Flavio Furlan, Author at Naturally Strong
Flavio Furlan

Author Archives: Flavio Furlan

Of Glucose and Finger Pricks — Is Personalized Nutrition Possible?

With the publication of the last book of our friend Robb Wolf "Wired to Eat", the concept of personalized nutrition has become mainstream.

I sincerely think that personalized nutrition constitutes the binary that nutritional science should follow to instruct humans on which is the "best diet" for them and how to manage it.

The fact is that personalized nutrition, to be "personalized", requires a higher degree of quantification than most people are capable, or willing to do.

In Wired to Eat, the reader learns about how a team of Israelis scientists has collected a sample of DNA and microbiome of several subjects, applying them subsequently a CGM (Continuous Glucose Monitor).

Thanks to the different glycemic response of the individuals at various meals (with high variation in macronutrient ratios), they have been able to develop an algorithm that can predict the glycemic response of the person to a given meal, with a surprisingly high degree of accuracy.

On top of that, the algorithm can develop two lists that consist of the top food choices and the worst food choices for the given individual.

Not bad, huh? Being as curious as I am, I would like to have instant access to that algorithm.

However, as for now, I must be content to follow the alternative DIY solution proposed in the book: playing with a glucometer to test the glycemic reactions to different kinds of carb-sources.

On the paper, this procedure should help me to have a better understanding of my insulin sensitivity (associated with a lab test) and eventual particular auto-immune reactions triggered by certain foods because we know that stress-levels and inflammation can influence glycemic control.

What's needed to run the experiment? A simple glucometer and the food source that you want to test, with a proper amount of net carbs (usually 50g NET for a medium-sized male).

Are we giving anything for granted?

It is assumable that glucometers are reliable by law, right? Therefore two different glucometers should provide similar measures when using the same drop of blood, or at least the trend should be the same when several recordings are taken.

Even better, now that CGMs are available for the general public, if one wants to have an idea of his or her glycemic response, it should be enough to stick one of those expensive gizmos on the arm and look at the results, without even have to bother spilling precious blood.

My Experiment

To verify the state of the art of this technology, during this summer I ran several experiments on myself, taking advantage of my regained high degree of insulin sensitivity (that required almost two years of hard old-school "Ketogains approved" dietary and physical work).

I have done so by testing different glucometers with various food sources (even a CGM) and then I have compared the results.

Let's start with fasted blood glucose, here's mine:

fasted glucose measure


Here's my fasted blood glucose one hour after waking up:

fasted glucose measures 1 hour after waking up

Let's test a quick carb source, shall we?

glucose meter comparison 1
glucose meter comparison 2

I hear you... which one is the correct?

According to my latest lab blood markers, the Precision Neo by Abbot is the most reliable one in term of taking a "realistic snapshot".

glucose blood test reference

Let's compare it with a CGM made from the same producer, the Freestyle Neo.

Mid afternoon

Mid afternoon

Night (before sleep)

Night (before sleep)

Morning fasted after waking up

Morning fasted after waking up

Fasted (1 hour after waking up)

Fasted (1 hour after waking up)

Carb test with cereal bar

Carb test with cereal bar (1h)

Carb test with cereal bar (2h)

Carb test with cereal bar (2h)

The reality is that, even if the idea of monitoring blood glucose excursion after a meal — by having a standard scale to compare it with — is rational and enough simple to apply, the devices that are currently available on the market are:

  1. Calibrated for people with diabetes, therefore the precision of the measurement is higher, the higher your blood glucose is.
  2. Overall, not so much precise, especially the CGM (unfortunately). Moreover, this should be a serious matter of concern for people with type one diabetes, because, considering the huge margin of error between devices, the suggested insulin dose to be taken in relation to a state of hyperglycemia could be noticeably different by using the same drop of blood.

Should we then trash the home-made glycemic testing proposed in the book?


However, given the relative state of immaturity of this technology, it is suggested to look at the results of this kind of home-made experiments with a grain of salt, placing them in the context of a safe and well-researched whole-food based diet.

The protocols that are suggested in Wired to Eat constitute a reliable baseline, and it is not a case that Rob suggests starting from there before running this kind of experiments.

Finally, I want to end this article by launching this question: if something that should be supposedly well established like glucose reading is so "relative" and device-dependent, how reliable could be something like BHB tracking for nutritional ketosis outside from a lab context?

