Nutrition (22 page)
Acid diet and heart disease
Mild metabolic acidosis is associated with a number of heart-disease risk factors – possibly because it increases your secretion of the stress hormone, cortisol. A recent study published in the
British Journal of Nutrition
involving 1,136 female dietetic students in Japan found that acid-forming diets were associated with a higher blood pressure, total and LDL-cholesterol, body mass index (BMI) and waist circumference – even after adjusting for other confounding variables such as smoking and physical activity level. Although this is an observational study and no definite links can be drawn, it adds to the body of evidence that a more alkaline-forming diet is most beneficial for health.
British Journal of Nutrition
involving 1,136 female dietetic students in Japan found that acid-forming diets were associated with a higher blood pressure, total and LDL-cholesterol, body mass index (BMI) and waist circumference – even after adjusting for other confounding variables such as smoking and physical activity level. Although this is an observational study and no definite links can be drawn, it adds to the body of evidence that a more alkaline-forming diet is most beneficial for health.
Acid diet and Alzheimer’s disease
An acid-forming diet affects the way metal ions are handled in the body, and is associated with higher blood and brain concentrations of aluminium than an alkaline-forming diet. This has been suggested as one cause of the neurological damage associated with Alzheimer’s disease. Although it is by no means proven, it is another potential reason to start thinking about eating less acid-forming foods and more alkaline-forming foods.
Some nutritionists and naturopathic doctors suggest following a diet that consists of 60 to 80 per cent alkaline foods and only 20 to 40 per cent acid foods. This is controversial among ‘orthodox’ nutritionists and doctors, who are unaware of the growing evidence for harm due to chronic, low-grade metabolic acidosis in the body. But, as it basically means eating more fruit and green leafy vegetables and cutting back on the amount of animal proteins and processed foods you eat, this approach to nutrition is exactly the one that orthodox clinicians suggest, although they may not be aware of all the mechanisms underpinning the benefits of those five portions a day.
The main dietary sources of acids and alkalis are shown in
Table 11
.
Table 11
.
Strongly acid-forming foods
Animal proteins (eggs, poultry, meats, seafood); beer; coffee; sugar; sweetened fruit juice; black tea; highly processed foods, carbonated soft drinks such as colas; artificial sweeteners; white vinegar; sauerkraut
Mildly acid-forming foods
Grains (barley, oats, quinoa, rice, wheat, flours, bread, pasta); some pulses (black beans, chickpeas, kidney beans); most nuts (pecans, cashews, peanuts, pistachios, walnuts); most dairy products (cream, cheese, milk, ice-cream, yogurt); wine; apple cider vinegar; sparkling water; vegetable oils
Neutral
Distilled water
Mildly alkaline-forming foods
Green tea; tomatoes; low-sugar fruits; berries; citrus fruit; figs; peppers; some pulses (alfalfa, lentils, lima beans, soybeans, navy beans); tofu; some nuts (almonds, pine nuts, chestnuts, coconut); onions; turnip; swede; potatoes and other root vegetables; cabbage, bicarbonate-rich mineral water
Strongly alkaline-forming foods
Green leafy vegetables (kale, broccoli, spinach, barley grass, wheat grass); herbs (parsley, coriander leaf, oregano); avocados; celery; asparagus; green beans; beetroot; radishes; garlic
Alcohol
Interest in the potential health benefits of alcohol initially arose because of the so-called French Paradox. Compared with Britain and the US, the French eat as much saturated fat, have similar high cholesterol levels, smoke as much (if not more), take as little exercise and drink significantly more wine, yet their risk of coronary heart disease is lower. In fact, Le Paradoxe Français was most evident in Gascony – home of the fatty saucisses de Toulouse and the cardiologist’s ultimate nightmare, pâté de foie gras. Researchers concluded that the most obvious explanation for this French paradox was red wine consumption. More recent data suggests that any form of alcohol, whether beer, wine or spirits, can prove beneficial – but only when consumed in moderation.
