The Lions face a tough schedule, playing all five of New Zealand's Super Rugby sides and a match against the Maori All Blacks in addition to the three tests in Auckland and Wellington.
Henry coached the Lions to a 2-1 series loss on their 2001 tour of Australia and four years later guided the All Blacks to a 3-0 series sweep over the famous touring side in New Zealand.
"There is huge pressure on the Lions," 70-year-old Henry said in comments published on ESPN.
"I know from my own experiences how much the players respect getting selected for the Lions. It is the pinnacle of their career. It is massive but they need to do well and I just wonder if the itinerary is suicidal. That is my concern."
New Zealand's Super Rugby sides have been dominating the competition and are unlikely to be a pushover for Warren Gatland's Lions team, as witnessed by the Waikato Chiefs' 40-7 demolition of Wales during their tour last June.
"They are playing New Zealand Maori, they are playing the five franchised teams - and those five franchised teams have nothing to lose, no pressure on them at all, so they will fire everything at the Lions and take them on.
"Hopefully (the Lions) have the ability to overcome that.
British and Irish Lions captain candidates
British and Irish Lions captain candidates
1/6 Alun Wyn Jones
Jones is probably still the leading candidate for the captaincy, even if his, and Wales’, Six Nations was not what they were hoping for. Jones took the Welsh armband from Sam Warburton for the championship but at times looked uneasy at making a call, such as when he was overruled when Wales opted to go for the corner against Scotland, rather than taking the shot at three points. Jones captained the Lions in the deciding third Test against Australia in 2013 and is a guaranteed starter if fit – something Gatland is keen for his captain to be, although not a necessity.
2/6 Sam Warburton
Had Wales not finished fifth in the championship with three defeats, there is a good chance Warburton would have been named player of the tournament. The way he reacted to losing the Wales captaincy and moving to blindside flanker has been phenomenal and he is now the bookies’ favourite after his performances and having already led the Lions to a tour victory. Of Warburton’s chances, Gatland said: “He's a different captain to some other players. He leads by example. He doesn't say a lot but he has had that experience. He's one of the guys potentially in contention, definitely.” However, he has been so good without the burden of the armband, would giving it to him hinder his performances?
3/6 Dylan Hartley
Before his red card for Northampton in December, Hartley was the frontrunner for the armband but now his place on the plane is not even assured. For England, Jamie George has impressed and could usurp his captain’s position over the next 12 months, with Hartley arguably not even the third most impressive Hooker the home nations boasted during this year’s Six Nations. However, his grit and fire has been one of the reasons for England’s success under Eddie Jones and it is that sort of personality which could be vital in the hotbed of New Zealand.
4/6 Rory Best
The way Best led Ireland to ending England’s unbeaten run shows that he has the ability to motivate the players around him in tough and gritty situations. He has also captained a side to a win over the All Blacks, the only candidate who is able to say that. Best is certainly a viable candidate but the question mark that remains hanging over him is if he is good enough to start at hooker against the All Blacks? Hartley, Best, George and Wales’ Ken Owens are all in with a shout.
5/6 Owen Farrell
Farrell was player of the tournament after a stunning Six Nations. His kicking is up there with Leigh Halfpenny’s as amongst the best in the world and he has the right mentality of a captain having been schooled under Eddie Jones. Farrell looks certain to start at 12 for the Lions and would make a fierce captain. However, having not captained an international side from the start, how would he fare leading the most intense tour the Lions have embarked on? It is a tough challenge for the most weathered of captains, never mind a novice.
6/6 Conor Murray
An outside shout for captain but the way he controls the game from around the ruck shows his importance to the Lions. He, like Best, has experience of beating the All Blacks and of a winning Lions Tour (like everyone on this list, other than Hartley). He has captaincy experience but while he was a certain starter a month ago, the performances of Rhys Webb have given Gatland a real decision to make. He said he wants to pick his squad first and then his captain and that could go against Murray in the decision-making process if Webb is now considered ahead of him.
"But really when you tour, you need to ensure some momentum is created by results and you just wonder how they are going to go into the test series with that itinerary.
"It is very demanding.
"You just want the Lions to do well because it is such a marvellous brand in world rugby and they need to do pretty well to maintain the potency of the brand, because it's huge for the southern hemisphere countries to have the Lions tour."
The Lions open the tour on June 3 against a New Zealand Barbarians side in Whangarei.