about the gastrointestinal tract as just being the place in the body where nutrients were absorbed. But what we now know is that nutrients are detected in the gut and a message sent to inform the central nervous system about the size and composition of a meal. Communication from the microbiome to the brain (via the vagus nerve) can also affect things like stress, mood, sleep and our level of sensitivity. While most of the literature associates gut microbiota composition with human health, development and disease, it should be noted that currently “evidence for causality remains sparse.” Nevertheless, it is at least possible that one day we may be treating anxiety and depression with microbiotic interventions.

The psychologist Kimberley Wilson (interviewed this week on the On Being podcast), gives an example of how stress, diet and our mental health are interrelated. She points out that when we are stressed, our brain will prioritise the nutrients to make stress hormones. This in turn depletes the availability of those nutrients for other functions, such as manufacturing the neurotransmitters that make you feel good, like serotonin or dopamine. Logically, the flipside of this is that improving your diet may help with resilience against stress and/or to avoid depression by ensuring your body has access to the nutrients it needs.

So what does all of this mean when we are confronted with the simple question of what to eat for dinner tonight? I think it is important to trust your own instincts about what is healthy and necessary for you to make you feel good. Know that eating is not just about what we put in our mouth and chew, what we taste or smell. Your whole body is involved in making sure you are getting the right nutrients you need, and will be impacted by the choices you make, including the microbiome in your gut. But having some of this knowledge is another reason to eat healthily, so we can support both our mental and physical health.

If you’re feeling stressed at the moment, one of the things you can do for yourself is to make sure you eat a varied, fibre-rich meal that helps a healthy microbiome flourish. Oh hi there, raw kohlrabi! But it’s not just veggies. Think about a varied diet with plenty of fruit and vegetables, beans and nuts and whole grains such as whole oats. The best way to promote a healthy gut is to focus on slowly introducing more fibre-intensive prebiotics like bananas, raw onion, garlic, asparagus, jerusalem artichokes, asparagus and seaweed, as well as fermented foods.

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You decide to try this week’s recipe for Greek-influenced veggie burgers. Just the sight of the stunning colour of the purple kohlrabi improves your mood. It looks like a first blush rose laid out on the plate like that with its creamy middle on display, lightly pickled by flakes of seasalt and lemon juice. You choose whole-grain buns with lots of seeds, layering the cloud-light, minty pea burgers with slices of the almost spicy, crunchy kohlrabi and topping it with the satisfying heft and substance of grilled, salty halloumi. You spoon over the potent yoghurt/feta sauce. You help yourself to a classic salad of raw tomato, cucumber, red onion and red capsicums, with a simple dressing of pomegranate molasses (or honey), olive oil and lemon juice.

No cutlery needed, you eat the burger with your hands, the sauce drips out as you take the first bite and you wipe your chin. You notice the pungent lemon, a little raw garlic and mint, the peas, the crunch of the seedy buns. The halloumi is so salty it makes you remember the time you took a last dip in the ocean before flying out from that island holiday, having no time or place to shower, wiping the sand off the best you could with a damp towel, the salt dried white against your skin as you check your bags in. As you eat, you sigh with contentment. This is good food, you tell yourself. You forget the microbiome and the science and the complex processes all taking care of themselves at some other level of which you are not even aware. Everything is going to be okay.

See you next week and thanks for reading!

Amelia

PS, our baby pigeons are doing well, though North is now around double the size of South. It is incredible how much difference being born one day earlier can make.

1. See: L. Hallberg et al, ‘Iron Absorption from Southeast Asian Diets’ (1977) (30) American Journal of Clinical Nutrition 539. A number of factors may explain the lower rates of absorption, which were even more pronounced when meals were mixed before serving versus being served with their component parts separate.