In the first part of this short series I emphasized the need for an all-around definition of a healthy (proper) diet, and wrote about the consequences of the lack thereof. Today I'll define healthy diet using the effective, qualitative, and practical definition.
Why the separation? I must admit that this is not how I envisioned this series when I started writing it. I planned to write about the part I now call qualitative definition. However, during the process I realized it doesn't answer all the questions so I decided to add two more definitions of a healthy diet.
Effective definition of a healthy diet
Let's start with the effective, general definition which answers the question of influence on health and why we strive for diet optimization. Healthy diet allows for maximal use of our own and environmental potential for a long and quality life. We could ask many sub questions here, but I believe this would lead us away from the point of this article. So let's leave it at this.
Qualitative definition of a healthy diet
This next definition is pretty fat – apologies, obese. I'll explain it in more detail than the other two, because I consider it to be central for understanding dietary needs. In a qualitative, content way, healthy diet:
Satisfies all physiological dietary needs of an individual, including the adequate intake of:
Essential macronutrients (proteins – amino acids, fats – fatty acids, fiber)
Micronutrients (vitamins, minerals)
Phyto- and zoonutrients
Minimizes the intake of harmful substances of bacterial, viral, herbal, fungal, animal or inorganic origin which are present in food itself or created during its processing.
Satisfies psychological and sociocultural needs of an individual.
Physiological dietary needs
They are individual However, this doesn't mean that it's justified to say „This suits me well, I feel good from it, I know best what my body needs and no one can tell me what to eat“.
This is harmful thinking because it makes person that thinks this way advice-resistant. Furthermore, if a person has no visible symptoms of disease, has a healthy body weight, and a visually pleasant ratio of muscle and fat tissue, it's harmful for his surroundings as well, because a non-critical observer can be led to think that physical appearance is a sign of healthy diet. And it's not, especially in youth.
One should distinguish differences in dietary needs for individuals and the ability to recognize their own. The body doesn't have an overly sensitive sensor of nutritive needs or deficits, other than ones for energy. Which is logical, because up until recently the only dietary concern fot humans was sufficient energy intake. We all belong to the same species, have a nearly identical metabolism, so our needs, the qualitative ones, are the same. Difference lies in quantity. In other words, John and Mary need the same nutrients, only in different quantities.
Instead of relying on our own non-existing sensors, it's better to look for answers in scientific literature. It bases the recommendations on the data from analyses of thousands of individuals, depending on their gender, age group, and possible special dietary needs (pregnancy, breastfeeding). However, we must point out that these recommendations (1) represent values that satisfy the needs of (only) 97-98% of the population, which means there's a 2-3% chance you might not get what you need by following them. Quite decent probability, I would say. Also, I believe that a great deal of the remaining insecurity could be fixed by enhancing the nutritive intake in individuals with very high energy consumption, who are the most common representatives of the population with higher nutritive needs.
Medicine, and nutrition science along with it, are getting more personalized. (I myself am working on a PhD in nutrigenomics and personalized nutrition). In future, maybe, not so near, we can expect the development of tools for individual diagnosis of nutritive needs and a complete individualization of the guidelines. Until then, the best approach is to keep track of scientific recommendations on nutrient intake.
Energy needs, other than being the most individual and therefore the most variable component of the diet, should be related to the goal we're trying to achieve with its manipulation (increased body/muscle weight, decreased body/fat weight, or the body weight maintenance).
The needs for essential macro and micronutrients are displayed in official tables. In the past American RDA tables were most common, and now we use DRI tables. (1) I don't claim these numbers to be set in stone. Moreover, I think we should continuously question them through scientific research, up to a rational point. Also, the genetic and environmental differences I mentioned earlier can significantly change the needs of and individual.
Unfortunately, there are still no official recommendations for an adequate intake of phyto- and zoonutrients – the non-nutritive items of herbal and animal origin with certain benefits on health. The reason for this is that there is little knowledge on the mechanisms of these compounds. So, the best recommendation we can currently follow is to be diverse in consuming all types of herbal and animal food.
This part of qualitative definition is probably the most contested one. It's a part of the human nature to find a guilty party for everything. However, nutrition science is very complex and the research results are often confusing (not contradictory) even for experts, let alone laypeople. That's why there's no surprise that they grasp at straws to avoid not knowing. Making peace with the lack of knowledge is a great virtue.
