Tuesday, April 26, 2011

Acid food, alkaline food

Should you be eating acid or alkaline foods? Let's see if I can make sense of this. We are oxygen breathing, carbon-based, mildly alkaline life forms. The pH of plasma is 7.35-7.45 and the pH inside our cells is 7.1. If they change much from these levels you will end up in hospital. The body has a number of systems to control the pH in your body (eg lungs and kidneys).

Que? What this thing pH?

Mmmm, I knew this would be tricky from the outset. You may have only heard about pH in shampoo ads. Other readers will remember pH from high school chemistry. The pH is a measure of the hydrogen ions in a solution (ie acidity), that is, the number of hydrogens missing their only electron. A pH of 7 is neutral. The higher the pH the more alkaline. The lower the pH the more acidic. As it is a logarithmic scale, every whole number is a 10-fold difference, so a pH of 5 is 10 times more acidic than a pH of 6. Stomach acid, which is hydrochloric acid, has a pH of about 1. That’s why it burns your throat during regurgitation. Still with me?

Kidneys will sort things out

For a century or so we have known that a high meat/protein diet produces excess acid that must be eliminated from the body via your pee. Foods like meat, chicken, fish, eggs and cheese will generate small amounts of sulphuric and phosphoric acid within the body. If you are a vegetarian then you will likely produce excess alkaline, and this will also exit the body through your pee. This is all quite normal and a happy, healthy body will sort all this out while you get on with life. You will not feel a thing.

Tomato is an acid food, right?

You have probably already deduced that we cannot pick an acid food based on taste. Would you have picked meat as an acid food? It is alkaline on the plate, but will leave an acid residue in the body. Is a tomato an acid food? Nope. Most of the natural acids in tomato will become carbon dioxide and water, leaving a residue of a little potassium bicarbonate, which is, da da da daah, alkaline. Tastes acidic, becomes alkaline. Even when you eat pickled onions, they will land in the hydrochloric acid in your stomach and then trickle into the small intestine where it all the vinegar gets neutralised to a pH of 7 by bicarbonate released from the pancreas.

Acid-base diet does have one major health effect

You will still hear clear-headed health professionals talk about the acid-base balance in your body. Nothing to do with the pH of oranges, tomatoes or lemons or whether they sting your tongue. (By the way, tomatoes don’t cause, or exacerbate, arthritis). As mentioned, eating carcasses of meat each day will generate excess acid which will easily be jettisoned in your pee, but, and here is the problem, along with the acid goes a whole pile of calcium. Eat a very high meat diet for a few years and it will be your bones that suffer. We are happy for you to have that steak sandwich, but please add a whack of salad too as plant foods will help you to keep hold of your calcium stores.

This is also the reason that soft drinks have been linked to poor bone health. Drink a vast amount of soft drink, with an acid pH of 2, and the body will have to rid itself of that extra acid, taking some calcium with it. Of course, when you are quaffing 2-3 litres of soft drink each day (that’s 67-100 ounces of soda) then you are probably not featuring milk in your diet and that compounds the calcium problem.

What does it all mean?

In a healthy body, food does not change the pH of the body, thankfully. Wonderful metabolic processes, evolved over millennia, actively keep the pH of your body within a very fine bandwidth. Forget the “acid” v “alkaline” chat and just eat well, you know, the standard “eat fruit and vegetables, go easy on the cookies, trim the fat off the meat blah, blah, blah” you’ve heard a zillion times. With an emphasis on fruits and vegetables, along with an adequate calcium intake and some sunshine, you will also help your body retain its calcium for bone strength. Just another reason to eat your vegies.


Nutrition Action November 2010

Essentials of Human Nutrition 3rd edition 2007; 110-111

Wednesday, April 6, 2011

Food and gout: a brief update

Recently I had to review the dietary treatment of gout for a client. Gout is a common form of arthritis, yet there is very little research on the role of food despite textbooks and the web being full of dietary advice and presumptions.

What is gout?

Gout is characterised by high levels of uric acid in the blood (hyperuricaemia), and is more likely to occur in men than in women. The high levels of uric acid can trigger the deposition of sodium urate crystals in joints, causing intense pain.

Uric acid is an end-product compound from the breakdown of purines made within the body and consumed in the diet. Uric acid is normally eliminated via the kidneys so that uric acid stays at normal levels. High levels come from reduced elimination or an increased production. Some medications, such as those for high blood pressure, can also raise uric acid levels.

Gout has long been associated with overweight, binge eating and alcohol consumption. Losing weight and avoiding alcohol is common advice for many people with gout as this reduces the incidence of gout attacks. Beer consumption especially seems to crank up uric acid levels.

Forget common dietary advice

The most common and effective treatment for gout is through medication such as uricosuric drugs that increase the excretion of uric acid in your pee.

There has long been speculation that high purine foods are also a culprit in gout. Cutting out very high purine foods like offal, yeast extracts, sardines and anchovies may have an additional modest benefit with drug therapy, although dietary changes rarely lower serum uric acid by much more than 10%. There is now evidence that most purine-containing food, especially non-animal food, have little effect on uric acid levels.

Today, common food advice is still to avoid foods with modest levels of purine, such as peas, legumes, lentils, spinach, asparagus and mushrooms. It is not clear why spinach, asparagus and mushrooms are mentioned so frequently, as green peas, broccoli and Brussels sprouts have more purine yet I have never seen them mentioned once in a text book (and I have a few) or websites giving advice on gout.

Eat dairy, legumes, veggies and nuts

The truth is that foods such as dairy foods, possibly due to the dairy proteins, nuts. legumes and vegetables, even those with moderate purine content, seem to be protective against gout. A thorough review of the lifestyle evidence on gout risk states that those eating the most vegetables had a 27% reduced risk of gout compared to those eating the least (ie purine-rich vegetables were associated with a lower gout risk). Low fat dairy foods like milk and yogurt also reduce gout risk.

What does it all mean?

Sure, if you eat lots of sardines, offal, and kilos of meat every week then maybe you should cut back. Otherwise, just eat and drink healthy if you have gout. Lose weight if necessary. If you are a boozer, cut back to a maximum of two drinks a day. Cutting out specific purine-containing vegetables will have no benefit at all. In fact, you would be doing yourself a nutritional disservice.

And why is the big toe often the site of the first gout attack? The big toe is at the extremity of the body and generally a wee bit cooler than the rest of your body. Sodium urate crystalises at cooler temperatures. When the pain hits, maybe put on a (second) pair of socks.


Seminars Arthritis & Rheumatism 2008; 37: 243-250

Current Opinions in Rheumatology 2010; 22: 165-172