A large 2008 meta-analysis that pooled data from 34 studies involving over a million people, found that the risk of coronary heart disease decreased with intakes of up to four drinks per day in men and two drinks per day in women. Higher intakes were associated with increased mortality related to abnormal heart rhythms, high blood pressure, liver disease and, in women, an increased risk of breast cancer. A more recent 2011 meta-analysis published in the
British Medical Journal
confirmed that, compared with teetotallers, people with a light to moderate alcohol intake appear to have a 29 per cent lower chance of developing coronary heart disease and a 25 per cent reduced risk of dying from it. The lowest risk for heart disease occurred with one to two drinks per day, but for stroke mortality the lowest risk was for those who drank around one drink per day.
British Medical Journal
confirmed that, compared with teetotallers, people with a light to moderate alcohol intake appear to have a 29 per cent lower chance of developing coronary heart disease and a 25 per cent reduced risk of dying from it. The lowest risk for heart disease occurred with one to two drinks per day, but for stroke mortality the lowest risk was for those who drank around one drink per day.
Alcohol also appears to have beneficial effects on factors associated with hardening and furring-up of the arteries (atherosclerosis), raising levels of ‘good’ HDL-cholesterol, lowering levels of a blood-clotting factor called fibrinogen and discouraging arterial calcification.
Overall, evidence suggests that moderate drinking (one to two units per day) is especially beneficial for men over 40 years of age and post-menopausal women. However, recent research suggests that the benefits of moderate alcohol intake do not apply equally to all people. In fact, those most likely to benefit are those who follow an unhealthy diet and lifestyle, who take little exercise or who smoke. Little additional benefit from alcohol is seen in those who do not smoke, eat fruit and vegetables daily and who exercise for three or more hours per week, probably because they are already obtaining the maximum benefits possible from following a healthy lifestyle.
Drinking excess alcohol can deplete the body of vitamin C and vitamins from the B group, which are used in its metabolism. Alcohol can also contribute to gaining weight and obesity. As an energy source, alcohol provides 7 kcal (29.4 kJ) per gram – more than protein and carbohydrate, but less than fat.
KNOW YOUR UNITS
In the UK, a unit of alcohol is equivalent to 10 ml or 8 g of pure alcohol. Half a pint (300 ml) of beer, lager or cider that is 3.5 per cent alcohol in strength contains one unit. But many lagers now contain 5 per cent alcohol, and some versions supply as much as 9 per cent alcohol. One small (100 ml) glass of wine that is 10 per cent alcohol in strength contains one unit. But most wines are now much stronger (12 per cent to 15 per cent alcohol) and many pubs sell wine in 250 ml glasses. Depending on its percentage alcohol content, a bottle of wine typically contains between 8 and 11 units of alcohol. A 25 ml bar or pub measure of 40 per cent spirit contains one unit. But many bars and pubs now serve 35 ml measures as standard, and will often serve a double unless you specifically say you want a single. To calculate how much you are drinking, use the handy unit calculator at
www.drinkaware.co.uk
.
www.drinkaware.co.uk
.
NB In the US the term ‘drink’ is used as a unit of alcohol, and usually means 14 g of alcohol, while in Australia a unit is 10 g.
Salt
Common table salt – known chemically as sodium chloride – is added to processed food to enhance flavour, act as a stabilizer, retain moisture and help products last longer on the shelf. It is also used to preserve foods such as fish and meats, as bacteria and moulds that would spoil these foods cannot grow in very salty environments. In fact, salt was so highly valued in fridge-free Ancient Rome, that soldiers received a salt allowance as part of their pay. They were literally ‘worth their salt’.
In the body, salt dissolves to form two electrolytes, sodium (Na
+
) and chloride (Cl
-
). Most sodium in the body is found outside your cells in the interstitial fluids and blood. Very little sodium is present inside your cells as millions of tiny salt pumps in cell membranes force sodium out of your cells in exchange for potassium ions. This action means the inside of every cell develops a small, negative electric charge, which is vital for life. Without it, your nerve and brain cells couldn’t pass messages to one another, and heart muscle cells would not be able to contract. Common salt is therefore essential for good health. So much so that the transport of salt in and out of our cells is one of the main energy-consuming processes in our body. It is estimated to account for 33 per cent of our daily energy needs.
