Carbohydrate loading is a good strategy to increase fuel stores in muscles before the start of the competition.

What does the muscle “eat” during endurance exercise?

Muscle “eats” carbohydrates, in the form of liver and muscle glycogen, carbohydrates ingested during the exercise or just before that, and fat.
During endurance exercise, the most likely contributors to fatigue are dehydration and carbohydrate depletion, especially of muscle and liver glycogen.
To prevent the “crisis” due to the depletion of muscle and liver carbohydrates, it is essential having high glycogen stores before the start of the activity.

What does affect glycogen stores?

• The diet in the days before the competition.
• The level of training (well-trained athletes synthesize more glycogen and have potentially higher stores, because they have more efficient enzymes).
• The activity in the day of the competition and the days before (if muscle doesn’t work it doesn’t lose glycogen). Therefore, it is better to do light trainings in the days before the competition, not to deplete glycogen stores, and to take care of nutrition.

The “Swedish origin” of carbohydrate loading

Very high muscle glycogen levels (the so-called glycogen supercompensation) can improve performance, i.e. time to complete a predetermined distance, by 2-3% in the events lasting more than 90 minutes, compared with low to normal glycogen, while benefits seem to be little or absent when the duration of the event is less than 90 min.
Well-trained athletes can achieve glycogen supercompensation without the depletion phase prior to carbohydrate loading, the old technique discovered by two Swedish researchers, Saltin and Hermansen, in 1960s.
The researchers discovered that muscle glycogen concentration could be doubled in the six days before the competition following this diet:

• three days of low carb menu (a nutritional plan very poor in carbohydrates, i.e. without pasta, rice, bread, potatoes, legumes, fruits etc.);
• three days of high carbohydrate diet, the so-called carbohydrate loading (a nutritional plan very rich in carbohydrates).

This diet causes a lot of problems: the first three days are very hard and there may be symptoms similar to depression due to low glucose delivery to brain, and the benefits are few.
Moreover, with the current training techniques, the type and amount of work done, we can indeed obtain high levels of glycogen: above 2.5 g/kg of body weight.

The “corrent” carbohydrate loading

If we compete on Sunday, a possible training/nutritional plan to obtain supercompensation of glycogen stores can be the following:

• Wednesday, namely four days before the competition, moderate training and then dinner without carbohydrates;
• from Thursday on, namely the three days before the competition, hyperglucidic diet and light trainings.

The amount of dietary carbohydrates needed to recover glycogen stores or to promote glycogen loading depends on the duration and intensity of the training programme, and they span from 5 to 12 g/kg of body weight/d, depending on the athlete and his activity. With higher carbohydrate intake you can achieve higher glycogen stores but this does not always results in better performance; moreover, it should be noted that glycogen storage is associated with weight gain due to water retention (approximately 3 g per gram of glycogen), and this may not be desirable in some sports.

References

1. Burke L.M., Hawley J.A., Wong S.H.S., & Jeukendrup A. Carbohydrates for training and competition. J Sport Sci 2011;29:Sup1,S17-S27. doi:10.1080/02640414.2011.585473
2. Hargreaves M., Hawley J.A., & Jeukendrup A.E. Pre-exercise carbohydrate and fat ingestion: effects on metabolism and performance. J Sport Sci 2004;22:31-38. doi10.1080/0264041031000140536
3. Jeukendrup A.E., C. Killer S.C. The myths surrounding pre-exercise carbohydrate feeding. Ann Nutr Metab 2010;57(suppl 2):18-25. doi:10.1159/000322698
4. Moseley L., Lancaster G.I, Jeukendrup A.E. Effects of timing of pre-exercise ingestion of carbohydrate on subsequent metabolism and cycling performance. Eur J Appl Physiol 2003;88:453-458. doi:10.1007/s00421-002-0728-8

“The acid-ash hypothesis posits that protein and grain foods, with a low potassium intake, produce a diet acid load, net acid excretion, increased urine calcium, and release of calcium from the skeleton, leading to osteoporosis.” (Fenton et al., 2009, see References).
Is it true?
Calcium, present in bones in form of carbonates and phosphates, represents a large reservoir of base in the body. In response to an acid load such as the high protein diets these salts are released into the circulation to bring about pH homeostasis. This calcium is lost in the urine and it has been estimated that the quantity lost with the such diet over time could be as high as almost 480 g over 20 years or almost half the skeletal mass of calcium!
Even these losses of calcium may be buffered by ingestion of foods that are alkali rich as fruit and vegetables, and on-line information promotes an alkaline diet for bone health as well as a number of books, a recent meta-analysis has shown that the causal association between osteoporotic bone disease and dietary acid load is not supported by evidence and there is no evidence that the alkaline diet is protective of bone health, but it is protective against the risk for kidney stones.

Note: it is possible that fruit and vegetables are beneficial to bone health through mechanisms other than via the acid-ash hypothesis.

What is the role of proteins?

Excess dietary proteins with high acid renal load may decrease bone density, if not buffered by ingestion of foods that are alkali rich, that is fruit and vegetables. However, an adequate protein intake is needed for the maintenance of bone integrity. Therefore, increasing the amount of fruit and vegetables may be necessary rather than reducing protein too much.
Therefore it is advisable to consume a normo-proteic diet rich in fruits and vegetables and poor in sodium, such as medieterranean diet, eating foods with a negative acid load together with foods with a positive acid load. Example: pasta plus vegetables or meats plus vegetables and fruits .