At state of the art, chasing macros and micros (nutrient density) should be more important than chasing ketones or glucose readings.

At state of the art, chasing macros and micros (nutrient density) should be more important than chasing ketones or glucose readings.

Click to Tweet

Bottom line

  • Personalized nutrition from real-time biomarker readings is the future -not the present- of nutrition.
  • The best form of personalized nutrition, today, is based on macro and micronutrients management, based on the body composition of the individual.
  • Certain models of glucometer are more reliable than others in reflecting lab data testing.
  • Glucometers tend to give relatively correct absolute values for people with diabetes. Healthy people should look at the trends rather than the absolute values.
  • CGM is an exciting yet young and poorly tested technology.

Have you experienced something similar? Let me know in the comments below.

Are Spinach Performance Enhancing Foods? On the Role of Dietary Nitrates as Ergogenic Aids

I'm not a medical doctor. Please consult your physician before attempting any of the things described in this post. Even more so if you have thyroid-related issues.

Do you remember Popeye the Sailor Man and the secret behind his super-human strength?

Before punching the bad guys in the face, he used to gulp down a can full of spinach.

And, yes, I'm aspiring to write quite seriously about a cartoon.

Does it mean that vegans are right and that therefore we should all ditch animal protein and replace it with vegetable sources of incomplete chains of amino acids? Clearly not, and that would be a misinterpretation.

The right answer behind Popeye's physical performance is this: nitrates.

Popeye loves nitrates!

What Are Nitrates?

Nitrates are anions (negative ions) which, once ingested, provide a plethora of significant benefits to the human body.

They're decomposed into nitrites by the action of the bacteria contained in the saliva. These littler molecules then function as "raw material" for producing nitric oxide (NO) upon further redox.[1][2][3]

Circulating nitric oxide is associated with: [4][5][6][7][8][9][10][11]

  • better energy output
  • better aerobic resistance
  • improved blood flow
  • improved muscle recovery

Also, nitrates tend to optimize the rate at which the body is capable of producing ATP from food.

Needless to say, more ATP, more available energy![12]

Which Foods Contain Nitrates?

Unfortunately, it is impossible to find nitrates in a supplement form because of the regulation against sodium nitrate.

Therefore, the only possible way to introduce more nitrates in your organism -even if it is still possible to enhance circulating NO trough citrulline supplementation [13]- is by eating more nitrate-rich whole food, green vegetables in particular.

The most used veggies which provide an appreciable amount of nitrates are spinach and beetroot (juice, in particular, is the preferred source in the athletic context) [14][15].

However, there are two issues with these sources:


Spinach source of nitrates

Spinach is also rich in oxalates: anti-nutrients that bind with minerals like magnesium, calcium, and iron preventing their absorption.

In particular, when oxalates bind with calcium, the resulting calcium oxalate forms insoluble crystals that are the main reasons behind the formation of kidney stones. For preventing

To prevent this risk, when you consume spinach for their nitrate content it is advisable to cook and drain them for removing the oxalate content. Nitrates, fortunately, aren't lost after the cooking process. In this condition, even the vitamins and minerals are more available.


Beetroots source of nitrates

Beetroots have a high net carbohydrate content, making the juice solution unpractical for those fitness enthusiasts who are following a low-carb diet such as the ketogenic diet.

Fortunately, there are other food sources which provide more dietary nitrates, less oxalate, and less net-carbs:


Arugula source of nitrates

Arugula: 100 grams of this leafy vegetable have an outstanding content of 332,3 mg of dietary nitrates with a minimal amount of oxalates (7.1 mg). Great source of Vitamin K as well and a net carb content of 2.1 grams.

Turnip Greens

Turnip Greens

Turnip Greens: my favorite source of dietary nitrates, are commonly used in the Italian cuisine. 100 grams contain 284,5 mg of nitrates and just 50 mg of oxalates. Usually, they are served cooked. Therefore it's easy to remove that little trace of oxalates.

On top of the nitrate content, turnip greens are literally a goldmine of vitamin K, A and copper. But the best thing is that 100 grams of cooked and drained turnip greens contain just 1 g of net carbs, making it one of the best choices for a well formulated ketogenic diet.

