One simple rule for healthy eating

We all know that a healthy diet is required for a healthy body and mind. But what is a healthy diet? What foods does a healthy diet include and exclude?

Public health messaging, media stories, and medical advice on what to (and what not to) eat are awash with confusing, contradictory, and, often, incorrect information. For decades it was all about reducing fat (especially saturated fat) intake. More recently the focus has been on eliminating sugar and restricting carbohydrates. And, of course, the propaganda war against meat (and other animal foods) grows ever more intense.

None of this is particularly helpful, of course. So, I have a new approach for you. A simple heuristic for nutrition excellence: Eat the most nutrient dense foods.

That really is it. Get this right, and everything else will work itself out. As I will explain.

Humans (and all other animals) require two things from our food:

  1. Energy
  2. Essential nutrients

Energy (typically measured in calories) is extracted from the macronutrients in our food – fat, carbohydrate, protein, and alcohol – and is needed for…well…everything. No energy = no life. But too much energy, as you know, is also problematic – metabolic disease is the biggest threat to our survival. Sustained energy excess (which drives weight gain and metabolic dysfunction) is largely caused by a breakdown of appetite control. Effective appetite regulation, therefore, is crucial.

Essential nutrients (often referred to as micronutrients) – which include amino acids, fatty acids, vitamins, and minerals – are the building blocks for every component and process in your body and brain. Getting sufficient essential nutrients is a health imperative, yet insufficiencies are relatively common, even in rich countries.

So, a truly healthy diet must achieve two things – appetite regulation and nutrient sufficiency. Eating the most nutrient dense foods gives you the best chance of achieving both.

Nutrient density is a measure of the quantity of essential nutrients per calorie of food. (I realise that this is not, strictly speaking, a ‘density’. Density is defined as quantity of mass per unit volume. However, in nutrition it’s more helpful to use calories as the denominator.)

How can we estimate the nutrient density of different foods? Fortunately, some kind scientists have done the work for us.

In a 2007 study, researchers calculated a ‘nutrient density score’ (NDS) for seven major food groups and 25 subgroups. An NDS of 100%, “indicates that the consumption of 8 MJ (i.e., 1913 kcal) of any one food group or subgroup covers a mean of 100% of the RDA (recommended daily allowance) for 23 nutrients”. The 23 nutrients included ten vitamins, eight minerals, three fatty acids, proteins, and fibre.

Here are the results:

Chart created by BioMe using the published data.

What inferences can we draw from this data?

  • Fresh, unprocessed foods are far more nutrient dense than processed foods. Eating the most nutrient dense foods means eating an unprocessed diet, which is known to regulate appetite, calorie intake, and body weight
  • Animal foods – including meat, fish, and eggs – dominate the top 10 most nutrient dense foods. This contradicts the increasingly popular theory that plant-only diets are the healthiest diets
  • Whole grains are not a health food (despite all the hype) and refined grains are the very definition of empty calories
  • Eating a diet of meat (including organs), fish (including shellfish), eggs, dairy, vegetables, and fresh fruit will give you the best chance of meeting your daily nutrient requirements (and regulating your appetite)

A more recent study – published in March of this year – found a similar ranking of foods for nutrient density.

In this case the ranking was based on the number of calories of each food required to meet one-third of daily requirements for six ‘priority’ micronutrients (in which diets across the world are often deficient) – vitamin A, folate, vitamin B12, calcium, iron, and zinc – for adults aged 25 years and older.

So, unlike the 2007 study, the lower the ‘score’ the better. The calculation here also included bioavailability (how much of the nutrient is actually absorbed) for iron and zinc, and a method to better account for the variety of nutrients contained in a food.

Bivalves – by the way – are a type of mollusc, and include clams, mussels, scallops and oysters. I didn’t know either!

The categorisation of foods was more granular in this study – for example, dark green leafy vegetables had their own group – but the overall pattern is similar to the 2007 study. Meat (especially organs), fish (especially shellfish), eggs, dairy, and vegetables (especially dark leafy greens) are the most nutrient dense – and therefore healthiest – foods. Grains – whole and refined – are practically devoid of nutrients.

There are a few surprises in here though. White meat, nuts and seeds, roots and tubers (such as potatoes and sweet potatoes), and many fruits are poor sources of the six ‘priority’ micronutrients.

When it comes to improving your diet, you should stop worrying about fat vs carbs, animals vs plants, the size and timing of your meals, and any other popular diet trend. Focus instead on eating more of the most nutrient dense foods and less of the least nutrient dense foods, and you won’t go far wrong.

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