Are 5 servings of fruits and vegetables a day really necessary?

The body needs vitamins and minerals to carry out many vital processes. Since the nutrients themselves are consumed in the processes, they must be taken up with the food on a regular basis. That’s why nutritionists recommend eating five servings of fruits and vegetables a day. But how can you reach these amounts? Do you really have to eat that much? Is a single dose sufficient, for example by drinking a smoothie? Or can the body not absorb this concentrated mix at once? These are all important questions, because everyone wants to be healthy. And in this case the saying is true; You are what you eat.

It is always better for the body if nutrients are consumed in their natural form. It is therefore advisable to eat fruit and vegetables rather than to use supplements1 . In addition, fresh food always provides a mix of several nutrients. This also includes fiber, which is very important for the microorganisms in our gut and thus for our health. Among other things, they support the immune system and also have positive effects on our mood. They help us digest our food and digest substances for us that we would otherwise excrete unused. These substances are needed to build immune cells, of which around 70% are located in the intestine. Healthy eating also helps prevent many diseases or provide relief of them. These include cardiovascular diseases, diabetes and depression 2, 3, 4.

“The body can only absorb a limited amount of nutrients at a time.“

But who has time to prepare so much healthy food? It would of course be most convenient to consume one large meal a day, for example a smoothie. Because the recommended five servings seem to be quite a lot at first. However, they are not if you clarify what a portion means, but more on that later.

Why do we have to consume nutrients regularly?

Not all vitamins can be stored in the body. An example is vitamin C, which is essential for the immune system.  Important for the storage capacity is whether the nutrients are fat-soluble or water-soluble molecules. If they can mix with fats, excess vitamins are stored in the fat reserves. If they are not able to do this, if they are water-soluble, any remaining residues are flushed out with the urine. Since there is no storage for them, they also have to be taken up with food more often. Therefore, fat-soluble vitamins can be eaten less often 5.

The group of B vitamins is water-soluble (B1, B2, B3, B5, B6, B7, B9, B12, not all are shown in the graphic) and vitamin C. Vitamins A, D, E and K are fat-soluble 5.

You need to consume fat-soluble vitamins together with fatty foods, because the fat is needed for absorption into the body. Because these vitamins are enclosed by fat droplets and then simply pass through the intestinal wall in this combination. But the membrane of the intestine is not infinitely permeable. Once the maximum amount has been reached, nothing more can pass through. Water-soluble vitamins and minerals often need transporters that allow entry into the body. If these are “busy”, no further molecules can be transported. However, some of the water-soluble vitamins can also diffuse through the intestinal wall. But there is also a maximum of passage for this process 5. Thus, there are only limited amounts of nutrients that can be absorbed by the body at once. Furthermore, if the vitamins are water-soluble, they must be used immediately, otherwise the body will excrete them. That is why we must eat them so often 5.

What are the maximum values of nutrient absorption?

There are so many variables in the absorption capacity that a general value cannot be determined. Every human’s body is different. One and the same body reacts differently depending on the situation. It is also very difficult to measure the uptake rate in the laboratory. Often it is only possible to determine which quantities have arrived in the blood and which have ended up in the urine. However, these are not always very clear values. And there are not many studies on the subject 6, 7.

If you drink 1 L of a smoothie from the supermarket at once, it could be difficult for your intestine to absorb all nutrients. Anyway, if you take in too many minerals, this can have negative consequences. Free radicals are formed that attack the cells and harm the body. A glass of a smoothie, on the other hand, is great because the mix makes the variety of nutrients particularly high 6.

For vitamin C it is known that several small doses can be taken in much better than a large portion 7. It is therefore clear that there must be several portions a day, unfortunately a large meal does not provide you with enough nutrients.

How big is one serving and how am I supposed to eat five of them?

A serving is about the size of a hand, so you don’t have to eat a whole plate of fruit or vegetables. For breakfast, for example, you can put an apple in your oatmeal, it doesn’t have to be a whole bowl full of fruit. For lunch, there could be a vegetable soup and a piece of whole grain bread instead of two salami sandwiches. A paprika or banana would be ideal as a snack in between. In the evening it could be rice with vegetables 8.

It is also important to vary between foods, as each product has a different nutrient composition. You can use the colors of the rainbow as a guide, because the colors of food often come from substances that are healthy for us. So, if you have eaten apple, grapes, broccoli, tomatoes, lamb’s lettuce and corn in one day, you have eaten quite well with this colorful mix. But cereals also contain many healthy substances and are not to be neglected. Dairy products and meat in moderation are also healthy. Scientific tests have shown that animal products from organic farming are better for us than those from factory farming 8.

You are what you eat and hopefully that is healthy!

Science has an answer to many questions about healthy eating. Even if this is not always the most convenient. Admittedly, maintaining a balanced lifestyle can be time consuming. But you can also start small. Since it is better to eat some fruit than none at all. This can prevent serious illnesses or at least alleviate some symptoms. So that everyone can live a long, healthy, and happy life.


References:

1. Sripanyakorn, S., Jugdaohsingh, R., Dissayabutr, W., Anderson, S. H., Thompson, R. P., & Powell, J. J. (2009). The comparative absorption of silicon from different foods and food supplements. British journal of nutrition, 102(6), 825-834.

2. Podcast Interviews mit- und Twitter von Dr Jenna Macciochi, Immunologin and der Universität of Wessex.

3. The Doctor’s Kitchen Podcast mit Rupy Aujla Staffel 3 Folge 1+2).

4. WHO Nutrition Landscape Information System (NLiS).

5. OpenStax Textbook; Anatomy and Physiology, Kapitel 23.7 Chemical Digestion and Absorption: A Closer Look https://opentextbc.ca/anatomyandphysiology/chapter/23-7-chemical-digestion-and-absorption-a-closer-look/

6. Invited review: Mineral absorption mechanisms, mineral interactions that affect acid–base and antioxidant status, and diet considerations to improve mineral status. Jesse P. Goff 2018.

7. Levine, M., Conry-Cantilena, C., Wang, Y., Welch, R. W., Washko, P. W., Dhariwal, K. R., … & Cantilena, L. R. (1996). Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proceedings of the National Academy of Sciences, 93(8), 3704-3709.

8. Information combined from; The Doctor’s Kitchen Blog and Podcast by Doctor Rupy Aujla https://thedoctorskitchen.com/

Published by Katrin Heidemeyer

Katrin Heidemeyer ist Doktorandin im Bereich Biochemie an der Wageningen University and Research. Durch ihre Arbeit möchte sie das Wissen über die Spezifität von Hormon-Signalen in Pflanzen erweitern. Da ihre Interessen über Pflanzenbiologie hinausreichen, schreibt sie in ihrer Freizeit über diverse Themen. Von Ernährung zu Psychologie, der Neugierde sind keine Grenzen gesetzt.

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