Category Archives: Nutrition

Nutrition is a key factor in maintaining good health throughout life.
Eating a balance diet, from birth with breastfeeding, and later during childhood, adolescence and adult life, is helpful in achieving and maintaining a good state of health and contributes, when associated with a healthy lifestyle, to the prevention of many chronic diseases such as cardiovascular diseases, osteoporosis, type II diabetes, and many types of cancers, conditions which are increasingly common nowadays.
And it is important to point out the relationship between nutrition and the intestinal microbiota, the community of microorganisms that colonize the gut: diet seems to be main factor in determining its composition, starting from breast milk.
Proper nutrition is essential even in the presence of allergic reactions to food components, as in the case of celiac disease, condition in which all food containing gluten must be avoided for life.
Proper nutrition is essential for athletes, and when combined with adequate training improves the performance in any sports.
And among the different types of diets, the Mediterranean diet is one of the healthiest. This dietary pattern was brought to the attention of the international scientific community in the 1950s by the work of Ancel Keys, an American physiologist. The Mediterranean diet, rich in plant products, such as extra virgin olive oil, vegetables, legumes, and whole grains, and low in red meats and derived products and high fat dairy products, ensures an good supply of fiber, compounds with anti-inflammatory and antioxidant actions, as well as a low intake of saturated fats.

Essential fatty acids: definition, synthesis, functions, and foods

Essential fatty acids or EFAs are fatty acids that cannot be synthesized by animals, and, like other essential nutrients, must be obtained from the diet. They are linoleic acid or LA or 18:2n-6, and alpha-linolenic acid or ALA or 18:3n-3.
Animals cannot synthesize these two fatty acids due to the lack of delta-12 desaturase (E.C. 1.14.19.6) and delta-15 desaturase (EC 1.14.19.25). These enzymes introduce cis double bonds beyond carbon 9, and are present in plants and microorganisms, such as some bacteria, fungi and molds. In particular, in plants:

  • delta-12 desaturase, present in the plastids, catalyzes the synthesis of linoleic acid from oleic acid, by introducing a double bond at delta-12 position, namely, between carbons 6 and 7 from the methyl end of the fatty acid;
  • delta-15 desaturase, present in the plastids and in the endoplasmic reticulum of phytoplankton and vascular terrestrial plants, catalyzes the synthesis of alpha-linolenic acid from linoleic acid by introducing a double bond at delta-15 position, namely, between carbons 3 and 4 from the methyl end of the fatty acid.
Synthesis of the essential fatty acids linoleic acid and alpha-linolenic acid
Synthesis of EFAs

Linoleic acid and alpha-linolenic acid are the precursors to omega-6 polyunsaturated fatty acids and omega-3 polyunsaturated fatty acids. Indeed, animals can synthesize, although with variable efficiency, the other omega-3 and omega-6 polyunsaturated fatty acids, molecules with 20, 22, or 24 carbon atoms, and up to 6 double bonds, such as arachidonic acid or ARA or 20:4n6 and docosahexaenoic acid or DHA or 22:6n3, due to the presence of desaturases that introduce double bonds at delta-5 and delta-6 positions and elongases that catalyze  the elongation of the carbon chain.
In the absence of dietary essential fatty acids, a rather rare condition, the other omega-3 and omega-6 fatty acids become essential, too. For this reason, they are defined by some as conditionally essential fatty acids.

It should be pointed out that all essential fatty acids are polyunsaturated molecules, but not all polyunsaturated fatty acids are essential, such as those belonging to the omega-7 and omega-9 families.

CONTENTS

Discovery of essential fatty acids

The first evidence of their existence dates back to 1918, when Hans Aron suggested that dietary fat could be essential for the healthy growth of animals and that, in addition to their caloric contribution, there was a inherent nutritive value due to the presence of certain lipid molecules.
In 1927, Herbert M. Evans and George Oswald Burr demonstrated that, despite the addition of vitamins A, D, and E to the diet, a deficiency of fat severely affected both growth and reproduction of experimental animals. Therefore, they suggested the presence of an essential substance in the fat that they called vitamin F.
Eleven years after Aron work, in 1929, George Burr and his wife Mildred Lawson hypothesized that warm-blooded animals were not able to synthesize appreciable amounts of certain fatty acids. One year later, they discovered that linoleic acid was essential for animals, and it was they who coined the term essential fatty acid.
However, EFA deficiency in humans was first described by Arild Hansen et al. only in 1958, in infants fed a milk-based formula lacking them.
And in 1964, thanks to the research of Van Dorp et al. and Bergstroem et al., one of their biological functions was discovered: being the precursors for the synthesis of prostaglandins.

