Do Whole-Grain Oat Cereals Reduce the Need for Antihypertensive Medications and Improve Blood Pressure Control?

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Original Research

Do Whole-Grain Oat Cereals Reduce the Need for Antihypertensive Medications and Improve Blood Pressure Control?

J Fam Pract. 2002 April;51(4):353-359

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References

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TABLE 2
BASELINE CHARACTERISTICS*

	Oats Group (n = 45)	Control Group (n = 43)
Sex (M/F)	23/22	22/21
Race (% Caucasian)	96	98
BMI (kg/m²)	31.2 ± 5.1	30.6 ± 4.7
Age (years)	48.7 ± 16.9	46.4 ± 15.3
LDL-C (mg/dL)	139.2 ± 29.3	137.7 ± 27.5
HDL-C (mg/dL)	43.1 ± 9.1	44.2 ± 10.2
TC (mg/dL)	211.6 ± 38.6	213.7 ± 42.3
SBP (mm Hg)	140 ± 16	138 ± 15
DBP (mm Hg)	88 ± 10	86 ± 9
TG (mg/dL)	185.4 ± 40.2	191.6 ± 41.9
Insulin (μU/mL)	16.9 ± 6.1	15.2 ± 5.9
Soluble fiber (g)	5.3 ± 1.6	4.8 ± 1.3
BMI denotes body mass index; DBP, diastolic blood pressure; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; SBP, systolic blood pressure; SD, standard deviation; TC, total cholesterol; TG, triglycerides.
* Values are means ± SD; means did not differ significantly.

TABLE 3
ANTIHYPERTENSIVE MEDICATION AND BLOOD PRESSURE CHANGES BY GROUP

	Oats Group (n = 45)	Control Group (n = 43)	P *
BP medication reduction, n (%)	33 (73%)	18 (42%)	<.05
BP changes in those without medication reduction (post treatment, baseline)^†
SBP in mm Hg	-7 ± 8	-1 ± 9	<.05
DBP in mm Hg	-4 ± 5	1 ± 6	.18
BP medication resumption, n (%)	23/33 (67%)	6/18 (33%)	<.05
*P < .05 between oats and control groups.
^† Values are means ± SD.
SBP denotes systolic blood pressure; SD, standard deviation; DBP, diastolic blood pressure.

TABLE 4
SECONDARY OUTCOME MEASURES BY GROUP*

	Oats Group		Control Group
	Baseline	Post Study	Baseline	Post Study
Total cholesterol (mg/dL) †	211.6 ± 5.9	179.9 ± 5.2	213.7 ± 6.7	206.2 ± 6.5
LDL cholesterol (mg/dL) †	139.2 ± 4.5	116.9 ± 4.2	137.7 ± 4.4	131.6 ± 4.7
HDL cholesterol (mg/dL)	43.1 ± 1.4	44.6 ± 1.7	44.2 ± 1.6	43.2 ± 1.5
Triglycerides (mg/dL)	185.4 ± 6.2	172.6 ± 6.5	191.6 ± 6.4	184.2 ± 6.8
Glucose (mg/dL) †	118.4 ± 4.1	106.1 ± 4.2	117.1 ± 5.2	119.8 ± 5.5
Side effects (score) †	58.2 ± 7.2	47.6 ± 6.9	56.7 ± 8.1	53.4 ± 7.2
Weight (kg)	82.5 ± 5.5	83 ± 5.9	83.7 ± 5.3	83.4 ± 5.8
* Values are means ± SEM except for body weight, which is represented as mean ± SD for all participants.
† Indicates statistical differences between groups (change score) at P <.05.

Discussion

The results of this trial suggest that an increased consumption of soluble fiber-rich, whole-grain, oat-based cereals can significantly reduce antihypertensive medication need among patients being treated for hypertension. Of the 45 participants in the oats group, 33 experienced at least half medication reduction compared with only 18 of the 43 participants in the control group. Positive BP changes were evident during the first 4 weeks of oat cereal treatment; BP levels rose steadily during the 6-week follow-up phase.

In addition, mean BP readings in the oat group participants who did not experience a medication reduction had improved at study completion compared with baseline. A significant number of participants in the refined cereal control group experienced at least half medication reduction (18/43), a finding that might be attributed to the increase in calcium, potassium, and total dietary fiber intake^8,9,18 as well as to the decreased intake of total and saturated fat.¹⁹ Additionally, during the follow-up phase, only 6 of the 18 (33%) versus 22 of the 33 (67%) in the oats group resumed taking their medication. Therefore, part of the medication reduction effect in the control group may have been the result of a greater percentage of participants who did not need their antihypertensive medication. This issue should be considered in the design of future trials.

As always, regression to the mean and the Hawthorne effect might explain some of the outcomes in this trial. However, it is likely that both increased soluble fiber and micronutrient intake explain the decrease in antihypertensive medication need observed in the treatment group. This study was designed to identify not the hypotensive effects of specific cereal components but the effects of a whole food intervention. Our findings are consistent with those of other whole-food interventions, such as the Dietary Approaches to Stop Hypertension (DASH) trial, tested in hypertensive populations.²⁰ Nonetheless, known diet-related determinants of BP (sodium chloride, alcohol, body weight, and level of physical activity) could not explain the treatment effect because no significant differences in these variables existed between the groups.

The soluble fiber fraction of the oat-based cereal intervention is probably partially responsible for the reduction in antihypertensive medication need observed in this trial. Previous studies that tested either soluble fiber supplements or diets rich in soluble fiber have noted significant reductions in BP.^21-23 Improvement in insulin sensitivity has been proposed as the pathway through which soluble fiber improves BP.²⁴ Insulin sensitivity was not determined in this study, yet the oats treatment group experienced a significant improvement in plasma glucose levels. This finding suggests that insulin sensitivity may have been enhanced. Impaired response to insulin was recently shown to precede endothelial dysfunction and subsequent elevations in BP.²⁵ Moreover, soluble fiber supplements and diets high in soluble fiber have been shown to improve insulin sensitivity.^25-28 Other components of whole grains, such as magnesium or grain flavonoids, may also contribute to the favorable medication reduction observed in the oats group.^29,30