The diet is also complemented by the belief that some people have that apple cider vinegar will cure all ills. Apparently, ingesting six teaspoons of this acid every day will produce a more alkaline body pH. (This idea is so backwards it can only be described as "scary".)
Health benefit claims vary, but are as wide as:
- IBS, Crohn’s and other digestive disorders
- Candida/Yeast Infections
- Fatigue, Chronic Fatigue & Fibromyalgia
- Weight Problems
- Being Underweight
- Low Libido & Other Sexual Disorders
- Migraines & Headaches
- Back Pain
- Blood Sugar Dips & Spikes
- Sugar Cravings
- Afternoon Mental Energy Dips
- And Much More...! 
The first thing to note is that claiming a treatment will help treat cancer without concrete evidence is illegal in the UK under The Cancer Act 1939. Most of the sites promoting the alkaline diet have a Quack Miranda Warning on them to bypass legal problems such as this.
 Theoretical problems
The main problem with the concept is that it is impossible to alter the pH of a patient's blood without causing severe health concerns. Mammalian blood contains a vast number of different pH buffers which evolved to automatically raise or lower the blood pH if a deviation occurs. If the buffers become saturated and the pH of the blood is altered more than +/-0.4 pH, death will result. It is commonly claimed by alkaline diet proponents that cancer cells are killed in an alkaline environment, which is true, but so are almost all other cells in the human body.
Proponents will attempt to disregard the above by reminding us that it is possible to alter the pH of urine by eating or drinking particular foods, which is also true, but is completely independent of the blood pH. This is based on the metabolites of certain food chemicals (referred to as "Ash") becoming concentrated in the urine. As a (healthy) bladder is an independent receptacle in the body, the pH of the fluid contained therein also has no effect on the blood pH.
Another clue of the ineffectiveness of an alkaline diet is that whatever food you eat will (obviously) pass through your stomach. The acidity of the stomach is affected by things such as stress, amount of food eaten, or infections. Eating acidic or alkaline foods has no effect on stomach PH, in much the same way as it has no effect on the PH of blood.
More recently, proponents claim that the benefits arise from reducing acid load in the body. It is claimed that when acid load is too high, "alkaline minerals" such as calcium are reclaimed by the body from bones leading to conditions such as osteoporosis. Meta-analysis studies have shown this is not the case.
Far from being healthy, alkaline diets could actually be harmful, as they recommend removing certain food groups altogether rather than reducing certain types within the groups. Examples would be removing all fats and oils from the diet which provide Essential Fatty Acids, and dairy products, which are excellent sources of vitamins and minerals, especially vitamin D which is difficult to find in foods outside of dairy products.
 Weight loss
As far as weight loss is concerned, a lot of patients will report a notable drop in body fat whilst following the alkaline diet. This is not, however, anything to do with the proclaimed method of action, and is instead because the diet classifies foods as either acid or alkali, and all acidic foods should be avoided. Browsing the list of acid and alkali foods, it should become instantly apparent that the foods to avoid are those classically associated with a high calorie diet (dairy products, fizzy drinks, confectionery, fast food, and just about all fats), and those marked as alkaline are generally fresh fruit, vegetables, nuts and seeds. If you avoid eating gobs of fat and sugar and otherwise keep the same lifestyle, your weight goes down - who'da thunk it?
 Alkaline water
Of course, with a new fad diet comes new expensive books and gadgets. On the top of the list are water filters or ionisers which claim to alkalinate drinking water and can cost several thousand pounds. Just adding some sodium bicarbonate to tap water is not sufficiently profitable.
Real Water® is claimed to have "millions of added electrons" which makes the water alkaline and improves cell hydration.
A blog entitled Real Water Health written by a Shelley Penney (a retired nurse interested in "health, peace and abundance") publishes many articles advocating the benefits of alkaline water. A list of 17 "Peer Reviewed Articles on Alkaline Water" is given on the site but while they all discuss research on acidosis, none of them mention any benefits from actually imbibing alkaline water. Shelley is not too hot on her chemistry as she claims "because it is very alkaline, ionized water may dissolve accumulated acid waste and return the body to a balance." Very alkaline products are caustic (e.g. drain cleaner); ionized water typically has a pH of 8 which is the same as sea-water. She further claims that "keeping our body fluid pH in an alkaline state may be the first line of defense in fighting any disease", as the body naturally regulates the pH of arterial blood between 7.35 and 7.45 you are likely to be dead before your blood stops being alkaline. As noted above, blood is a buffer solution which has the property that the pH changes very little when a small amount of strong alkali is added to it.
Ray Kurzweil sells alkaline water filters on his website. His transhumanist fans tend to gloss over this really obvious left turn into blatant alternative medicine pseudoscience, preferring to concentrate on his computer pseudoscience.
- Real Water Health - A pro alkaline water blog by Shelley Penney
- The works of Waterworks4u - A particularly nasty account of how one water ionizer proponent, Peter Goodgold (who thinks that there exists only one disease, acidosis), operates and, in particular, deals with criticism.
- ↑ Claimed benefits of the Alkaline diet
- ↑ The Cancer Act 1939
- ↑ "Energise for Life" disclaimer, displaying Quack Miranda Warning
- ↑ "pH Buffers in the Blood" - Rachel Casiday and Regina Frey Department of Chemistry, Washington University
- ↑ "pH Significance of Blood" - Newton BBS
- ↑ "Acid/Alkaline Theory of Disease Is Nonsense" - Gabe Mirkin, M.D.
- ↑ http://www.ehow.com/about_5039184_ph-stomach-acid.html#ixzz17pJQtQj8
- ↑ Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality
- ↑ InteliHealth: Can the alkaline diet be harmful?
- ↑ List of Alkaline Foods
- ↑ Alkaline Water Ionizers - energiseforlife.comimg
- ↑ Real Water Health: Peer-reviewed papers.
- ↑ Real Water Health: Ionized Water Is Alkaline