Functions of EFAs and their PUFA derivatives

EFAs and their polyunsaturated fatty acid derivatives play important biological functions.

  • They are structural components of cellular membranes, modulating, for example, their fluidity, particularly DHA.
  • They are essential for the development and functioning of the nervous system, particularly ARA and DHA.
  • They are involved in signal transduction, particularly omega-6 polyunsaturated fatty acids, such as ARA.
  • They are involved in the regulation of genes encoding lipolytic and lipogenic enzymes, being strong inducers of fatty acid oxidation, as well as inhibitors of their synthesis and that of triglycerides, at least in animal models.
    They act, for example, as:

    • activators of the peroxisome proliferator-activated receptor α (PPAR-α) that stimulates the transcription of genes encoding lipolytic enzymes as well as mitochondrial and peroxisomal beta-oxidation enzymes, and inhibitors of transcription of genes encoding enzymes involved in lipogenesis;
    • inhibitors of sterol responsive element binding protein-1c (SREBP-1c) gene transcription, a transcription factor required for liver fatty acid and triglyceride synthesis induced by insulin.
      Note: PUFAs also increase SREBP-1c mRNA degradation as well as SREBP-1 degradation.
  • They are precursors for signaling molecules, with autocrine and paracrine action, that act as mediators in many cellular processes, such as eicosanoids
  • They are essential in the skin, especially linoleic acid in sphingolipids of the stratum corneum, where they contribute to the formation of the barrier against water loss.
  • They have a crucial role in the prevention of many diseases, particularly coronary heart disease, acting as antihypertensive, antithrombotic, and triglyceride-lowering agents.
  • Noteworthy, their energy storage function is quantitatively unimportant.

Foods rich in essential fatty acids

Linoleic acid is the most abundant polyunsaturated fatty acid in the Western diet, and accounts for 85-90% of dietary omega-6 polyunsaturated fatty acids.
The richest dietary sources are vegetable oils and seeds of many plants, such as:

  • safflower oil, ~ 740 mg/g;
  • sunflower oil, ~ 600 mg/g;
  • soybean oil, ~ 530 mg/g;
  • corn oil, ~ 500 mg/g;
  • cottonseed oil, ~ 480 mg/g;
  • walnuts, ~ 340 mg/g;
  • brazil nuts, ~ 250 mg/g;
  • peanut oil, ~ 240 mg/100 g;
  • rapeseed oil, ~ 190 mg/g;
  • peanuts, ~140 mg/g;
  • flaxseed oil, ~ 135 mg/g.

Linoleic acid is present in fair amounts also in animal products such as chicken eggs or lard, because it is present in their feed.
It should be noted that some of the major sources of linoleic acid, such as walnuts, flaxseed oil, soybean oil, and rapeseed oil are also high in alpha-linolenic acid.

Some of the richest dietary sources of alpha-linolenic acid are:

  • flaxseed oil, ~ 550 mg/g
  • rapeseed oil, ~ 85 mg/g
  • soybean oil, ~ 75 mg/g

Other foods rich in ALA include nuts, ~ 70 mg/g, and soybeans, ~ 10 mg/g.

References

Akoh C.C. and Min D.B. “Food lipids: chemistry, nutrition, and biotechnology” 3th ed. 2008

Bergstroem S., Danielsson H., Klenberg D. and Samuelsson B. The enzymatic conversion of essential fatty acids into prostaglandins. J Biol Chem 1964;239:PC4006-PC4008

Burr G. and Burr M. A new deficiency disease produced by the rigid exclusion of fat from the diet. J Biol Chem 1929;82:345-367

Chow Ching K. “Fatty acids in foods and their health implication” 3th ed. 2008

Evans H. M. and G. O. Burr. A new dietary deficiency with highly purified diets. III. The beneficial effect of fat in the diet. Proc Soc Exp Biol Med 1928;25:390-397. doi:10.3181/00379727-25-3867

