Category Archives: Mediterranean Diet

Alkaline diet and health benefits

Alkaline diet and bone health

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).
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.

And protein?
Excess dietary protein 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, that is, a Mediterranean Diet-like eating patterns, 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 (see figure below).

Alkaline Diet: Food and Acid Load
Fig. 1 – Food and Acid Load

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 K/Na 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 (e.g. 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

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):1835-40 [Abstract]

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:article 41 [Abstract]

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:article 41 [Abstract]

Schwalfenberg G.K. The alkaline diet: is there evidence that an alkaline pH diet benefits health? J Environ Public Health 2012; Article ID 727630:7 pages doi:10.1155/2012/727630 [Abstract]

Metabolic acidosis and “modern diet”

Metabolic acidosis and pH level

Metabolic Acidosis: The pH Scale
Fig. 1 – The pH Scale

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 (a slightly alkaline range of 7.35 to 7.45) 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 (CO2) deposition with a negative impact on life in the ocean (it may lead to the collapse of the coral reefs).
Even the mineral content of the food we eat (minerals are used as buffers to maintain pH within the aforementioned range) is considerabled influence 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 (last 10,000 years) and even more recently with industrialization (last 200 years) it has been seen:

  • an increase in sodium compared to potassium (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 in the diet,;
  • a poor intake of magnesium and fiber;
  • a large intake of simple sugars and saturated fat.

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

Metabolici Acidosis: pH of Selected Fluids, Organs, and Membranes
Fig. 2 – pH of Selected Fluids, Organs, and Membranes

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

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):1835-40 [Abstract]

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:article 41 [Abstract]

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:article 41 [Abstract]

Schwalfenberg G.K. The alkaline diet: is there evidence that an alkaline pH diet benefits health? J Environ Public Health 2012; Article ID 727630:7 pages doi:10.1155/2012/727630 [Abstract]

Fruits and vegetables in season

Health benefits of seasonal fruits and vegetables

Numerous studies showed that seasonality plays a key role in optimizing the antioxidant properties of fruits and vegetables. For example, a recent Chinese study have investigated the influence of growing season (summer vs winter) on the synthesis and accumulation of phenolic compounds and antioxidant properties in five grape cultivars. The study showed that both phenolic compounds and antioxidant properties in the skin and seed of winter berries were significantly higher than those of summer berries for all of the cultivars investigated. Finally, to choose seasonal fruits and vegetables also ensures considerable saving of money.

List of fruits and vegetables in season

Fruits and Vegetables: Fruits in Season
Fig. 1 – Fruits in Season

 

 

 

 

 

Fruits and Vegetables: Vegetables in Season
Fig. 2 – Vegetables in Season

 

 

 

 

 

 

Xu C., Zhang Y., Zhu L., Huang Y., and Jiang Lu J. Influence of growing season on phenolic compounds and antioxidant properties of grape berries from vines Grown in Subtropical Climate. J Agric Food Chem 2011:59(4);1078–1086

Income, education, adherence to a Mediterranean diet pattern and obesity prevalence

Income, education, Mediterranean diet and obesity

In a study published on British Medical Journal a research team has examined cross-sectional associations of income and education with an adherence to a Mediterranean dietary pattern and obesity prevalence on a sample of 13262 subjects (mean age 53±11, 50% men) out of 24 318 citizens (citizens of Molise, a region placed between Central and Southern Italy) randomly enrolled in the Moli-sani Project, a population based cohort study.
Household net income categories were considered as:

  • high (>40000 Euro/year);
  • medium–high (>25000 <40000 Euro/year);
  • low–medium (>10000<25000 Euro/year);
  • low (< 10000 Euro/year).

Education level was divided into three categories:

  • ≤8 (low) years of studies;
  • >8 and ≤13 (medium) years of studies;
  • >13 (high) years of studies.

Household higher income were significantly associated with greater adherence to a Mediterranean diet and to olive oil and vegetables dietary pattern, with odds of having the highest adherence to a Mediterranean diet clearly increased according to income levels (diet quality showed a continued improvement across the relatively small range of economic strata). Obesity prevalence was higher in the lowest-income group in comparison with the highest-income category.
Education was positively associated with adherence to Mediterranean diet and lower prevalence of obesity.

Conclusion

The study showed that a higher income and education are independently associated with a greater adherence to Mediterranean diet-like eating patterns and a lower prevalence of obesity.

