Fw: Arbor Clinical Nutrition Update #156: fasting as treatment of hypertension

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ARBOR CLINICAL NUTRITION UPDATES ©

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This week we review an unusual approach to lowering blood pressure using a

sustained period of water fasting, followed by a strict vegan diet.

 

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NUTRITION RESEARCH REVIEW

 

 

Study 1: Fasting lowers BP in hypertensives

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A water-only fast followed by a strict vegan diet lowered blood pressure in

hypertensive subjects in an American study.

 

Subjects: 174 self-referred adults consecutively admitted over a three year

period for in-patient care for treatment of various health concerns, with

baseline BP of either systolic >140 or diastolic > 90 mm Hg.

 

Method: Open intervention trial with three phases:

Phase 1: 2 day preliminary vegetable/fruit-only diet.

Phase 2: Water-only diet (in-patient, along with activity restriction).

Fasting continued until symptoms attributable to fasting and the BP had

both stabilised.

Phase 3: Vegan diet, (several days vegetable/fruit as juices then raw

food), plus moderate exercise. Subjects were then continued on a vegan

diet which also excluded added oil, salt, sugar, bread products and other

processed foods.

 

Results: There was a fall in weight (by a mean of 6.9 kg) and BP (by a mean

of 37/13 mm Hg). Normal BP was achieved by 89% of subjects. The greatest

proportion of these falls occurred during the water fast stage - see Table.

 

The greater BP falls occured in patients with higher initial BP - in 25

subjects with grade III hypertension (mean baseline BP 194/96) the fall was

60/17 mm Hg.

 

A sub-set of 42 subjects were able to be followed up (in the main because

they lived locally). After an average post-treatment period of 27 weeks,

their mean BP was 123/77 mm Hg.

 

 

 

Table 1: Mean weight and BP: hypertension

 

Baseline Pre-fast Fast Vegan diet

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Duration 2.8 10.6 6.8 days

Syst BP 159 148 127 122 mm Hg

Diast BP 89 86 78 76 mm Hg

BMI 28.9 28.7 26.5 26.5

 

p<0.05 for each variable individually from baseline to fast and to vegan

diet

 

 

Reference: J Manipulative Physiol Ther 2001 Jun;24(5):335-9

 

 

 

Study 2: Fasting lowers BP at borderline elevated levels

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In another study by this research group, the same water-fast and vegan diet

protocol was found to lower BP in subjects with borderline elevated BP.

 

Subjects: 68 adults on a similar basis to study 1, except that their

baseline BP were systolic 120­140 and diastolic < 91 mm Hg.

 

Method: the same as study 1.

 

Results: There was a similar pattern of weight and BP fall as was seen in

Study 1. Mean fall in BP was 20/7 mm Hg with the largest part occuring

during fasting phase and higher drops in those with higher initial BP.

 

There were no significant correlations between fall in BP on the one hand

and either weight loss or length of water fasting period on the other hand.

 

 

Reference: J Altern Complement Med 2002 Oct;8(5):643-50

 

 

 

COMMENTS

Fasting as therapy has a long tradition within medical history. Whilst

short term fasting is closely studied in relation to surgical and

anaesthetic practice, therapeutic fasting is nowadays more likely to lie

within the province of naturopaths than orthodox physicians.

 

We therefore found this study interesting. The results seem, on first

inspection, to be impressive.

 

Three obvious questions to ask about the results are:

.. Is this a placebo or non-specific lifestyle effect?

.. If it is a dietary effect, is it really necessary to fast, or could a

similar result come from something less rigorous (e.g. vegetarian, low-fat,

low-salt diet)?

.. Is the effect long-lasting?

 

Placebo

These were both open trials on self-referred patients, without controls,

involving an intrusive lifestyle change whose duration was partly

determined by subjective patient symptoms. So there was obviously

substantial potential for placebo or confounding effects.

 

For example, the BP changes might have been largely due to the enforced

curb on activity or the freedom from external stresses that follows from

having the subjects resting as in-patients over several weeks.

 

Some aspects of these results suggest - but do not prove - a real

physiological effect, rather than placebo. For example, the magnitude of

the hypotensive effect, its universality (nearly 90% of hypertensive

subjects became normotensive), the persistence of improvement in the small

follow-up sample out to 6 months. and its greater magnitude in the most

hypertensive patients.

 

The authors themselves point out in their discussion that the size of BP

fall is much greater than that seen in studies using similar lifestyle

changes to theirs, apart from fasting. For example, vegetarian diet, stress

management and in-patient admission (e.g. see ref.1).

 

But when considering the placebo issue, it could be assumed that none of

these other changes have the placebo potential of something as dramatic as

fasting.

 

Is fasting necessary?

This is obviously relevant since, whilst the results are impressive,

prolonged fasting is a major undertaking. The need for dairy elimination

has to be judged against evidence that dairy foods lower rather than raise

BP (ref. 2).

 

Evidence in favour of a specific fasting effect includes the fact that the

biggest BP falls in these studies occurred during fasting. On the other

hand, since there was no study arm in which patients were first placed on

the vegan diet for a comparable period and then fasted, it remains possible

that this was a timing effect rather than due to fasting itself.

 

Fasting has consistently been shown in many studies - human and animal - to

lower BP. The literature suggests that, although weight and BP both fall

during an ongoing fast, the hypotensive effect occurs quite early on and is

not directly related to the weight loss (refs.3-9).

 

At the same time, several of those studies involved less than full fasts,

for example very low calorie diets (refs. 7, 8, 9). The specificity of

fasting (rather than food restriction) in the the BP reduction remains a

little uncertain.

 

It is also unclear what mechanism might cause the hypotensive effect of

fasting. Some authors have suggested an impact on the sympathetic nervous

system, but others have disputed this (refs. 6, 8, 9).

 

Longevity of effect

There is just not enough long term data to answer this question. The

follow-up results from Study 1 add to our knowledge, but were only

preliminary data and based on a sub-sample that was not randomly selected.

 

In conclusion, these studies provide an intriguing `proof of concept' that

hypertensive patients can have significant BP falls through fasting

followed by vegan diet, and that this can be practically carried out in an

in-patient setting. Many questions remain to be answered, including the

specificity and optimal duration of the protocol elements, the practicality

and cost-effectiveness of such approaches in the larger community, and the

long term impact and safety.

 

 

References:

1. J Am Coll Nutr 1995 Oct;14(5):491-6

2. Sacks FM. et al. Effects on blood pressure of reduced dietary sodium and

the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium

Collaborative Research Group.N Engl J Med 2001 Jan 4;344(1):3-10

3. Forsch Komplementarmed Klass Naturheilkd 2002 Aug;9(4):221-7

4. J Hypertens 1995 Nov;13(11):1241-6

5. Am J Hypertens 1988 Jul;1(3 Pt 3):153S-157S

6. Acta Med Scand 1988;223(6):485-90

7. Postgrad Med 1986 Mar;79(4):263-7

8. Am J Physiol 1984 Aug;247(2 Pt 1):E190-7

9. Int J Obes 1983;7(6):569-74

 

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