Smith W., Mukhopadhyay R. Essential fatty acids: the work of George and Mildred Burr. J Biol Chem 2012;287(42):35439-35441. doi:10.1074/jbc.O112.000005

Van Dorp. D.A., Beerthuis R.K., Nugteren D.H. and Vonkeman H. Enzymatic conversion of all-cis-polyunsaturated fatty acids into prostaglandins. Nature 1964;203:839-841. doi:10.1038/203839a0

Nutrition for athletes: strategies for training and competition

The right diet is one of the basic foundations for achieving the best athletic performance.
Unfortunately, there aren’t special diets or “magic” foods.Nutrition for Athletes
Athletes, as the rest of the population, should follow a Mediterranean-type diet, so providing an adequate intake of energy, of mineral salts, vitamins, antioxidants, fiber and water, keeping at the same time  good  balance  of caloric intake by wisely splitting it during the day.
Finally, they should avoid as much as possible industrial foods or fast foods.

Nutrition for athletes and the distribution of meals and calories

Still more than sedentary man, because of his greater caloric intake, athlete will have to consume more meals during the day to avoid concentrating an excessive amount of calories (and food) in one meal.
In this way, he will:

  • avoid reaching lunch-time and especially dinner-time with an excessive hunger;
  • digest foods more easily, not engaging the digestive system with too much abundant meals.
  • avoid any increases in blood chemistry parameters associated with an increased risk of cardiovascular disease, such as hypertriglyceridemia and hypercholesterolemia.

Of course, in nutrition for athletes, the distribution of the meals will have to consider also training and competition times. The best distribution might be: breakfast, lunch and dinner plus two snacks, one in the morning and the other in the afternoon.

Breakfast

It is of one of most important and often underestimated meals of the day, that should never be skipped.
Typical breakfast foods are milk and/or yogurt, fruit juice (better if freshly squeezed seasonal fruit; when you buy a packaged fruit juice, select it without added sugar/sweeteners and with a caloric content of about 45 kcal/100 g), freshly made tea,bread, dry cookies without cream (however moderately), corn flakes without addition of syrup, honey, fresh/dry fruit, chocolate, and jam/honey (the last three in moderation).
Breakfast will be consumed considering the time when physical activity, and still more the competition, is made.
In nutrition for athletes, as for sedentary population,the breakfast should represent about 15% of the daily caloric intake, to pass to 20% without mid-morning snack.

Lunch

It should represent the meal in which the major part of complex carbohydrates is taken up that is pasta, rice, barley, cous-cous, oats, millet, etc (better if “al dente” with a light seasoning), based on personal preferences.
To limit glycemic increase it is advisable to eat, after a dish rich in carbohydrates, vegetables, fresh or cooked (in the latter when possible, better if steamed), but avoiding potatoes, cooked carrots and onions (foods with an high glycemic index). Bread, if present, should be eaten moderately.
At the end of the lunch a fruit can be eaten as well (if it doesn’t cause feelings of bloating when eaten at the end of the meal; in the case, fruit may be eaten during snacks) and/or a dessert without cream.
Seasonal fruit and vegetable will ensure an adequate intake of mineral salts, vitamins, fiber and water.
It is advisable having lunch at least two-three hours before the start of training sessions/competition, in order to allow a complete digestion, normalization of postprandial glycemic peaks and of insulin response before starting workout.
In nutrition for athletes, the lunch should represent 25-30% of the daily caloric intake.

Dinner

In this meal, it is advisable to give priority to proteins rather than carbohydrates, hence fish, white or red meat (the last one lean and less frequently) or legumes (rich in slow absorption carbohydrates, fiber and mineral salts) will be present, with seasonal vegetables, fresh or cooked, (recommended is also a vegetable soup, that will help in restoring liquids), moderate bread, and fruit (if it doesn’t cause feelings of bloating when eaten at the end of the meal, as seen for lunch).
It is advisable to eat legumes at dinner to avoid bothersome bloating during training.
In nutrition for athletes, the dinner should represent 25-30% of the daily caloric intake.

Snacks

In nutrition for athletes, to ensure adequate distribution of calories, often much higher than in the sedentary man and avoid an excessive accumulation at major meals, at least two snacks must be present, one at mid-morning and the other at mid-afternoon. Assume preferably fruit (moderately also dry fruit, advisable walnuts and almonds), yogurt/milk, dry cookies or a sandwich with lean sliced salami (e.g. lean raw ham or cured raw beef), cottage cheese (soft fresh cheese) or simply with extra-virgin olive oil and tomato or other vegetables (always choose seasonal vegetables).
The snack should represent 10-15% of the daily caloric intake.

