If you don't 'eat the rainbow,' you could be missing out on key nutrients your body needs, according to a nutritionist

• Eating the same foods every day can lead to nutritional deficiencies.
• We should aim to "eat the rainbow," registered nutritionist Jenny Rosborough told Insider.

If you're eating the same select foods over and over again in your diet, you might be missing out on key nutrients.

"No single food or food group can provide all the nutrients you need, they all contain different nutrients required to promote good health," registered nutritionist Jenny Rosborough told Insider.

"The reason we're encouraged to 'eat the rainbow' is because different colored fruits and vegetables vary in terms of the vitamins, minerals, and amount of fiber they provide," she said, adding that eating a variety of plant-based foods — fruit, vegetables, seeds, nuts, whole grains and legumes (ie. lentils, chickpeas and beans) — is beneficial for our gut health.

Eating the same foods every day long term can lead to nutritional deficiencies

It's easy to get stuck in a rut and find yourself cooking the same meals and eating the same foods every week, and this is fine in the short term, Rosborough said.

"But variety over time is the most important way of ensuring our diets are nutritionally adequate," she said.

Aside from vitamin D, which your body produces in sunlight and isn't found naturally in many foods, most people should be able to meet their nutritional needs without supplements.

If your diet isn't varied enough, however, this may not be the case.

Research, such as this 2015 study by researchers at Harvard and New York University, also suggests that eating a wide variety of foods may prevent against metabolic syndrome (the combination of diabetes, high blood pressure, and obesity).

Aim to make your diet as colorful as possible

To build a balanced diet and avoid nutritional deficiencies, Rosborough and other nutrition experts recommend trying to eat as many different colors as possible.

"Including each food group at every meal isn't necessarily feasible, but aim for a balance across the day or week," she said. "This includes fruits and vegetables, starchy carbohydrates including wholegrains, dairy or fortified alternatives, and a variety of protein sources including beans and pulses, nuts, oily fish and lean meat."

If you don't eat meat, eating multiple different plant-based protein sources is key, Rosborough said — you need to combine them to get the full range of essential amino acids, which are the building blocks of protein.

If you're on a budget or busy, Rosborough recommends opting for frozen and canned foods, ideally in unsalted and unsweetened water.

"These options are often cheaper and quick and easy to prepare," she said. "They also have the added benefit of reducing food waste due to their longer shelf life, while promoting variety."

If you always opt for broccoli with your dinner, next time you're in the grocery store, try green beans or cauliflower instead.