Should we take diet advice from our Stone Age ancestors, wonders Jane E. Brody
- Published 12.09.18
It seems these days that every third person I meet is either already on the "Paleo" diet or planning to try it. Their goals are either weight loss or better health, but certainly not to save the planet.
The main premise of the Paleo diet: if the cavemen didn't eat it, you shouldn't either. But is this sound nutritional advice? Let's start with three basic facts.
• There is no such thing as a Paleo diet. The Paleolithic era lasted 2.5 million years and involved different and evolving populations with a wide dietary range determined by climate, geography, season and availability.
• Human beings today and the composition of foods they eat are not the same as they were in Paleo time. Genetic changes have resulted in very different organisms for both.
• There have been no studies of large groups of people who have followed the currently popular versions of the Paleo diet for decades to assess their long-term health effects.
Keep in mind that the life expectancy of people before the advent of agriculture 15,000 years ago rarely reached or exceeded 40, so their risk of developing the so-called diseases of civilisation is unknown.
There is one basic premise of the Paleo diet that could benefit everyone's health: avoid all foods that are packaged and processed. That said, consider a daily menu of 2,200 calories suggested in a popular book on how to eat like a caveman.
Breakfast: 12 ounces broiled salmon, 1-3/4 cups cantaloupe
Lunch: 3 ounces broiled lean pork, 4-1/2 cups salad dressed only with lemon juice.
Dinner: 8 ounces lean sirloin tip roast, 3 cups steamed broccoli, 4-1/2 cups salad (again, no oil, though some versions of the diet include olive oil), 1 cup strawberries.
Snacks: 1/2 orange, 3/4 cup carrots, 1 cup celery.
With so many vegetables and fruits, the diet contains plenty of fibre and most essential vitamins and minerals. Despite a few serious nutritional deficiencies like calcium and vitamin D from the lack of dairy foods spurned by Paleo enthusiasts, it sounds healthy enough, as long as your kidneys can handle so much protein.
But is it practical? How many people trying to get the kids off to school in the morning and themselves ready for work will take the time to broil salmon? What will they do when they dine out, especially in someone else's home? And most important, can they stay on the diet indefinitely and live happily without a piece of bread, cracker or, heaven forfend, a serving of ice cream?
And not all Paleolithic diets are equally nourishing. Those who choose the ancestors of the Inuits as their guide would be eating mostly meats and seafood and few if any fruits and vegetables, which grow poorly in the Arctic. As Marlene Zuk, an evolutionary biologist at the University of Minnesota and author of Paleofantasy, told Nutrition Action three years ago, the fact that people like the Inuits can adapt to a diet with little plant food "doesn't mean they should live that way if they have a choice".
I also wonder whether Paleo diners faced with currently available choices will stick to lean animal foods (grass-fed meats, skinless poultry), or would they be tempted to choose more succulent, fattier cuts like brisket, burgers and pork ribs. Even worse, they might select processed meats like bacon (allowed on some Paleo diet lists) and sausages that have been linked to an increased risk of cancer and heart disease. Would they succumb to using butter and salt to enhance the flavour of steamed vegetables?
As I see it, a Mediterranean-style diet, now promoted by most dietitians and researchers who study the effects of what we eat, is far easier to incorporate into modern lives with minimal risk to lasting health. It is also better balanced and a whole lot tastier. The Mediterranean diet features only small portions of animal foods and depends more on plant proteins like beans and peas. It includes olive oil and other monounsaturated fats. It is more varied, less expensive, less taxing on the environment, and easier to fit into the demands of life today.
Several short-term studies among small groups of people (often with no control groups) suggest that the Paleo diet is more effective than the Mediterranean approach at promoting weight loss and reducing risk factors for Type 2 diabetes and coronary heart disease. Still, my vote goes for the more flexible and far more thoroughly researched Mediterranean diet.
I can offer a real-world testimonial. I was recently a speaker on a weeklong New York Times Journeys Mediterranean cruise on a small luxurious ship with four dining areas and 24-hour room service. I ate plenty - three deliciously satisfying meals prepared under the direction of an Italian chef. I enjoyed a nightly cocktail hour, a glass of wine with dinner and gelato for dessert. (Full disclosure, I also walked the deck for an hour and swam for half an hour every day, in addition to walking onshore and up and down the ship's stairs.) And I came home weighing not a half-pound more than when I left.
A popular claim of Paleo dieters, among others, is that we are the only mammals that drink milk after weaning, which is true. Many people lose the ability to digest the lactose in milk in early childhood. On the other hand, Zuk pointed out, many others have evolved a lifelong ability to produce the lactose-converting enzyme lactase, a change that has occurred during the last 5,000 to 7,000 years and is but one example of how humans can and have changed, and rather quickly, since Paleo days.
And while it is wise (consistent with the Paleo diet) to eat far fewer starches, especially white flour and refined grains that our bodies quickly convert to sugar, Zuk noted that people have continued to evolve genes for amylase, the enzyme that breaks down starches in saliva and the small intestine. It is also true that our microbiome - the billions of organisms that reside in our guts and elsewhere - is vastly different now than in Paleo times and affects how our bodies process what we eat.
Finally, there remains one critical aspect of Paleolithic populations that is vastly different from how most people live today. Paleo people were hunter-gatherers and spent most of their waking hours walking and running around in search of food, with additional time and effort spent preparing it for consumption. If you're willing to do all that, go for it.