Nutritional guidelines and recommendations are constantly changing in the light of new research. It can be difficult to keep up with which foods are healthy and which aren’t. Here we look at five foods that have gone through the cycle of being the villains of nutritional science but are now, based on some old and some new science, apparently okay to eat again.

Eggs

For a long time, eggs were thought to be bad for your heart. A large egg contains a hefty 185mg of cholesterol. Dietary cholesterol was believed to contribute to high blood cholesterol levels. But for the last 20 years, nutrition and medical research has shown repeatedly that at normal intakes dietary cholesterol has very little influence on a person’s blood cholesterol levels.

Although it’s taken a while, nutrition experts are now correcting the record for eggs and other foods that contain cholesterol (such as chicken liver and shellfish) by removing it as a nutrient of concern from dietary guidelines. Eggs are an excellent source of protein, healthy fats, and several vitamins and minerals.

Fat spreads

The story of fat spreads, such as margarine and butter, is probably one of the most confusing stories in nutrition. The origin of margarine, which is made from vegetable fat, dates back to the mid-1800s. Since that time, margarine has replaced butter as the fat spread of choice in most developed countries. This switch was driven by the lower price of margarine compared with butter as well as recommendations from health professionals to eat less saturated fat in order to prevent coronary heart disease (CHD).

While this switch away from saturated fats began to show reduced CHD incidence in the population, researchers also identified an independent link between trans fat (a fat produced when partially hydrogenating vegetable fats to make margarines) intake and CHD. Since this link between trans fat and CHD was confirmed by multiple studies regulatory agencies around the world have sought to eliminate trans fats from the diet.

The food industry was quick to respond and has been producing trans fat-free margarine for years now. However, there is still confusion among consumers as to whether vegetable, fat-based spreads are safe to eat. The short answer is yes, as long as the food label doesn’t list “partially hydrogenated vegetable oil” as an ingredient.

Modern vegetable oil-based fat spreads are a way to replace dietary saturated fat while increasing polyunsaturated fat – a dietary change that has been shown to reduce CHD in large cohort studies.

Potatoes

Potatoes are one of the few vegetables considered to be unhealthy. Because they’re a high glycaemic index food they tend to get lumped in with foods made from refined carbohydrates as foods to avoid. But potatoes are a rich source of carbohydrates, vitamin C, some B vitamins and trace minerals.

How you prepare potatoes also changes the aspects of those starches that get a bad rap. Cooking and cooling potatoes increases the amount of resistant starch in the potatoes. This resistant starch then acts like dietary fibre which “resists” digestion in the gut, potentially having a positive impact on your gut bacteria.

Dairy

Dairy – including milk, butter, yogurt and cheese – was once considered a staple in many people’s diet, but consumption patterns have changed, in part, due to difficult-to-interpret health messages.

Positive aspects of dairy include the high protein and calcium content. Fat content and fat type are important when choosing dairy products as some contain high amounts of fat per serving and this fat tends to be high in saturated fat.

Although it’s best to avoid a diet high in saturated fat (a risk factor for CHD), regularly consuming dairy products doesn’t need to be a concern if your overall calorie intake and fat intake is healthy. Because there are numerous studies that point toward both the healthy and unhealthy aspects of dairy it is difficult to recommend specific intakes or types of dairy foods for improving health. The recent updates to the UK Eat Well Plate still promotes dairy foods as part of a healthy diet, as long as the dairy choices are lower in fat.

Raw nuts and nut butters

Nuts also get a bad reputation for being high in fat and high in calories, leading some to suggest they should be avoided by anyone looking to lose weight. But there is mounting evidence to suggest that raw nuts are key to a healthy diet and maintaining healthy body weight. A recent study, published in the British Journal of Nutrition, showed that eating raw nuts reduces death from all causes, cardiovascular diseases, coronary heart disease and sudden cardiac death.

Although studies are still ongoing to determine what components of tree nuts are promoting these positive health outcomes, we already know the nutritional benefits. Raw nuts contain protein, healthy fats (low saturated fat and high monounsaturated and polyunsaturated fat), dietary fibre and micronutrients.

Nut butters, such as peanut butter, can also be part of a healthy diet. The fat in peanut butter has a healthy profile and peanut butter is also an excellent source of protein, fibre, vitamin B6 and magnesium. Some recent evidence has shown increased weight loss for people that replace less healthy proteins, such as processed meats, with peanut butter.

Nut and nut butter consumption can be a part of a healthy diet, but you need to be mindful of the calories.

Remember, when it comes to food and health: all foods fit into a healthy diet. Don’t fall into the trap of believing in “superfoods” or “food villains”. Enthusiastic consumption of one particular “superfood” can be worse than consuming a so called “food villain”.