Seven of the most frequently asked nutrition questions, answered

• Is the keto diet everything it's cracked up to be?
• Should I eat that? Everything you need to know about eating right

One of my favourite parts of being a dietitian is teaching group nutrition classes, whether at workplaces, hospital wellness clinics or community centres. I enjoy answering common food and health questions, and I often surprise people with facts that run counter to their long-held beliefs. Some nutrition questions are asked so frequently that I thought it would be helpful to share them and the answers here.

1. Is vegetarian (or keto, or . . . ) the best way to eat?

In any given class, the subject may be "keto" or "the Mediterranean diet" or "vegetarian," and the answer is always the same: There's not one best way to eat. We are all different, and it would be impossible to choose one plan that would be right for everyone. The best plan for you is the one that meets your medical and nutritional needs while also being affordable, accessible, enjoyable and something you can stick with for the long term. Sometimes that may not be clear, but seeing a dietitian can help you figure it out.

2. Is sugar (or salt, or fat) the biggest problem in our diets?

No single nutrient or ingredient is the cause of poor diets. We live in an environment where highly palatable and cheap food is available everywhere. Pizza, chips, pastries and soft drinks are dietary staples. What's most problematic is eating too much of those ultra-processed foods and not enough whole foods (such as vegetables, fish and nuts) over a long period of time.

3. Do microwaves cause cancer?

Many have asked about the safety of using these appliances to warm up last night's lasagna. They worry when they hear the word "radiation." Although radiation may be linked to damaged cells and an increased cancer risk when it's high frequency and there's prolonged exposure (think gamma rays and some ultraviolet radiation), microwaves use low-frequency radiation for short periods. Microwaves operate only when the oven is on and the door is shut - so they are not constantly emitting radiation. Well-functioning microwaves are deemed safe by the World Health Organisation and the World Cancer Research Fund, as long as the door closes properly and the microwave has no dents or leaks.

4. Is food labelled "organic" more nutritious?

Organic refers to a method of farming, but it's not a health claim. An organic logo tells you nothing about the calories, fat, salt, sugar or vitamin content of food. A cake made with organic white flour, organic sugar and organic butter is still cake - it's not suddenly "healthy cake" because the ingredients were grown using organic farming methods. Nutritious foods - whether conventionally or organically grown - are those that provide the body with fibre, vitamins, minerals, protein and other key nutrients.

5. Are fresh vegetables better than frozen?

The nutritional differences between fresh, frozen and canned vegetables is minuscule. Only 9 per cent of Americans get enough vegetables daily, so it's much more important to consume any vegetables, in any state. Vegetables are filled with vitamins, minerals and fibre, which help reduce the risk of developing heart disease, Type 2 diabetes and some types of cancer. The best advice is to buy whatever vegetables you can source and afford, and then prepare them in ways you enjoy most.

6. Is discarding the salt shaker enough to cut sodium intake?

People may be told to slash sodium consumption when battling heart or kidney problems, but skipping a sprinkle of salt is not enough. Only 11 per cent of the sodium we consume comes from salt that is added at the table or when cooking. A whopping 71 per cent of sodium comes from processed, packaged and restaurant food. (The rest is naturally occurring in items such as milk, water and vegetables.) If you need to cut salt, choose fresh and whole foods over packaged products and fast foods. When that's not possible, compare food labels on similar products, and choose the option with lower sodium.

7. Will eating soy give men "man boobs"?

Soy contains an estrogen-like compound that weakly mimics human estrogen, which makes some men concerned that eating soy will cause enlarged breasts. We can trace this back to a 2008 case study in a medical journal, which described a man who did develop breasts after ingesting soy, but he was eating upward of 12 servings of soy foods daily. Once he reduced his intake, his breasts disappeared. Guidelines suggest that one or two servings of soy foods per day is fine, so feel free to enjoy some edamame or a tofu stir-fry, as long as the serving size remains moderate.

The Washington Post