Blood Pressure and Fat

What do a stick of butter and a bottle of olive oil have in common? They’re both fat and provide 9 calories per gram or 252 calories per ounce—or about 85 calories per tablespoon.

But olive oil is much better for you than butter. Most animal fat, for example, butter or the white fat around beef, is solid at room temperature. In contrast, vegetable fat—more specifically vegetable oil—is liquid at room temperature.

It’s obvious why nutritionists call animal fat “hard fat” and vegetable oil “soft fat.” Saturated and unsaturated fats differ in their chemical structure. The terms saturated and unsaturated refer specifically to their chemical structure or molecular configuration.

Chemists tell us the structure of highly saturated or hard fat is dense and uniform because the molecular linkages holding the carbon atoms together are all used up. In contrast, vegetable oils are not dense and uniform. The linkages holding their carbon atoms together are not used up.

The spaces in their molecular structure are open and reactive. When you see “hydrogenated vegetable oil” on a label, it means hydrogen was added to those open spaces, which turns the oil into a solid fat.

Olive oil, a monounsaturated fatty acid (MFA), is an excellent example of an oil that has only one open space. MFA oils are liquid at room temperature, tend to be amber in color, and are somewhat thick or moderately viscous.

Beef lard is a saturated fatty acid (SFA). SFAs are not liquid at room temperature; they are white and hard. This is true of most animal fat. Sunflower oil is a polyunsaturated fatty acid (PUFA), an oil that has many open spaces.

PUFA oils vary in their degree of saturation. The more unsaturated they are, the lighter in color and the more fluid they are. Some are nearly as clear as water. PUFAs help keep blood pressure normal. In fact, some of these oils can help reduce blood pressure.

Vegetable oil supplies linoleic acid, a plant oil essential for health. Linoleic acid is the raw material for prostaglandin number 2 (PG2), a substance the body produces.

PG2 and other materials produced from it are important in the relaxation and contraction of the muscles that line the arterioles. Therefore, linoleic acid has a metabolic effect that helps to maintain normal blood pressure.

PUFAs also reduce blood pressure by reducing blood viscosity. Remember that reduced viscosity decreases total peripheral resistance to blood flow, and decreased resistance means lower blood pressure.

Saturated fats have a tendency to increase blood pressure by increasing blood viscosity. Increased viscosity contributes to total peripheral resistance, and that increases blood pressure.

Obviously, the dietary objective should be to reduce saturated fat; emphasize the unsaturated fat in the diet; and obtain sufficient amounts of a special PUFA, called the omega-3 oils, from fish and vegetable sources. These changes are achieved by shifting emphasis from meat and butter to foods that contain unsaturated fats.

There’s another reason to eat more PUFAs and MFAs and fewer SFAs: heart disease. Cholesterol and triglycerides are fats in your blood that your doctor uses as an index to show how clogged your arteries are with fatty deposits.

These deposits or plaque, as it is commonly called, consist of cholesterol, among other fats. So, your doctor wants you to maintain both low cholesterol and low triglycerides, since the triglycerides contribute to the plaque as well.

Medical scientists have determined that the lower your blood cholesterol and triglycerides, the less likely your body is depositing plaque on your arterial walls. How high should your cholesterol and triglycerides be?

Cholesterol, triglycerides, blood sugar, and many other blood components are expressed as so many milligrams in 100 milliliters of blood. It conveniently allows the use of milligram percent and usually works with whole numbers between 50 and about 300.

It is so widely practiced that we often simply use the number. Therefore, it’s very likely you’ll hear cholesterol expressed as, for example, 180. It really means 180 milligrams percent.

There are a number of steps you can take to reduce cholesterol. Eat a diet that’s low in fat. Avoid or reduce SFAs and use SFAs and MFAs. MFAs, such as olive oil, are ideal for many reasons.

Most health professionals recommend that they constitute the major part of our fat intake. Total fat intake should not exceed 30 percent of calories; I recommend keeping fat intake at 25 percent of calories.

Table below shows the composition of commonly used fats and oils.



Butter 68 28 4
Coconut 92 6 2
Corn 13 25 62
Cottonseed 27 18 55
Lard 41 43 16
Olive* 14 77 9
Palm 53 38 9
Peanut 18 48 34
Safflower 9 13 78
Sesame 14 42 44
Shortening 25 68 7
Soft margarine 19 53 28
Soybean 15 25 60
Sunflower 11 21 68

*Considered by most health experts to be the best all-around oil.

There are three prostaglandins. The body doesn’t store them, but every cell can make them on demand if the raw materials are present. Prostaglandins have profound effects on human health.

Two have important roles in blood pressure. The first, PG2 (prostaglandin number 2), is made from either of two fatty acids, linoleic acid or arachidonic acid.

Linoleic acid is a polyunsaturated fat obtained from plants, and arachidonic acid, which is converted from linoleic acid by animals, is found in meat. Linoleic acid is designated essential because it is required for the synthesis of arachidonic acid, which is then converted to PG2.

