 Under-nutrition causes nutrition deficiency, and over nutrition leads to obesity, hypertension, hyperlipidemia, diabetes, and cancer.
It also highlights that nutritional requirements of the body may vary among different individuals with different heredity and family backgrounds, different dietary habits, and living in different countries. Even different gut microbes may affect the requirement of nutrition. Although a research on personalized nutrition and nutritional genomics is proposed, results from epigenetic studies have shown that dietary habits and experience of a person can change epigenetic characteristics through DNA imprinting and histone modification. This indicates that dietary requirements are not decided by genome. Diets determine the expression, regulation, modification, imprinting, and heredity of the genome without altering DNA sequences. Obviously, this is a challenge for nutritional genomics. Thus, the problem seems to be at the origin, i.e., how to provide a scientific diet and formula for different individuals?
(II) Contribution of foods and nutrition to the immune system is apparent, which is also a hot topic of research on functional foods.
However, increasing number of studies indicate that immune defense is the first priority of nutrition. Hypo-immunity is only observed in infants, children, and elderly and in individuals with diseases and serious nutrition defects. Thus, when nutrition is abundant, even commonly redundant, excessive immunity can cause inflammation, autoimmune diseases, and metabolic syndromes. Like a double-edged sword, immunity can cause diseases when it is too low or too high. Therefore, the question is what is the appropriate immunity and how should it be quantified. Unfortunately, no method is available to quantify the immune system thus far.
(III) Another problem is that precise effect of foods on organs or tissues within the body is unclear.
Some studies have shown that food mainly interacts with the GI mucous membrane system. Communication between organs and tissues is established through the circulatory and signaling systems of the GI tract and inner system. Food does not enter target organs or tissues directly, which results major problem that we face, i.e., quantitative description of this complex nonlinear system. The metabolic and cellular communication networks provide feasible ways and can be evaluated by obtaining only a few millimeter cube of peripheral blood.
(IV) Finally the last one is related to Public health being a social and political concept aimed at the improving health, prolonging life and improving the quality of life among whole populations through health promotion, disease prevention and other forms of health intervention.
A distinction has been made in the health promotion literature between public health and a new public health for the purposes of emphasizing significantly different approaches to the description and analysis of the determinants of health, and the methods of solving public health problems. This new public health is distinguished by its basis in a comprehensive understanding of the ways in which lifestyles and living conditions determine health status, and recognition of the need to mobilize resources and make sound investments in policies, programmes and services which create, maintain and protect health by supporting healthy lifestyles and creating supportive environments for health.
Despite wide differences in opinion among researchers and the general public over recent years, dietary fats remain a potent regulator of physiological function. This calls for caution in supplementing more than a few grams of any uncommon fat per day. Food sources remain the preferred method of intake in most situations.
The various fatty acids provide perhaps the most important aspect of dietary fat manipulations, although increasing the percentage of fat in the diet also has an impact on exercise and resting metabolism. Nutrition, especially sensing and absorption of energy substances, not only plays an important role in the intensity of life activ