+
) and chloride (Cl
-
). Most sodium in the body is found outside your cells in the interstitial fluids and blood. Very little sodium is present inside your cells as millions of tiny salt pumps in cell membranes force sodium out of your cells in exchange for potassium ions. This action means the inside of every cell develops a small, negative electric charge, which is vital for life. Without it, your nerve and brain cells couldn’t pass messages to one another, and heart muscle cells would not be able to contract. Common salt is therefore essential for good health. So much so that the transport of salt in and out of our cells is one of the main energy-consuming processes in our body. It is estimated to account for 33 per cent of our daily energy needs.
Before the advent of processed and fast food, we obtained our salt from adding it to preserve foods, during cooking and at the table. Now these sources are minimal compared to the amount of salt consumed in processed foods. For example, a typical microwave meal contains around 5 g salt, a bowl of breakfast cereal provides 1 g while a serving of canned soup gives 2 g.
Humans evolved on a diet providing less than 1 g salt per day. The average Western diet currently provides as much as 10 g salt per day or more. This tenfold rise in sodium intake is responsible for the age-related rise in blood pressure seen in Western populations, as the kidneys of many people are unable to excrete the additional salt load. The retained salt stimulates thirst and promotes fluid retention, which causes blood pressure to rise.
Populations with salt intakes of less than 3 g per day do not show increased blood presure with increasing age. Yanomamo Indians, for example, whose traditional diet contains less than 1 g of salt per day have an average blood pressure of 96/60 mmHg and do not develop hypertension. Populations following a Western-style diet that is high in salt typically have a blood pressure of around 140/90 mmHg, which is the borderline above which a diagnosis of high blood pressure (hypertension) is made if the high readings are consistent.
Not adding salt during cooking, or at the table, can lower systolic blood pressure (the peak pressure achieved as your heart beats) by as much as 5 mmHg. If everyone did this, it is estimated that the incidence of stroke in the population would be reduced by as much as 26 per cent and coronary heart disease by 15 per cent. Since eight times more dietary salt is present in processed foods, the effects of cutting back on these is even greater.
Research suggests that a realistic sodium reduction (equivalent to cutting out 4.6 g salt per day) over at least four weeks can lower blood pressure by an average of 2.03/0.97 mmHg for those with normal blood pressures, and by 4.96/2.73 mmHg in those with hypertension. Reducing salt intake by 6 g salt per day was predicted to lower blood pressure by 3.57/1.66 mmHg for people with normal blood pressure, and by 7.11/3.88 mmHg in those with hypertension.
Salt restriction can reduce the dose and number of drugs needed to control high blood pressure. Recent research also indicates that people whose high blood pressure does not respond to multiple medications are likely to be eating too much salt, which suggests that the fluid retention associated with a high dietary salt intake is counteracting the effects of medication. This is supported by the fact that sodium restriction can produce sharp reductions in blood pressure in these cases of up to 22.7/9.1 mmHg.
Dietary salt intake is also strongly correlated with the thickness of the wall of the left ventricle of the heart (which has to pump a larger volume of blood out into the body) and, in people with hypertension, a high sodium intake is associated with a decreased diameter and increased stiffness of the arteries, whether or not atherosclerosis is present.
Overall, it is estimated that reducing your salt intake by 3 g per day (for example, from 12 g down to 9 g) would reduce your risk of a stroke by 13 per cent, and your risk of a heart attack by 10 per cent. Restricting salt intake down to 6 g per day could double this preventive effect, while restricting salt intake to 3 g daily might triple the benefits.
EXCESS DIETARY SALT
A high intake of salt has also been linked with other health problems such as bone-thinning (osteoporosis, as sodium increases calcium losses through the kidney), fluid retention (equivalent to 1 kg to 2 kg at some times of the month for women), asthma, congestive heart failure, liver cirrhosis and even stomach cancer.
How much salt do you need?
An average male weighing 70 kg has around 225 g salt in his body, and can maintain a healthy sodium balance with an intake of as little as 1.25 g salt per day – as long as he does not sweat heavily. Ideally, an adult should obtain no more than 6 g salt per day – around one level teaspoon. Target maximum intakes for children are proportionately smaller, as shown in
Table 12
.
Table 12
.
Age | Target salt intake (grams per day) |
0 to 6 months | less than 1 g daily |
7 to 12 months | 1 g per day |
1 to 3 years | 2 g per day |
4 to 6 years | 3 g daily |
7 to 10 years | 5 g daily |
Over 11 years | 6 g daily (as per adults) |
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