Let's see how these two vegetables compared to the most common spinach and beetroot:

Vegetable (100g)

Nitrates (mg)

Oxalates (mg)




Turnip Greens









I'm not saying that you must completely substitute spinach and beetroot juice (especially if limiting net carb isn't a priority), but the sources above could add some variety to your diet and a significant boost in dietary nitrates!

High-Protein Turnip Greens Recipe Ideas

Let's see how to prepare turnip greens and some idea for coupling them in some easy to make high-protein recipes:

How to Prep and Store Turnip Greens

  1. Cut the lower part of the stem (half to one inch) and keep the top.
  2. Wash well with plenty of  cold water.
  3. Cut the upper part of the stem in pieces of 2 inches length.
  4. In a pot, add water (around 2 inches).
  5. Add the turnip greens cut in pieces and some marine salt.
  6. Cook for 20 minutes, covering the pot with a lid.
  7. After 20 min and turning the heat off, let them set and, when the turnip greens are cool enough, drain the excess water with a colander.
  8. Grease a pan with a fat source of your choice (I like to use a drop of extra virgin olive oil), sautè the turnip greens with salt, garlic and aromatic herbs of your choice.

You can prepare up to a kilo of turnip greens in this way, portion them and store in the fridge or in the freezer.

You'll have only to lightly re-heat them in the microwave or on the stove and couple with a protein source of your choice.

Let's now check some recipes!

​Grilled Salmon With Zucchini, Turnip Greens, Apple Cider Vinegar, Curcumin and Black Pepper


Salmon, pink, raw: 180 grams
Turnip greens cooked: 375 grams
Zucchini cooked: 175 grams


Protein: 43 grams
Net Carbs: 6.2 grams
Fat: 9 grams
Kcal: 330

Ggrilled Salmon With Zucchini, Turnip Greens, Apple Cider Vinegar, Curcumin and Black Pepper

Boiled Beef With Turnip Greens, Vinegar, Curcumin, Black Pepper and Italian Herbs.


Beef, plate, lean only, cooked: 200 grams
Turnip greens, cooked 270 grams


Protein: 56 grams
Net Carbs: 2.3 grams
Fat: 21 grams
Kcal: 422

Boiled Beef With Turnip Greens, Vinegar, Curcumin, Black Pepper and Italian Herbs.

Sauteed Lean Beef Slices With Fried Quail Eggs, Turnip Greens, Curcumin, Black Pepper, Italian Herbs and Apple Cider Vinegar.


Beef eye of round lean only raw: 130 grams
Egg, quail, raw: 4 whole eggs
Turnip greens cooked: 380 grams


Protein: 37 grams
Net Carbs: 3.4 grams
Fat: 8 grams
Kcal: 284

Sauteed Lean Beef Slices With Fried Quail Eggs, Turnip Greens, Curcumin, Black Pepper, Italian Herbs and Apple Cider Vinegar.


Here you can see how turnip greens could be a great versatile addition to your diet.

They provide a softer taste compared to spinach, but a crunchier texture because of the higher fiber content. You could easily alternate them with spinach and other leafy green vegetables with your favorite sources of animal protein!

However, athletes who want to take in a large dose of nitrates for supporting their workout session should consume between 6.5 and 13 mg of dietary nitrate per Kg of body weight two hours before in an easily digestible source [9][2]. This is what makes beetroot juice so practical.

I dare you to eat 500g of cooked spinach or turnip greens one or two hours before a heavy resistance training session.

In the upcoming part of this article, I will explore some practical solutions (aka smoothies) for fueling yourself with dietary nitrates before your workout. Blending your vegetables indeed enhances dietary nitrate availability[2].

In the meantime, please, obey to your mom and eat your green veggies! They're good for your circulatory system!


  • Dietary nitrates enhance blood flow, muscle recovery, energy output, aerobic resistance and ATP production.
  • There's no available supplementation for dietary nitrates. You have to eat your greens!
  • Cooking your vegetables do not reduce nitrates availability.
  • For enhancing your physical performance, you should take between 6,5 and 13 mg of dietary nitrate per Kg of body weight two hours prior your workout session.
  • Blending your green veggies enhance dietary nitrate availability.
  • You should cook and drain oxalate-rich greens (spinach) for preventing kidney stones formation.
  • The best sources of dietary nitrates are, in order of content: arugula, turnip greens, beetroot, spinach.

Image from https://www.flickr.com/photos/jean_pierre_gallot_69009/8138274071

Post edited by Alex Ferrari