Drugs that inhibit prostaglandin production, such as aspirin or indomethacin, increase blood pressure by increasing total peripheral resistance. This tells a biochemist that PG2, made from linoleic acid, is involved in the dilation of the peripheral arterioles and facilitates blood flow in the kidneys.

PG2 also facilitates the release of leukotrienes that help the kidneys remove sodium from the blood. Impaired production of prostaglandin from linoleic acid will very likely contribute to, if not cause, high blood pressure.

Prostaglandins, especially PG2 from linolenic acid, are also important for maintaining good tone of the muscle cells that line the peripheral arterioles. If these muscle cells are too contracted, peripheral resistance increases and blood pressure goes up.

The other important prostaglandin, PG3, is made from eico-sapentaenoic acid (EPA). EPA is an omega-3 fatty acid. These poly-unsaturated acids are unique because of their detailed structure.

EPA is found in the chloroplasts of green plants, but the best source for EPA is blue-skinned cold-water fish, such as mackerel, salmon, and trout. Unlike PG2, PG3, made from EPA, does not specifically influence peripheral resistance or the kidneys.

Ideally a person will eat a diet that provides about three times as much omega-3 oil to omega-6 oil. This will allow the tissues to produce sufficient PG3 to counter the effects of PG2. Since that ratio is difficult to achieve, sensible supplementation with omega-3 oils is recommended.

On the other hand, EPA, which produces PG3, does have specific effects on cells. Blood cells and the cells that line the arteries and arterioles absorb EPA and other omega-3 fatty acids, which act as a natural lubricant, facilitating the flow of cells through the vessels and capillaries.

In this way, people who have adequate EPA usually have lower blood pressure than people who don’t. The omega-3 oil’s effect on high blood pressure might explain in part why vegetarians generally don’t have as much high blood pressure as people who eat meat.

Although the research is limited, it consistently shows that the rate of high blood pressure is significantly lower among vegetarians, especially vegans, than people who eat meat.

People with high blood pressure and people who want to maintain their normal blood pressure should be sure their diet contains some linoleic acid and reasonable levels of EPA. That means eating lots of vegetables and fish, especially cold-water fish.

People who don’t eat fish regularly should either take fish-oil capsules, which contains EPA, or flax-oil supplements, which are a source of alpha linolenic oil (ALA), an omega-3 oil.

I recommend eating about 2 grams of fish-oil daily. This means you must eat cold-water blue-skinned fish about twice weekly, or take three capsules of fish oil daily (excluding cod liver oil).

This will provide about 500 milligrams of EPA and a similar level of the similar fatty acid, DHA, or 1 gram daily of these fatty acids. Some scientists are cautious about fish-oil capsules. They generally base their caution on the high levels of eighteen or more capsules used in clinical studies.

Some also point out, erroneously, that these oils contain cholesterol. In the early years, these supplements did; now they don’t. At the levels I recommend, these supplements can do a great deal of good and no harm. ALA is made in the chloroplasts of green plants from linoleic acid.

Only plants can make this conversion. Animals, including people, can’t make ALA and are dependent on plants for it. Unfortunately, the diet of most people is just about devoid of ALA because they don’t eat sufficient vegetables or range-fed animals (such as rabbits, venison) that accumulate both EPA and ALA.

So, the only way we can get ALA is to take a flax oil supplement. Adding flax oil to your diet, even if you take EPA, will confer an additional benefit by stimulating your metabolism to produce more PG3.

Additionally, for those who are vegetarian, it is a completely vegetable oil. Flax oil, which is 52 percent ALA, is a rich golden color and practically tasteless and odorless.

It can be purchased in liquid form in bottles, so it can easily be added to your food. Don’t fry or bake with it; ALA doesn’t tolerate heat well. I personally add one tablespoon of flax oil to my morning bowl of oatmeal or any other cereal.

Alternatively, it can be added to salad dressing or used along with vinegar, oil, and spices to make your own vinaigrette. Use it on baked potatoes in place of butter and sour cream. You cannot take too much flax oil, and it will help your program succeed.

Flax oil is also conveniently sold in capsules. Just don’t substitute flax oil capsules for EPA completely unless you’re a vegetarian. For example, if you take three flax oil capsules or use a tablespoon of liquid flax oil daily, it will equal a 1-gram EPA capsule.

This three-to-one requirement is necessary because not all ALA is converted to EPA. Even if you use three tablespoons, or 45 grams, of flax oil (equivalent of three EPA capsules), please take one EPA capsule daily as extra insurance; I recommend this because your metabolism might not convert flax oil to EPA.

By the way, reduced heart disease and breast cancer in women are added benefits of using both EPA and flax oil. In 1982, three distinguished scientists were awarded the Nobel Prize for their work in elucidating the workings of the prostaglandins.

Research is continuing on their effects. Someday derivatives of them may help reduce blood pressure in people with impaired prostaglandin production.

But for now, food is still the only natural way to obtain sufficient prostaglandins by eating a diet with a variety of vegetables, lots of fish, and natural condiments like garlic and onions.