Daily caloric intake

In nutrition for athletes, caloric intake must be matched to energy consumption that, in turn, depends on:

  • sex;
  • age;
  • growing phase;
  • physical structure;
  • level of physical activity (training plane, competition, recovery);
  • even possible pathological states.

Athlete’s diet must consider energy consumption due to workload sustained during training sessions.
In fact, if there are sports (as swimming, running, rowing or cross-country skiing) whose training sessions cause an increase of energy requirement in excess of 50% compared to needs referred to a moderately active lifestyle, in other sports (as artistic or rhythmic gymnastics, shooting etc.) the consumption related to the activity may be modest.
So, the only difference in nourishment between a sedentary or moderately active man and an athlete engaged in sports causing a large increase of energy requirement will be of quantitative type: the greater is the energy expenditure linked to physical activity, the greater will be the caloric intake.

References

Jeukendrup A.E. Nutrition for endurance sports: marathon, triathlon, and road cycling. J Sport Sci 2011:29;sup1, S91-S99. doi:10.1080/02640414.2011.610348

Invert sugar: definition, production, and uses

Invert sugar (also known as inverted sugar) is sucrose partially or totally cleaved into fructose and glucose (also known dextrose) and, apart from the chemical process used (see below), the obtained solution has the same amount of the two carbohydrates.

Honey has a fructose and glucose composition almost equal to that of 100% invert sugar
Moreover, according to the product, not cleaved sucrose may also be present.

Invert sugar production

The breakdown of sucrose may happen in a reaction catalyzed by enzymes, such as:

  • sucrase, active at our own intestinal level;
  • invertase, an enzyme secreted by honeybees into the honey and used industrially to obtain invert sugar.

Another process applies acid action, as it happens partly in our own stomach and as it happened in the old times, and still happens, at home-made and industrial level. Sulfuric and hydrochloric acids was used, heating the solution with caution for some time; in fact the reaction is as fast as the solution is acid, regardless of the type of acid used, and as higher the temperature is. The acidity is then reduced or neutralized with alkaline substances, as soda or sodium bicarbonate.

A chemical process as described occurs when acid foods are prepared; i.e. in the preparation of jams and marmalades, where both conditions of acidity, naturally, and high temperatures, by heating, are present. The situation is analogous when fruit juices are sweetened with sucrose.
The reaction develops at room temperature as well, obviously more slowly.
What is the practical outcome of that?
It means that, during storage, also sweets and acid foods, even those just seen, go towards a slow reaction of inversion of contained/residue sucrose, with consequent modification of the sweetness, since invert sugar at low temperatures is sweeter (due to the presence of fructose), and assumption of a different taste profile.

Properties and uses

It is principally utilized in confectionery and ice-cream industries thanks to some peculiar characteristics.

  • It has an higher affinity for water (hydrophilicity) than sucrose (see fructose) therefore it keeps food more humid: e.g. cakes made with invert sugar dry up less easily.
  • It avoids or slows down crystal formation (dextrose and fructose form less crystals than sucrose), property useful in confectionery industries for icings and coverage.
  • It has a lower freezing point.
  • It increases, just a bit, the sweetness of the product in which it has been added, as it is sweeter than an equal amount of sucrose (the sweetness of fructose depends on the temperature in which it is present).
  • It may take part to Maillard reaction (sucrose can’t do it) thus contributing to the color and taste of several bakery products.

It should be noted that honey, lacking in sucrose, has a fructose and glucose composition almost equal to that of 100% invert sugar (fructose is slightly more abundant than glucose). So, diluted honey, better if not much aromatic, may replace industrial invert sugar.