Dietary toxins include all substances we ingest along with food that have a harmful effect on the human body – everything that diminishes or halts the before mentioned maximal use of our own genetic and environmental potential for a long and quality life.
What is poison to someone though, doesn't need to be so to someone else. Dietary allergies are a great example of this, where a certain substance, usually protein, can cause a deadly reaction in some, while others absorb it and digest it with no issues. Also, dose makes the poison, which means that the dose below the limit level set for every known poisonous substance (NOAEL) (2) won't have a negative effect on health. On the other hand, you can die from ingesting too much water as well. (3)
A lot of dietary substances people consider poisonous, are not so in quantities eaten in normal circumstances. Fats aren't. Carbs aren't. Sugar isn't. Aspartame isn't. Taking this into consideration, I emphasize that healthy diet is inclusive, not exclusive. So, focus on satisfying your dietary needs rather than getting rid of popular poisons. I do not claim under any circumstances that real poisons should be neglected. Trans fats are poison. Acrylamide probably is. Some pesticides probably are. You shouldn't go overboard with saturated fats. But also, don't panic about their harmfulness.
This is the most commonly neglected component of a healthy diet. When satisfied, it results in psychological benefits that manifest themselves as physiological benefits – enjoying food, not limiting and fussing, and socializing while eating. I plan to do an article on this subject so let's leave it at that for now.
Relative importance of components
I propose the ratio of importance for mentioned components:
The ratio can vary, depending on individual differences in the importance of psychological component.
The importance of balance
This is a different type of balance than energetic one which we always listen about. The tricky thing about diet, and life in general, is the cost and benefit ratio. This next hypothetical example might illustrate the importance of this.
The development of dietary industry has prolonged our average lifespan for 10 years by allowing lower prices, greater accessibility and food diversity, and a higher quality nutritive intake.
On the other hand, side effects of this development like introducing trans unsaturated fatty acids into diet, have shortened the life span for 3 years. You don't need to be a scientist to calculate we are 7 years in the surplus.
In other words, dietary industry has had a positive impact on our health.
This doesn't mean that we need to accept the negative side effects though. On the contrary, we should identify and minimize them, and if possible, find a way tp remove them. As a positive example, the US Food and Drug Administration recently removed trans unsaturated fatty acids from the GRAS substances list (the ones safe for human consumption – Generally Recognized As Safe). In other words, their use is in the process of banning. (4)
I believe there is a fine line over which the attempts at having a perfect diet start to have a negative effect on an individual, where psychological pressure connected to dietary choices exceeds the potential benefits. This is true even with the assumption that a person has the most correct definition of a proper diet, and that going over the line is physiologically legitimate, i.e. has nutritive benefits. Which is mostly not true. In other words, the line is lower than many think.
Speaking of the cost-benefit, two things to consider as well are the price of food items and the time necessary for food preparation. Both of these, if they become too high, can compromise the physiological and/or psychological component of healthy diet. For example, if buying organic vegetables makes you spend so much money you generally eat less vegetables or not go to the movies, you didn't do yourself a favor.
Alternative dietary regimes
Even though evil minds will say otherwise based on my Facebook page, I do not claim that alternative dietary ways are inherently bad, or unhealthy. Vegetarian, vegan, Paleo, LCHF (low carb) can be a healthy diet under some conditions. The fact that this is possible shows that these regimes are based on irrelevant dietary factors.
Practical definition of a healthy diet
Eat enough, but not too much. Eat diverse, mostly plants. Avoid harmful substances, but don't forget to enjoy food – if possible, in good company.
Every similarity with Michael Pollan's words is not accidental.
Next time you judge the quality of someone's diet, use the above mentioned criteria, and not moral opinions and personal preferences.
Healthy diet isn't black and white. But, except for people who research it, it doesn't need to be overly detailed either. There is no one perfect diet. It can be achieved in many ways. And that's wonderful because it allows for diversity of dietary traditions. Diet shouldn't be a nuisance. Food is one of the fundamental human sources of pleasure. Don't allow the choice of food to rule your life. We don't live to eat, we eat to live.
1. Hellwig, Jennifer Pitzi, Jennifer J. Otten, and Linda D. Meyers, eds. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. National Academies Press, 2006.
2. Dorato, Michael A., and Jeffery A. Engelhardt. "The no-observed-adverse-effect-level in drug safety evaluations: use, issues, and definition (s)." Regulatory Toxicology and Pharmacology 42.3 (2005): 265-274.