There's not much agreement about nutrition. On many topics — fat, salt and carbs, to name a few — government guidelines will say one thing, but fans of paleo or vegan or fad diets will insist that the opposite is true. Pretty soon, you just don't know what to think about eggs, white bread or low-fat salad dressing.
But there's at least a little good news. Most people agree on three basic things: sugar, trans fat and vegetables.
From stodgy mainstream government guidelines, to sometimes-controversial movements, such as paleo, to decidedly non-scientific folks, including the Food Babe, these are the things almost everyone's on board with. While I'm sure there is somebody out there who will disagree (and they will probably show up in the comments of this post), these three statements are as close to consensus as you can hope to get.
Consensus #1: We Should Minimise Sugar
The only disagreement on sugar is whether it's bad for you, or really bad for you. The World Health Organisation states that the evidence linking sugar to obesity and tooth decay is strong enough to support a strict limit: no more than 10 per cent of your calories should come from added sugar. (Five per cent would be even better, they note.) That means that a single can of Coke accounts for 80 per cent of your allowed sugars for the day.
To be clear, added sugars include regular table sugar (sucrose) as well as corn syrup and natural sweeteners like honey and maple syrup: all are basically the same, and the slight differences between them aren't enough to make a real difference in your health. We should be limiting all of them.
Why no love for sugar? At best, it's empty calories: Instead of that can of Coke, you could "spend" the same number of calories on a glass of milk, a side salad, a handful of nuts or a few bites of a burger. Along with those calories, you'd get vitamins, protein or other useful nutrients. The Coke brings none of that to the table.
There's evidence that sugar is bad news for other reasons too. It increases your triglycerides and bad cholesterol, and it's convincingly linked to diabetes. Endocrinologist Robert Lustig is one of sugar's most respected vilifiers, and he argues that sugar, especially its fructose half, causes fatty liver disease and "every chronic metabolic disease that you can think of."
Who else is against sugar? Paleo gurus such as Robb Wolf and Mark Sisson. Sustainable food spokesman Michael Pollan. Even the Food Babe. I did find one exception to the rule: The Sugar Association would love for you to eat more sugar, saying that it can be "part of a healthy diet" and that the only thing wrong with it is its calorie content. In other words, their best argument for sugar is the same as one of the arguments against sugar: that it's empty calories.
Consensus #2: Avoid Artificial Trans Fats
The process that makes partially hydrogenated oils creates "trans" fats that aren't found in nature. The resulting oil works beautifully in doughnuts and pie crusts, for frying oil, and to make margarine. Because it can stand in for "unhealthy" saturated fats, it became extremely popular, and is only recently being phased out. (Those saturated fats turned out not to be so unhealthy, but that's another story.)
By the way, there is a family of trans fats that are found in nature, especially in dairy products. These, including conjugated linoleic acid, seem to be somewhere between harmless and beneficial. That complicates labelling because you can't make everything trans fat free, nor should you try to. When we're talking about the "bad" trans fats, we mean the artificial kind in partially hydrogenated oils.
These trans fats have been linked to heart disease, and possibly diabetes and obesity. It's hard to say for sure if trans fat is the culprit, since it tends to be part of a diet that includes a lot of junk food, like fried foods and mass-produced cupcakes. It's possible that trans fat isn't as bad as everyone is making it out to be, but it makes this list because nobody is defending it.
The USDA has trans fat on their naughty list (they were one of the "solid fats" in SoFAS — saturated fat was the other — and are still on the list of things to avoid in the new guidelines). The World Health Organisation concurs. Meanwhile, anybody in favour of "natural" foods, from paleo to vegan and beyond (Food Babe: check) recommends avoiding them and the processed foods they're part of.
Consensus #3 Vegetables Are Good For You
This one is almost too easy. Vegetarians like vegetables because, well, the obvious. Paleo and natural food folks point out that vegetables have been part of our diet since before we were officially humans. Nutrition Australia has drawn vegetables as the largest segment on its Healthy Living Pyramid. Every "detox" diet that includes solid food is heavy on the veggies, and we've noted before that most diets can be boiled down to the words "eat more vegetables".
The quibbles are few and far between: potatoes are sometimes controversial because they're so starchy. Paleo folks don't like beans. But leafy greens and other standard-issue vegetables have a lot of health benefits nobody argues with: they're full of vitamins and fibre, and they have been linked to a lower risk of heart disease. So listen to your mum and eat those veggies.
I almost want to include fruits in this list, but then you get into arguments about whether some fruits have too much sugar. Still, whole fruits are almost universally lauded — even Robert Lustig says the sugar in fruit is fine because nature packaged it with fibre.
A Final Warning
Oddly, these three things — because they're so agreed-upon — are used prominently by purveyors of crap science. They make good gateway claims to get you agreeing before they bring out their weirder beliefs and sales pitches.
"There's too much sugar in our diet," they say, and you nod. "A clean, healthy diet includes lots of vegetables!" they continue, and you're really agreeing now. That's when they sell you their customised detox plan or shiny new blender.
Instead, take these three principles as givens: these are what you will need to keep in mind on any diet or healthy eating plan. And if you get these right, you know you're off to a good start.