Contradictory diet advice is making healthy eating even harder

The studies aimed at finding long-term benefits from a particular diet aren’t all that rigorous. (Representative image)

‘Tis the season of wavering New Year’s resolutions. And 2024 might be an especially hard time to keep to a new diet because there are so many contradictory claims — and so little left on the menu that isn’t being vilified by someone with initials after their name.

Mainstream experts are still warning us against meat, cheese, sugar, and the ill-defined group known as ultra-processed foods. Now there arepeople saying to avoid tomatoes, peppers and eggplant and even one theory that we’re poisoning ourselves with spinach.

On everyone’s good list? Cauliflower. At least, for now.

Spinach and kale are on the bad list of Sally K. Norton, who has a degree in public health but has strayed from the mainstream by advising against foods high in substances called oxalates. Her bad list also includes beans, grains, almonds, potatoes, beets and chocolate — what she calls “toxic superfoods.”

Oxalates are real compounds and there’s some scientific debate about their contribution to kidney stones. Norton’s hypothesis is that oxalates caused her chronic pain and may also cause nervous system problems, premature aging, hearing loss and eye floaters.

Meanwhile, heart surgeon Steven Gundry argues that we might be sickened by a different group of plants — ones high in lectins, which are part of plants’ defense systems. He blames lectins for a host of problems from bad digestion to autoimmune disease to weight gain. In his diet, spinach and greens are acceptable but not tomatoes, peppers, seeds, beans or whole grains.

The Center for Science and Society at McGill University has a nice write-up puncturing the oxalate theory. Chemist Joe Schwarcz, who heads the center, debunks the widespread dangers of lectins in a chapter in his diet-myth-busting book A Grain of Salt.

When I called Schwarcz, he told me some plants contain minute traces of compounds that are toxic at vastly higher doses. It makes no sense, he said, to talk about something as toxic without considering the amount. He said the preponderance of evidence suggests the more fruits, vegetables and whole grains you eat — and the less fat — the better off you are.

But even age-old assumptions about fats are now contested. Olive oil is considered a good fat, and many now say the saturated fats found in meat and dairy are not the dietary villains they’ve been made out to be. Some recent studies suggest those who ate full-fat dairy were healthier than those who went for low-fat or nonfat options.

Journalist Gary Taubes, author of the recent book Rethinking Diabetes, has been a longtime critic of the mainstream advice to eat a low-fat diet. It’s based, he said, not on rigorous science but observations comparing people in different countries. Those kinds of studies can’t easily untangle which health differences might be due to socioeconomic factors and other variables.

Another reason for some of the conflicting evidence over which foods are healthy is that many studies simply ask study subjects to remember what they ate — that doesn’t always make it clear which foods make a difference.

The studies aimed at finding long-term benefits from a particular diet aren’t all that rigorous. One of the most widely publicized studies of longevity — the Blue Zones — examined the diet and lifestyle of people in five regions of the world with purportedly unusual longevity. It’s an intriguing observation and made for an entertaining Netflix series, but it’s impossible to pin longevity in these regions on diet, let alone any particular kind of food.

But out of all the contradictory claims, there’s one area of agreement: Diet influences health, and it’s possible to benefit from experimenting on yourself. Any individual might have food sensitivities that differ from the population at large.

A diet that makes you feel energetic and helps you achieve a healthy weight might indeed be better for you, as an individual, than what’s been associated with longevity in large populations. Some people feel better avoiding gluten even if they don’t have celiac disease, and others might feel better skipping dairy products. Maybe a few people are sensitive to lectins or oxalates and benefit from avoiding them. And it will be easier to stick with any diet plan if it’s giving you short-term benefits.

So instead of New Year’s resolutions, we could have New Year’s experiments. If a change doesn’t make you feel better, you can still consider it a lesson learned. And there’s always cauliflower.

FD Flam is a Bloomberg Opinion columnist. Views do not represent the stand of this publication. 

Credit: Bloomberg