Bonaccio M., Bonanni A.E., Di Castelnuovo A., De Lucia F.,Donati M.B.,de Gaetano G.,Iacoviello L., on behalf of the Moli-sani Project Investigators. Low income is associated with poor adherence to a Mediterranean diet and a higher prevalence of obesity: cross-sectional results from the Moli-sani study. BMJ Open 2012;2:e001685. doi:10.1136/bmjopen-2012-001685

Potassium intake and cardiovascular risk factors

Potassium intake and health

In a study published on British Medical Journal a research team has conducted a systematic review of the literature and meta-analyses on potassium intake and health in apparently healthy adults and children without renal impairment that might compromise its handling.
Eleven cohort studies (127038 participants) reporting all cause mortality, stroke, cardiovascular disease, or coronary heart disease in adults and twenty-two randomized controlled trials (1606 participants) reporting blood lipids, blood pressure, renal function, and catecholamine concentrations were included in the study.
In adult with hypertension an increased potassium intake reduced systolic blood pressure by 3.49 mm Hg and diastolic blood pressure by 1.96 mm Hg.
No effect was seen in adult without hypertension (however, the studies were of relatively short duration and did not consider the effect that increased potassium intake may have over time) and in children (there is a lack of data in children: only three controlled studies with 156 partecipants).
There was no adverse effect of increased potassium intake on blood lipids, or catecholamine concentrations in adults whereas an inverse statistically significant association was seen between its intake and the risk of incident stroke (a 24% lower risk).
In healthy adult there was no significant adverse effect on renal function.
This study suggests that, in people without impaired renal function, increased potassium intake (at least 90 mmol/day) is potentially beneficial for the prevention and control of elevated blood pressure and stroke.

How to increase potassium intake

Potassium Intake: Fruits and Vegetables: Rich in Potassium
Fig. 1 – Fruits and Vegetables: Rich in Potassium

It should be noted that an increased potassium intake can be achieved following the largely plant-based Mediterranean Diet, which is characterized by the consumption of large quantities of fresh fruit, vegetable, legumes and unrefined cereals, all rich in potassium (that is also accompanied by a variety of other nutrients).

Aburto N.J., Hanson S., Gutierrez H., Hooper .L, Elliott P., Cappuccio F.P. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ 2013;346:f1378

Adherence to the Mediterranean Diet, cognitive status and cognitive decline in women

Adherence to the Mediterranean Diet and cognitive status in women
Adherence to the Mediterranean Diet: Cognitive status in women

In a large-scale prospective epidemiological study published on Journal of Nutrition a research team examined associations of long-term adherence to the Mediterranean Diet (adherence was based on intakes of: vegetables, legumes, fruits, nuts, whole grains, fish, red and processed meats, moderate alcohol, and the ratio of monounsaturated:saturated fat) and subsequent cognitive function and its decline.
The participants, 16,058 women from the Nurses’ Health Study, aged ≥70 y, underwent cognitive testing 4 times during 6 y.
The study showed that long-term Mediterranean Diet adherence was related to moderately better cognition but not with cognitive decline in this very large cohort of older women.

Samieri C., Okereke O.I., E. Devore E.E. and Grodstein F. Long-Term adherence to the Mediterranean Diet is associated with overall cognitive status, but not cognitive decline, in women. J Nutr 2013;143:493-9

Primary prevention of cardiovascular disease and Mediterranean Diet

Mediterranean diet and primary prevention of cardiovascular disease

Primary prevention: Walnuts and extra-virgin olive oil: healthy fats
Fig. 1 – Walnuts and extra-virgin olive oil: healthy fats

A Spanish research team conducted a multicenter randomized trial of Mediterranean Diet pattern for the primary prevention of cardiovascular events.
The participants (7447; age range 55 to 80 years; 57% women) were with no cardiovascular disease but at high cardiovascular risk at enrollment (they had either type 2 diabetes mellitus or at least three of the following major risk factors: hypertension, smoking, overweight or obesity, elevated low-density lipoprotein cholesterol levels, low high-density lipoprotein cholesterol levels or a family history of premature coronary heart disease).
They were randomly assigned to one of three diets:

  • a Mediterranean Diet supplemented with mixed nuts (30 g of mixed nuts: 7.5 g of almonds, 7.5 g of hazelnuts and 15 g of walnuts);
  • a Mediterranean Diet supplemented with extra-virgin olive oil (≥4 tbsp/day);
  • a control diet (advice to reduce dietary fat).

It should be noted that extravirgin olive oil is the cornerstone of Mediterranean Diet.

Moreover, in comparison with those in the control group, participants in the two Mediterranean-Diet groups significantly increased weekly servings of legumes and fish. These were the only between-group differences.
No physical activity was promoted, nor total calorie restriction advised.
Participants were followed for a median of 4.8 years.
The primary end point was the rate of myocardial infarction, stroke, or death from cardiovascular causes that is the rate of major cardiovascular events.

This study have shown that among persons at high cardiovascular risk, a Mediterranean Diet supplemented with nuts or extra-virgin olive oil has proved to be effective in the primary prevention of cardiovascular disease, reducing the incidence of major cardiovascular events.

Estruch R., Ros E., Salas-Salvadó J., et al. Primary prevention of cardiovascular disease with a Mediterranean Diet. N Engl J Med 2013