References

Belitz .H.-D., Grosch W., Schieberle P. “Food Chemistry” 4th ed. Springer, 2009

Bender D.A. “Benders’ Dictionary of Nutrition and Food Technology”. 8th Edition. Woodhead Publishing. Oxford, 2006

Jordan S. Commercial invert sugar. Ind Eng Chem 1924;16(3):307-310. doi:10.1021/ie50171a037

Stipanuk M.H., Caudill M.A. Biochemical, physiological, and molecular aspects of human nutrition. 3rd Edition. Elsevier health sciences, 2012

Body weight: what to do not to increase it

In order to maintain your body weight, energy intake with foods must match your individual needs, depending on age, sex and level of physical activity; calories exceeding needs accumulate in form of fat that will deposit in various parts of the body (typically in men, as in postmenopausal women, the accumulation area for excellence is abdomen).Body Weight: Adjust Caloric Intake According to Consumption
An example: let’s assume an energy requirement of 2000 kcal with an intake of 2100 kcal. The extra 100 kcal could result from 30 g of pasta or 35 g of bread or a 25 g package of crackers or 120 g of potatoes or 10 g of oils from any source etc., not a particularly large amount of food. This modest calories surplus, if performed daily for one year leads us to take:
100 kcal x 365 days = 36500 kcal/year extra calories compared to needs.
Since a kilogram of body fat contains approximately 7000 kcal, if we assume that 36500 kcal in excess accumulate exclusively in form of fat (very plausible approximation), we obtain: 36500/7000 = about 5 kilogram of body fat.
So, even a modest daily calorie surplus, over a year, can lead to a substantial body weight gain in the form of fat mass.
This example shows the importance of estimating with accuracy our daily energy requirements.

Split daily caloric intake into multiple meals

Let’s assume that daily caloric requirement to maintain body weight is equal to 2000 kcal.
Is it the same thing if they are consumed in just two meals, maybe dividing them in half between lunch and dinner, or is it advisable to take three to five meals during a day?
In order to mantain body weight, the best choice  is to divide calories into five meals: breakfast, lunch and dinner, the most abundant, plus two snacks, one on mid-morning and the other on mid-afternoon. Why? There are various reasons.

  • Consuming only two meals during the day, lunch and dinner or breakfast and dinner, it is likely to approach both meals with a hunger difficult to control; we eat what we have on our plate already thinking about what else to eat, having the feeling of not being able to satisfy the hunger. We eat, but there is always room for more food. Among the reasons for this there are too many hours between meals. Two examples:

dinner at 8:00 p.m. and, the next day, lunch at 1:00 p.m.: the interval is 17 hours, more than 2/3 of a day;

breakfast at 7:00 a.m. and dinner to 8:00 p.m., 13 hours have passed, most of which are spent in working activities and therefore more energy-consuming than hours of sleep.

Then, drops in blood sugar levels (glycemia) can also occur: liver glycogen stores, essential for maintaining normal glycemia, with time intervals between meals previously seen, can easily reach values close to depletion.

Therefore, by splitting the daily caloric intake into two meals, it is most likely difficult to meet the target of assuming 2000 kcal (the suggested daily calorie intake).

  • The concentration of too many calories in a single meal may promote the increase of plasma triglycerides, the excess of which is linked to the onset of cardiovascular disease.
  • When accumulating almost all or all of the calories in just two meals we are likely to grow stout, have feelings of bloating and getting real digestive problems due to excess of ingested food, not to mention that could occur even a postprandial sleepiness or difficulties in getting asleep.

Exercise regularly

Physical activity has a central role both in maintaining the reached body weight and in the loss of fat mass.
Make physical activity on a regular basis has several advantages.

  • If exercise is conducted on a regular basis and is structured in the proper way, is possible that, even without appreciable changes in weight, a redistribution of fat occurs between fat mass, which drops, and free fat mass, which, on the contrary, increases. Such a result can’t obviously be reached by simple walk; we need a specific training program, better if planned by a professional, and a proper diet, always of Mediterranean type.
  • We protect muscle mass (and as suggested in point 1. we can also increase it).
  • We maintain a high metabolism.
  • Muscle burn energy during and especially after exercise.
  • The body is toned.
  • Appetite is controlled more easily.
  • Making physical activity on a regular basis makes the prevention of weight gain easier, due to the inevitable “escapades” (indulging in a bit of chocolate, an ice cream etc..).

References

Haskell W.L., Lee I.M., Pate R.R., Powell K.E., Blair S.N., Franklin B.A., Macera C.A., Heath G.W., Thompson P.D., Bauman A..Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 2007;39(8):1423-1434. doi:10.1249/mss.0b013e3180616b27

Shils M.E., Olson J.A., Shike M., Ross A.C.: “Modern nutrition in health and disease” 9th ed. 1999