[New Scientific Study] Not All Plant-Based Diets Created Equal?


by The Health Sciences Academy — Get free science updates here.


Today, let’s review a new scientific study hot off the press… about plant-based diets!

We see plant-based studies in the news quite often. But what’s a “plant-based diet” anyway?

The definition of a plant-based diet is highly debated these days…

Some say it’s a vegan diet.

Others include vegetarian eating.

While many argue it’s a diet where you eat mostly whole foods coming from plants (70-90% of calories), PLUS a relatively small amount of food from animal sources (typically yogurt, eggs, fish or poultry).

What are plant foods specifically?

As the name indicates, plant foods are edible food substances derived from plants.

Plant foods include:

  • wholegrains (such as quinoa, oats and rye)
  • fruits
  • vegetables
  • nuts
  • seeds
  • legumes
  • oils
  • tea
  • coffee
  • herbs
  • spices
  • fruit juices
  • sweetened beverages
  • refined (white) grains
  • fries
  • sweets

Now, let’s take a look at this list again…

Are all these really “healthful” just because of their plant origin? Or could eating some of them regularly increase our health risks?

The devil is in the detail

When the team and I review plant-based diet studies, we often notice that they are inconsistent, because different researchers use different definitions of a “plant-based diet”…

This makes it very difficult to compare studies “like for like”, since the findings are about different ways of eating!

That’s why a group of researchers are steering a new direction to fix these inconsistencies… and I personally like that.

So, to overcome the problem, they created 3 versions of a plant-based diet:

  • An overall plant-based diet which emphasizes the consumption of all plant food, and reduces (but doesn’t eliminate) animal food intake
  • A healthful plant-based diet that emphasizes the intake of “healthful” plant foods such as wholegrains, fruits and vegetables, and without animal food intake
  • An unhealthful plant-based diet which emphasizes the consumption of “less healthy” plant foods such as fries, but without animal food intake

Comparison between different types of plant-based diets (Satija et al., 2017)

I think these variations initially make sense. Also, including different dietary choices feels more “democratic” and inclusive.

But the researchers took things a step further…

Introducing the Plant-Based Diet Index

After close analysis, the same researchers developed a “Plant-Based Diet Index” to score the diets of 209,298 participants:

  • Healthier plant foods (wholegrains like quinoa, fruits, vegetables, nuts/legumes, oils, tea/coffee) received positive scores
  • Less-healthy plant foods (juices/sweetened beverages, refined grains, fries, sweets) and animal foods received reverse scores

Then based on that, they grouped plant foods into 2 groups:

  • The Healthful Plant-Based Diet Index (which they call called “hPDI”)
  • The Unhealthful Plant-Based Diet Index (called “uPDI”)

After that, the researchers measured the amount of either hDPI or uPDI foods eaten by the participants over 2 years, while performing medical check-ups on their health.

All 209,298 participants were healthy men and women at the start of the study.

How did their plant-based eating affect their health?

Well, the answer is in the type of foods they ate… and the amounts!

(In science, everything is “dose or amount dependant”).

Participants with higher hPDI scores had lower disease risk, in particular heart risk. A high hPDI score is based on eating more of the foods listed in the Healthful Plant-Based Diet Index.

Conversely, those with higher uPDI scores showed higher heart disease risk. A high uPDI score is based on eating more of the foods listed in the Unhealthful Plant-Based Diet Index.

Researchers measured food types/amounts eaten and heart risk (Satija et al., 2017)

Overall, higher amounts of “healthier” plant foods were associated with lower risk.

Whereas higher amounts of either “less healthy” plant foods were associated with higher risk.

How is this study making us smarter?

Saying that someone eats a plant-based diet doesn’t always mean they are “healthier” or that they have a lower health risk…

Because if a person’s plant-based diet consists PRIMARILY of chips, crisps, fried foods, sweets, brioche buns and juices, the person’s health risks may be higher.

The nutritional quality of plant foods can vary significantly. So it’s crucial that we take into consideration the quality of foods in someone’s plant-based eating practices.

For that reason, when assessing, planning or personalising a client’s diet, it’s important to be specific.

Your key takeaways

We’ve seen that not all plant foods are created equal…

And when we look for diet quality, the devil is in the detail.

Sugar is a plant food. Fructose is a plant food. Fries are a plant food.

Sometimes, smaller yet SMARTER dietary tweaks (rather than massive changes) can also be encouraging and go a long way!

What about you?

Are you a plant-based eater? If so, which of the 3 definitions of plant-based eating are you closer to? Mostly plants with some animal foods? Or all vegan?

Tell us in the comments below, and share this with someone who enjoys plant-based eating!

P.S. Okay, I’ll go first! In case you’re wondering, in our team of scientists we have 1 vegan, 2 vegetarians, a plant-based eater “with benefits” (yours truly!), a couple of (very healthy) meat and cheese eaters, a sporadic low-carber/keto, some meal-skippers… and the list continues… because guess what?

Everyone’s biochemistry is different. We all metabolise nutrients differently. And each of us operate optimally through different nutritional strategies…

As you’ll often hear me say: “If it’s not personalised, it’s not effective!

Take the next step

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Alex Ruani, Doctoral Researcher, leads the research division at The Health Sciences Academy, where her team of accomplished scientists and PhDs are training a new breed of over 100,000 highly-specialised nutrition professionals who are leveraging the latest personalisation strategies to help their clients. She is a Harvard-trained scientist and UCL Doctoral Researcher who is fanatical about equipping health professionals with the latest science-based tools so they can succeed in their practices – from identifying the unique nutrient needs to building highly personalised nutrition programs. Besides investigating and teaching the latest advances in health and nutrition biochemistry, Alex makes it easier to be smarter with her free email updates.


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