How does healthy eating prevent disease?
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“What is a healthy diet?” Providing an easy answer to this question is understandably difficult. In fact, numerous physicians might struggle to find a concise and clear answer to this common question from patients.
While there are many publications available in the field of food and nutrition, sometimes with contradictory conclusions, there are also continuous dietary recommendations paralleled with an overwhelming amount of misinformation from different media sources. Consequently, answering the question, “What is a healthy diet”, might seem like finding a solution to an impossible equation.
However, there is a solid amount of data now available from trustworthy sources to guide simple yet convincing recommendations about balanced food and nutrition strategies. Understanding the impact of a diet on the overall wellbeing of an individual requires granulating the multifaceted complexity in an easy and comprehensive way.
From a dietary point of view, it is now undebatable that the calories we consume are not simply necessary to build, sustain and heal our bodies. The food and the amount of calories we consume have a critical role in influencing our health, including modulating our risk of suffering from chronic conditions, ranging from cardiovascular conditions (such as stroke and heart disease) and metabolic diseases (such as diabetes and osteoporosis) to cancer.
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Obviously, diet is just one of the factors we can control to reduce our risk of developing some conditions, the so-called “modifiable risk factors”. Having a balanced diet along with limiting caloric intake to control a healthy weight, staying active and avoiding smoking are three pillars for a healthy life.
Healthy diets to prevent diseases
When experts talk about prevention, they usually refer to primary or secondary prevention. More recently the concept of primordial prevention has been added to the list. While all three present some similarities, they differ in starting times and effects. Modifications of dietary patterns towards a healthy diet might apply to each of the three steps of prevention:
- Primary prevention aims to keep an individual at risk of a condition from having a first event or developing the full-blown disease. Primary prevention focuses on controlling risk factors including making healthy lifestyle changes.
- Secondary prevention aims to avert the recurrence of a disease or event in an individual who already had such a condition. Changes in the dietary patterns along with physical activity, for instance, can prevent a second heart attack in an individual who suffered from a previous myocardial infarction. This ultimately reduces the risk of early death. It may sound obvious, but the main killer among individuals who survive a first myocardial infarction is a second heart attack.
- Primordial prevention has been recently introduced and aims at avoiding the development of risk factors in the first place, working on the mechanisms underlying a specific condition, such as inflammation, atherosclerosis, and endothelial dysfunction, among others. Ideally, primordial prevention can start from childhood. Therefore, it’s never too early to develop healthy eating habits.
Healthy diets for healthy systems and tissues
Solid data are now available supporting the theory that healthy lifestyle patterns (healthy diet, physical activity and avoiding smoking) might dramatically reduce the risk of cardiovascular events over a long-term follow-up.
The immune system is complex and pervasive, involving numerous cell types that either circulate in the bloodstream or reside in particular tissues. Several micronutrients (such as zinc, iron, selenium, vitamin C, vitamin D) play a key role in many phases of the immune response, being critical for the function of immune cells.
A diet that lacks one or more nutrients can have a negative impact on activity of immune systems. For instance, it is now common understanding that maternal nutritional deficiencies during pregnancy may alter to different degrees the humoral and/or cell-mediated immune responses of newborn babies.
Further evidence supporting the complex crosslinks between diet, metabolism and immune system is provided by the role of adipose tissue in producing adipocytokines that can stimulate inflammatory processes. Vascular inflammation and oxidative stress are now recognised as major triggers for cardiovascular events.
Bones and musculoskeletal system
Dietary habits are important “modifiable” factors that influence the development and maintenance of bone mass and play a key role in the prevention of diseases affecting bone metabolism, such as osteoporosis.
Calcium is the nutrient most commonly associated with the development and metabolism of bone mass. Many published studies show that low calcium intake throughout life is associated with low bone mass and high fracture rates.
A correct intake of calcium during prepuberal age along with genetic factors contributes to the physiological development of bone mass reaching its peak at the end of growth.
Once the bone mass has developed, healthy dietary patterns and regular physical activity help to maintain the bone mass gained and reduce the loss. However, other micronutrients (Vitamins A, C, E, K) and minerals (phosphorus, fluoride, iron, zinc, copper and boron) are similarly necessary for physiological bone metabolism.
Omega-3 fatty acids have been also shown to play a role in bone metabolism, protecting against bone mass loss by decreasing osteoclast activation and bone reabsorption via a down-regulation of pro-inflammatory cytokines.
The role of diet has been an aspect with less focus than other topics when referring to skin disorders, which has been confined mainly to cosmetic aspects. It is now common understanding that changes in dietary patterns may modulate the course of some skin conditions, such as acne or lower the risk of some skin cancer.
It has been observed that diets consisting of foods rich in vitamin D and carotenoids and low in alcohol may lower the risk for melanoma.
There is a growing body of data supporting that dietary patterns are critical modifiers of brain plasticity, impacting the health of the central nervous system. Similar to physical activity, recent findings indicate that molecular events regulating neurons, energy metabolism, and synaptic plasticity might be influenced by changes in dietary patterns, similar to physical activity.
Experiments in animal models have shown that some nutrients (such as omega-3 fatty acids and curcumin, either introduced as whole foods or as dietary supplements) may reduce the effect of neural damage, suggesting that dietary changes could represent an effective strategy to counteract some neurological and cognitive conditions.
On the contrary, unhealthy diets rich in saturated fats and sugars have been proven to negatively impact the molecular systems that serve neuronal function and plasticity in the brain and spinal cord.
There are several elements that regulate human fertility. This includes what we consume in our diets. It has been shown that diets containing unsaturated fats, whole grains, vegetables, and fish support positive fertility outcomes in both women and men.
On the other hand, diets containing high levels of sugar and saturated fats might have negative fertility outcomes. Additionally, an extreme body mass index (BMI) (either BMI <20 kg/m2 or ≥ 30 kg/m2) has also been shown to be associated with worse fertility outcomes.
There are ongoing investigations into best strategies to prevent adverse kidney outcomes in persons at risk for chronic kidney disease.
Emerging evidence is showing a healthy diet is linked to more favorable kidney outcomes. Researchers investigating best diets as strategies to prevent or improve renal diseases link to patterns such as the Mediterranean diet (rich in fruits, fibres and vegetables), the Dietary Approaches to Stop Hypertension diet (so called DASH) and other dietary patterns that are low in dietary acid load.
In fact, the DASH diet specifically aims to limit the sodium in the diet while introducing potassium, calcium and magnesium, all foods rich in nutrients that might help lower blood pressure.
Also, recent studies emphasize the risks of high consumption of sugary beverages associated with an elevated risk of renal disease. In order to keep our kidneys healthy, we should consider reducing the amount of sugar in our drinks.
All in all, to answer the question: “What is the role of a healthy diet?”, requires a multifaceted and holistic approach to diet and its impact on the health and wellbeing of the individual. The different factors for prevention (primary, secondary, and primordial) are valuable ways to integrating a healthy diet pattern.
Of course, diet is just one of the modifiable risk factors we have to reduce our risk of developing serious health conditions. Having a balanced diet, along with limiting caloric and alcohol intake to control a healthy weight, staying active, and avoiding smoking are important dietary factors for a healthy life.
Authors: Dr. Savino Sciascia, and Dr. Gregory Winston Gilcrease
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