Alkaline diet and muscle mass

As we age, there is a loss of muscle mass, which predispose to falls and fractures. A diet rich in potassium, obtained from fruits and vegetables, as well as a reduced acid load, results in preservation of muscle mass in older men and women.

Alkaline diet and growth hormone

In children, severe forms of metabolic acidosis are associated with low levels of growth hormone with resultant short stature; its correction with potassium or bicarbonate citrate increases growth hormone significantly and improves growth. In postmenopausal women, the use of enough potassium bicarbonate in the diet to neutralize the daily net acid load resulted in a significant increase in growth hormone and resultant osteocalcin.
Improving growth hormone levels may reduce cardiovascular risk factors, improve quality of life, body composition, and even memory and cognition.

Conclusion

Alkaline diet may result in a number of health benefits.

• Increased fruits and vegetables would improve the potassium/sodium ratio and may benefit bone health, reduce muscle wasting, as well as mitigate other chronic diseases such as hypertension and strokes.
• The increase in growth hormone may improve many outcomes from cardiovascular health to memory and cognition.
• The increase in intracellular magnesium is another added benefit of the alkaline diet; for example, magnesium, required to activate vitamin D, would result in numerous added benefits in the vitamin D systems.

It should be noted that one of the first considerations in an alkaline diet, which includes more fruits and vegetables, is to know what type of soil they were grown in since this may significantly influence the mineral content and therefore their buffering capacity.

References

1. Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009;24(11):1835-1840. doi:10.1359/jbmr.090515
2. Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Phosphate decreases urine calcium and increases calcium balance: a meta-analysis of the osteoporosis acid-ash diet hypothesis. Nutr J 2009;8:41. doi:10.1186/1475-2891-8-41
3. Fenton T.R., Tough S.C., Lyon A.W., Eliasziw M., Hanley D.A. “Causal assessment of dietary acid load and bone disease: a systematic review and meta-analysis applying Hill’s epidemiologic criteria for causality.” Nutr J 2011;10:41. doi:10.1186/1475-2891-10-41
4. Schwalfenberg G.K. The alkaline diet: is there evidence that an alkaline pH diet benefits health? J Environ Public Health 2012; Article ID 727630. doi:10.1155/2012/727630

Life depends on appropriate pH levels around and in living organisms and cells.
We requires a tightly controlled pH level in our serum of about 7.4 to avoid metabolic acidosis and survive. As a comparison, in the past 100 years the pH of the ocean has dropped from 8.2 to 8.1 because of increasing carbon dioxide deposition with a negative impact on life in the ocean.

Even the mineral content of the food we eat is considerable influenced by the pH of the soil in which plants are grown. The ideal pH of soil for the best overall availability of essential nutrients is between 6 and 7: an acidic soil below pH of 6 may have reduced magnesium and calcium, and soil above pH 7 may result in chemically unavailable zinc, iron, copper and manganese.

Metabolic acidosis and agricultural and industrial revolutions

In the human diet, there has been considerable change from the hunter gather civilization to the present in the pH and net acid load. With the agricultural revolution, in the last 10,000 years, and even more recently with industrialization, in the last 200 years, it has been seen:

• an increase in sodium compared to potassium, as the ratio potassium/sodium has reversed from 10 to 1 to a ratio of 1 to 3 in the modern diet, and in chloride compared to bicarbonate;
• a poor intake of magnesium and fiber;
• a large intake of simple carbohydrates and saturated fatty acids.

This results in a diet that may induce metabolic acidosis which is mismatched to the genetically determined nutritional requirements.
Moreover, with aging, there is a gradual loss of renal acid-base regulatory function and a resultant increase in diet-induced metabolic acidosis.
Finally, a high protein low-carbohydrate diet with its increased acid load results in very little change in blood chemistry, and pH, but results in many changes in urinary chemistry: urinary calcium, undissociated uric acid, and phosphate are increased, while urinary magnesium, urinary citrate and pH are decreased.
All this increases the risk for kidney stones.

pH as a protective barrier

The human body has an amazing ability to maintain a steady pH in the blood with the main compensatory mechanisms being renal and respiratory.
The pH in the body vary considerably from one area to another. The highest acidity is found in the stomach (pH of 1.35 to 3.5) and it aids in digestion and protects against opportunistic microbial organisms. The skin is quite acidic (pH 4-6.5) and this provides an acid mantle as a protective barrier to the environment against microbial overgrowth (this is also seen in the vagina where a pH of less than 4.7 protects against microbial overgrowth).
The urine have a variable pH from acid to alkaline depending on the need for balancing the internal environment.

References

1. Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009;24(11):1835-1840. doi:10.1359/jbmr.090515
2. Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Phosphate decreases urine calcium and increases calcium balance: a meta-analysis of the osteoporosis acid-ash diet hypothesis. Nutr J 2009;8:41. doi:10.1186/1475-2891-8-41
3. Fenton T.R., Tough S.C., Lyon A.W., Eliasziw M., Hanley D.A. Causal assessment of dietary acid load and bone disease: a systematic review and meta-analysis applying Hill’s epidemiologic criteria for causality. Nutr J 2011;10:41. doi:10.1186/1475-2891-10-41
4. Schwalfenberg G.K. The alkaline diet: is there evidence that an alkaline pH diet benefits health? J Environ Public Health 2012; Article ID 727630. doi:10.1155/2012/727630