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Understanding Triglycerides

Image: Kiwis/Getty Images
Image: Kiwis/Getty Images
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Understanding Triglycerides

Image: Kiwis/Getty Images
Image: Kiwis/Getty Images

Q. I just got the results of my lipid profile. My cholesterol is high, but so are my triglycerides. What exactly are triglycerides, and how are they different from cholesterol?

A. Triglycerides are the most common form of fat in the bloodstream. They consist of three fatty acid chains linked by a molecule called glycerol.

When you eat food, enzymes in your gut break down fats into their component fatty acids, which are then reassembled to create triglyceride particles. These fatty particles can't move freely through the watery bloodstream. So they combine with cholesterol and protein to form lipoproteins. Your lipid profile lists two of these lipoproteins: low-density lipoprotein (better known as LDL cholesterol) and high-density lipoprotein (also called HDL cholesterol).

But there are actually several other types of lipoproteins, including some that contain mainly triglycerides. Triglycerides can provide energy to fuel your body, while the extras are deposited in fat tissue. After a very heavy, fatty meal, your bloodstream may contain so many triglyceride particles that a blood sample may have a milky tint. But within a few hours, they're mostly cleared out. When you need energy between meals, hormones release the stored triglycerides into the bloodstream.

Your liver also converts carbohydrates into triglycerides. When you eat extra calories — especially from carbohydrate-rich foods such as sweets and white bread — your liver churns out extra triglycerides. Other things that can raise blood levels of triglycerides include being overweight or obese, smoking, or heavy drinking. Certain medical conditions —including diseases affecting the liver, kidneys, or thyroid, and poorly controlled type 2 diabetes — can also lead to high triglycerides.

For healthy adults, normal triglyceride levels are under 150 milligrams per deciliter (mg/dL). Values of 151 to 200 mg/dL are considered borderline high; those 201 to 499 are high, and those 500 and higher are very high (and increase the risk of inflammation of the pancreas gland, called pancreatitis). Growing evidence suggests that above-normal triglyceride levels can raise the risk of cardiovascular disease independent of cholesterol levels.

To get your triglycerides back into a normal range, start with lifestyle changes. Aim for a healthy weight, get regular exercise, and eat more whole, unprocessed grains. Eat fewer refined carbohydrates, and cut back on saturated fat from meat. If you drink alcohol and aren't willing to stop, do not exceed moderate amounts (no more than a drink a day for women or two daily for men).

— by Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter

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Sunshine Abounds as the Summer Solstice Arrives

Children cool off as they run through a public fountain in Colmar, eastern France, on August 21, 2023, as France experiences a late summer heatwave. (AFP)
Children cool off as they run through a public fountain in Colmar, eastern France, on August 21, 2023, as France experiences a late summer heatwave. (AFP)
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Sunshine Abounds as the Summer Solstice Arrives

Children cool off as they run through a public fountain in Colmar, eastern France, on August 21, 2023, as France experiences a late summer heatwave. (AFP)
Children cool off as they run through a public fountain in Colmar, eastern France, on August 21, 2023, as France experiences a late summer heatwave. (AFP)

Peak sunshine has arrived in the Northern Hemisphere: the summer solstice.

Friday is the longest day of the year north of the equator, where the solstice marks the start of astronomical summer. It's the opposite in the Southern Hemisphere, where it is the shortest day of the year and winter will start.

The word “solstice” comes from the Latin words “sol” for sun and “stitium” which can mean “pause” or “stop.” The solstice is the end of the sun's annual march higher in the sky, when it makes its longest, highest arc. The bad news for sun lovers: It then starts retreating and days will get a little shorter every day until late December.

People have marked solstices for eons with celebrations and monuments, including Stonehenge, which was designed to align with the sun's paths at the solstices. Here’s what to know about the Earth’s orbit.

Solstices are when days and nights are at their most extreme

As the Earth travels around the sun, it does so at an angle relative to the sun. For most of the year, the Earth’s axis is tilted either toward or away from the sun. That means the sun’s warmth and light fall unequally on the northern and southern halves of the planet.

The solstices mark the times during the year when this tilt is at its most extreme, and days and nights are at their most unequal.

During the Northern Hemisphere’s summer solstice, the upper half of the earth is tilted toward the sun, creating the longest day and shortest night of the year. This solstice falls between June 20 and 22.

Meanwhile, at the winter solstice, the Northern Hemisphere is leaning away from the sun, leading to the shortest day and longest night of the year. The winter solstice falls between December 20 and 23.

The equinox is when there is an equal amount of day and night

During the equinox, the Earth’s axis and its orbit line up so that both hemispheres get an equal amount of sunlight.

The word equinox comes from two Latin words meaning equal and night. That’s because on the equinox, day and night last almost the same amount of time, though one may get a few extra minutes, depending on where you are on the planet.

The Northern Hemisphere’s spring, or vernal, equinox can land between March 19 and 21, depending on the year. Its fall, or autumnal, equinox can land between Sept. 21 and 24.

On the equator, the sun will be directly overhead at noon. Equinoxes are the only time when both the north and south poles are lit by sunshine at the same time.

What's the difference between meteorological and astronomical seasons? These are just two different ways to carve up the year.

While astronomical seasons depend on how the Earth moves around the sun, meteorological seasons are defined by the weather. They break down the year into three-month seasons based on annual temperature cycles. By that calendar, spring starts on March 1, summer on June 1, fall on Sept. 1 and winter on Dec. 1.