Nutrition and diet are both important for health. They have different meanings but are closely related to each other. Your diet is what you eat and nutrition is what you get from what you eat.
Nutrition
It is the process of taking in food and using it for growth, metabolism, and repair. We get nutrition from the different nutritive components in the foods that we eat. Good nutrition means eating foods that are of good quality and helps nourish the body with all the nutrients needed to function optimally. The key nutrients in food are the macronutrients - Proteins, Carbohydrates and Fats. The micronutrients in food are - Vitamins and Minerals. Not all nutrients are acquired from food. For example: The primary source of Vitamin D is sunlight.
Diet
It implies the use of specific intake of nutrition either for weight management reasons, a specific health condition or to maintain good health. Diet is the sum of food and drinks consumed by a person on a regular basis. It does not mean deprivation of food. People may choose to eat all sorts of diets: vegetarian, vegan, low carb, high protein, etc. They may follow a specific diet plan for weight gain, weight loss or a diet specific for a chronic condition. There are also many fad diets that have become popular in recent years. For example Atkins Diet, Ketogenic Diet, Paleo Diet, etc. Fad diets may often be nutritionally unbalanced and not sustainable in the long run.
Combining Nutrition with Diet
Good nutrition ensures that we are eating as per our dietary needs. There is no one diet that fits all. Every individual is different and diets may differ as per the age, activity level, any medical condition or even as per the desired goal of an individual (e.g. weight loss, weight gain, muscle gain, etc.). An individual’s nutritional needs change over their lifetime. For example, children and teenagers have different dietary needs than someone in their fifties or sixties; a pregnant or lactating woman’s dietary needs will differ from their spouse, an overweight individual will need to adjust their diet if their goal is weight loss.
A poor diet would mean poor nutrition. It can lead to nutrient disorders, poor metabolic efficiency and other health related issues.
Good Nutrition is needed to fuel Growth, Development, Repair and Recovery. It helps to achieve a A Healthy Body and also A Healthy Mind.